RSAA Colloquia / Seminars / Feast-of-Facts: Thursday, 10 November 2016, 11:00-12:00; Duffield Lecture Theatre

Arpita Roy

"Superbubble: energetics, feedback to ISM, escape path for ionizing photons, and molecule formation"

I will discuss the conditions for disk galaxies to produce superbubbles that can break out of the disk and produce galactic winds. With the help of 2D hydrodynamic simulations, we study superbubbles created by multiple supernova explosions. I will present our results which show that energy injection rate (surface density) needs to be ∼ 0.1 M_solar yr^−1 kpc^−2 to create superbubbles that break out of the disk with sufficient speed for producing galactic winds. We also calculate the escape fraction of ionizing photons through the dynamically evolving superbubble. We find that the ionizing photons escape within a narrow cone angle of approximately 40 degrees , consistent with observations of nearby galaxies. We show how the escape fraction depends on the disk parameters (density, scale height). Recent observations of nearby starburst galaxies have found molecular outflows with molecular mass of 10^7 – 10^8 M_solar and with speeds of a few 10s of km/s at distances around 500 pc. We outline a scenario in which molecules can form in dense superbubble shells of starburst nuclei.