Searching for large-scale structures around high-redshift radio galaxies with Herschel

Author(s)

Emma E. Rigby, N. A. Hatch, H. J. A. Röttgering, Helmut Dannerbauer, Bruce Sibthorpe, Y. K. Chiang, R. Overzier, R. Herbonnet, Stefano Borgani, David L. Clements, Carlos De Breuck, G. De Lucia, J. D. Kurk, F. Maschietto, G. Miley, A. Saro, N. Seymour, B. Venemans

Abstract

This paper presents the first results of a far-infrared search for protocluster-associated galaxy overdensities using the Spectral and Photometric Imaging REciever (SPIRE) instrument onboard the Herschel Space Observatory. Large (~400 arcmin

²) fields surrounding 26 powerful high-redshift radio galaxies (2.0 < z < 4.1; L

_500MHz > 10

^28.5 WHz

_-1) are mapped at 250, 350 and 500 μm to give a unique wide-field sample. On average, the fields have a higher than expected, compared to blank fields, surface density of 500 μm sources within 6 comoving Mpc of the radio galaxy. The analysis is then restricted to potential protocluster members only, which are identified using a far-infrared colour selection; this reveals significant overdensities of galaxies in two fields, neither of which are previously known protoclusters. The probability of finding two overdensities of this size by chance, given the number of fields observed, is 5 × 10

_-4. Overdensities here exist around radio galaxies with L

_500MHz ≳ 10

₂₉ WHz

_-1 and z < 3. The radial extent of the average far-infrared overdensity is found to be ~6 comoving Mpc. Comparison with predictions from numerical simulations shows that the overdensities are consistent with having masses >10

₁₄M⊙. However, the large uncertainty in the redshift estimation means that it is possible that these far-infrared overdensities consist of several structures across the redshift range searched.

Organisation(s)

Department of Astrophysics

External organisation(s)

University of Nottingham, Leiden University, University of Texas, Austin, Ludwig-Maximilians-Universität München, SRON Netherlands Institute for Space Research , Max-Planck-Institut für Astronomie, INAF Astronomical Observatory of Triest, Observatório Nacional/MCT, Imperial College London, European Southern Observatory (Germany), Max-Planck-Institut für extraterrestrische Physik, Commonwealth Scientific and Industrial Research Organisation (CSIRO)

Journal

Monthly Notices of the Royal Astronomical Society

Volume

437

Pages

1882-1893

No. of pages

12

ISSN

0035-8711

DOI

https://doi.org/10.1093/mnras/stt2019

Publication date

01-2014

Peer reviewed

Yes

Austrian Fields of Science 2012

103003 Astronomy, 103004 Astrophysics

Keywords

ASJC Scopus subject areas

Astronomy and Astrophysics, Space and Planetary Science

Portal url

https://ucrisportal.univie.ac.at/en/publications/d7ee6c25-b25c-4aa5-8ba5-675207d65ad6