The XXL Survey

Astronomy and Astrophysics, vol. 638, pp. A46

Abstract

We study the space density evolution of active galactic nuclei (AGN) using the 610 MHz radio survey of the XXL-North field, performed with the Giant Metrewave Radio Telescope. The survey covers an area of 30.4 deg 2 , with a beamsize of 6.5 arcsec. The survey is divided into two parts, one covering an area of 11.9 deg 2 with 1 σ rms noise of 200 μ Jy beam −1 and the other spanning 18.5 deg 2 with rms noise of 45 μ Jy beam −1 . We extracted the catalog of radio components above 7 σ . The catalog was cross-matched with a multi-wavelength catalog of the XXL-North field (covering about 80% of the radio XXL-North field) using a likelihood ratio method, which determines the counterparts based on their positions and their optical properties. The multi-component sources were matched visually with the aid of a computer code: Multi-Catalog Visual Cross-Matching. A flux density cut above 1 mJy selects AGN hosts with a high purity in terms of star formation contamination based on the available source counts. After cross-matching and elimination of observational biases arising from survey incompletenesses, the number of remaining sources was 1150. We constructed the rest-frame 1.4 GHz radio luminosity functions of these sources using the maximum volume method. This survey allows us to probe luminosities of 23 ≲ log( L 1.4 GHz [W Hz −1 ]) ≲ 28 up to redshifts of z ≈ 2.1. Our results are consistent with the results from the literature in which AGN are comprised of two differently evolving populations, where the high luminosity end of the luminosity functions evolves more strongly than the low-luminosity end.

Authors 7

1. B. Šlaus

   University of Zagreb

   Affiliation as printed

   Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, 10000 Zagreb, Croatia

2. S. Fotopoulou

   University of Geneva · Durham University

   Affiliation as printed

   Center for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK

   Department of Astronomy, University of Geneva, ch. d’Ecogia 16, 1290 Versoix, Switzerland

3. K. Tisanić

   University of Zagreb

   Affiliation as printed

   Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, 10000 Zagreb, Croatia

4. M. Birkinshaw

   University of Bristol

   Affiliation as printed

   H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK

5. L. Chiappetti

   National Institute for Astrophysics

   Affiliation as printed

   INAF, IASF Milano, Via Corti 12, 20133 Milano, Italy

6. Huib T. Intema Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands

7. Somak Raychaudhury

   Inter-University Centre for Astronomy and Astrophysics

   Affiliation as printed

   Inter-University Centre for Astronomy and Astrophysics Ganeshkhind, Post Bag 4, Puné 411 007, India