HERSCHEL-ATLAS: TOWARD A SAMPLE OF {approx}1000 STRONGLY LENSED GALAXIES

Journal Article · Tue Apr 10 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/749/1/65· OSTI ID:22020464

Gonzalez-Nuevo, J; Lapi, A; Bressan, S; Danese, L; De Zotti, G; Cai, Z -Y; Fan, L ^[1]; Fleuren, S; Sutherland, W ^[2]; Negrello, M ^[3]; Baes, M ^[4]; Baker, A J ^[5]; Clements, D L ^[6]; Cooray, A ^[7]; Dannerbauer, H ^[8]; Dunne, L; Dye, S ^[9]; Eales, S ^[10]; Frayer, D T ^[11]; others, and

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1. SISSA, Via Bonomea 265, I-34136 Trieste (Italy)
2. School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS (United Kingdom)
3. Department of Physical Sciences, Open University, Milton Keynes MK7 6AA (United Kingdom)
4. Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent (Belgium)
5. Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854-8019 (United States)
6. Astrophysics Group, Imperial College, Blackett Lab, Prince Consort Road, London SW7 2AZ (United Kingdom)
7. Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)
8. Institut fuer Astronomie, Universitaet Wien, Tuerkenschanzstrasse 17, 1180 Wien, Oesterreich (Austria)
9. School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)
10. School of Physics and Astronomy, Cardiff University, The Parade, Cardiff CF24 3AA (United Kingdom)
11. National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States)

While the selection of strongly lensed galaxies (SLGs) with 500 {mu}m flux density S{sub 500} > 100 mJy has proven to be rather straightforward, for many applications it is important to analyze samples larger than the ones obtained when confining ourselves to such a bright limit. Moreover, only by probing to fainter flux densities is it possible to exploit strong lensing to investigate the bulk of the high-z star-forming galaxy population. We describe HALOS (the Herschel-ATLAS Lensed Objects Selection), a method for efficiently selecting fainter candidate SLGs, reaching a surface density of {approx_equal} 1.5-2 deg{sup -2}, i.e., a factor of about 4-6 higher than that at the 100 mJy flux limit. HALOS will allow the selection of up to {approx}1000 candidate SLGs (with amplifications {mu} {approx}> 2) over the full H-ATLAS survey area. Applying HALOS to the H-ATLAS Science Demonstration Phase field ({approx_equal} 14.4 deg{sup 2}) we find 31 candidate SLGs, whose candidate lenses are identified in the VIKING near-infrared catalog. Using the available information on candidate sources and candidate lenses we tentatively estimate a {approx_equal} 72% purity of the sample. As expected, the purity decreases with decreasing flux density of the sources and with increasing angular separation between candidate sources and lenses. The redshift distribution of the candidate lensed sources is close to that reported for most previous surveys for lensed galaxies, while that of candidate lenses extends to redshifts substantially higher than found in the other surveys. The counts of candidate SLGs are also in good agreement with model predictions. Even though a key ingredient of the method is the deep near-infrared VIKING photometry, we show that H-ATLAS data alone allow the selection of a similarly deep sample of candidate SLGs with an efficiency close to 50%; a slightly lower surface density ({approx_equal} 1.45 deg{sup -2}) can be reached with a {approx}70% efficiency.

• OSTI ID: 22020464
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 749; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
AMPLIFICATION
CATALOGS
FLUX DENSITY
GALAXIES
PHOTOMETRY
RED SHIFT
STARS