Unveiling the roles of mass, environment and structure in galaxy quenching


James Trussler(KICC, Cambridge, UK)

Octy 5, 2020

Star-forming galaxies can be transformed into passive systems by a multitude of processes that quench star formation, such as the halting of cold gas accretion (starvation) or the rapid removal of gas in AGN-driven outflows. However, it remains unclear which processes are the most significant, primary drivers of the star-forming—passive bimodality. In this talk, I will leverage on the statistical power of the Sloan Digital Sky Survey, having analysed the chemical properties of tens of thousands of local star-forming, green valley and passive galaxies, to discuss how galaxy quenching depends on the internal properties of galaxies (stellar mass), external factors (environment), and how it varies radially within galaxies. I will show that the significant difference in stellar metallicity between local passive galaxies and their star-forming progenitors implies that for galaxies at all masses, quenching must have involved an extended phase of starvation, with outflows only playing a minor role in quenching massive galaxies. By separating star-forming, green valley and passive galaxies, I will further show that the imprint of environment on the stellar populations of galaxies is much weaker than previously thought. Satellite galaxies are only marginally more metal-rich (< 0.03 dex) and older (< 0.5 Gyr) than central galaxies of the same stellar mass, with stellar metallicities that only increase weakly with the density of the environment within which they reside. Finally, using integral field spectroscopic data from the SDSS-IV MaNGA galaxy survey, I will show that the stellar metallicity difference between star-forming and passive galaxies decreases with radial distance. I will discuss how this indicates that, while starvation plays a prominent role in quenching the central regions of galaxies, it plays a less important role in quenching their outskirts.

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