A z = 2.5 protocluster associated with the radio galaxy MRC 2104-242: star formation and differing mass functions in dense environments

Cooke, E.A.; Hatch, Nina A.; Muldrew, S.I.; Rigby, E.E.; Kurk, J.D.

Abstract

We present results from a narrow-band survey of the field around the high-redshift radio galaxy MRC 2104−242. We have selected Hα emitters in a 7 arcmin2 field and compared the measured number density with that of a field sample at similar redshift. We find that MRC 2104−242 lies in an overdensity of galaxies that is 8.0 ± 0.8 times the average density of a blank field, suggesting it resides in a large-scale structure that may eventually collapse to form a massive cluster. We find that there is more dust obscured star formation in the protocluster galaxies than in similarly selected control field galaxies and there is tentative evidence of a higher fraction of starbursting galaxies in the denser environment. However, on average we do not find a difference between the star formation rate (SFR)–mass relations of the protocluster and field galaxies and so conclude that the SFR of these galaxies at z ∼ 2.5 is governed predominantly by galaxy mass and not the host environment. We also find that the stellar mass distribution of the protocluster galaxies is skewed towards higher masses and there is a significant lack of galaxies at M < 1010M_ within our small field of view. Based on the level of overdensity we expect to find ∼22 star-forming galaxies below 1010M_ in the protocluster and do not detect any. This lack of low-mass galaxies affects the level of overdensity which we detect. If we only consider high-mass (M > 1010.5M_) galaxies, the density of the protocluster field increases to ∼55 times the control field density.

Citation

Cooke, E., Hatch, N. A., Muldrew, S., Rigby, E., & Kurk, J. (2014). A z = 2.5 protocluster associated with the radio galaxy MRC 2104-242: star formation and differing mass functions in dense environments. Monthly Notices of the Royal Astronomical Society, 440(4), https://doi.org/10.1093/mnras/stu522

• Journal Article Type: Article
• Acceptance Date: Mar 13, 2014
• Publication Date: Apr 17, 2014
• Deposit Date: Sep 28, 2016
• Publicly Available Date: Sep 28, 2016
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 440
• Issue: 4
• DOI: https://doi.org/10.1093/mnras/stu522
• Keywords: Cluster galaxies, MRC 2104-242, High-redshift galaxies
• Public URL: https://nottingham-repository.worktribe.com/output/726822
• Publisher URL: http://dx.doi.org/10.1093/mnras/stu522
• Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2014 The authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.