A comparative study of surviving dwarf galaxies versus what we have uncovered of cannibalized dwarf galaxies.
succeed (or not) at predicting the observed properties of galaxies
as inferred from both local group and high-redshift observations.
Malaysia has never previously hosted an IAU (International Astronomical Union) conference, neither have Malaysia’s neighboring countries: Cambodia, Singapore, Thailand, and Vietnam. Indonesia last held one in 1990, about 30 years ago. Together, these Southeast Asian countries are home to about 500 million people, a larger population than the EU. This conference aims to provide an opportunity to grow the international astronomical community.
The fields of Galactic archaeology and near-field cosmology have been revolutionized by a plethora of rich data from virtually every observational domain. This breadth from the most ancient field of astronomy (astrometry) to one of the newest (asteroseismology). We now know the precise kinematics, detailed chemical abundances, and approximate ages for millions of stars across much of the Milky Way, from the Bulge to the Solar Neighbourhood through to the Halo. This incredible bounty of astronomical data is accompanied by increasingly sophisticated astrophysical models in hierarchical galaxy assembly, galactic dynamics, stellar evolution, and nucleosynthetic yields.
These resources have led to an emerging picture of the Milky Way's first three billion years. The first phase of star-formation was likely dominated by metal-poor ([Fe/H] <= -3.0) gas and stars, whose chemical abundances represent a zoo in their suggested diversity of early chemical polluters. Some brief time later, the Milky Way formed its first globular clusters, its Bulge, and its Thick Disk, with the earliest phases of that epoch likely having been dominated by globular clusters. Simultaneous to these developments, the early Milky Way experienced several significant accretion events, such as the recently discovered systems Gaia-Enceladus and Sequoia. We can trace these structures dynamically, and chemically, and we may even be able to identify which globular clusters belonged to them. These accretion and dissolution events stand in contrast to the Milky Way’s puzzlingly quiescent state today.
In parallel to these developments in Galactic astronomy, the field of galaxy formation is also undergoing a revolution due to high-redshift data from Atacama Large Millimeter/submillimeter Array (ALMA). This progress will soon be accelerated by data from the Christmas 2021 launch of the James Webb Space Telescope (JWST). The question of how galaxies form and evolve will be constrained by a deluge of information from the earliest epochs, which will be both challenging and fascinating to analyze, interpret, and understand. We will ascertain the spread in abundances of gas at the same early cosmological epoch, the structural state of galaxies when the progenitors of globular clusters are driving the first significant star formation events, and the mass distribution of star formation events at high redshift. JWST will also probe the stellar mass functions of low-metallicity stellar populations, enabling new insights into the physical processes that drive the formation of stars and the resulting chemical enrichment of the universe.
Magnificent data (from both the Local Group and the high-redshift Universe) and state-of-the-art models are optimally insightful when used together. Given recent developments, the time is now to bring in experts from these three areas (Galactic astronomy, high-redshift astronomy, and theory and modeling of galaxy formation and evolution). The conference will enable a more holistic understanding of the Milky Way's and all disk galaxies’ early star formation and structural assembly.
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Yuan-Sen TingAustralian National University
Simon WhiteMax-Planck-Institut fuer Astrophysik
The broad outline of how galaxies form has been understood for 40 years, and the last decade has seen plausible and relatively detailed numerical simulations of the process both for individual objects and for the population as a whole. Topics of current interest vary between communities. Cosmologists need details of the statistical relationship between galaxies and their haloes in order to test the LambdaCDM paradigm. High-redshift observers care about the onset of galaxy formation and its relation to the first generations of stars and black holes, and hence to the reionisation process. Observers of diffuse media need to clarify how these are structured by the feedback processes that also drive the exchange of material between galaxies and their environment. Galactic archaeologists focus on the accretion of dwarf galaxies onto larger systems in order to interpret the structure of the old stellar haloes of the Milky Way and its neighbours. Galactic astronomers are interested in the the diversity of the galaxy population and in the origin and maintenance of the various gaseous and stellar structures (disks, bars, bulges, spirals, warps...) that characterise today's galaxies. Finally, chemical evolution modellers explore heavy element patterns within galaxies in order to understand the relevant nucleosynthetic pathways and the attendant mixing processes. Recent advances made by these various communities are not always well communicated between them, and I will review some areas where I think such "cross-disciplinary" understanding could be helpful.
Andrey KravtsovUniversity of Chicago
I will present a simple model for evolution of dwarf galaxies, which can reproduce a remarkably broad range of observed properties of dwarf galaxies over seven orders of magnitude in stellar mass. In particular, we show that the model can simultaneously match observational constraints on the stellar mass-halo mass relation, as well as observed relations between stellar mass and gas phase and stellar metallicities, gas mass, size, and star formation rate, as well as general form and diversity of star formation histories of observed dwarf galaxies. We use the model to forward model population of the Milky Way (MW) satellites down to the faintest luminosities probed by observations (M_V~0) and properly taking into account observational selection effects, effects of disk disruption and effects of LMC. We show that 1) observed luminosity function (LF) favors early reionization (z_rei~8) of the local volume, 2) model can reproduce radial distribution of the MW satellites without use of orphans, 3) analyses of a sample of MW-sized halos show that observed planar distribution of the Milky Way satellites and correlation of their orbital poles is somewhat unusual, but is statistically consistent with LCDM.
Jorge MorenoPomona College
The standard cold dark matter plus cosmological constant model predicts that galaxies form within dark-matter haloes, and that dwarf galaxies are more dark-matter dominated than massive ones. The unexpected discovery of two low-mass galaxies lacking dark matter immediately provoked concerns about the standard cosmology and ignited explorations of alternatives, including self-interacting dark matter and modified gravity. Apprehension grew after several cosmological simulations using the conventional model failed to form adequate numerical analogues with comparable internal characteristics. In this talk I will show that the standard paradigm naturally produces galaxies lacking dark matter with internal characteristics in agreement with observations. Using FIREbox, a state-of-the-art cosmological simulation based on the `Feedback In Realistic Environments' (FIRE) model, and a meticulous galaxy-identification technique, we find that extreme close encounters with massive neighbours can be responsible for this. We predict that ~30% of massive central galaxies (with at least 1e11 solar masses in stars) harbour at least one dark-matter-deficient satellite (with 1e8–1e9 solar masses in stars). This distinctive class of galaxies provides an additional layer in our understanding of the role of interactions and tidal stripping in shaping galactic properties. Future observations surveying galaxies in the aforementioned regime, with facilities like the Rubin and JWST, will provide a crucial test of this scenario. If time allows, I will also speak of future plans to conduct ultra-high resolution zooms capable of probing the formation and nature of globular clusters in these galaxies. Paper: Moreno et al., Nature Astronomy, 6, pages 496–502 (2022)
Yao-Yuan MaoUniversity of Utah
The Satellites Around Galactic Analogs (SAGA) Survey is a spectroscopic survey that identifies satellite galaxies brighter than Mr,o=-12.3 around a statistical sample of Milky Way (MW) analogs at z∼0.01 (25-40 Mpc). We have obtained more than 50 thousand galaxy redshifts, which significantly increase spectroscopic coverage for very low redshift objects in 17 < r < 20.75 around SAGA hosts, creating a unique data set that places the Local Group in a cosmological context. The SAGA Data Release II (Mao et al. 2021) delivered results from 127 satellites around 36 MW analogs. SAGA Data Release III includes a satellite census of 100 MW systems, and will be released in the very near future. We find that the number and luminosities of MW satellites are consistent with being drawn from the same underlying distribution as SAGA systems. The SAGA satellite luminosity functions and radial distributions are broadly in agreement with theoretical predictions based on cold dark matter simulations and an empirical galaxy-halo connection model. We also find that the quenched fraction increases as satellite stellar mass and projected radius from the host galaxy decrease, however, the majority of confirmed SAGA satellites are star-forming. Overall, the star-forming satellite luminosity function appears to have a higher normalization than that in the Local Group and from theoretical prediction.
Shany Danieli*Princeton University
Quantifying the connection between galaxies and their host dark matter halos has been vital for testing cosmological and galaxy formation models on various scales. For galaxies with M*~< 10^9 Msun, studies have primarily relied on the satellite galaxy population orbiting the Milky Way. I will present new constraints on the connection between satellite dwarf galaxies and their host dark matter subhalos, using the largest sample of satellite galaxies in the Local Volume (D < 12 Mpc). The sample, constructed as part of the Exploration of Local VolumE Satellites (ELVES) Survey, comprises 250 confirmed and 71 candidate dwarf satellites around 27 Milky Way-like hosts. I will discuss our recent results using this sample, suggesting that the scatter between the stellar mass and the halo mass of dwarf satellites originates in a combination of star formation stochasticity and host-to-host scatter. Compared to what was previously constrained by the Milky Way satellites alone, we find that the scatter increases towards low halo masses at a higher rate. I will end by discussing the implications of our results for understanding baryonic-induced effects in such low-mass galaxies, the role of the environment, and dark matter physics.
Nicolas Garavito CamargoFlatiron Institute
The vast multidimensional data observed in the Local Group (LG) provide us with the unique opportunity of comparing the properties of the LG with their simulated analogs in cosmological simulations. In such a comparison it has been found that the observed kinematic properties of satellite galaxies in the LG are very unusual when compared to cosmological simulations. In both the Milky Way and the Andromeda galaxy, satellite galaxies are found to be distributed and moving in flattened co-rotating systems. A configuration that is only found in 0.3-3% of the simulated galaxies. Such disagreement is known as the planes of satellites problem. More intriguing is that the disagreement is persistent even in different dark matter models and unlike other 'small-scale problems' it is not sensitive to the inclusion of baryonic processes in the simulations. In this talk, I would provide evidence of how a natural explanation of the observed co-rotation patterns are associated with the out-of-equilibrium state of the galaxy. Recent missions and surveys, such as Gaia, have revealed that the Milky Way galaxy is not in dynamical equilibrium. The barycenter of the galaxy is moving due to the ongoing interaction with the Large Magellanic Cloud. Using the Latte hydrodynamical high-resolution zoom-in simulation of MW-like galaxies A massive satellite moves the reference frame of the inner halo with respect to the outer halo. Resulting in some cases in apparent co-rotation motions of the outer halo when observed from the disk of the galaxies. I'll show how the orbital poles distribution of outer halo objects is strongly affected during the pericenter passages. I will further discuss what properties of the mergers, mass ratios, pericenter passages, and eccentricities, would be needed to reproduce the observational co-rotations pattern observed in the Milky Way and M31. These results provide new insight into how the observed co-ration patterns can inform us about the out-of-equilibrium stare of the galaxy. Which is a natural explanation that does not depend on the nature of the Dark Matter particle and in baryonic processes. These results also highlight the importance of taking into account the dynamic state of the LG when comparing it with LG analogs in cosmological simulations.
Janvi MadhaniJohns Hopkins University
There has been a long standing conflict between observations of planes of dwarf satellites around local galaxies and numerical simulations of similar galaxies. Observations find planes of satellites around the Milky Way, Andromeda, Centaurus A and possibly several other local galaxies. Numerical simulations find that planes are rare, present in less than 2% of Milky Way-type systems, or are spurious and short-lived. This discrepancy has been interpreted as a challenge to our accepted cosmology, namely the Lambda CDM paradigm. We present results that show that this conflict can be resolved if one simulates a larger volume, while forcing small-scale resolution across it, to better capture inflow along cosmic filaments. We use the New Horizon simulation and find that ~30% of Milky Way-type systems have satellite planes, therefore, solving this conflict. We also discuss the likely origins of these planes and a new window into the dynamics of the Local Universe they may provide.
Haining Li*National Astronomical Observatory of China
Large-scale surveys have provided us a great opportunity to explore the early history of Galactic evolution and formation. In this talk, we would like first to present the results that have been obtained through a joint project between LAMOST and Subaru in the past few years. The main product is a homogeneous sample for about 400 very metal-poor stars, which provides stellar parameters and abundances for more than 20 species, covering a rather wide range in evolutionary status, and thus an unprecedentedly valuable sample to constrain the Galactic chemical evolution models, as well as the production of elements at early times. We will also briefly summarize other interesting discoveries based on this project, including a number of alpha-deficient stars in the Milky Way halo, the origin of a halo moving group, etc. Besides, we will introduce the Stellar Abundances and Galactic Evolution Survey (SAGES) Northern Survey, a narrow-band wide-field photometric survey which is conducted by NAOC, and employs a self-designed v-band that is very sensitive to stellar metallicities. The topics will briefly cover its survey strategy, first data release, synergy in the field of Galactic archaeology, and early science.
