RSAA Colloquia / Seminars / Feast-of-Facts: Friday, 21 November 2014, 14:20-14:40; Duffield Lecture Theatre

Rebecca Davis

"The Extended Emission Line Region of the "Green Bean" Galaxy SDSS J2240-0927: a quasar ionization echo illuminating the remnant of a quasar-driven outflow?"

We use Integral Field Spectroscopic data from the Gemini Multi-Object Spectrograph to analyse the 3D kinematics, ionization state, temperature and density of ionized gas in the "Green Bean" (GB) galaxy quasar ionization echo candidate J2240-0927. We model the emission line spectrum of each spaxel as a superposition of up to three Gaussian components and analyse the physical properties of each component individually. Two narrow components, tracing the velocity fields of the disc and the ionized gas cloud, are superimposed over the majority of the galaxy. A broader kinematic component is also ubiquitous across the galaxy disc. Fast shocks produce hot, dense, turbulent, [O III]-bright regions with large [N II]/Halpha and [S II]/Halpha ratios. The most prominent such spot is consistent with a radio jet shock-heating the interstellar medium. However, the active galactic nucleus (AGN) is still responsible for > 82% of the galaxy’s total [O III] luminosity, confirming that J2240 is a quasar ionization echo. The ionized gas cloud has a strong kinematic link to the central AGN and is co-rotating with the main body of the galaxy, suggesting that it may be the remnant of a quasar-driven outflow. The extremely low space density of GB galaxies suggests that they may be manifestations of normal but short-lived stages in the lives of quasar host galaxies. Detailed 3D spectroscopic analysis of other GB galaxies will provide further insight into the evolutionary history of this unique class of objects.