Star formation rates and luminosity functions in the low-redshift Universe

The cosmic star-formation history is a key constraint on theoretical models of galaxy formation and evolution. However, currently we do not know whether the mismatch between some models and observations signals a true failure of the model due to the level of systematic uncertainties in the star-formation tracers. In the first part of my talk, I will present a critical look at the most commonly used star-formation rate indicators by exploiting the impressive and well-vetted GAMA multi-wavelength database. Our main conclusion is that it is possible to successfully reconcile different SFR tracers as long as one performs careful dust attenuation corrections. However, UV-based SFR corrected for dust using the observed spectral slope can not give accurate SFR measurements within a factor of 5 and it exhibits systematic trends with respect to a number of physical parameters.  In the second half of my talk, I will present a new analysis on the 250 micron luminosity function (LF) at z <0.5. There are several reasons why it is important to measure the 250 micron LF. First, half of the energy produced by stars is absorbed and re-radiated in the far-infrared (FIR) and sub-millimetre (sub-mm). Second, the spectra of most IR luminous galaxies peak in the FIR and sub-mm.  Finally, our knowledge of the LFs, which represent fundamental statistical properties of the observed galaxy population, is very poor in the FIR and sub-mm part of the electromagnetic spectrum. The success of Herschel has made it possible for us to make significant progress in this area. However, past studies of the 250 micron LF has been hampered by many difficulties. I present a modified stacking method which bypasses some major problems in previous measurements. I show that very good agreement can be found between our new measurements and previous results in the literature in the overlapping luminosity range. More importantly, our method allows us to probe the LF down to much fainter luminosities and for the first time we  can measure the LF below the characteristic luminosity at 0.2<z<0.5.