The Arecibo Galaxy Environment Survey (AGES)

Abstract

Context. Many galaxy properties are known to correlate with the environment in which the galaxies are embedded. Their cold, neutral gas content, which is usually assessed through 21 cm H I observations, is related to many other galaxy properties as it is the underlying fuel for star formation. With its high sensitivity and broad sky coverage the blind Arecibo Galaxy Environment Survey (AGES) brings significant improvement to the census of H I properties of galaxies in a wide range of environments, from voids to the core of a massive cluster. Here we present an H I census over a volume of ∼44 000 Mpc3 towards the merging cluster Abell 1367 and extending well beyond. Aims. We measure the effects that different environments have on the H I content of their constituent galaxies. Methods. We use AGES- a deep, blind, H I survey carried out with the Arecibo radio telescope, which covers 20 square degrees on the sky centred on the merging cluster Abell 1367, mapping the large-scale structure (LSS) surrounding the cluster out to cz = 20 000 km s−1. The survey is sensitive down to a column density of NH I = 1.5 × 1017 cm−2 for emission filling the beam and a line width of 10 km s−1. As an approximate mass sensitivity limit, a member of A1367 (at a distance of 92 Mpc), containing MH I = 2.7 × 108 M⊙ distributed over a top-hat profile of 50 km s−1 width would be detected at 4σ. The results are analysed in combination with optical spectroscopy data from SDSS which we use to estimate the local galaxy density based on the Voronoi-Delaunay method. Results. We present the results of the complete AGES survey of the A1367 field. In total, we detect 457 H I sources, 213 of which are detected for the first time by the AGES survey, and 134 of which are presented in this article for the first time. Of the 457 detections, 225 are in the cluster and 232 are in the remaining volume surveyed. Here we present the full catalogue of H I detections and their basic properties, including optical ones. We concentrate on the difference between the cluster and the foreground and background LSS, revealing a continuous correlation of H I-detected fraction (and H I deficiency) with local galaxy density, independent of global environment.