Galaxy And Mass Assembly (GAMA): Gas Fueling of Spiral Galaxies in the Local Universe. I. The Effect of the Group Environment on Star Formation in Spiral Galaxies

Abstract

We quantify the effect of the galaxy group environment (for group masses of 10 12.5 -1014.0 M e ) on the current star formation rate (SFR) of a pure, morphologically selected sample of disk-dominated (i.e., late-type spiral) galaxies with redshift 0.13. The sample embraces a full representation of quiescent and star-forming disks with stellar mass M * 10 9.5 M e . We focus on the effects on SFR of interactions between grouped galaxies and the putative intrahalo medium (IHM) of their host group dark matter halos, isolating these effects from those induced through galaxy-galaxy interactions, and utilizing a radiation transfer analysis to remove the inclination dependence of derived SFRs. The dependence of SFR on M * is controlled for by measuring offsets Δlog(ψ * ) of grouped galaxies about a single power-law relation in specific SFR,, exhibited by non-grouped "field" galaxies in the sample. While a small minority of the group satellites are strongly quenched, the group centrals and a large majority of satellites exhibit levels of ψ * statistically indistinguishable from their field counterparts, for all M * , albeit with a higher scatter of 0.44 dex about the field reference relation (versus 0.27 dex for the field). Modeling the distributions in Δlog(ψ * ), we find that (i) after infall into groups, disk-dominated galaxies continue to be characterized by a similar rapid cycling of gas into and out of their interstellar medium shown prior to infall, with inflows and outflows of ∼1.5-5 x SFR and ∼1-4 x SFR, respectively; and (ii) the independence of the continuity of these gas flow cycles on M * appears inconsistent with the required fueling being sourced from gas in the circumgalactic medium on scales of ∼100 kpc. Instead, our data favor ongoing fueling of satellites from the IHM of the host group halo on ∼Mpc scales, i.e., from gas not initially associated with the galaxies upon infall. Consequently, the color-density relation of the galaxy population as a whole would appear to be primarily due to a change in the mix of disk-and spheroid-dominated morphologies in the denser group environment compared to the field, rather than to a reduced propensity of the IHM in higher-mass structures to cool and accrete onto galaxies. We also suggest that the required substantial accretion of IHM gas by satellite disk-dominated galaxies will lead to a progressive reduction in the specific angular momentum of these systems, thereby representing an efficient secular mechanism to transform morphology from star-forming disk-dominated types to more passive spheroid-dominated types.

A radiative transfer model for the spiral galaxy M33★

“…16 shows the "main sequence" relation between integrated quantities SFR and M * for a flux-limited subset (complete to 19.4 mag in the SDSS r-band) of 5202 disc-dominated GAMA galaxies located within redshift 0.13, and which are not classified as belonging to a galaxy group (see Table 1 and Sect. 4.3 of Grootes et al 2017). We refer to this subsample, plotted as dots on the figure, as the "field" reference sample of disc-dominated galaxies.…”

“…SFR versus stellar mass for a field reference sample of local universe disc-dominated galaxies (black points) and the global emission from M33 (red rhomboid). The field reference sample is comprised of of 5202 morphologically selected, diskdominated galaxies drawn from the GAMA survey by Grootes et al (2017), which are not members of groups of galaxies. The vertical and horizontal apexes of the rhomboid containing the M33 point are placed at the 1-sigma bounds in SFR and M * , respectively.…”

“…The vertical and horizontal apexes of the rhomboid containing the M33 point are placed at the 1-sigma bounds in SFR and M * , respectively. SFR for the GAMA galaxies were derived following Grootes et al (2017), while stellar masses for both the GAMA and M33 data were derived from intrinsic i and g-band photometry following Taylor et al (2011). The solid line is the regression fit to a single power law model given in Table 2 of Grootes et al (2018).…”

Galaxy and Mass Assembly (GAMA): Morphological transformation of galaxies across the green valley

“…This could be interpreted as the result of their environment acting to prematurely reduce the cold gas supply to an increasing subset, presumably through galaxy-galaxy, or galaxy-intra group medium interactions (strangulation, ram pressure stripping etc. -see Grootes et al 2017 for an extensive discussion). The velocity dispersions (from Robotham et al 2011) of the less rich environments vary from typically ∼ 200 to ∼ 350 kms −1 for systems with multiplicities up to 20 galaxies, but can be ∼ 500 kms −1 or more for the richest subset in Table 1.…”

Galaxy Zoo: the interplay of quenching mechanisms in the group environment★

“…Using a similar method, Oman & Hudson (2016) derive an infall time of ∼ 4 Gyr and quenching timescales between 4 − 6 Gyr for galaxies in the mass range of the gz2-group-q sample. However, studies such as Peng et al (2010); Wetzel et al (2013); Hahn et al (2016); Crossett et al (2017) and Grootes et al (2017) have found much shorter quenching timescales of ∼ < 1 Gyr for satellite galaxies.…”