An ultraviolet-selected galaxy redshift survey - III. Multicolour imaging and non-uniform star formation histories
Abstract
We present panoramic u′ and optical ground‐based imaging observations of a complete sample of low‐redshift (0 < z < 0.4) galaxies selected in the ultraviolet (UV) at 2000 Å using the balloon‐borne FOCA instrument of Milliard et al. This survey is highly sensitive to newly formed massive stars and hence to actively star‐forming galaxies. We use the new data to investigate further the optical, stellar population and star formation properties of this unique sample, deriving accurate galaxy types and k‐corrections based on the broad‐band spectral energy distributions. When combined with our earlier spectroscopic surveys, these new data allow us to compare star formation measures derived from aperture‐corrected Hα line fluxes, and UV(2000 Å) and u′(3600 Å) continuum fluxes on a galaxy‐by‐galaxy basis. As expected from our earlier studies, we find broad correlations over several decades in luminosity between the different dust‐corrected star formation diagnostics, though the scatter is larger than that from observational errors, with significant offsets from trends expected according to simple models of the star formation histories (SFHs) of galaxies. Popular galaxy spectral synthesis models with varying metallicities and/or initial mass functions seem unable to explain the observed discrepancies. We investigate the star formation properties further by modelling the observed spectroscopic and photometric properties of the galaxies in our survey. We find that nearly half of the galaxies surveyed possess features that appear incompatible with simple constant or smoothly declining SFHs, favouring instead irregular or temporally varying SFHs. We demonstrate how this can reconcile the majority of our observations, enabling us to determine empirical corrections that can be used to calculate intrinsic star formation rates (as derived from Hα luminosities) from measures based on UV (or u′) continuum observations alone. We discuss the broader implications of our finding that a significant fraction of star‐forming galaxies have complex SFHs, particularly in the context of recent determinations of the cosmic SFH.
Additional Information
© 2004 RAS. Received: 17 January 2004. Accepted: 20 January 2004. Published: 01 May 2004. MS acknowledges support from a PPARC fellowship. The authors thank Roy Gal for providing us with the DPOSS data for the SA57 and A1367 survey fields, Andrew Firth for assisting with the CFHT data collection, Andrew Hopkins for useful discussions and Stèphane Arnouts for his advice on using sextractor. The authors are grateful to Yannick Mellier and Mireille Dantel for their invaluable assistance with the CFHT data reduction at the TERAPIX centre. The authors thank Mark Metzger and Rob Simcoe for assistance using the LFC on the Palomar 200‐inch telescope. The authors also thank Chuck Steidel and Jean‐Charles Cuillandre for providing Palomar and CFH12k filter response curves, respectively. The WIYN Observatory is a joint facility of the University of Wisconsin–Madison, Indiana University, Yale University and the National Optical Astronomy Observatories. The William Herschel Telescope is operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. The Canada–France–Hawaii Telescope (CFHT) is operated by the National Research Council of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique of France and the University of Hawaii.Attached Files
Published - 350-1-21.pdf
Accepted Version - 0310388.pdf
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Additional details
- Eprint ID
- 103750
- Resolver ID
- CaltechAUTHORS:20200608-110444448
- Particle Physics and Astronomy Research Council (PPARC)
- Created
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2020-06-08Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field