Abstract
Context. IRAS observations show the existence of a correlation between the infrared luminosity LIR and dust temperature Td in star-forming galaxies, in which larger LIR leads to higher dust temperature. The LIR–Td relation is commonly seen as reflecting the increase in dust temperature in galaxies with higher star formation rate (SFR). Even though the correlation shows a significant amount of dispersion, a unique relation has been commonly used to construct spectral energy distributions (SEDs) of galaxies in distant universe studies, such as source number counting or photometric redshift determination. Aims. In this work, we introduce a new parameter, namely the size of the star-forming region r IR and lay out the empirical and modelled relation between the global parameters LIR, Td and r IR of IR-bright non-AGN galaxies. Methods. IRAS 60-to-100 µm color is used as a proxy for the dust temperature and the 1.4 GHz radio contiuum (RC) emission for the infrared spatial distribution. The analysis has been carried out on two samples. The first one is made of the galaxies from the 60 µm flux-limited IRAS Revised Bright Galaxy Samples (RBGS) which have a reliable RC size estimate from the VLA follow-ups of the IRAS Bright Galaxy Samples. The second is made of the sources from the 170 µm ISOPHOT Serendipity Sky Survey (ISOSSS) which are resolved by the NRAO VLA Sky Survey (NVSS) or by the Faint Images of the Radio Sky at Twenty-cm survey (FIRST). Results. We show that the dispersion in the LIR–Td diagram can be reduced to a relation between the infrared surface brightness and the dust temperature, a relation that spans 5 orders of magnitude in surface brightness. Conclusions. We explored the physical processes giving rise to the ΣIR–Td relation, and show that it can be derived from the Schmidt law, which relates the star formation rate to the gas surface density.
Highlights
The sky survey by the IRAS satellite (Neugebauer et al 1984) led to the discovery of strong connections between global parameters of galaxies in the local universe
To better understand star formation processes on a global scale, we introduced an additional parameter to the LIR–Td analysis, the size of the star-forming region rIR derived from the FWHM of the radio contiuum (RC) profiles according to Eq (1)
We constructed two well-defined local datasets selected at 60 μm and 170 μm, which are made of 430 IR-bright, non-active galactic nucleus (AGN) galaxies with reliable radio continuum sizes
Summary
The sky survey by the IRAS satellite (Neugebauer et al 1984) led to the discovery of strong connections between global parameters of galaxies in the local universe. The quantitative understanding of these correlations is not straightforward because the optical surface brightness results from stars that may not be related to the dust emission and because in the second study, in addition to the small size of the sample (32 galaxies), the authors used Hα maps to estimate the star-forming region size without applying an extinction correction which turns out to be crucial (Chanial et al, in prep.). Roussel et al (2001) studied a sample of galaxies mapped by the ISOCAM camera on board ISO (Cesarsky et al 1996) and found a correlation between the 15to-7 μm flux density ratio and the 15 μm effective surface brightness Their sample only consists of quiescent spirals of moderate infrared luminosities and the authors only considered the circumnuclear region.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