Federico SestitoUniversity of Victoria
The most metal-poor stars (MMPs) are rare objects located mainly in the Milky Way halo. It is assumed that they formed in the relative pristine Galaxy shortly after the Big Bang, and they belong to the earliest generations of stars. The search for the MMPs is therefore important to answer questions on the masses of the first stars, the universality of the IMF, and the assembly of the Galaxy both in terms of chemistry and dynamics. Gaia started a revolution providing exquisite astrometric data, which are crucial for Galactic archaeology studies. In synergy with high-resolution spectroscopic data, we can now dissect the Galaxy in a multi-dimensional space. I will show a chemo-dynamical investigation of MMPs focusing on the Galactic bulge. Stars are selected from the Pristine Inner Galaxy survey, which uses the Ca HK filter at CFHT/MegaCam to select the MMP candidate stars. The chemistry from high-resolution Gemini/GRACE observations suggests these are among the oldest stars and brought in during the very early Galactic assembly. The abundances of three stars are compatible with second generation globular clusters stars. This indicates the presence of ancient and disrupted globular clusters in the inner Galaxy. One star points to the feasibility of forming extremely metal-poor ([Fe/H]<-3.0) structures in the early Universe, which are now dissolved. Another star with confined to the disk orbit seems to be accreted very early from a fossil dwarf galaxy, which was polluted by only one low-mass supernovae.
Madeline LuceyUniversity of Texas at Austin
The chemo-dynamics of the stellar populations in the Galactic Bulge inform and constrain the Milky Way's formation and evolution. The metal-poor population is particularly important in light of cosmological simulations, which predict that some of the oldest stars in the Galaxy now reside in its center. The metal-poor bulge appears to consist of multiple stellar populations that require chemo-dynamical analyses to disentangle. In this presentation, I will describe our detailed chemo-dynamical study of the metal-poor stars in the inner Galaxy, named The COMBS Survey which uses VLT/FLAMES spectra of ~350 metal-poor stars. I will discuss the results and the implications for early Milky Way formation and chemical evolution. In addition, I will preview results from an ongoing survey of carbon-enhanced metal-poor stars, which are thought to be solely enriched by the first generation of stars.
Karl GlazebrookSwinburne University of Technology
JWST's deep infrared covering in imaging and spectroscopy promise to reveal new secrets of faint and evolved massive galaxies at high-redshift. In particular massive galaxies at z > 3 that can be impossible to observe in the optical and too faint for ground-based infrared are looked for. In the wealth of data in the first six months of operation we have received numerous deep fields, which have provided a new perspective on morphological evolution, discovery of numerous z > 10 star forming galaxies, and the first spectra of a population of z > 3 massive quiescent galaxies that were 'impossible from the ground.' These constrain the mass and star-formation histories of these previously unprobed objects. I will give an overview of these exciting results.
Nicha LeethochawalitNational Astronomical Research Institute of Thailand
I will discuss the James Webb Space Telescope/NIRCam-led determination of 7 < z < 9 galaxy properties based on broadband imaging as part of the GLASS-JWST Early Release Science program. This is the deepest dataset acquired at these wavelengths to date. We robustly identify 13 galaxies with SNR>8 in F444W from 8 arcmin2 of data at m< 28 from a combination of dropout and photometric redshift selection. I will present how their star formation main sequence is consistent with predictions from simulations. I will also introduce an analytical framework to constrain main-sequence evolution at z < 7 based on galaxy ages and basic assumptions, through which we find results consistent with expectations from cosmological simulations. If time allows, I will also mention the number density of these sources and whether their UV luminosity function is consistent with those previously determined from Hubble Space Telescope data.
Themiya NanayakkaraSwinburne University of Technology
The first JWST/NIRCam observations from JWST has revealed a very blue Universe. The UV slopes are found to be bluer than what traditional stellar population models can predict, leading to possibilities of stellar populations with high nebular continuum escape and/or very low-metallicities. JWST/NIRSpec observations demonstrate the extreme nature of the z > 6 emission line galaxies with limited metal content. In my talk I will discuss early results from the JWST GLASS ERS survey and put these results in the context of the local extremely metal poor galaxies observed with VLT/MUSE and Keck/KCWI. Specially, I will discuss results from our campaign to spatially map the metallicity and element abundances of two lowest metallicity galaxies in the local Universe. Our results show the these galaxies with log(O/H)< 2% solar and are Fe/O enhanced. I will show how we need to move to non-traditional supernovae enrichment mechanisms to explain the observed abundances and implications there of for our understanding of the true nature of first galaxies in the Universe in the era of JWST.
Hidenobu YajimaUniversity of Tsukuba
Observations by JWST have successfully discovered candidates of galaxies at redshifts greater than ten (e.g., Donnan et al. 2022 Naidu et al. 2022). Interestingly, some candidates indicate quite large stellar masses (e.g., Harikane et al. 2022) and extended or very compact sizes (Ono et al. 2022). To understand the galaxy formation in the early Universe and develop theoretical models for comparisons with JWST or ALMA data, we perform cosmological radiative-hydrodynamics simulations of the first massive galaxy formation with a new simulation project: FOREVER22 (Yajima et al. 2022, MNRAS, 509, 4037). We find that galaxies in overdense regions have high star formation rates larger than ten solar masses per year at z = 10 and their stellar masses reach 10^9 solar masses. The morphology of galaxies drastically changes with time via major mergers and stellar feedback, which nicely match recent observations by JWST. In my talk, I will also present multi-wavelength radiative properties of galaxies with radiative transfer simulations.
Christina C. WilliamsNOIRLab
JWST, with its groundbreaking infrared sensitivity and novel observing modes in space, is now probing unchartered territory in early galaxy astrophysics. In particular, the first billion years of the universe is a critical era when the star formation in typical galaxies is thought to drive Reionization. In this talk I will discuss two complementary imaging surveys using JWST's Near-Infrared Camera (NIRCam) that target galaxies from the end of the Reionization era into Cosmic Dawn. The first survey uses the new capability of medium band imaging at 2-5 micron, efficiently imaging and spatially resolving strong rest-frame optical emission lines, promising probes of ionizing photon escape. I will secondly present the upcoming PANORAMIC survey, a large-area program to discover massive and intrinsically bright high-redshift galaxies, which may be the signposts of early Reionization. I will present first science results from these programs and anticipated outcomes once the programs have completed. The data from both programs are publicly available and I will outline our plans for releasing science-ready data products to the community.
Roberto MaiolinoUniversity of Cambridge
I will present the early results from the NIRSpec GTO programme focussing on its multi-object spectroscopic programme, which is the most extensive NIRSpec-MOS programme in Cycle 1. By the time of the conference sensitive spectra will already be obtained for more than a thousand galaxies from z ~ 1.5 out to z > 9, opening a new window on the exploration of early galaxy formation. A large fraction of the observed galaxies will be early disk systems or disk progenitors. NIRSpec's sensitivity and spectral range will access stellar and nebular diagnostics which have been impossible to observe from ground so far, hence enabling an unprecedented characterisation of the physical properties of the early phases of galaxy formation. On behalf of the NIRSpec-GTO team, I will illustrate the early results of our programme and discuss the implications for our understanding of the early phases of the evolution of the stellar populations, of the chemical enrichment of galaxies, of their ISM properties and their co-evolution with AGNs. I will also discuss constraints and prospects on the detectability of PopIII stars in primeval galaxies.
Hannah UeblerUniversity of Cambridge
JWST enables for the first time observations of rest-frame optical emission lines such as Halpha or [OIII] in star-forming galaxies at 3 < z < 9. These lines have been well studied at lower redshifts, allowing us to directly connect early galaxy formation to later phases in cosmic history. With JWST’s NIRSpec Integral Field Spectrograph (IFS) we can study spatially resolved emission lines to measure and model the kinematics of early galaxies. I will present first results from the Galaxy Assembly IFS program of 42 3 < z < 9 galaxies of the NIRSpec GTO team, with a focus on disk galaxy kinematics and outflows. Our data will provide important constraints on theoretical models of galaxy formation, and aid the interpretation of complementary studies with ALMA of e.g. [CII] kinematics.
Alessandro SavinoUniversity of California, Berkeley
I will present updates from the JWST Early Release Science (ERS) program on resolved stellar populations (JWST-DD1334). This program serves as a pathfinder for JWST-based resolved stellar population studies and has gathered deep near-infrared photometry of three nearby prototypical stellar systems: the globular cluster M92, the ultra-faint dwarf Draco II and the star-forming dwarf WLM. I will present design, data content, publicly available analysis tools and early scientific results of the ERS program. I will characterize the stellar catalogs, showcasing the deepest color-magnitude diagrams ever obtained in near-infrared bands. I will illustrate results on the star formation history, sub-Solar initial mass function, proper motion, evolved stars and dust content of our targets. I will describe lessons learned from the ERS program, recommendations for nearby stellar system observations and a post-launch perspective on the transformative contribution of JWST to the study of the Milky Way and of its surroundings.
Jessica Lu*University of California, Berkeley
The inner regions of disk galaxies embody the rich history of early galaxy formation, major mergers, intense feedback, and complex dynamical phenomena. Our own Milky Way contains a bar/bulge on scales of >1kpc, the central molecular zone containing rich young star clusters on scales of 300 pc, a nulcear star cluster with both young (<10 Myr) and old (>8 Gyr) stars on scales of a few pc, and a supermassive black hole. I will present a review of the structures and stellar populations in the inner Milky Way and what they tell us about galaxy formation. I will review results from probes such as the IMF, current star formation efficiency, star formation history, metallicity distribution, stellar dynamics, and the distribution of stellar remnants. The inner regions of galaxies are often more difficult to probe, including for the Milky Way; and I will briefly discuss prospects for improving our understanding of this region using JWST, Roman, and the ELTs.
Kaley BrauerMassachusetts Institute of Technology
In the age of Gaia, we are gaining a better understanding of the major mergers experienced by the Milky Way throughout its formation, such as the Gaia-Enceladus and Sequoia events. The low mass end of the Milky Way's assembly history is still poorly understood, however. The smallest dwarf galaxies accreted by the Milky Way, the ultra faint dwarfs (UFDs), were among the first galaxies in the Universe and could provide important insight into early galaxy formation and chemical enrichment. Currently, though, we lack ways to identify stars which accreted from UFDs. By utilizing the Caterpillar simulation suite, a suite of 35 Milky Way-mass galaxies forming, we find that chemical tagging with r-process elements and clustering in kinematic phase space can help us identify stars which accreted together from these dwarf galaxies. We are expanding on this work with highly-resolved hydrodynamic simulations of the earliest dwarf galaxies to quantify the low-mass end of the Milky Way assembly history. Identifying stars from UFDs that still exist in the Local Group is particularly vital because even JWST cannot directly observe these low-mass high-redshift galaxies.
Long Wang*Sun Yat-sen University
Dense stellar systems, including massive star clusters and nuclear star clusters, are important environments favouring production of binary mergers. Mergers of compact objects, such as binary black holes (BBHs) produce gravitational waves (GWs) observed by LIGO/VIRGO/KAGRA. The hierarchical mergers of stars and black holes in population III star clusters and nuclear star clusters might produce very massive stars and intermediate-mass black holes (IMBHs), which are important sources for the formation of supermassive black holes at high redshift. The major driver of mergers are frequent dynamical encounters between stars during the life time of star clusters. In this talk, we show how stellar dynamics affect mergers, and what are the roles of initial conditions of host star clusters, including initial mass functions, properties of primordial binaries and galactic environment. We discuss the possibility of detecting population III stars from JWST and gravitational waves of IMBH-BH mergers from the new generation of GW detectors. Finally, we show how large N-body simulations can help to study the mergers and long-term evolution of massive star clusters.
Kim Venn*University of Victoria
High resolution spectral observations provide high precision radial velocities and chemical abundances for faint stars associated with structures in the MW and Local Group, complimenting the exquisite phase space information provided by the Gaia mission. I would like to present recent results for stars selected from Gaia DR3 at large half-light radii in nearby UFDs to discuss the accretion history and/or disruption of these very low mass systems. I also hope to present new results for stars in MW streams found by combining Gaia with the Pristine survey to disentangle their origins ranging from the merging of small satellite galaxies to the destruction of star clusters over billions of years.
