Year: 2006
Type: article
Abstract: Using integrated optical spectrophotometry for 412 star-forming galaxies at z ~ 0, and fiber-aperture spectrophotometry for 120,846 SDSS galaxies at z ~ 0.1, we investigate the Hα λ6563, Hβ λ4861, [O II] λ3727, and [O III] λ5007 nebular emission lines and the U -band luminosity as quantitative star formation rate (SFR) indicators. We demonstrate that the extinction-corrected Hα λ6563 luminosity is a reliable SFR tracer even in highly obscured star-forming galaxies. We find that variations in dust reddening dominate the systematic uncertainty in SFRs derived from the observed Hβ, [O II], and U -band luminosities, producing a factor of ~1.7, ~2.5, and ~2.1 scatter in the mean transformations, respectively. We show that [O II] depends weakly on variations in oxygen abundance over a wide range in metallicity, 12 + log(O/H) = 8.15-8.7 ( Z / Z ☉ = 0.28-1.0), and that in this metallicity interval galaxies occupy a narrow range in ionization parameter (-3.8 ≲ log U ≲ -2.9). We show that the scatter in [O III] λ5007 as a SFR indicator is a factor of 3-4 due to its sensitivity to metal abundance and ionization. We develop empirical SFR calibrations for Hβ and [O II] parameterized in terms of the B -band luminosity, which remove the systematic effects of reddening and metallicity and reduce the SFR scatter to ±40% and ±90%, respectively, although individual galaxies may deviate substantially from the median relations. Finally, we compare the z ~ 0 relations between blue luminosity and reddening, ionization, and [O II]/Hα ratio against measurements at z ~ 1 and find broad agreement. We emphasize, however, that optical emission-line measurements including Hα for larger samples of intermediate- and high-redshift galaxies are needed to test the applicability of our locally derived SFR calibrations to distant galaxies.
Source: The Astrophysical Journal
DOI: 10.1086/500964
Institutions: University of Arizona, University of Cambridge
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W1977609574