The XXL Survey. XXXII. Spatial clustering of the XXL-S AGN

M. Plionis, L. Koutoulidis, E. Koulouridis, L. Moscardini, C. Lidman, M. Pierre, C. Adami, L. Chiappetti, L. Faccioli, S. Fotopoulou, F. Pacaud, S. Paltani

Research output: Contribution to journalArticle (Academic Journal)peer-review

7 Citations (Scopus)


The XMM-XXL Survey spans two fields of 25 deg2 each observed for more than 6 Ms with XMM, which provided a sample of tens of thousands of point sources with a flux limit of 2.2 × 10-15 and 1.4 × 10-14 erg s-1 cm2, corresponding to 50% of the area curve, in the soft band (0.5-2 keV) and hard band (2-10 keV), respectively. In this paper we present the spatial clustering properties of 3100 and 1900 X-ray active galactic nuclei (AGNs) in the soft and hard bands, respectively, which have been spectroscopically observed with the AAOmega facility. This sample is 90% redshift complete down to an optical magnitude limit of r ≲ 21.8. The sources span the redshift interval 0 < z < 5.2, although in the current analysis we limit our samples to z ≤ 3, with corresponding sample median values of z̅ ≃ 0.96 and 0.79 for the soft band and hard band, respectively. We employ the projected two-point correlation function to infer the spatial clustering and find a correlation length r0 = 7.0(±0.34) and 6.42(±0.42) h-1 Mpc, respectively, for the soft- and hard-band detected sources with a slope for both cases of γ = 1.44(±0.1). The power-law clustering was detected within comoving separations of 1 and 25 h-1 Mpc. These results, as well as those derived in two separate redshift ranges, provide bias factors of the corresponding AGN host dark matter halos that are consistent with a halo mass of log10[Mh/(h-1M)] = 13.04 ± 0.06, confirming the results of most recent studies based on smaller X-ray AGN samples. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA....
Original languageEnglish
JournalAstronomy and Astrophysics
Publication statusPublished - Nov 2018


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