Anirudh ChitiUniversity of Chicago
We present the detailed chemical abundances of stars in the outskirts (out to ~9 half-light radii) of the Tucana II ultra-faint dwarf galaxy (UFD). The Milky Way’s UFDs are “relic” galaxies (~13 Gyr old) from the early universe, making their stars unique probes of the first stages of galactic and chemical evolution in a simple, self-contained environment. Previous spectroscopic studies had largely been limited to stars within the core of these galaxies (~2 half-light radii) due to the sparseness of their distant stars. This work presents the first detailed abundances of a population of stars outside a UFD’s core region (~4 half-light radii) that appear to be bound to the galaxy. The distant stars are, on average, more metal-poor than the central population, affirming Tucana II to be the most metal-poor known UFD (<[Fe/H]>~-2.85). This difference between inner and outer stars suggests Tucana II, and perhaps other ultra-faints, plausibly were influenced by early, strong feedback or a galactic merger. In particular, the alpha-element abundances in Tucana II indicate some delayed chemical evolution, consistent with Tucana II being formed by an early merger of two first galaxies that triggered star formation. Such distant stars also imply that Tucana II harbors a massive, spatially extended dark matter halo. Collectively, these results suggest that key factors in understanding the early evolution of relic dwarf galaxies lie in their outskirts and were missed by previous observations. We demonstrate that detailed studies of such stars in the halos of relic galaxies are now possible.
Paul HoEast Asian Observatory
Malaysian Astronomy is poised for rapid growth as being promoted by the GMAC and the IAUS377 Meetings. These meetings show the research activities of Malaysian astronomers all over the world, as well as the current excitement as stimulated by JWST. We propose that the East Asian Observatory is a path forward where Malaysian astronomers can access frontier instruments directly. Via the EAO, Malaysia already has access to the JCMT for submillimeter wavelength astronomy, including access to the EHT studies of the shadows of black holes. Through collaboration with the partner institutions of EAO, Malaysia can also access other frontier instruments such as SMA, ALMA, Subaru, among other regional facilities. The goal of EAO is to provide Malaysia with access to frontier science without first having to make capital investments, while Malaysia can focus on supporting local research infrastructures and manpower. As Malaysian astronomy grows, we look forward to a future where Asia will work together to construct and operate the next generation of facilities for Asia.
Nurul Fatini JaafarUniversiti Malaya
Astronomers in the field of galactic archaeology use stars as fossils to study the history of Milky Way and other galaxies. On the flip side, archaeo-astronomers analyse material culture and environmental data to study human’s conception concerning the sky in the past. Archaeology is a sub-field of Anthropology—the science of mankind. While Archaeology is thriving in Malaysia, Archaeoastronomy lags behind. This presentation will review the development of Archaeoastronomy in the Malaysian context and its’ link to Ethnoastronomy and History of Astronomy. These three interdisciplinary fields are grouped as Cultural Astronomy. We will discuss answers to question on why Archaeoastronomy appears to be sidelined at the national level, explore the prospective of Archaeoastronomy as an academic field, and look into its potential in communicating science to public.
Mohd Hafiz bin Mohd SaadonUniversiti Malaya
Malaysia has a long history and is largely shaped by the evolution of local culture, including archeoastronomy. Based on the Terengganu Inscription Stone, Islam began to gain a foothold in this region in the 14th century and the development of Islamic knowledge was brought in by traders and preachers from the Middle East, including Islamic astronomy. The daily and annual life of a Muslim places great emphasis on time periods (such as prayer and fasting) and directional coordinates (determining the direction of Makkah,) resulting in the field of Islamic astronomy still and always being practised among the Muslim Malaysian community and continuously being studied and improved by local researchers and scholars until now. This presentation provides a retrospective view of the development of Islamic astronomy from the foundation centred on the Quran and Hadith until it found its place among the Malaysian community, especially in the history of more than 600 years. The research also proposes a perspective view, which defines Islamic astronomy as a synergic medium, not just for preserving Islamic traditional knowledge but also for fostering STEM skills within 21st-century education in the era of JWST.
Ide Nada ImandiharjaBandung Institute of Technology
The Dinoyo inscription dated 760 AD from Malang, East Java, Indonesia, mentions the ceremony of making the Agastya statue by Ananah from the Kanjuruhan Kingdom. Kanjuruhan is currently the oldest kingdom in the eastern part of Java. In Vedic religion, Agastya is the main deity who is a manifestation of the star Canopus (ɑ Carinae). One of the rhymes in the Rig Veda tells about the relationship between Agastya and King Nahusha which correlates with the comet event that leads to the star Canopus. Based on the comet catalog of Gary W. Kronk (1999), comet 1P/Halley visited Earth in 760 AD, the same year with Dinoyo inscription. By reviewing the contents of the inscription and conducting literature studies, hypotheses regarding the two events are connected. We analyzed aspects of chronology, geography, biography, and mythology. The initial result of this research conveys the results of the analysis of chronological and geographical aspects. Both aspects support the proposed hypothesis.
Miho IshigakiUniversity of Tokyo
One of the major goals of modern spectroscopic surveys of stellar populations in the Galaxy and its satellites is to constrain astrophysical sources of metals at different times and places in the Universe. Thanks to large-scale spectroscopic surveys, detailed elemental abundance estimates for statistical samples of various Galactic stellar populations are rapidly increasing. Interpreting those data sets in terms of nucleosynthesis yields of stars and supernovae, such as core-collapse supernovae or Type Ia supernovae, will help understanding their explosion mechanisms as well as the progenitor stars. I would like to review current constraints on the origin of metals by comparing supernova yield models with observed elemental abundance patterns, with particular emphasis on the oldest or the most metal-poor stars. The prospects and limitations of using a set of supernova yield models to infer the relative contribution of different types of supernova in the earliest epoch of the Galaxy formation will be discussed.
Norhasliza YusofUniversiti Malaya
Massive and very massive stars have tremendous impact in the cosmic evolution. The nucleosynthesis both during their advanced stages and their final explosion likely contribute greatly to the overall enrichment of the Universe. Their extreme conditions lead also to very important radiative and mechanical feedback effects, from local to cosmic scale. In order to determine their fate, it is important to determine what is the final masses, for example for low metallicities massive or very massive stars, it can retain huge core masses and this could bring the possibility as the candidate of PISNe progenitors. Pair-instability supernovae (PISNe) are very luminous explosions of massive, low-metallicity stars. They can potentially be observed out to high redshifts due to their high explosion energies, thus providing a probe of the Universe prior to reionization.
Henrique ReggianiCarnegie Observatories
The progenitor systems and explosion mechanisms responsible for the thermonuclear events classified as Type Ia supernovae are uncertain and difficult to constrain using traditional observations of Type Ia properties (e.g., light curves). Even though we do not fully understand their progenitors, we rely on our knowledge of these events to model galactic chemical evolution, as thermonuclear explosions are the main site in which iron-peak elements are synthesized. Understanding the underlying properties of thermonuclear explosions would allow us to, among others, better model galactic chemical evolution and understand the physics behind Type Ia supernovae. To better constraint Type Ia progenitors, the prolific producers of iron, we used theoretical nucleosynthetic yields to identify a set of elemental abundance ratios infrequently observed in metal-poor stars but shared across a range of Type Ia progenitor systems and explosion mechanisms. We label stars with this abundance signature ``iron-rich metal-poor'' stars (IRMP). IRMP stars formed in environments dominated by Type Ia nucleosynthesis and their chemical pattern can be used to constrain both the progenitor systems and explosion mechanisms responsible for Type Ia supernovae. We identify three IRMP stars in the literature and homogeneously infer their elemental abundances. We find that they can be best explained by deflagration-to-detonation transitions in sub- or near-Chandrasekhar mass progenitors. I will also show how the occurrence rates of IRMP stars in our Galaxy and beyond, to provide an extra constraint on their nature.
Vasily Belokurov*University of Cambridge
We use accurate estimates of aluminium abundance from the APOGEE Data Release 17 and Gaia Early Data Release 3 astrometry to select a highly pure sample of stars with metallicity -1.5≲[Fe/H]≲0.5 born in-situ in the Milky Way proper. The low-metallicity ([Fe/H]≲-1.3) in-situ component we dub Aurora is kinematically hot with an approximately isotropic velocity ellipsoid and a modest net rotation. Aurora stars exhibit large scatter in metallicity and in many element abundance ratios. The median tangential velocity of the in-situ stars increases sharply with metallicity between [Fe/H]=-1.3 and -0.9, the transition that we call the spin-up. The observed and theoretically expected age-metallicity correlations imply that this increase reflects a rapid formation of the MW disk over≍1-2 Gyr. The transformation of the stellar kinematics as a function of [Fe/H] is accompanied by a qualitative change in chemical abundances: the scatter drops sharply once the Galaxy builds up a disk during later epochs corresponding to [Fe/H]>-0.9. Results of galaxy formation models presented in this and other recent studies strongly indicate that the trends observed in the MW reflect generic processes during the early evolution of progenitors of MW-sized galaxies: a period of chaotic pre-disk evolution, when gas is accreted along cold narrow filaments and when stars are born in irregular configurations, and subsequent rapid disk formation. The latter signals formation of a stable hot gaseous halo around the MW progenitor, which changes the mode of gas accretion and allows development of coherently rotating disk.
Ioana CiucaAustralian National University
We employ our Bayesian Machine Learning framework BINGO (Bayesian INference for Galactic archaeOlogy) to obtain precise relative stellar age estimates with uncertainties for 68,865 red giant and red clump stars observed by the high-resolution (R~22,000) spectroscopic survey APOGEE DR17. By combining the age and metallicity information, we dissect the Galactic disk stars into four radial components, namely, the inner disk (R < 6kpc), the local disk (6 < R < 8kpc), the outer disk (8 < R < 10kpc) and the most outer disk (12 > R >10kpc). We then examine the age-metallicity relationship across all radial regions and find our results to be consistent with a transition of the phase from the thick to thin disk starting approximately 10 Gyr ago. We also identify, albeit tentatively, a sharp dip in metallicity happening around 12 Gyr ago, observed most clearly within the 8 < R < 10 kpc region. To understand its possible origins, we explore the AMR in two of the Auriga suite of zoom-in cosmological simulations, Au18 and Au23, where we can also observe a dip of 0.1 dex in metallicity in the outer regions, with the dip being broader in Au23. In both these simulations, this dip coincides with a gas-rich merger (Au 18) or galactic fountain event (Au 23), further supporting the scenario that the metallicity dip is likely the result of a gas dilution event. Contingent upon a proper treatment of the measurement error in the observed AMR of the Milky Way, the existence of such a dip in metallicity is a valuable diagnostic for when the last massive merger of the Milky Way took place.
Danny HortaFlatiron Institute
Galactic haloes in a Λ-Cold Dark Matter (ΛCDM) universe are predicted to host today a swarm of debris resulting from cannibalised dwarf galaxies that have been accreted via the process of hierarchical mass assembly. The chemo-dynamical information recorded in the Galactic stellar populations associated with such systems helps elucidate their nature, placing constraints on the mass assembly history of the Milky Way. Using data from the APOGEE and Gaia surveys, I will present an examination of APOGEE targets belonging to the following substructures in the stellar halo: Heracles, Gaia-Enceladus/Sausage (GES), Sagittarius dSph, the Helmi stream, Sequoia, Thamnos, Aleph, LMS-1, Arjuna, I’itoi, Nyx, Icarus, and Pontus. By examining the distributions of all substructures in chemical space considering the abundances of elements sampling various nucleosynthetic pathways, in this talk I will show results that help elucidate the reality and nature of halo substructures in the Milky Way. The results from this work help place constraints on the accretion history and mass assembly history of the Galaxy.
