BULGE GROWTH AND QUENCHING SINCEz= 2.5 IN CANDELS/3D-HST

Abstract

Exploiting the deep high-resolution imaging of all 5 CANDELS fields, and accurate redshift information provided by 3D-HST, we investigate the relation between structure and stellar populations for a mass-selected sample of 6764 galaxies above 10 10 M ⊙ , spanning the redshift range 0.5 < z < 2.5. For the first time, we fit 2-dimensional models comprising a single Sérsic fit and two-component (i.e., bulge + disk) decompositions not only to the H-band light distributions, but also to the stellar mass maps reconstructed from resolved stellar population modeling. We confirm that the increased bulge prominence among quiescent galaxies, as reported previously based on rest-optical observations, remains in place when considering the distributions of stellar mass. Moreover, we observe an increase of the typical Sérsic index and bulge-to-total ratio (with median B/T reaching 40-50%) among starforming galaxies above 10 11 M ⊙ . Given that quenching for these most massive systems is likely to be imminent, our findings suggest that significant bulge growth precedes a departure from the starforming main sequence. We demonstrate that the bulge mass (and ideally knowledge of the bulge and total mass) is a more reliable predictor of the star-forming versus quiescent state of a galaxy than the total stellar mass. The same trends are predicted by the state-of-the-art semi-analytic model by Somerville et al. In the latter, bulges and black holes grow hand in hand through merging and/or disk instabilities, and AGN-feedback shuts off star formation. Further observations will be required to pin down star formation quenching mechanisms, but our results imply they must be internal to the galaxies and closely associated with bulge growth.

The impact of galactic properties and environment on the quenching of central and satellite galaxies: a comparison between SDSS, Illustris and L-Galaxies

“…4 & 5,respectively. sion, than by halo, stellar, bulge or disk mass, bulge-to-total stellar mass ratio (B/T ) or overdensity of galaxies evaluated at the 5th nearest neighbour (δ5). These observational findings are in agreement with prior analyses of the role of central velocity dispersion in quenching (e.g., Wake et al 2012;Teimoorinia, Bluck & Ellison 2016), and are consistent with the strong dependence of central galaxy quenching on surface mass density within 1 kpc (e.g., Cheung et al 2012;Fang et al 2013;Woo et al 2015;Lilly & Carollo 2016) and bulge mass (Bluck et al 2014;Lang et al 2014;Omand et al 2014). Furthermore, we find that varying local density, stellar, halo or bulge mass at fixed central velocity dispersion leads to essentially no impact whatsoever on the quenched fraction (even when these parameters are varied by over three orders of magnitude).…”

“…Recent observations have established that the quenched (or red) fraction of central galaxies is most tightly correlated with the inner regions of these galaxies, e.g., surface mass density within 1 kpc, bulge mass or central velocity dispersion (Cheung et al 2012;Wake et al 2012;Fang et al 2013;Bluck et al 2014;Lang et al 2014;Omand et al 2014;Woo et al 2015). Teimoorinia et al (2016) found strong evidence from an ANN analysis that central velocity dispersion is the most predictive, and hence most tightly constraining, observable for central galaxy quenching out of the following list of variables: stellar, halo, bulge and disk mass; local galaxy density and galactic structure (B/T ).…”

“…bulge-to-total light/ mass ratio, B/T , or Sérsic index, nS (e.g., Driver et al 2006;Wuyts et al 2011;Mendel et al 2013;Bluck et al 2014;Lang et al 2014;Omand et al 2014). Additionally, the quenched fraction depends on environment, particularly the surface density of galaxies in a given region of space, the halo mass of the group or cluster, and the distance a galaxy resides at from the centre of its group (e.g., Balogh et al 2004;van den Bosch et al 2007Peng et al 2012;Woo et al 2013;Bluck et al 2014).…”

“…More recent work has linked the quenched (or red) fraction of large populations of galaxies to the central density within 1 kpc (Cheung et al 2012, Fang et al 2013, the central velocity dispersion (Wake et al 2012), and to the mass of the galactic bulge (Bluck et al 2014, Lang et al 2014, Omand et al 2014). An artificial neural network (ANN) analysis performed by Teimoorinia, Bluck & Ellison (2016) established that for central galaxies the most accurate predictions for whether a galaxy will be star forming or not are given by central velocity dispersion, which outperforms all other variables considered, including bulge mass, stellar mass and halo mass.…”

Galaxy Growth at Early Times from 3D Studies

“…Concurring evidence for the prevalence of high-z disks has come from HST-based studies of rest-UV/optical morphologies and stellar mass distributions of large mass-selected samples out to z ∼ 2.5, which showed that MS SFGs typically have a disk-like stellar structure with a systematic increase of bulge-to-disk ratio towards high masses (e.g. Wuyts et al 2011;Lang et al 2014). These results from kinematics and stellar structure provided some of the compelling evidence that smoother mass accretion modes onto galaxies and internal dynamical processes within galaxies play an important -if not dominant -role in growing galaxies.…”