Astrophys. J., 698, 1934-1942 (2009/June-3)
Spectroscopic confirmation of two massive red-sequence-selected galaxy clusters at z ∼ 1.2 in the SpARCS-north Cluster Survey.
MUZZIN A., WILSON G., YEE H.K.C., HOEKSTRA H., GILBANK D., SURACE J., LACY M., BLINDERT K., MAJUMDAR S., DEMARCO R., GARDNER J.P., GLADDERS M. and LONSDALE C.
Abstract (from CDS):
The Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) is a deep z'-band imaging survey covering the Spitzer Wide-Area Infrared Extragalactic Survey (SWIRE) Legacy fields designed to create the first large homogeneously selected sample of massive clusters at z > 1 using an infrared adaptation of the cluster red-sequence method. We present an overview of the northern component of the survey which has been observed with Canada-France-Hawaii Telescope (CFHT)/MegaCam and covers 28.3 deg2. The southern component of the survey was observed with Cerro Tololo Inter-American Observatory (CTIO)/MOSAICII, covers 13.6 deg2, and is summarized in a companion paper by Wilson et al. We also present spectroscopic confirmation of two rich cluster candidates at z ∼ 1.2. Based on Nod-and-Shuffle spectroscopy from GMOS-N on Gemini, there are 17 and 28 confirmed cluster members in SpARCS J163435+402151 and SpARCS J163852+403843 which have spectroscopic redshifts of 1.1798 and 1.1963, respectively. The clusters have velocity dispersions of 490±140 km/s and 650±160 km/s, respectively, which imply masses (M200) of (1.0 ±0.9)x1014 M☉ and (2.4±1.8)x1014 M☉. Confirmation of these candidates as bonafide massive clusters demonstrates that two-filter imaging is an effective, yet observationally efficient, method for selecting clusters at z > 1.
Text: SpARCS JHHMMSS+DDMMSS N=2. Tables 1-4: SpARCS JHHMM.m+DDMM mN NNNN N=29+44.
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