Emma DoddUniversity of Groningen
Galaxies stellar haloes are known to build up through the accretion of smaller systems, with stars from a single merger being deposited onto similar orbits. Since orbits can be characterized by their integrals of motion such as energy or angular momenta, we can thus search for the stellar debris of past accretion events by looking for over-densities in integrals of motion space (IOM). Using the Gaia DR3 data-set we identify such merger debris in the Milky Way halo near the Sun. We utilise a parameter-free clustering algorithm that allows us not only to find over-densities in IOM space but also to assess their statistical significance. We characterise the statistically significant over-densities using metallicity and chemical abundance information from Gaia DR3, LAMOST LRS DR7 and APOGEE DR17. We find that the local stellar halo contains 7 main dynamical groups, including in-situ structures, several previously known accreted substructures and one new substructure. In addition, we identify a large number of smaller clumps that are interesting dynamically with chemistry suggestive of an accreted origin. I will present an updated view of the Milky Way's accretion history that emerges from this analysis.
Takuya HashimotoUniversity of Tsukuba
Understanding properties of galaxies in the epoch of reionization (EoR) is a frontier in the modern astronomy. With ALMA, it has become possible to detect far-infrared fine structure lines (e.g., [CII] 158 μm and [OIII] 88 μm) and dust continuum emission in star-forming galaxies in the EoR. In this talk, we will first show ALMA observations that have demonstrated that i) some [OIII] 88 μm emitters have matured stellar populations at z > 6, implying early star formation activity at z > 10, and that ii) high-z star-forming galaxies typically have very high [OIII] 88 μm-to-[CII] 158 μm luminosity ratios ranging from 3 to 12 or higher, indicating that the interstellar medium of high-z galaxies could be highly ionized. Secondly, we will discuss initial results of a medium-sized JWST GO1 program that targets a sample of 12 z ~ 6-8 ALMA [OIII] 88 μm emitters with NIRCam and NIRSPec IFU modes (PIs: J. Álvarez-Márquez & T. Hashimoto). Our JWST GO1 program, in conjunction with ALMA data, will characterize the stellar, nebular, and dust properties of these [OIII] 88 μm emitters and place this galaxy population in a context of the cosmic reionization.
Akio InoueWaseda University
MACS1149-JD1 is a confirmed z = 9.1 galaxy. New ALMA observations spatially resolved the [OIII] 88 um line of this galaxy and enabled us to make a morpho-kinematic analysis. We have found a rotation-dominated signature from an empirical criterion. We have also performed a rotational disk model fitting, yielding a result consistent with the rotation-dominated interpretation. This example is the most distant case of a rotation disk.
Mahsa KohandelScuola Normale Superiore
In the past decade, ALMA has been extraordinary in resolving spatially and spectrally the cold gas in the interstellar medium (ISM) of galaxies at z > 4 through FIR emission lines such as [CII] at 158 micron. Analyzing [CII] line kinematics observables have revealed hints of the regular rotation in high-z galaxies and in some cases existence of surprisingly evolved systems (with substantial support from rotation) in the very early universe (when it had less than a Giga year). With JWST in operation, we will soon have complimentary information about the ionized ISM of early galaxies through nebular emission lines such as the Hα line. With a load of data coming from observations, a solid prediction from theory is needed more than ever to help interpret the data. In this talk, I will introduce the SERRA suite of cosmological galaxy simulations which are tailored to the Epoch of Reionization (z > 6). In particular, I will present our results analyzing the synthetic hyperspectral datacubes for the far-infrared [CII] and nebular Hα emission lines for SERRA galaxies which is the first attempt to have predictions on the dynamical state of EoR galaxies that will be (are) probed by JWST (ALMA). The questions I will touch upon are: I) When do galaxies form their disk structure in cosmological simulations? II) If the early disks exist, what are their observable signatures in FIR and nebular emission lines? III) Are high-z disks very turbulent structures or they are supported by ordered motions? IV) What are the main drivers of galaxy scale velocity dispersion in the early Universe?
Ana Carolina Posses NascimentoUniversidad Diego Portales
We analyzed the spatial distribution and kinematics of the cold ionized gas of the normal star-forming galaxy COS-2987030247 at z = 6.8076, based on new high-resolution observations of the [C II] 158um line emission obtained with the Atacama Large Millimeter/submillimeter Array. These observations allowed us to compare the spatial distribution and extension of the [C II] and rest-frame UV emission, and model the [C II] line data-cube. The system is found to be composed of a main central source, a fainter northern extension, and candidate [C II] companions located 10-kpc away. The [C II] velocity map reveals a velocity gradient in the north-south direction suggesting ordered motion, as commonly found in rotating-disk galaxies. If this rotating nature is confirmed, a low average velocity dispersion implies a dispersion lower than the expected value from observations and semi-analytic models of high redshift galaxies. Our findings support the necessity of kpc-scale resolved observations to unveil the nature and properties of the ISM in galaxies early in the Universe.
Arianna LongUniversity of Texas at Austin
For nearly a decade, researchers have hunted for the ancestors to massive quiescent galaxies at high redshifts (z > 2). Several lines of evidence suggest that heavily dust obscured star-forming galaxies (DSFGs) are the likely progenitor population for these giants, such as their extreme star formation rates that build incredible stellar mass over short periods of time, and the similar comoving volume densities between the two populations. One trait that is often used to link these two populations is a similarity between their morphologies: resolved dust emission in DSFGs is often found to be highly compact, potentially tracing a centrally concentrated burst of star formation that may later evolve into a quiescent bulge or larger spheroid. However, ALMA follow up observations have also discovered rotating dusty disks in some DSFGs at high-z. Identifying any trends in the stellar morphologies of DSFGs at high-z has been incredibly difficult due to their heavily obscured nature. Only a small percentage of DSFGs at z > 3 have been successfully detected by HST, but now JWST ushers in a new era with the resolutions, depths, and wavelength coverage required to finally chart the morphological evolution of dust-obscured galaxies. I will highlight recent results on the morphologies and evolution of dust-obscured galaxies at high redshifts, including a first look on the JWST / stellar morphologies of z > 3 DSFGs detected in the ongoing ALMA Ex-MORA survey of the COSMOS field.
Francesca RizzoUniversity of Copenhagen
The dynamics of high redshift galaxies reveals important clues on their formation and assembly, providing also strong constraints on galaxy formation models. Measurements of the gas rotation allow us to trace the distribution of the different matter components and study galaxy scaling relations. In contrast, measurements of the gas velocity dispersions give information about the turbulence within the interstellar medium, mainly driven by stellar feedback and gravitational instabilities. At the moment, dynamical studies of high-z galaxies have been obtained mainly using warm gas tracers (e.g. Halpha, [OII], [OIII]), which may be strongly affected by non-circular motions driven by inflows, outflow, and mergers. In this talk, I will present the dynamical properties of a sample of star-forming galaxies at z = 1 - 4 on sub-kpc scales, obtained using ALMA observations of the CO or [CI] emission lines tracing the cold gas component. This is the largest sample of cosmic-noon galaxies with high-quality data and 1-kpc scale resolutions so far. I will show how the combination of ALMA and JWST observations allows one to obtain key constraints on the formation of disk galaxies and the role played by dark matter in the build-up of early structures.
Fernanda Roman de OliveiraUniversity of Groningen
Recent discoveries of dynamically cold disk galaxies at z > 4 have challenged galaxy formation models that predict, instead, chaotic systems as a consequence of copious gas accretion, mergers, and efficient feedback. I will present 3D dynamical models of 4 of the most well-resolved galaxies with ALMA, seen in the [CII] 158-micron emission at z ~ 4.5. The sample is diverse in galaxy type and all galaxies show evidence of radial motions that could be due to minor mergers or gas accretion. However, we found that all of them host regularly rotating discs with gas velocity dispersions that are significantly lower than predicted by current cosmological hydrodynamical simulations with ratios of ordered-to-random motions (V/sigma) ranging from 2.6 to 9. We have also estimated the thickness of the gas discs and found that they are of the order of 1 kpc, similar to thick discs of local galaxies like the Milky Way. These findings show that dynamically cold discs can form earlier than previously thought and suggest that some thick discs could be formed in situ in the early stages of galaxy formation.
Chelsea SharonYale-NUS College
Theoretical work suggests that AGN plays an important role in ending star formation in massive galaxies. In addition to molecular outflows observed in the local universe, emission from very high-J CO rotational transitions has been a key piece of evidence for AGN directly affecting the molecular gas reservoirs that fuel star formation. However, very few observations exist of CO rotational lines past the peak of the CO spectral line energy distribution (SLED) for galaxies in the early universe. Here we will present ALMA observations of high-J CO rotational lines (J_upper>10) in several z > 2 IR-bright galaxies. We will discuss the heterogenous results for the sample's AGN and AGN-free galaxies, as well as the unique spectral signatures that suggest AGN is affecting some of these galaxies' molecular gas.
Fatemeh Tabatabaei*Institute for Research in Fundamental Sciences, Iran
Investigating the thermal and non-thermal processes in galaxies is vital to understanding the evolution of galaxies over cosmic time. This can be best studied by combining the emission observed in the optical and radio domains in galaxies. The JWST will soon resolve the evolution of the thermal processes by mapping ionized gas and dust in distant galaxies. This information combined with the upcoming deep SKA surveys will make a major break through in mapping the non-thermal processes and understanding their role in the evolution of galaxies. Based on our recent simulations, the SKA1-MID surveys will be able to trace the evolution history of spiral galaxies such as M51 and NGC 6946 back to a redshift of z = 3. This study indicates that the non-thermal pressure inserted by cosmic rays and magnetic fields could have played a significant role in the evolution of structures at earlier cosmic times.
Geraint LewisUniversity of Sydney
Karl GlazebrookSwinburne University of Technology
Paul HoEast Asian Observatory
Dante Minniti*Universidad Andres Bello
The ESO Public Survey ”VISTA Variables in the” Via Lactea (VVV) and its extension called ”VVV eXtended Survey” (VVVX) have been mapping the Milky Way bulge and the Southern mid-plane in the near-IR, with observations starting in the year 2010 and ending in the year 2022. We monitored >2x109 point sources in total, within an area of about 1700 sq deg. This area includes about 50 known globular clusters, and >1000 known open clusters, with many more clusters to be found. The final products of our survey are deep JHKs-band images, catalogs of variable point sources, and proper motions. I will summarize some results and final maps from the complete VVVX observations. Only < 1% of the MW stars have been measured to date. One particular pervasive problem for Galactic (and some extragalactic) studies is how far we can see at different wavelengths in the presence of extinction. We have used different distance indicators to trace the extinction horizon along the Galactic plane. I will present the results of our study, critically discussing the advantages and disadvantages of the various distance indicators (RC giants, RR Lyrae, Cepheids, LPVs/Miras, star clusters), also using complementary information from Gaia DR3. These results will be contrasted with the expected observations from major ground-based facilities like the Vera Rubin Telescope, and space missions, like the James Webb Space Telescope and the Nancy Roman Space Telescope.
Carrie FilionJohns Hopkins University
Many disk galaxies host galactic bars, which exert time-dependent, non-axisymmetric forces that could play a key role in re-arranging stars throughout the disk. The resultant torques are expected to create an azimuth angle-dependent signal in (e.g.) the median distance that stars have traveled to enter a given radial annulus. We analyze an N-body simulation to examine the changes in the radial locations of stars (‘radial mixing') that occur in a disk galaxy after a bar has formed. We find that angle-dependent trends are present at all radii we consider, and radius-dependent trends roughly divide the disk into three radial ‘zones'. These ‘zones’ are characterized by whether the angle-averaged mean distance that stars have traveled to enter a given radial annulus is positive, negative, or approximately zero. The angle- and radius-dependent trends that we present here should be generic results for galaxies that host evolving bars. We discuss recent observational evidence for angle-dependent metallicity variations in the Milky Way in the context of this analysis, and we investigate the extent to which similar observations can be used to provide information about the radial re-arrangement that occurred in the disk. Finally, we suggest avenues for future analyses that will be possible with the data from upcoming surveys performed with massively multiplexed spectrographs, such as the Subaru Prime Focus Spectrograph
Virginia Cuomo*Universidad de Atacama
Stellar bars play a crucial role in driving the secular evolution of their host galaxies. Indeed, they rotate around the galaxy centre with a given angular frequency, the bar pattern speed, sweeping material within the central regions of the galaxy and driving strong structural modifications. In the standard LCDM model, bars are expected to slow down by efficiently exchanging angular momentum with the other galaxy components and/or through dynamical friction exerted by the dark matter halo. The only direct method to derive the bar pattern speed, the Tremaine-Weinberg method, revealed that real bars rotate fast, stressing a tension between the observations, conducted to date in the local Universe, and the LCDM model. Measuring the bar pattern speed by applying the Tremaine-Weinberg method to bars up to z ~ 1 - 2 will reveal if the expected bar evolutionary path is actually taking place and/or to confirm if the dark matter is able to exert an efficient friction. Using high resolution N-body simulations, we tested and confirmed the applicability of the Tremaine-Weinberg method to deep spectroscopy of the NIRSpec IFU mounted to the JWST for a sample of bars at z ~ 1 - 2 recently revealed with the CEERS NIRCam. Here, we present the result of our preliminary analysis, which will be used to prepare an observational proposal to get dedicated NIRSpec@JWST in the next call.
