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An excess of star-forming galaxies in the fields of high-redshift QSOs

Stevens, JA; Jarvis, MJ; Coppin, KEK; Page, MJ; Greve, TR; Carrera, FJ; Ivison, RJ; (2010) An excess of star-forming galaxies in the fields of high-redshift QSOs. Monthly Notices of the Royal Astronomical Society , 405 (4) 2623 - 2638. 10.1111/j.1365-2966.2010.16641.x. Green open access

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Abstract

We present submillimetre (submm) and mid-infrared (MIR) imaging observations of five fields centred on quasi-stellar objects (QSOs) at 1.7< z<2.8. All five QSOs were detected previously at submm wavelengths. At 850 (450) m, we detect 17 (11) submillimetre galaxies (SMGs) in addition to the QSOs. The total area mapped at 850 m is arcmin2 down to rms noise levels of 1–2 mJy beam−1, depending on the field. Integral number counts are computed from the 850-m data using the same analytical techniques adopted by ‘blank-field’ submm surveys. We find that the ‘QSO-field’ counts show a clear excess over the blank-field counts at deboosted flux densities of mJy; at higher flux densities, the counts are consistent with the blank-field counts. Robust MIR counterparts are identified for all four submm detected QSOs and per cent of the SMGs. The MIR colours of the QSOs are similar to those of the local ultraluminous infrared galaxy (ULIRG)/active galactic nuclei (AGN) Mrk 231 if placed at 1< z<3 whilst most of the SMGs have colours very similar to those of the local ULIRG Arp 220 at 1< z<3. MIR diagnostics therefore find no strong evidence that the SMGs host buried AGN although we cannot rule out such a possibility. Taken together our results suggest that the QSOs sit in regions of the early universe which are undergoing an enhanced level of major star formation activity, and should evolve to become similarly dense regions containing massive galaxies at the present epoch. Finally, we find evidence that the level of star formation activity in individual galaxies appears to be lower around the QSOs than it is around more powerful radio-loud AGN at higher redshifts.

Type: Article
Title: An excess of star-forming galaxies in the fields of high-redshift QSOs
Open access status: An open access version is available from UCL Discovery
DOI: 10.1111/j.1365-2966.2010.16641.x
Publisher version: http://dx.doi.org/10.1111/j.1365-2966.2010.16641.x
Language: English
Additional information: © 2010 RAS Definitive versions of articles pre-2013 are available at http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-2966, now published by http://mnras.oxfordjournals.org
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/1330247
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