The Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS): Survey design, data catalogue and GAMA/WiggleZ spectroscopy

John H Y Ching, Elaine M. Sadler, Scott Martin Croom, Helen M Johnston, Michael B Pracy, Warrick John Couch, Margaret A Hopkins, Russell J Jurek, K. A. Pimbblet

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Abstract

We present the Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS), a spectroscopic catalogue of radio sources designed to include the full range of radio AGN populations out to redshift z ~ 0.8. The catalogue covers ~800 deg2 of sky, and provides optical identifications for 19 179 radio sources from the 1.4 GHz Faint Images of the Radio Sky at Twenty-cm (FIRST) survey down to an optical magnitude limit of imod < 20.5 in Sloan Digital Sky Survey (SDSS) images. Both galaxies and point-like objects are included, and no colour cuts are applied. In collaboration with the WiggleZ and Galaxy And Mass Assembly (GAMA) spectroscopic survey teams, we have obtained new spectra for over 5000 objects in the LARGESS sample. Combining these new spectra with data from earlier surveys provides spectroscopic data for 12 329 radio sources in the survey area, of which 10 856 have reliable redshifts. 85 per cent of the LARGESS spectroscopic sample are radio AGN (median redshift z = 0.44), and 15 per cent are nearby star-forming galaxies (median z = 0.08). Low-excitation radio galaxies (LERGs) comprise the majority (83 per cent) of LARGESS radio AGN at z < 0.8, with 12 per cent being high-excitation radio galaxies (HERGs) and 5 per cent radioloud QSOs. Unlike the more homogeneous LERG and QSO sub-populations, HERGs are a heterogeneous class of objects with relatively blue optical colours and a wide dispersion in mid-infrared colours. This is consistent with a picture in which most HERGs are hosted by galaxies with recent or ongoing star formation as well as a classical accretion disc.

Original languageEnglish
Pages (from-to)1306-1332
Number of pages27
JournalMonthly Notices of the Royal Astronomical Society
Volume464
Issue number2
DOIs
Publication statusPublished - 2017

Keywords

  • Catalogues
  • Galaxies: active
  • Radio continuum: galaxies
  • Surveys

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