On the occupation of X-ray-selected galaxy groups by radio active galactic nuclei since z = 1.3

Authors

  • V. Smolčić,

    Corresponding author
    1. European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching b. München, Germany
    2. Argelander Institut for Astronomy, Auf dem Hügel 71, Bonn D-53121, Germany
      E-mail: vs@astro.uni-bonn.de ESO ALMA COFUND Fellow.
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  • A. Finoguenov,

    1. Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany
    2. University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
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  • G. Zamorani,

    1. INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna, Italy
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  • E. Schinnerer,

    1. Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
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  • M. Tanaka,

    1. European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching b. München, Germany
    2. Institute for the Physics and Mathematics of the Universe, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8583, Japan
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  • S. Giodini,

    1. Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, the Netherlands
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  • N. Scoville

    1. California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125, USA
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  • Based on observations with the National Radio Astronomy Observatory which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc., and with XMM–Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.

E-mail: vs@astro.uni-bonn.de

ESO ALMA COFUND Fellow.

ABSTRACT

Previous clustering analysis of low-power radio active galactic nuclei (AGNs) has indicated that they preferentially live in massive groups. The X-ray surveys of the Cosmic Evolution Survey (COSMOS) field have achieved a sensitivity at which these groups are directly detected out to z = 1.3. Making use of the surveys Chandra, XMM–Newton and VLA-COSMOS, we identify radio AGN members [1023.6≲ L1.4 GHz/(W Hz−1) ≲ 1025] of galaxy groups (1013.2≲ M200/M≲ 1014.4; 0.1 < z < 1.3) and study (i) the radio-AGN–X-ray group occupation statistics as a function of group mass; and (ii) the distribution of radio AGNs within the groups. We find that radio AGNs are preferentially associated with galaxies close to the centre (<0.2r200). Compared to our control sample of group members matched in stellar mass and colour to the radio-AGN host galaxies, we find a significant enhancement of radio-AGN activity associated with 1013.6≲ M200/M≲ 1014 haloes. We present the first direct measurement of the halo occupation distribution (HOD) for radio AGNs, based on the total mass function of galaxy groups hosting radio AGNs. Our results suggest a possible deviation from the usually assumed power-law HOD model. We also find an overall increase in the fraction of radio AGNs in galaxy groups (<1r200), relative to that in all environments.

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