Herschel-ATLAS: First data release of the Science Demonstration Phase source catalogues

TL;DR

This paper presents the first data release and source catalogues from the Herschel-ATLAS survey's Science Demonstration Phase, including source extraction methods, catalogue reliability, and flux correction factors for far-infrared and submillimetre sources.

Contribution

It introduces a new source extraction method for Herschel data and provides the first catalogue from the Science Demonstration Phase of Herschel-ATLAS.

Findings

Catalogue contains 6876 sources at 250 microns.

Flux density enhancements due to source confusion can be up to a factor of 2.

Correction factors for flux density biases are provided.

Abstract

The Herschel-ATLAS is a survey of 550 square degrees with the Herschel Space Observatory in five far--infrared and submillimetre bands. The first data for the survey, observations of a field 4x4 sq. degrees in size, were taken during the Science Demonstration Phase, and reach a 5 sigma noise level of 33 mJy/beam at 250 microns. This paper describes the source extraction methods used to create the corresponding Science Demonstration Phase catalogue, which contains 6876 sources, selected at 250 microns, within ~14 sq. degrees. SPIRE sources are extracted using a new method specifically developed for Herschel data; PACS counterparts of these sources are identified using circular apertures placed at the SPIRE positions. Aperture flux densities are measured for sources identified as extended after matching to optical wavelengths. The reliability of this catalogue is also discussed, using full simulated maps at the three SPIRE bands. These show that a significant number of sources at 350 and 500 microns have undergone flux density enhancements of up to a factor of ~2, due mainly to source confusion. Correction factors are determined for these effects. The SDP dataset and corresponding catalogue will be available from http://www.h-atlas.org/.