Sioree AnsarIndian Institute of Astrophysics
Despite decades of research, the mechanism of bar formation in galaxies is still a subject of debate. From isolated galaxy simulations we have gained valuable insight into how bars form and evolve. However, bars in the Universe evolve in galaxies in highly complex environments with multiple satellite interactions, mergers, gas accretion events, star-formation and gas infall to the central supermassive blackhole (SMBH) while simultaneously interacting with their dark matter halo. Investigating bar formation and reproducing their observed properties in cosmological simulations is important for understanding formation of galaxies and galactic bars. We study 13 high resolution MW-mass galaxies from the zoomed-in cosmo-hydro simulation FIRE2 (Feedback in Realistic Environments) to first ask: Do the FIRE galaxies have bars? If so, how do bars form and when does bar formation fail? We find examples where bars form due to satellite interactions and others where bars form secularly in the disk. Using predictions from isolated galaxy simulations for varied dark matter and stellar distributions at the galaxy centre, we explain the morphological differences between the bars in FIRE2 and TNG50 and connect them to differences in the physics implementations of the two codes. We find that the stellar feedback prescription in FIRE2, which affects starburst and gas dynamics, and the lack of blackhole feedback to mitigate the gas in the galaxy center, together make the disk kinematically hot, such that bars are shorter than the MW-bar, rotate faster, and are mostly short-lived. We hypothesize that the FIRE3 simulations will address some of the issues with improved stellar feedback and AGN, such that bars are closer to those in observations.
Susan Kassin*Space Telescope Science Institute
Our JWST Cycle 1 program of deep spectroscopy of ~40 galaxies over 1 < z < 6 will result in maps of rest-frame optical and near-UV lines. It is scheduled for September 2023. The NIRSpec MSA will be used to create high resolution sub-kiloparsec maps of emission and absorption lines in galaxies spanning the first third of cosmic time, from soon after cosmic dawn at z=6 to well past cosmic noon at z=1. Science goals include the evolution of galaxy outflows, the evolution of ordered versus disordered motions, Balmer-decrement measurements for both the broad (wind) and narrow (ISM) components of emission lines; spatially resolved nebular diagnostics of metallicity, excitation, and ISM pressure; AGN and shock signatures in both the centers and extended regions of galaxies; and star-formation and extinction maps from multiple spectroscopic indicators. These observations will be made public immediately and will serve as a pathfinder for the JWST community to explore the revolutionary science return from deep JWST spectroscopy of high-z galaxies at high spatial and spectral resolution.
Irene ShivaeiUniversity of Arizona
The unprecedented infrared capabilities, high sensitivity, and high angular resolution of JWST compared to its mid-IR predecessors, such as Spitzer, open a new window to study dust and star formation at z ~ 1-3, dubbed as Cosmic Noon. MIRI provides the first view of obscured star formation in individually detected typical (L* and sub-L*) galaxies at these redshifts. In this talk, I will present the MIRI US-GTO survey, which is a 30 square arcmin centered on GOODS-S/HUDF with a wealth of ancillary data including the JADES GTO NIRCam imaging data. In this survey, we took full advantage of the multi-wavelength capability of MIRI to study dust obscured star formation and AGN activity at Cosmic Noon by observing in all 8 bands of MIRI from 5 to 25 micron. We expect to detect 100s of galaxies with star formation rates of >10 Msun/year at 21 micron and ~100-200 AGN of known types out to z ~ 3.5 with robust SED constraints. Furthermore, there will be NIRSpec multi-slit spectroscopy followup observations of the MIRI-selected sources to study the gas and ISM properties of Cosmic Noon galaxies and connect them to their dust properties. I will discuss the main goals of the multi-band MIRI HUDF survey and show some initial results: (1) measuring obscured star formation rates down to 10 Msun/yr and out to z ~ 2.5 using our deep 21 micron images, (2) measuring aromatic band strengths and hot dust continuum using multi-band MIRI photometry and NIRSpec spectra to probe the nature of the interstellar medium in star-forming galaxies and refine total IR luminosity determinations down to low masses at z ~ 1-2, and (3) identifying and studying the heavily obscured AGN at z ~ 1-2 by tracing the stellar minimum at rest-frame 4-5 micron with MIRI multi-band observations.
Tucker JonesUniversity of California, Davis
Spatially resolved spectroscopy is an invaluable tool for studying the formation and evolution of disk galaxies at high redshifts. This technique is most powerful when combining the diffraction limit of large telescopes with strong gravitational lensing, providing the best possible spatial resolution and sensitivity. I will discuss observations of lensed star forming galaxies spanning the stellar mass range expected for Milky Way progenitors at “cosmic noon” (z ~ 1 - 3). Measurements of the resolved kinematics, star formation, gas metallicity distribution, and outflows together show that energetic feedback from star formation plays a dramatic role in disk galaxy formation at these redshifts. This feedback may even destroy gaseous disks and alter dark matter density profiles at the lowest observed masses (Mstar < 10^9 Msun), as indicated by the data and comparison with cosmological simulations. The disk fraction shows a clear mass dependence, with rotation-dominated disk galaxies being more common at higher masses, although with high velocity dispersions (i.e., “thick disk” kinematics). I will also describe a novel JWST Cycle 1 program (GO-02136) which aims to establish the emergence of the first dynamically cold “thin disk” galaxies by mapping the kinematics of ~50 galaxies at z ~ 0.5 - 1.5. JWST provides 5-10 times better spatial resolution than ground-based efforts at these redshifts, where moderately massive galaxies expectedly transit from turbulent thick disks to the thin spiral disks of the modern Hubble sequence. Data from this program will be immediately public, and we will additionally make processed data available as a resource for the community.
Benjamin MethaUniversity of Melbourne
Star-forming galaxies in the local universe take the shapes of grand-design spirals, with a larger fraction of metals in their center than on their outskirts, often modeled by a linear gradient. On the other hand, star-forming galaxies at cosmic noon are more irregular, with large, kpc-scale metal-rich clumps. The linear gradient models that describe the local universe cannot be applied to these distant galaxies. In this talk, I demonstrate the potential of geostatistical modeling to improve our understanding of the chemical substructures of galaxies at both low- and high-redshift (z ~ 3). By fitting a hierarchical model to JWST-GLASS data, I investigate how the spatial extent of metal-rich clumps evolves throughout cosmic time. This enables an understanding of the spread of metals throughout galaxies on sub-kpc scales, testing subgrid models of metal mixing and ultimately improving our understanding of galaxy evolution.
Benedetta VulcaniINAF Padova
The characteristic mass that sets the peak of the stellar initial mass function (IMF) is closely linked to the thermodynamic behavior of interstellar gas, which controls how gas fragments as it collapses under gravity. As the Universe has grown in metal abundance over cosmic time, this thermodynamic behavior has evolved from a primordial regime dominated by the competition between compressional heating and molecular hydrogen cooling to a modern regime where the dominant process in dense gas is protostellar radiation feedback, transmitted to the gas by dust–gas collisions. We study the gas thermodynamics in collapsing dusty molecular clouds at a wide range of metallicities, from primordial-like to super-Solar like, in different ISM conditions. We show the transition from the primordial regime to the modern regime begins at metallicity Z ~ 0.0001 Zsun, passes through an intermediate stage where metal line cooling is dominant, and then transitions to the modern dust- and feedback-dominated regime at Z ~ 0.05 Zsun. This transition is accompanied by a dramatic change in the characteristic stellar mass, from ∼50Msun at Z∼10^-6 Zsun to ∼0.3Msun once radiation feedback begins to dominate, which marks the appearance of the bottom-heavy Milky Way IMF. The exact transition from top- to bottom-heavy IMF occurs at intermediate metallicities and is sensitive to the adopted abundances of elements like C and O, which observations of both metal-poor stars and H II regions in metal-poor dwarf galaxies show is non-Solar-scaled. Our work brings together the stellar and galaxy communities by revealing the impact of the IMF on our understanding of the metal-poor Universe.
Robert Grand*Canaries Institute for Astrophysics
The build-up and formation times of galactic discs and bars depend on a range of galaxy formation physics, including the accretion of gas into halos, the dynamical interplay between baryonic and dark matter, and galaxy mergers. Cosmological hydrodynamic simulations model a wide variety of such processes and, as such, they have become powerful tools to provide insights into disc/bar formation through the interpretation of both high-redshift data and star-by-star observations of the Milky Way, which can, in turn, help constrain models. This talk will highlight some recent simulation-based theoretical predictions for the build-up of rotationally-supported discs and bars at early epochs, and explore their connection to baryonic processes and dark matter. To connect with the local Universe, we will discuss how we may interpret the early formation history of the Milky Way from observational signatures seen in large Galactic surveys, including the impact of the Galaxy’s most significant merger events, such as the Gaia Enceladus/Sausage and Kraken, on the thick disk and bar.
Andrew WetzelUniversity of California, Davis
I will present predictions from the FIRE-2 cosmological zoom-in simulations for the formation history of the Local Group in a cosmological context. First, I will discuss the formation history of the MW and M31 galaxies, including when the main progenitor of the MW/M31 likely formed and how this depends on them being in the Local Group paired environment. Then, I will discuss the formation and settling of their stellar and gaseous disks, including the relevant importance of disk setting versus post-formation heating for determining the observable relation between stellar kinematics and stellar age today. Finally, I will discuss the formation histories of the satellite galaxies in these simulations, showing that the current satellite population is a highly incomplete census of the progenitor population that formed the Local Group, and I will quantify how well the stellar populations of surviving low-mass galaxies provide fossil records of the overall galaxy population at z > 6, to inform the use of galactic archeology in probing the epoch of reionization.
Vicente Rodriguez-GomezUniversidad Nacional Autónoma de México
We use the TNG100 simulation of the IllustrisTNG project to investigate the stellar specific angular momenta (j*) of ~12,000 central galaxies at z = 0 in a full cosmological context, with stellar masses (M*) ranging from 10^9 to 10^12 Msun. We find that the j*-M* relations for early-type and late-type galaxies in IllustrisTNG are in good overall agreement with observations, and that these galaxy types typically 'retain' ~10-20 and ~50-60 per cent of their host haloes' specific angular momenta, respectively, with some dependence on the methodology used to measure galaxy morphology. We present results for kinematic as well as visual-like morphological measurements of the simulated galaxies. Next, we explore the scatter in the j*-M* relation with respect to the spin of the dark matter halo and the mass of the supermassive black hole (BH) at the galactic centre. We find that galaxies residing in faster spinning haloes, as well as those hosting less massive BHs, tend to have a higher specific angular momentum. We also find that, at fixed galaxy or halo mass, halo spin and BH mass are anti-correlated with each other, probably as a consequence of more efficient gas flow towards the galactic centre in slowly rotating systems. Finally, we show that halo spin plays an important role in determining galaxy sizes - larger discs form at the centers of faster rotating haloes - although the trend breaks down for massive galaxies with M*>10^11 Msun, roughly the mass scale at which a galaxy's stellar mass becomes dominated by accreted stars.
Andrew CooperNational Tsing Hua University
I will present simulations of the stellar halos of low-mass disk galaxies (ranging from the mass of the LMC to the mass of M33). These simulations combine the Galform semi-analytic model, the COCO cosmological N-body simulation and the STINGS particle tagging technique. These models provide a broader context for earlier studies, which have focused on more massive galaxies (Milky-Way analogues), and demonstrate how the well-known scatter between the stellar mass and the virial mass contributes to the diversity of stellar halo properties in stellar mass-selected samples. I will show comparisons to current low surface brightness observations of low-mass disk galaxies. I will then summarize predictions for surface brightness profiles and stellar populations in the outskirts of these galaxies and the potential use of those observables as probes of mass assembly history, with a view to upcoming datasets from Euclid, LSST and other surveys. I will briefly introduce the public release of particle data from our simulations.
