The Open UniversitySkip to content
 

The nature of the mid-infrared population from optical identifications of the ELAIS-S1 sample

La Franca, F.; Gruppioni, C.; Matute, I.; Pozzi, F.; Lari, C.; Mignoli, M.; Zamorani, G.; Alexander, D. M.; Cocchia, F.; Danese, L.; Franceschini, A.; Héraudeau, P.; Kotilainen, J. K.; Linden-Vørnle, M. J. D.; Oliver, S.; Rowan-Robinson, M.; Serjeant, S.; Spinoglio, L. and Verma, A. (2004). The nature of the mid-infrared population from optical identifications of the ELAIS-S1 sample. Astronomical Journal, 127(6) pp. 3075–3088.

URL: http://arxiv.org/abs/astro-ph/0403211
DOI (Digital Object Identifier) Link: http://dx.doi.org/10.1086/420987
Google Scholar: Look up in Google Scholar

Abstract

We present a multiwavelength catalog (15 μm, R-band, K-band, and 1.4 GHz flux) plus spectroscopic identifications for 406 15 μm sources detected in the European Large Area ISO Survey (ELAIS) region S1, over the flux density range 0.5<S15μm<150 mJy. Three hundred thirty-two (~82%) sources are optically identified down to R~23.0. Spectra or bona fide stellar identifications are obtained for 290 objects (~88% of the optically identified sources). The areal coverage, mid-infrared (MIR) and optical completeness of the sample are discussed in order to allow statistical and evolutionary analyses. Two main spectroscopic classes have been found to dominate the MIR extragalactic population: z<0.5 star-forming galaxies [from absorbed to extreme starbursts: νLν(15μm)~108-1011 L], which account for ~75% of the sources, and active galactic nuclei (AGNs; both type 1 and 2), which account for ~25% of the sources. About 20% of the extragalactic sources are dust-enshrouded starburst galaxies [e(a) spectra], and all the starburst galaxies appear more dust-extincted in the optical than nearby normal galaxies. We also identified 91 stellar objects (~22% of the MIR sources). The counts for starburst galaxies and AGNs down to 0.6 mJy have been derived. A general trend is found in the optical-MIR spectral energy distribution of the galaxies, where the MIR-luminous objects have larger MIR to optical luminosity ratios. Based on a variety of analyses, we suggest that the ELAIS sources fainter than R~23 are luminous and ultraluminous MIR galaxies (LIG-ULIGs νLν(15μm)=1011-1012 L) at intermediate redshifts (z=0.5-1.5), and that consequently the present sample is virtually 100% spectroscopically complete up to z=0.5.

Item Type: Journal Article
Copyright Holders: 2004 The American Astronomical Society.
ISSN: 1538-3881
Keywords: cosmology; observations; active; galaxies; distances; redshifts; evolution; starburst; infrared
Academic Unit/Department: Science > Physical Sciences
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 5673
Depositing User: Users 13 not found.
Date Deposited: 25 Oct 2006
Last Modified: 03 Jul 2014 09:27
URI: http://oro.open.ac.uk/id/eprint/5673
Share this page:

Actions (login may be required)

View Item
Report issue / request change

Policies | Disclaimer

© The Open University   + 44 (0)870 333 4340   general-enquiries@open.ac.uk