The local star formation rate and radio luminosity density |
| |
Authors: | StephenSerjeant CarlottaGruppioni SebOliver |
| |
Affiliation: | 1Unit for Space Sciences and Astrophysics, School of Physical Sciences, University of Kent, Canterbury, Kent CT2 7NR; 2Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy; 3Astronomy Centre, CPES, University of Sussex, Falmer, Brighton BN1 9QJ; 4Astrophysics Group, Blackett Laboratory, Imperial College of Science Technology and Medicine, Prince Consort Road, London SW7 2BW |
| |
Abstract: | We present a new determination of the local volume-averaged star formation rate from the 1.4-GHz luminosity function of star forming galaxies. Our sample, taken from the B ≤12 Revised Shapley–Ames catalogue (231 normal spiral galaxies over an effective area of 7.1 sr) has ≃100 per cent complete radio detections and is insensitive to dust obscuration and cirrus contamination. After removal of known active galaxies, the best-fitting Schechter function has a faint-end slope of −1.27±0.07 in agreement with the local H α luminosity function, characteristic luminosity L ∗=(2.6±0.7)×1022 W Hz−1 and density φ ∗=(4.8±1.1)×10−4 Mpc−3. The inferred local radio luminosity density of (1.73±0.37±0.03)×1019 W Hz−1 Mpc−3 (Poisson noise, large-scale structure fluctuations) implies a volume-averaged star formation rate ∼2 times larger than the Gallego et al. H α estimate, i.e. ρ 1.4 GHz=(2.10±0.45±0.04)×10−2 M⊙ yr−1 Mpc−3 for a Salpeter initial mass function from 0.1–125 M⊙ and Hubble constant of 50 km s−1 Mpc−1. We demonstrate that the Balmer decrement is a highly unreliable extinction estimator, and argue that optical–ultraviolet (UV) star formation rates (SFRs) are easily underestimated, particularly at high redshift. |
| |
Keywords: | surveys galaxies: evolution galaxies: formation galaxies: Seyfert galaxies: starburst infrared: galaxies |
|
|