Yuan-Sen TingAustralian National University
A key yet unresolved question in modern-day astronomy is how galaxies formed and evolved under the paradigm of the ΛCDM model. The quest to understand the connection between the near-field cosmology and the high-redshift cosmic past has led to many semi-analytical models to infer the galaxy’s properties from their merger history. However, most of these classical approaches rely on studying the global statistical connection between dark matter haloes and galaxies, often reducing the study to focusing on the connection of individual haloes and galaxies or summarizing their formation environment with crude summary statistics based on human heuristics. The advancement in graph neural networks has opened up many new possibilities for studying the evolutionary history of galaxies. That is because a graph is a natural descriptor of the systems at hand – any progenitor system at a high redshift can be regarded as a graph, with individual progenitors as nodes on the graph. In this presentation, I will discuss the power of the Equivariant Graph Normalizing Flows Model to connect high-redshift progenitor graphs with local observables. We demonstrate that, by treating the progenitors as a graph, our model robustly recovers their distributions, including their masses, merging redshifts and pairwise distances at redshift z = 2 conditioned on their z = 0 properties. In addition, the generative nature of the model enables other downstream tasks, including inferring probabilistically the property at z = 0 given the configuration at z = 2, detecting anomalies and identifying subtle correlations of progenitor features.
David WeinbergThe Ohio State University
I will discuss four interconnected issues about the interpretation of chemical abundance patterns. (1) The absolute scale of nucleosynthetic yields, and its implications for outflows, accretion, and black hole formation. (2) The [alpha/Fe]-[Fe/H] track of low metallicity halo stars, and its suggestion of a "simmer-to-boil" transition in the star formation history of the early Galaxy. (3) The scatter in [X/Fe] and [X/Mg] ratios for halo stars with -2 < [Fe/H] < -1, and its implications for stochastic supernova enrichment and the mass scale of gas mixing during this phase of Galactic evolution. (4) The physical factors that determine the metallicity distribution functions of dwarf galaxies, and routes to constraining star formation histories from MDFs.
Chiaki KobayashiUniversity of Hertfordshire
Metallicities and elemental abundances can constrain physical processes during galaxy formation and evolution. This approach, Galactic Archaeology, has been popularly used for our Milky Way Galaxy. It can also be applied to external galaxies thanks to recent and future observations with integral field spectrographs. My team has been running hydrodynamical simulations from initial cosmological conditions including detailed chemical enrichment. I will show how our Milky Way Galaxy formed, analyzing inflow, outflow, radial flow, and stellar migration in our simulation. I will also predict the distribution of elemental abundances by comparing with the Galactic Archaeology survey data. Then, using the same chemical enrichment code, I will show how other galaxies formed and evolved across Cosmic Time, including a barred spiral galaxy at z = 2 in our simulation. I will also predict the evolution of mass-metallicity relations and metallicity radial gradients. These predictions can be tested with future observations such as the James Webb Space Telescope and the Atacama Large Millimeter Array.
Jianhui LianMax Planck Institute for Astronomy
Our picture of how galaxies evolve and enrich the Universe relies directly on our understanding of when, where, and how our own Galaxy’s stars evolved and died. Currently, massive stellar surveys are yielding spectroscopic datasets of unprecedented size and quality for Milky Way stars well beyond the Sun. These observations reveal complex, position-dependent patterns of age and abundance that comprise the most rigorous observational constraints to date for models of Galactic star formation. In this talk, I will present our series of works in which we propose an intriguing multi-phase accretion and star formation scenario that can coherently explain the position-dependent complex patterns of age and chemical abundances (e.g., bimodal [α/Fe][Fe/H] distribution and interrupted age[Fe/H] relation) observed in the bulge, inner and outer disk of our Galaxy. This multi-phase star formation picture highlights the importance of an early quenching process in the transition from thick to thin disk formation and of a recent accretion and starburst event, possibly triggered by the pericenter passage of the Sagittarius dwarf galaxy, in the thin disk formation. Taking advantage of the wide radial coverage of APOGEE data, we further quantify the radial properties of the recent gas accretion to better understand the source of this accretion event. The results of these works provide revealing insights into the thick-to-thin disk transition in the early Universe and gas accretion fueling disk formation at a large range of redshift.
Erwin Boquan ChenAustralian National University
Other than hydrogen, helium, and a trace amount of lithium created in the Big Bang, about eighty naturally occurring elements are forged in stellar nucleosynthesis. The diverse chemical compositions of stars and interstellar gas are products of the environment and the evolutionary history of their host galaxies. Large-scale spectroscopic surveys including APOGEE, GALAH, and LAMOST have delivered precisely measured abundances for at least several hundred thousand stars up to 30 elements, including several elements heavier than iron. Combined with the astrometry from the Gaia mission and asteroseismology with the Kepler mission, we now have an unprecedented amount of data covering a wide area of our Galaxy and are able to map the chemical distribution and trace how the chemical abundances evolved over time in the solar neighbourhood and beyond. The goal of galactic chemical evolution (GCE) models is to probe the mechanisms and conditions of galaxy evolution at different epochs and reproduce the chemical properties of galaxies, particularly the Milky Way. These models implement simple physical laws to generate aggregate chemical trends for a galaxy or a region within a galaxy or multiple regions simultaneously. They have far less computational demands than cosmological chemodynamical simulations and thus can cover a large area in parameter space in a short amount of time. In this talk, I will show how my GCE model reproduces the chemical distribution at different locations in the Milky Way and detailed age-abundance relationship in the solar neighbourhood. I will discuss what we can infer about the conditions of the Milky Way from the GCE model.
Anna Fabiola Marino*INAF Firenzo
Globular clusters have always been among the most intensively studied stellar systems. However, we have never really understood how they formed at high-z, and in such a widespread fashion. With the presence of more than one stellar population in these ancient stellar aggregates, answering these questions became harder than ever. Multiple stellar populations in the M-dwarf regime down to ~0.5 Msun, may provide the key to understand the formation mechanism of this phenomenon and disentangle between different scenarios. However, due to the faintness of these stars, this remains a mostly unexplored territory. The JWST opens the observation window to the mid-infrared domain, never explored in the context of multiple populations. This telescope will be able to observe the faint M-dwarf stars in GCs quite efficiently. I will show early results for the multiple stellar populations among the M dwarfs of 47 Tucanae as obtained from the new JWST observations. I will also discuss how these results impact on our knowledge about the origin of the multiple stellar populations.
Antonino Milone*University of Padova
The presence of more than one stellar population in globular clusters (GCs) is one of the most fascinating discoveries in the field of stellar populations. Yet, the phenomenon remains an enigma. To now, the best tool to investigate and constrain the properties of the different populations of stars is by means of the nicknamed "Chromosome Maps" diagram, which exploit UV multi-band photometry to maximize the separation of stellar populations on a plane mostly sensitive to light elements. I will present our latest observational results about the properties of the multiple stellar populations as read on the Chromosome Maps diagrams. These diagrams have revealed amazing features about the phenomenon, moving in fact towards a new definition of GC, which should no longer be considered as a mono-metallicity mono-Fe stellar system. With the launch of the JWST, however, we will move our focus to a different region of the spectrum, never explored for the investigation of the multiple stellar populations. I will discuss how the different stellar populations are observed in the mid-IR region of the spectrum available from NIRCam on board the JWST and the new frontiers that this telescope will open in the field.
Ricardo SchiavonLiverpool John Moores University
Globular clusters are among the most intriguing objects in astrophysics. Albeit they are often used as tracers of early structure formation, quantitative models for their formation are only now beginning to solidify. Significant gaps in our understanding of these systems still exist—for instance, the ultimate fate of globular clusters (GC). We still do not entirely understand how GCs are destroyed or how efficiently, and as a result their contribution to the stellar mass budget of galaxies is poorly constrained. In the past decade, field stars with an abundance pattern characteristic of so-called second generation GC populations have been identified, whose existence has been proposed to result from GC disruption. The SDSS/APOGEE survey has made major progress through the detection of a large population of second generation GC stars in the Galactic halo field, estimating that the contribution by GC disruption to the halo stellar mass varies from a few percent at Rgc ~ 10 kpc to approximately ~25% within the inner 2 kpc of the Galactic centre. In this talk I will present the results of a thorough evaluation of the incidence of second generation GC stars in all components of the Milky Way, and its Local Group dwarf companions, based on the 17th data release of the APOGEE 2 survey. I will also discuss the constraints posed by these measurements on models of the formation and destruction of globular clusters, as well as their implications for our understanding of the early history of the Milky Way.
Madeleine McKenzieAustralian National University
In the context of hierarchical galaxy assembly, globular clusters and dwarf galaxies are indispensable probes of the formation of our Milky Way. M22 is a curious stellar system with chemical abundances reminiscent of an accreted dwarf galaxy such as Omega Centauri, yet has disk-like kinematics suggesting a Milky Way origin. Unlike the vast majority of clusters, M22 contains a population of stars enhanced in slow neutron-capture (S-)process elements. Although no universally accepted formation scenario exists for this system, our investigations suggest that this s-process element enhancement is due to pollution from low-mass AGB stars. Recently, large high-precision spectroscopic surveys have revealed the in-situ component of our Galaxy, dubbed Aurora. This component is said to be the precursor to the Milky Way disk. Further analysis has revealed that Aurora is enhanced in s-process elements compared to other chemical structures at similar metallicity. This provides a tantalizing link between the original in-situ stars of the Milky Way and the formation of M22. I will discuss how our recent high-precision chemical abundance measurements suggest that M22 may be coeval with Aurora, and what the formation mechanisms of this s-process population can tell us about the chemical evolution of our Galaxy before the establishment of the disk.
The PHANGS collaboration has been building a reference dataset for the multi-scale, multi-phase study of star formation and the interstellar medium in nearby galaxies. With the successful launch and commissioning of JWST, we are now conducting an imaging survey with NIRCam and MIRI in 8 bands from 2-21μm of 19 nearby spiral galaxies. For the first time, JWST high-resolution imaging allows us to probe the youngest stellar populations and dust emission on the scales of star clusters and molecular clouds (∼5-50 pc) in galaxies beyond the Local Group. The PHANGS-JWST survey is designed to enable a full inventory of star formation, accurate measurement of the mass and age of star clusters, identification of the youngest embedded stellar populations, and characterization of the physical state of small dust grains. When combined with Hubble catalogs of ∼10,000 star clusters, MUSE spectroscopic mapping of ∼20,000 HII regions, and ∼12,000 ALMA-identified molecular clouds, it becomes possible to measure the timescales and efficiencies of the earliest phases of star formation and feedback, build an empirical model of the dependence of small dust grain properties on local ISM conditions, and test our understanding of how dust-reprocessed starlight traces star formation activity, all across a diversity of galactic environments. In this talk, I will give an overview of PHANGS-JWST Treasury survey, and present some of our first results based on the remarkable imaging obtained in the first few months of science operations.
Jesse van de SandeUniversity of Sydney
Due to the complexity of internal and external processes acting on disk galaxies, many outstanding questions regarding their evolution remain. Our Milky Way provides an unparalleled view of disk evolution, but building a comprehensive framework from a single object is unrealistic. In this talk, I will present the GECKOS survey (Generalizing Edge-on galaxies and their Chemical bimodalities, Kinematics, and Outflows out to Solar environments), a new ESO VLT/MUSE large program. The main aim of GECKOS is to reveal the variation in key physical processes of disk formation by connecting Galactic Archaeology with JWST studies of turbulent star-forming disks in the early Universe. Edge-on galaxies are ideal for this task: they allow us to disentangle the assembly history imprinted in thick disks and provide the greatest insights into outflows. The GECKOS sample of 35 nearby, edge-on disk galaxies is designed to determine the assembly histories and properties of galaxies across a large range of SFRs, B/T ratios, and boxy and non-boxy bulges. At this meeting, I will present the survey’s first few months of IFS data, with 2D measurements of stellar abundance, age, and kinematics, as well as ionized gas metallicities, ionization parameters, and outflow kinematics; all core ingredients for chemical evolution models. With these data, we aim to extend Galactic methods to the wider galaxy population, reaping the benefits of detailed Milky Way studies, while probing the diverse mechanisms of galaxy evolution.
