Study of 230 IRAS-FSC galaxies

To understand the nature of these objects we have compared them with a sample of bright ULIRGs with fluxes f>1Jy at 60-micron and with 14 optically faint IRAS FSC galaxies, showing that IRAS galaxies are not always strong infrared sources. We also have calibrated Star Formation Rates based on luminosities of the PAH feature at 7.7-micron and 1.4GHz radio flux densities, which confirmed the consistency between these two SFRs.

We have estimated the extinction for our 230 objects using SFRs calibrated from the PAH feature compared to ultraviolet flux, which shows that only 1% of the ultraviolet continuum typically escapes extinction by dust within a starburst. As our 230 galaxies have no spectra available from Spitzer Space Telescope (SST) archive, to estimate the infrared flux at 7.7 (for SB galaxies) or 8.0 (for AGN and composite) micron, we have used the median ratios of the IRAS fluxes at 25-micron to fluxes at 7.7 or 8.0-micron estimated for each 41.0<logL(IR)<41.9, 42.0<logL(IR)<42.9, 43.0<logL(IR)<43.9, 44.0<logL(IR)<44.9, and 45.0<logL(IR)<45.9 luminosity bins, using objects having spectra from SST archive.