Spectroscopic characterization of galaxy clusters in RCS-1: spectroscopic confirmation, redshift accuracy, and dynamical mass–richness relation. Issue 2 (9th February 2018)

• Record Type: Journal Article
• Authors: Gilbank, David G; Barrientos, L Felipe; Ellingson, Erica; Blindert, Kris; Yee, H K C; Anguita, T; Gladders, M D; Hall, P B; Hertling, G; Infante, L; Yan, R; Carrasco, M; Garcia-Vergara, Cristina; Dawson, K S; Lidman, C; Morokuma, T
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 476:Issue 2(2018)
• Page Start: 1991
• Page End: 2012
• Publication Date: 2018-02-09
• Subjects: galaxies: clusters: general -- galaxies: distances and redshifts; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty355
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: We present follow-up spectroscopic observations of galaxy clusters from the first Red-sequence Cluster Survey (RCS-1). This work focuses on two samples, a lower redshift sample of ∼30 clusters ranging in redshift from z ∼ 0.2–0.6 observed with multiobject spectroscopy (MOS) on 4–6.5-m class telescopes and a z ∼ 1 sample of ∼10 clusters 8-m class telescope observations. We examine the detection efficiency and redshift accuracy of the now widely used red-sequence technique for selecting clusters via overdensities of red-sequence galaxies. Using both these data and extended samples including previously published RCS-1 spectroscopy and spectroscopic redshifts from SDSS, we find that the red-sequence redshift using simple two-filter cluster photometric redshifts is accurate to σ z ≈ 0.035(1 + z ) in RCS-1. This accuracy can potentially be improved with better survey photometric calibration. For the lower redshift sample, ∼5 per cent of clusters show some (minor) contamination from secondary systems with the same red-sequence intruding into the measurement aperture of the original cluster. At z ∼ 1, the rate rises to ∼20 per cent. Approximately ten per cent of projections are expected to be serious, where the two components contribute significant numbers of their red-sequence galaxies to another cluster. Finally, we present a preliminary study of the mass–richness calibration using velocity dispersions to probe the dynamical masses of the clusters. We find a relation broadly consistent with that seen in the local universe from the WINGS sample at z ∼ 0.05.