Far infrared and Ultraviolet emissions of individual galaxies at z=0: selection effects on the estimate of the dust extinction

TL;DR

This study cross-correlates FIR and UV data of local galaxies to assess dust extinction effects, revealing that brighter galaxies exhibit higher FIR/UV flux ratios and that both FIR and UV emissions contribute similarly to star formation rate estimates.

Contribution

It provides a quantitative analysis of dust extinction effects on star formation rate estimates using combined FIR and UV observations of local and distant galaxies.

Findings

FIR to UV flux ratio increases with galaxy brightness.

Both FIR and UV emissions contribute equally to star formation rate.

Local universe star formation rate is approximately 0.03 h M_solar/yr/Mpc^3.

Abstract

We have cross-correlated Far Infrared (IRAS) and UV (FOCA) observations of galaxies to construct a sample of FIR selected galaxies with a UV observation at 0.2 microns. The FIR and UV properties of this sample are compared to the mean properties of the local Universe deduced from the luminosity distributions at both wavelengths. Almost all the galaxies of our sample have a FIR to UV flux ratio larger than the ratio of the FIR and UV luminosity densities, this effect becoming worse as the galaxies become brighter: the increase of the UV (0.2 microns) extinction is about 0.5 mag per decade of FIR (60 microns) luminosity. Quantitative star formation rates are estimated by adding the contribution of the FIR and UV emissions. They are found consistent with the corrections for extinction deduced from the FIR to UV flux ratio. A total local volume-average star formation rate is calculated by summing the contribution of the FIR and UV wavelengths bands. Each band contributes for an almost similar amount to the total star formation rate with rho_{SFR} = 0.03 +/- 0.01 h M solar/yr/Mpc^3 at z=0. This is equivalent to a global extinction of 0.75 mag to apply to the local luminosity density at 0.2 microns. The trend of a larger FIR to UV flux ratio for a larger FIR luminosity found for our sample of nearby galaxies is extended and amplified toward the very large FIR luminosities when we consider the galaxies detected by ISOCAM in a CFRS field and the Ultra Luminous Infrared Galaxies at low and high redshift. A UV extinction is tentatively estimated for these objects.