SHALOS: Statistical Herschel-ATLAS Lensed Objects Selection

Abstract

The statistical analysis of large sample of strong lensing events can be a powerful tool to extract astrophysical and/or cosmological valuable information. However, the number of such events is still relatively low, mostly because of the lengthily observational validation process on individual events. In this work we propose a new methodology with a statistical selection approach in order to increase by a factor of $\sim 5$ the number of such events. Although the methodology can be applied to address several selection problems, it has particular benefits in the case of the identification of strongly lensed galaxies: objectivity, minimal initial constrains in the main parameter space, preservation of the statistical properties. The proposed methodology is based on the Bhattacharyya distance as a measure of the similarity between probability distributions of properties of two different cross-matched galaxies. The particular implementation for the aim of this work is called SHALOS and it combines the information of four different properties of the pair of galaxies: angular separation, luminosity percentile, redshift and optical/sub-mm flux density ratio. The SHALOS method provided a ranked list of strongly lensed galaxies. The number of candidates for the final associated probability, $P_{tot}>0.7$, is 447 with an estimated mean amplification factor of 3.12 for an halo with a typical cluster mass. Additional statistical properties of the SHALOS candidates, as the correlation function or the source number counts, are in agreement with previous results indicating the statistical lensing nature of the selected sample.

9 pages, 6 figures, submitted to Astronomy & Astrophysics

References in corpus (13)

• The Detection of a Population of Submillimeter-Bright, Strongly-Lensed Galaxies
• Intense Star Formation within Resolved Compact Regions in a Galaxy at z=2.3
• Astrophysical and Cosmological Information from Large-scale sub-mm Surveys of Extragalactic Sources
• The Herschel-ATLAS Data Release 1 Paper I: Maps, Catalogues and Number Counts
• The Herschel-ATLAS: a sample of 500μm-selected lensed galaxies over 600 square degrees
• Probabilistic Cross-Identification of Astronomical Sources
• The space density of luminous dusty star-forming galaxies at $z>4$: SCUBA-2 and LABOCA imaging of ultrared galaxies from $Herschel$-ATLAS
• The Herschel-ATLAS Data Release 1 Paper II: Multi-wavelength counterparts to submillimetre sources
• The Herschel-ATLAS Data Release 2, Paper I. Submillimeter and Far-infrared Images of the South and North Galactic Poles: The Largest Herschel Survey of the Extragalactic Sky
• Lens Models of Herschel-Selected Galaxies From High-Resolution Near-IR Observations
• Herschel-ATLAS and ALMA: HATLAS J142935.3-002836, a lensed major merger at redshift 1.027
• The second Herschel-ATLAS Data Release - III: optical and near-infrared counterparts in the North Galactic Plane field
• Colour matters: the effects of lensing on the positional offsets between optical and submillimetre galaxies in Herschel-ATLAS

Cited by in corpus (1)

• A search for the lenses in the Herschel Bright Sources (HerBS) Sample