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

We present infrared views of the environmental effects on the dust properties in star-forming (SF) galaxies at z similar to 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 < log10(M*/M circle dot). We select SF galaxies based on their Ha equivalent width (EWH alpha > 4 angstrom) 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 (SSFRSDSS), and environment. We derive total infrared luminosity (L-IR) for each subsample using the average flux densities at WIDE-S (90 mu m) and WIDE-L (140 mu m) bands, and then compute infrared (IR)-based SFR (SFRIR) from LIR. We find a mild decrease of IR-based SSFR (SSFRIR) amongst SF galaxies with increasing local density (similar to 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 mu m bands. We confirm a strong positive correlation between Tdust and SSFRIR, consistent with recent studies. The most important finding of this study is that we find a marginal trend that Tdust 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 Tdust holds down to relatively low-density environments.