Ling ZhuShanghai Astronomical Observatory
In the last decade, IFU observations have provided kinematical, age, and metallicity maps of thousands of nearby galaxies. By applying a novel population-orbit superposition method to the IFU data, we have been able to obtain a galaxy’s internal stellar orbit distribution, as well as the age and metallicity of different orbital structures. We have applied this method to a few hundreds of CALIFA, MaNGA, and Fornax 3D (observed by MUSE/VLT) galaxies, and the results lead to direct comparisons of galaxy structures with simulations systematically. For galaxies in the field, we find that the stellar orbit distribution of Illustris TNG50 galaxies matches that of the CALIFA galaxies remarkably well, quantitatively in the fractions of dynamical cold/hot orbits as a function of galaxy mass in the range of 10^9.5 -10^12 Msun. For galaxies in the Fornax cluster, we find that the recent infallers have similar stellar orbit distribution to the field galaxies, while ancient infallers have much lower fractions of dynamically cold orbits for galaxies in all mass ranges. This trend is also found similarly in TNG50 cluster galaxies. With these direct comparisons and remarkable agreements between observations and simulations, the stellar orbit distribution thus provides us with a clean interface for quantitatively investigating the origin of galactic structures from simulations. I will show how the combination of secure evolution and mergers leads to the stellar orbit distribution in present-day galaxies from TNG50.
Piyush ShardaLeiden Observatory
The characteristic mass that sets the peak of the stellar initial mass function (IMF) is closely linked to the thermodynamic behaviour of interstellar gas, which controls how gas fragments as it collapses under gravity. As the Universe has grown in metal abundance over cosmic time, this thermodynamic behaviour has evolved from a primordial regime dominated by the competition between compressional heating and molecular hydrogen cooling to a modern regime where the dominant process in dense gas is protostellar radiation feedback, transmitted to the gas by dust–gas collisions. We study the gas thermodynamics in collapsing dusty molecular clouds at a wide range of metallicities, from primordial-like to super-Solar like, in different ISM conditions. We show the transition from the primordial regime to the modern regime begins at metallicity Z ∼ 0.0001 Z, passes through an intermediate stage where metal line cooling is dominant, and then transitions to the modern dust- and feedback-dominated regime at Z ∼ 0.05 Z. This transition is accompanied by a dramatic change in the characteristic stellar mass, from ∼50Msun at Z ∼ 10−6 Z to ∼0.3Msun once radiation feedback begins to dominate, which marks the appearance of the bottom-heavy Milky Way IMF. The exact transition from top- to bottom-heavy IMF occurs at intermediate metallicities, and is sensitive to the adopted abundances of elements like C and O, which observations of both metal-poor stars and H II regions in metal-poor dwarf galaxies show is non-Solar-scaled. Our work brings together the stellar and galaxy communities by revealing the impact of the IMF on our understanding of the metal-poor Universe.
Emily WisnioskiAustralian National University
Galaxy evolution is an inherently messy process to disentangle. To achieve a holistic understanding, we need to combine our observations and models to ask: how does the Milky Way's evolution path fit within modern observations of the high-z universe? Kinematics and structural studies have revealed that the majority of 'normal' star-forming galaxies at cosmic noon host a thick disk-like structure and a turbulent gas-rich interstellar medium, while new CII observations reveal possibly cold disks at cosmic dawn. Chemical studies reveal that the resolved abundance patterns of disks are also evolving with radial gradients being subdominant at early times. How does this relate to the state-of-the-art models of the MW's past? I will present results that show how combining new analytic models (e.g. Sharda et al. 2021 and Leaman et al. 2022) with high redshift surveys of molecular and ionized gas and local galactic/extragalactic archeology studies can provide insight into the evolutionary history of local galaxies, including the Milky Way. I will discuss observational results within the framework of theoretical models for the formation of the local stellar age-velocity dispersion relation, the size-scale height relation, and the history of metallicity gradients in local group galaxies.
David Nidever*Montana State University
The recent era of large, ground-based abundance surveys has unraveled the chemical structures of our Milky Way galaxy. The most striking abundance feature is the alpha-abundance bimodality. The low-alpha stars are younger (1-8 Gyr) while the high-alpha stars are older (8-12 Gyr) and have a thicker distribution. There are a number of different models that attempt to explain this chemical feature, but so far none have been strongly favored by the data. However, they do make different predictions about the prevalence of the alpha-bimodality in Milky Way-mass galaxies. Our Cycle 1 JWST NIRspec program has obtained high-S/N, medium-resolution spectra of over 100 stars in one M31 disk field. We have measured stellar parameters, radial velocities, and alpha abundances for these stars using sets of synthetic spectra. I will present the first M31 JWST alpha abundance results and discuss the implications for our understanding of the alpha-bimodality.
Geraint LewisUniversity of Sydney
The Pan-Andromeda Archaeological Survey of M31 has revealed a wealth of globular clusters out to 150 kpc. Roughly half of these halo globular clusters are associated with stellar substructures, streams, shells, and debris of tidally disrupting systems, whilst the remainder are not. A kinematic analysis of these two populations reveals distinct, orthogonal rotation signatures, suggestive of two distinct, separate accretion events, one ancient and the other modern. As well as exploring the implications of this result, I will also present a new analysis of the inner globular clusters of Andromeda, finding the outer halo kinematics imprinted on this inner sample, providing further evidence for distinct accretion events into the halo.
Souradeep BhattacharyaInter-University Center for Astronomy and Astrophysics
The nearest spiral galaxy to our Milky Way (MW) and the largest member of our local group, the Andromeda galaxy (M31) has experienced a tumultuous merger history as evidenced by the many substructures that are present in its inner halo. Through the kinematics and chemical abundance measurements of Planetary Nebulae (PNe) in M31, in conjunction with the star-formation history derived from the photometry of resolved stellar populations as well as the kinematics of red giant branch (RGB) stars, we have obtained stringent conditions on the recent formation history of M31. In contrast to the MW which had a quieter merger history since its last major merger ~10 Gyr ago, M31 had its last major merger only ~2.5-4 Gyr ago. The infalling satellite fell along the giant stream (the most prominent M31 substructure seen as an extended tail of stellar debris), consistent with PN and RGB LOSVs and chemical abundance measurements, in multiple pericenter passages (inferred from the PN and RGB position-velocity phase space) that lead to the formation of other prominent M31 inner-halo substructures (again inferred from the PN and RGB position-velocity phase space). The satellite disrupted the M31 disk forming an older dynamically hotter thick disk and a younger dynamically colder thin disk. The radial chemical abundance gradient (inferred from PNe) and the chemical enrichment history of the two discs, deciphered from Galactic chemical evolution models consistent with the PN [O/Ar] vs [Ar/H] (analogous to [α/Fe] vs [Fe/H] but for emission-line objects), imply that the M31 thicker disk formed in an extended star-formation episode but reached its current dynamically heated state (accompanied by a flat chemical abundance gradient) following the merger of the satellite; while the M31 thin disk formed in a burst from metal-poor gas brought in by the infalling satellite that mixed with the relatively enriched pre-merger M31 gas at certain radii. From the aforementioned results, we find that the satellite would have been gas-rich with a mass about twice that of M33 and it would have fallen into M31 ~2.5-4 Gyr ago also consistent with the burst of star-formation seen throughout M31’s disk from resolved stellar populations. Our kinematic results are consistent with major merger simulations of M31 having a 1:4 merger ~2-3 Gyr ago. We thus uncover the properties of the cannibalized dwarf galaxy in M31 with great detail (amongst the if not the most stringently constrained in any galaxy) from its present-day structure, dynamics, and chemistry.
Ivanna EscalaPrinceton University
The Milky Way (MW) is the cornerstone of our understanding of galaxy disk formation. However, there is growing evidence that the MW’s relatively quiescent formation history sets it apart from its sister galaxy, Andromeda (M31). At the nexus of near- and far-field galaxy evolution, M31 provides an exquisite opportunity to expand our knowledge of hierarchical galaxy assembly and galactic chemodynamics. Outstanding questions remain concerning M31's structural assembly: has its disk survived a major merger within the last few billion years and does this merger coincide with the formation of its Giant Stellar Stream? In this talk, I will present novel results on the nature of M31's inner stellar halo and disk based on data from the Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo (SPLASH) and Panchromatic Hubble Andromeda Treasury (PHAT) surveys. With measurements of over 3500 individual red giant branch stars, this represents the first large-scale chemodynamical analysis of M31's inner disk region. I will discuss evidence in favor of (1) an inextricable connection between the formation of M31's inner stellar halo and disk, (2) distinct channels driving the formation of the stellar halo along the major versus minor axes, and (3) a uniformly thick structure for the disk. I will conclude by placing these findings in the context of the MW and disk galaxy formation in general.
Sally OeyUniversity of Michigan
Early cosmic epochs are characterized by low metallicity and high specific star-formation rates. These conditions are dominated by massive-star feedback that may be dramatically different than the traditional model dominated by hot, thermal superwinds driven by supernova explosions. Instead, metal-poor feedback from massive stars may be radiation-dominated, with weak mechanical feedback, possibly aiding the escape of Ly-alpha and Lyman continuum radiation. I will describe our understanding that is emerging from observations of starburst galaxies in the local universe.
Daniel McPhersonSwinburne University of Technology
The early growth of disk galaxies was significantly impacted by galaxy-scale winds. Current models of galaxy evolution propose that these outflows regulate star formation by removing star-forming material from the galaxy disk and enriching the surrounding circumgalactic medium with higher metallicity gas. However, direct observations of outflows at redshifts corresponding to early disk growth (z > 3) are extremely difficult, even with JWST, due to their faintness. I will discuss detailed imaging with Keck/KCWI of outflows in local star bursting, high [OIII] EW, and low metallicity (~5-10% solar) disk galaxies, which we can use as analogues of the early universe. I have created sub-kiloparsec resolved maps of the outflows reaching ~10 kpc from the disk, and directly measured the opening angle, covering fraction and mass loading factors. I present a new method for characterising star-formation-driven outflows in edge-on galaxies, which can be applied to larger surveys with JWST or in the future ELT. I also will present work making direct estimates of the metallicity of the outflow using the auroral emission lines. This represents the first-ever full image of the baryon cycle, as viewed through metallicity, on a starbursting disk galaxy. We can use these observations to inform models of how the Milky Way may have grown early on and to help interpretation of results from JWST.
Dandan Xu*Tsinghua University
The connection between halo gas acquisition through the circumgalactic medium (CGM) and galaxy star formation has long been studied. We put this interplay within the context of the galaxy environment on large scales (several hundreds of kpc), which, to a certain degree, maps out various paths for galaxy interactions. Using the IllustrisTNG-100 simulation, we show that the large-scale environment around a star-forming galaxy is responsible for triggering new episodes of star formation. Such an episodic star formation pattern is well synced with a pulsating motion of the circumgalactic gas, which, on the one hand, receives angular momentum modulations from the large-scale environment, yielding in-spiralling gas to fuel the star-forming reservoir; on the other hand, is affected by the feedback activities from the galaxy centre. As a result, a present-day star-forming galaxy may have gone through several cycles of star-forming and quiescent phases during its evolutionary history, with the circumgalactic gas carrying out a synchronized cadence of "breathing in and out" motions out to ∼100 kpc.
Chris HaywardFlatiron Institute
It is broadly agreed that stellar feedback-driven outflows are a critical physical process in galaxy formation, but a complete understanding has not yet been achieved. In particular, models vary widely in terms of outflow properties. I will present predictions for how outflows depend on galaxy properties, and thus redshift, yielded by simulations from the Feedback in Realistic Environments (FIRE) project. I will interpret these results with the aid of analytic toy models. I will then discuss the implications for the emergence of disk galaxies and highlight how JWST can yield insight into this key component of galaxy formation models.
