A multiwavelength approach to the star formation rate estimation in galaxies at intermediate redshifts

Abstract

We use a sample of seven starburst galaxies at intermediate redshifts (z similar to 0.4 and 0.8) with observations ranging from the observed ultraviolet to 1.4 GHz, to compare the star formation rate (SFR) estimators that are used in the different wavelength regimes. We find that extinction-corrected Halpha underestimates the SFR, and the degree of this underestimation increases with the infrared luminosity of the galaxies. Galaxies with very different levels of dust extinction as measured with SFRIR/SFR(Halpha, uncorrected for extinction) present a similar attenuation A [Halpha], as if the Balmer lines probed a different region of the galaxy than the one responsible for the bulk of the IR luminosity for large SFRs. In addition, SFR estimates derived from [O II] lambda3727 match very well those inferred from Halpha after applying the metallicity correction derived from local galaxies. SFRs estimated from the UV luminosities show a dichotomic behavior, similar to that previously reported by other authors in galaxies at z less than or similar to 0.4. Here we extend this result up to z similar to 0.8. Finally, one of the studied objects is a luminous compact galaxy (LCG) that may be suffering similar dust-enshrouded star formation episodes. These results highlight the relevance of quantifying the actual L-IR of LCGs, as well as that of a much larger and generic sample of luminous infrared galaxies, which will be possible after the launch of SIRTF.