The clustering and bias of radio-selected AGN and star-forming galaxies in the COSMOS field

Hale, C. L. and Jarvis, M. J. and Delvecchio, I. and Hatfield, P. W. and Novak, Mario and Smolčić, Vernesa and Zamorani, G. (2018) The clustering and bias of radio-selected AGN and star-forming galaxies in the COSMOS field. Monthly Notices of the Royal Astronomical Society, 474 (3). pp. 4133-4150. ISSN 0035-8711

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Dark matter haloes in which galaxies reside are likely to have a significant impact on their evolution. We investigate the link between dark matter haloes and their constituent galaxies by measuring the angular two-point correlation function of radio sources, using recently released 3 GHz imaging over ∼2 deg2 of the Cosmological Evolution Survey (COSMOS) field. We split the radio source population into star-forming galaxies (SFGs) and active galactic nuclei (AGN), and further separate the AGN into radiatively efficient and inefficient accreters. Restricting our analysis to z < 1, we find SFGs have a bias, b = 1.5+0.1 −0.2, at a median redshift of z = 0.62. On the other hand, AGN are significantly more strongly clustered with b = 2.1 ± 0.2 at a median redshift of 0.7. This supports the idea that AGN are hosted by more massive haloes than SFGs. We also find low accretion rate AGN are more clustered (b = 2.9 ± 0.3) than high accretion rate AGN (b = 1.8+0.4 −0.5) at the same redshift (z ∼ 0.7), suggesting that low accretion rate AGN reside in higher mass haloes. This supports previous evidence that the relatively hot gas that inhabits the most massive haloes is unable to be easily accreted by the central AGN, causing them to be inefficient. We also find evidence that low accretion rate AGN appear to reside in halo masses of Mh ∼ 3–4 × 1013 h−1 M at all redshifts. On the other hand, the efficient accreters reside in haloes of Mh ∼ 1–2 × 1013 h−1 M at low redshift but can reside in relatively lower mass haloes at higher redshifts. This could be due to the increased prevalence of cold gas in lower mass haloes at z ≥ 1 compared to z < 1.

Item Type: Article
Keywords: galaxies: active, galaxies: evolution, cosmology: observations, large-scale structure of Universe, radio continuum: galaxies
Date: 2018
Subjects: NATURAL SCIENCES > Physics > Astronomy and Astrophysics
Additional Information: © 2017 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2017 November 13. Received 2017 November 7; in original form 2017 May 12.
Divisions: Faculty of Science > Department of Physics
Publisher: Oxford University Press
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 21 Mar 2018 15:33
Last Modified: 21 Mar 2018 15:33

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