[en] We quantify the effect of the galaxy group environment (for group masses of 10^12.5–10^14.0 M _⊙) 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 _⊙. 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, ${\mathrm{\psi <!--\; ??\; -->}}_{\ast <!--\; ???\; -->}\propto <!--\; ???\; -->M_{\ast <!--\; ???\; -->}^{-<!--\; ???\; -->0.45\pm <!--\; ??\; -->0.01}$, 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.

[en] We report the discovery of a well-defined correlation between B-band face-on central optical depth due to dust, τ^f_B, and the stellar mass surface density, μ_*, of nearby (z ≤ 0.13) spiral galaxies. This relation was derived from a sample of spiral galaxies taken from the Galaxy and Mass Assembly (GAMA) survey, which were detected in the FIR/submillimeter (submm) in the Herschel-ATLAS science demonstration phase field. Using a quantitative analysis of the NUV attenuation-inclination relation for complete samples of GAMA spirals categorized according to stellar mass surface density, we demonstrate that this correlation can be used to statistically correct for dust attenuation purely on the basis of optical photometry and Sérsic-profile morphological fits. Considered together with previously established empirical relationships of stellar mass to metallicity and gas mass, the near linearity and high constant of proportionality of the τ_B^f - μ_* relation disfavors a stellar origin for the bulk of refractory grains in spiral galaxies, instead being consistent with the existence of a ubiquitous and very rapid mechanism for the growth of dust in the interstellar medium. We use the τ_B^f - μ_* relation in conjunction with the radiation transfer model for spiral galaxies of Popescu and Tuffs to derive intrinsic scaling relations between specific star formation rate (SFR), stellar mass, and stellar surface density, in which attenuation of the UV light used for the measurement of SFR is corrected on an object-to-object basis. A marked reduction in scatter in these relations is achieved which we demonstrate is due to correction of both the inclination-dependent and face-on components of attenuation. Our results are consistent with a general picture of spiral galaxies in which most of the submm emission originates from grains residing in translucent structures, exposed to UV in the diffuse interstellar radiation field.