Environmental impacts on dust temperature of star-forming galaxies in the local Universe

Abstract

We present infrared views of the environmental effects on the dust properties in star-forming (SF) galaxies at z ∼ 0, using the AKARI Far-Infrared Surveyor all-sky map and the large spectroscopic galaxy sample from Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). We restrict the sample to those within the redshift range of 0.05 < z < 0.07 and the stellar mass range of 9.2 < log ₁₀(M_*/M_⊙). We select SF galaxies based on their Hα equivalent width (EW_Hα > 4 Å) and emission line flux ratios. We perform far-infrared (FIR) stacking analyses by splitting the SDSS SF galaxy sample according to their stellar mass, specific star formation rate (SSFR_SDSS), and environment. We derive total infrared luminosity (L_IR) for each subsample using the average flux densities at WIDE-S (90 μm) and WIDE-L (140 μm) bands, and then compute infrared (IR)-based SFR (SFR_IR) from L_IR. We find a mild decrease of IR-based SSFR (SSFR_IR) amongst SF galaxies with increasing local density (∼0.1-dex level at maximum), which suggests that environmental effects do not instantly shut down the SF activity in galaxies. We also derive average dust temperature (T_dust) using the flux densities at 90 and 140 μm bands. We confirm a strong positive correlation between T_dust and SSFR_IR, consistent with recent studies. The most important finding of this study is that we find a marginal trend that T_dust increases with increasing environmental galaxy density. Although the environmental trend is much milder than the SSFR-T_dust correlation, our results suggest that the environmental density may affect the dust temperature in SF galaxies, and that the physical mechanism which is responsible for this phenomenon is not necessarily specific to cluster environments because the environmental dependence of T_dust holds down to relatively low-density environments.