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Optical and infrared diagnostics of SDSS galaxies in the SWIRE survey

Davoodi, P. and Pozzi, F. and Oliver, S. A. and Polletta, M. and Afonso-Luis, A. and Farrah, D. and Hatziminaoglou, E. and Rodighiero, G. and Berta, S. and Waddington, I. and Lonsdale, C. and Rowan-Robinson, M. and Shupe, D. L. and Evans, T. and Fang, F. and Smith, H. E. and Surace, J. (2006) Optical and infrared diagnostics of SDSS galaxies in the SWIRE survey. Monthly Notices of the Royal Astronomical Society, 371 (3). pp. 1113-1124. ISSN 0035-8711.

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We present the rest-frame optical and infrared colours of a complete sample of 1114 z < 0.3 galaxies from the Spitzer Wide-Area Infrared Extragalactic (SWIRE) Legacy Survey and the Sloan Digital Sky Survey (SDSS). We discuss the optical and infrared colours of our sample and analyse in detail the contribution of dusty star-forming galaxies and active galactic nuclei (AGN) to optically selected red sequence galaxies. We propose that the optical (g-r) colour and infrared log(L-24/L-3.6) colour of galaxies in our sample are determined primarily by a bulge-to-disc ratio. The (g-r) colour is found to be sensitive to the bulge-to-disc ratio for disc-dominated galaxies, whereas the log (L-24/L-3.6) colour is more sensitive for bulge-dominated systems. We identify similar to 18 per cent (195 sources) of our sample as having red optical colours and infrared excess. Typically, the infrared luminosities of these galaxies are found to be at the high end of star-forming galaxies with blue optical colours. Using emission-line diagnostic diagrams, 78 are found to have an AGN contribution and 117 are identified as star-forming systems. The red (g-r) colour of the star-forming galaxies could be explained by extinction. However, their high optical luminosities cannot. We conclude that they have a significant bulge component. The number densities of optically red star-forming galaxies are found to correspond to similar to 13 per cent of the total number density of our sample. In addition, these systems contribute similar to 13 per cent of the total optical luminosity density, and 28 per cent of the total infrared luminosity density of our SWIRE/SDSS sample. These objects may reduce the need for 'dry mergers'.

Item Type:Article
Related URLs:
URLURL TypeDescription
Polletta, M.0000-0001-7411-5386
Farrah, D.0000-0003-1748-2010
Rodighiero, G.0000-0002-9415-2296
Berta, S.0000-0002-0320-1532
Lonsdale, C.0000-0003-0898-406X
Shupe, D. L.0000-0003-4401-0430
Evans, T.0000-0001-5442-1300
Surace, J.0000-0001-7291-0087
Additional Information:© 2006 The Authors. Journal compilatoins © 2006 RAS. Accepted 2006 July 6. Received 2006 June 29; in original form 2006 March 29. PD is supported by a PPARC studentship (PPA/S/S/2002/03500/), SJO is supported by a Leverhulme Research Fellowship, SJO and IW are supported by PPARC standard grant (PPA/G/S/2000/00508 and PPA/G/S/2002/00481). We thank Jon Loveday for his advice on certain aspects of the SDSS data. We thank the referee Randall Rojas for his helpful comments and suggestions. The support for this work, part of the Spitzer Space Telescope Legacy Science Program, was provided by NASA through an award issued by the Jet Propulsion Laboratory, California Institute of Technology under the NASA contract 1407.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Particle Physics and Astronomy Research Council (PPARC)PPA/S/S/2002/03500
Leverhulme TrustUNSPECIFIED
Particle Physics and Astronomy Research Council (PPARC)PPA/G/S/2000/00508
Particle Physics and Astronomy Research Council (PPARC)PPA/G/S/2002/00481
Subject Keywords:galaxies: elliptical and lenticular, cD; galaxies: evolution; galaxies: formation; infrared: galaxies
Issue or Number:3
Record Number:CaltechAUTHORS:DAVmnras06b
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:12399
Deposited By: Tony Diaz
Deposited On:11 Dec 2008 04:30
Last Modified:20 Nov 2019 05:24

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