What shapes a galaxy? – unraveling the role of mass, environment, and star formation in forming galactic structure

Abstract

We investigate the dependence of galaxy structure on a variety of galactic and environmental parameters for ∼500,000 galaxies at z<0.2, taken from the Sloan Digital Sky Survey data release 7 (SDSS-DR7). We utilise bulge-to-total stellar mass ratio, (B/T) * , as the primary indicator of galactic structure, which circumvents issues of morphological dependence on waveband. We rank galaxy and environmental parameters in terms of how predictive they are of galaxy structure, using an artificial neural network approach. We find that distance from the star forming main sequence (∆SFR), followed by stellar mass (M * ), are the most closely connected parameters to (B/T) * , and are significantly more predictive of galaxy structure than global star formation rate (SFR), or any environmental metric considered (for both central and satellite galaxies). Additionally, we make a detailed comparison to the Illustris hydrodynamical simulation and the LGalaxies semi-analytic model. In both simulations, we find a significant lack of bulge-dominated galaxies at a fixed stellar mass, compared to the SDSS. This result highlights a potentially serious problem in contemporary models of galaxy evolution.

Are galactic star formation and quenching governed by local, global, or environmental phenomena?

“…All global and environmental parameters are taken from the SDSS value added catalogues (as referenced above). Full details on the parameters used in this study are provided in many other publications, most recently in Section 2 of Bluck et al (2019). As such, we will not present a detailed explanation of each parameter here.…”

Galaxy interactions in IllustrisTNG-100, I: The power and limitations of visual identification

“…The star formation main sequence (e.g., Noeske et al 2007; Daddi et al 2007;Elbaz et al 2007;Salim et al 2007;Rodighiero et al 2011;Bluck et al 2016Bluck et al , 2019Donnari et al 2019, hereafter SFMS) defines a general trend of all star forming galaxies: the star formation rate is tightly correlated with the stellar mass. That this relationship holds for a wide range of redshifts (e.g., Noeske et al 2007;Lee et al 2015), several orders of magnitude in stellar mass, and a relatively small spread in star formation rate implies that star forming galaxies behave in a self-regulatory manner with a fairly consistent star formation history throughout cosmic time (e.g., Bouché et al 2010;Lilly et al 2013).…”

“…This implies that centrals are likely to quench before their satellites. It may be that the evolution of satellites is more sensitive to environment, whilst the evolution of centrals is depends more strongly upon mass; perhaps an example of the interplay between "environment quenching" and "mass quenching" (e.g., Peng et al 2010;Bluck et al 2016Bluck et al , 2019. Thus, the relative importance of environment and stellar mass depends upon which component of the interaction is the subject of inquiry.…”

Galaxies hosting an active galactic nucleus: a view from the CALIFA survey

“…Moreover, the growth of the bulge could explain the dominance of inside-out over outside-in quenching (e.g. González Delgado et al 2016;Ellison et al 2018;Lin et al 2019;Bluck et al 2019). Thus, there seem to be a connection between AGN activity, bulge and SMBH growth and SF quenching.…”