Yuan-Sen TingAustralian National University
Hidenori Matsui*Asahikawa College
Rachel Lee McClureUniversity of Wisconsin, Madison
Sandeep Kumar Kataria*Shanghai Jiao Tong University
Virginia Cuomo*Universidad de Atacama
Kazuki DaikuharaTohoku University
Ming Jian TehNational Tsing Hua University
Minh Ngoc LeNational Tsing Hua University
Sang-Hyun ChunKorea Astronomy and Space Science Institute
Abdurrahman NaufalNational Astronomical Observatory of Japan
Andras Peter Joo*Eotvos Lorand University
Chloe ChengLeiden Observatory
Hajime FukushimaUniversity of Tsukuba
Elham Eftekhari*Institute for Research in Fundamental Sciences, Iran
Kamal BoraSwinburne University of Technology
Koki OtakiUniversity of Tsukuba
Li-Wen LiaoNational Tsing Hua University
Micheli Trindade Moura*Universidade Federal do Rio Grande do Sul
Miftahul HilmiUniversity of Melbourne
Monserrat Martinez-MarinSwinburne University of Technology
Siou-Yu ChangNational Tsing Hua University
Tim RawleEuropean Space Agency
Andrew Crombie MasonLiverpool John Moores University
Chung-Wen WangNational Tsing Hua University
Damir GasymovLomonosov Moscow State University
Dyna Ibrahim*University of Hertfordshire
Genta SatoTohoku University
Gerhard HenslerUniversity of Vienna
Hesti WulandariBandung Institute of Technology
Jaeweon Lee*Jungwon University
Maryam Khademi*Institute for Research in Fundamental Sciences, Iran
Matthew Orkney*University of Barcelona
Michael FellhauerUniversidad de Concepcion
Mochammad Dafa WardanaTohoku University
Mohammad Hosseinirad*Institute for Research in Fundamental Sciences, Iran
Nondh PanithanpaisalUniversity of Pennsylvania
Nondh PanithanpaisalUniversity of Pennsylvania
Pratik GandhiUniversity of California, Davis
Purmortal Zixian Wang*University of Sydney
Purmortal Zixian Wang*University of Sydney
Qianhui ChenAustralian National University
Sena Matsui*Nagoya University
Sioree AnsarIndian Institute of Astrophysics
Yuka KanedaUniversity of Tsukuba
Akshara ViswanathanUniversity of Groningen
Anke Arentsen*University of Cambridge
Ankit KumarIndian Institute of Astrophysics / Indian Institute of Science
Chiung-Yin ChangNational Tsing Hua University
Mochamad Ikbal ArifyantoBandung Institute of Technology
Muhammad Ali SyaifudinBandung Institute of Technology
Namitha Kizhuprakkat RamachandranNational Tsing Hua University
Raj Kumar Pradhan*Tribhuvan University, Nepal
Rizky Maulana NurhidayatBandung Institute of Technology
Shobhit Steven KiskuLiverpool John Moores University
Sy-Yun PuNational Tsing Hua University
Tetsuro AsanoUniversity of Tokyo
Valeria Grisoni*Università di Bologna
Yoshihisa Suzuki*Tohoku University
Bijaya Chandra LuitelYale-NUS College
Golshan EjlaliInstitute for Research in Fundamental Sciences, Iran
Helena RichieUniversity of Pittsburgh
Ikki MitsuhashiUniversity of Tokyo
Patrick Kamieneski*Arizona State University
Qingxiang ChenYale-NUS College
Ryota IkedaSokendai / National Astronomical Observatory of Japan
The Global Malaysian Astronomy Convention, a conference celebrating works from Malaysian astronomers worldwide, will be held around the same time. Join us there too.
Everything you need to know about Malaysia and the conference.
We will email the Zoom links and the invitation to the official Slack channel before the symposium. Recordings will be made available through Slack.
Posters should be ideally 36’’ in height and 24’’ in width. But the size is flexible as long as it fits onto the poster board -- i.e. any size (potrait or landscape) smaller than 36’’ in height and 24’’ in width should work.
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Cancellations should be requested by contacting the IAUS377 Secretariat via email at email@example.com no later than the 6th of January, 2023. In addition, applications are transferable, so that could be an alternative.
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We have negotiated for a special rate for the Pullman hotel -- MYR 295 for a deluxe room with a king bed and MYR 315 for a deluxe room with two twin beds. The special code was sent by email. Please make sure you choose "1 person" for the king bed option to show up. If you did not receive the special code from us, please contact the IAUS377 Secretariat via email at firstname.lastname@example.org. Alternatively, a comprehensive list of other hotels is included in the "Venue" section above. Travel advice and guides are available under "Travel Resources."
Unfortunately, the special code system is set up in a way that will not automatically generate the invoice. But you can request the invoice upon arrival at front desk of the Pullman hotel.
Detailed travel advice and guides are available under “Travel Resources.”
Please contact Lost & Found either through Pullman front desk (for visitors staying in Pullman, dial 0 from your room) or through the banquet-in-charge.
Luggage storage is available in the concierge lobby, level G. The Pullman concierge team will assist in storing luggage.
You can find information on respective airline websites and https://mysafetravel.gov.my for COVID-related details. Travel advice and guides are also available under “Travel Resources.”
The first aid kit room is located on every level. However, in case of an emergency, get in touch with the Pullman Emergency Response Team immediately.
Please bring your ID for verification to the registration desk, where you will receive a replacement.
We are proud to be a multi-ethnic country. The multi-ethnicity is largely because Malaysia (in particular, the Strait of Malacca) was the central hub of commerce in the 1400-1500s. Many Chinese and Indians came here to do business and subsequently stayed here since. During the colonial time (Malaysia was basically colonized by everyone - Portugese, Spanish, Dutch, British), many Chineses and Indians were also brought here by the colonizers (especially British) to build the railroads. The current ethnicity composition consists of about 65% Malay, 25% Chinese, 7% Indian, and a small population of indigenous people (about 0.7% in the peninsula and 11% in the Borneo island).
Durian is commonly known as the "king of all fruits," but is also highly polarized. Some people find it extraordinarily fragrant, and some find it pungent beyond belief. In fact, Singapore bans durian across all public transport because it is too smelly. Durian was produced mostly in Malaysia and Thailand, but it has gained popularity in large parts of Asia in recent years. Some countries are so into durian that durian is made into almost everything imaginable -- durian pizza, durian milkshake, durian mooncake, durian puff. You name it. And yes, you can use durian as a physical defense weapon (Google it).
Since Malaysian is a multi-ethnic country, most Malaysians speak about 2-5 languages (including dialects). Nearly all Malaysians speak decent English and Malay (part of the Austronesian [Malayo-Polynesian] language family). On top of that, most Malaysian Chinese also speak proper Mandarin and at least a few dialects (mainly Cantonese, Hokkien, Hakka in Kuala Lumpur). Many Malaysian Indians also speak fluent Tamils and sometimes Hindu. It should be noted that, while most Malaysians can speak proper English (after all, we were part of the British colony until 1957 -- and yes, you might find older generation to speak fluent English because of that), it is not uncommon for Malaysians to mix three or more languages (in a single sentence!) in verbal communication. And that can be confusing if you are not used to it.
Food. Here is a non-exhaustive list: Nasi Lemak (Malay), Laksa (Malay), Rendang (Malay), Satay (Malay), Roti Canai (Indian), Roti Tissue (Indian), Nasi Briyani (Indian), Chow Kuay Teow (Chinese), Hokkien Mee (Chinese), Popiah (Chinese), Pan Mee (Chinese). You can thank us later.
The living expense in Kuala Lumpur (even being one of the most expensive cities in Malaysia) is still highly affordable. You can get a decent restaurant meal at about 5 USD, and probably even cheaper in a night market. A metro ticket is about 1 USD, and a short taxi ride is about 5 USD.
Since Malaysia is a multi-cultural country with a vast population of international travelers, most foreigners do not find any problem traveling in Malaysia. We do note that different people in Malaysia might have different restrictions. For example, Muslims cannot drink alcohol. That said, alcohol is accessible for other populations in Malaysia (and hence foreigners). There is also a decent population of vegetarians in Malaysia (e.g., Buddhism). The important thing is to be mindful -- for instance, you might want to consider other places than an alcohol bar when bringing your ethnic Malay friends for a science chat. But need not worry, Malaysians are very easy to get along with because of our upbringing -- we are very used to discussing our differences openly and restrictions (if any).
Kuala Lumpur. A city that is truly one-of-a-kind. You'll find the world in this city but you'll never find anything quite like it anywhere else in the world.
For starters, KL (as we fondly call it) has its very own global icon in the PETRONAS Twin Towers, soaring 452 metres above street level and 88 stories tall. This mega structure towers majestically over KL, presenting a universal view of the icon from any corner of the city. Just beneath the Twin Towers are Malaysia's best shopping spots, featuring haute couture brands to trendy street fashions. For those with a penchant for Broadway-like theatres, meet KL's talented acting community that brings you fine shows and performances from the traditional to the satirical. Partygoers will find KL's vibrant night scenes perfect to satiate their appetite for the most happening places to party.
But of course, if you yearn to experience the traditional old-world appeal of Malaysia's culture and values, the old streets of KL with its captivating day-to-day activities and aromatic smells will charm you. You'll experience this city, with the echoing music of its entertainment outlets, the beam of vehicle lights searching for the perfect late-night snack and colourful streetlights - a spectacle that proves KL as a definite place to visit for world travellers.
Here, we will show you the must-see destinations and must-do activities that will thrill you for sure. With so many places to go, a trip to KL may seem overwhelming. But to help, we've rounded up the best attractions that'll guide you in and around this amazing city.
• Main international airport
• Two main buildings (Main terminal KLIA1 & KLIA2)
• Connects Malaysia with 101 destinations in 35 countries
• World's 23rd-busiest airport by total passenger traffic
• More information: http://airports.malaysiaairports.com.my
(2) Langkawi International Airport (LGK)
• Connecting flights to capitals in Asia & domestic flights
• International flights: Singapore
• More information: https://airports.malaysiaairports.com.my/langkawi
(3) Penang International Airport (PEN)
• Eight international direct flights & domestic flights
• International Flights: Singapore, Indonesia, Thailand, China, Taiwan
• More information: https://airports.malaysiaairports.com.my/penang
(4) Kota Kinabalu International Airport (BKI)
• Second busiest airport after KLIA
• 27 destinations with 12 airlines
• International flights: Singapore, South Korea, Philippines, Brunei, Thailand, Japan, China, Macao, Taiwan
• More information: https://airports.malaysiaairports.com.my/kota-kinabalu
(5) Kuching International Airport (KIA)
• 16 destinations with 7 airlines
• International flights: Singapore, Brunei, Indonesia
• More information: https://airports.malaysiaairports.com.my/kuching
From KLIA to Pullman Kuala Lumpur Bangsar
• KLIA Express (KLIA – KL Sentral): https://www.kliaekspres.com
• SkyBus Airport Shuttle (KLIA - KL Sentral): https://www.skybus.com.my
• Direct airport taxi: https://airports.malaysiaairports.com.my/getting-around-transport-car/taxi/metered-taxi
• E-hailing services such as Grab (read more below)
• Use Kelana Jaya Line (KJL), Line No 5 and stop at Kerinchi (KJL18) and it will take 10 mins to walk to the Pullman hotel
• Download the LRT map: https://kualalumpurmap360.com/kuala-lumpur-%28kl%29-transport-map
|Bus Station||Google Map Location||Bus No||Walking Time to Pullman|
|KL1191 IPD Pantai||Google Link||751, 782, 780||8 mins|
|KL1100 LRT Kerinchi||Google Link||T791||9 mins|
|KL1102 Masjid Arrahman UM||Google Link||750, 751, 772, 780, T789||11 mins|
|KL1440 LRT Universiti (Timur)||Google Link||T788, T789||13 mins|
• One of the most popular e-hailing service is GrabCar. You can download the application in your phone and book your ride as you wish. Remember that the price is varied by demand and request.
• More information via https://www.grab.com/my/transport/
• You can go around KL using a registered budget taxi (white red colored). The list and contact no can be found here.
• More information via http://www.visitkl.gov.my/visitklv2/index.php?r=column/ctwo&id=25
IAUS377 will be held in Kuala Lumpur which is located in Peninsular Malaysia, while the other part of Malaysia, Sabah & Sarawak which is a part of Borneo Island also included as Malaysia. Malaysia is located in South East Asia, neighbouring with Singapore, Thailand, Indonesia and Brunei.
Time Zone: MYT = GMT +8 nationwide
Malaysia is located almost at the equator line and thus did have four seasons winter summer spring and autumn. Instead, we have a very sunny or rainy season. It is expected that during the IAUS377 will be the rainy season, hence preparing an umbrella or rain jacket is advisable. More information about Malaysian can be checked via the official website of the Malaysian Meteorology Department (MET Malaysia): https://www.met.gov.my