Astronomy and Astrophysics, volume 516, A101-101 (2010/6-3)
Spectroscopic confirmation of a galaxy cluster associated with 7C 1756+6520 at z=1.416.
GALAMETZ A., STERN D., STANFORD S.A., DE BREUCK C., VERNET J., GRIFFITH R.L. and HARRISON F.A.
Abstract (from CDS):
We present spectroscopic follow-up of an overdensity of galaxies photometrically selected to be at 1.4<z<2.5 found in the vicinity of the radio galaxy 7C 1756+6520 at z=1.4156. Using the DEIMOS optical multi-object spectrograph on the Keck 2 telescope, we observed a total of 129 BzK-selected sources, comprising 82 blue, star-forming galaxy candidates (sBzK) and 47 red, passively-evolving galaxy candidates (pBzK*), as well as 11 mid-infrared selected AGN candidates. We obtain robust spectroscopic redshifts for 36 blue galaxies, 7 red galaxies and 9 AGN candidates. Assuming all foreground interlopers were identified, we find that only 16% (9%) of the sBzK (pBzK*) galaxies are at z<1.4. Therefore, the BzK criteria are shown to be relatively robust at identifying galaxies at moderate redshifts. Twenty-one galaxies, including the radio galaxy, four additional AGN candidates and three red galaxy candidates are found with 1.4156±0.025, forming a large scale structure at the redshift of the radio galaxy. Of these, eight have projected offsets <2Mpc relative to the radio galaxy position and have velocity offsets <1000km/s relative to the radio galaxy redshift. This confirms that 7C 1756+6520 is associated with a high-redshift galaxy cluster. A second compact group of four galaxies is found at z∼1.437, forming a sub-group offset by Δv∼3000km/s and approximately 1.5' east of the radio galaxy.
large-scale structure of Universe - galaxies: clusters: general - Galaxy: evolution - galaxies: individual: 7C 1756+6520 - galaxies: clusters: individual: 7C1756+6520
Table 1, col(1): [GSS2010] Cl1756.NN (Nos 1-20). Tables 1-2, col(2): [GSS2010] sBzK.NNNNN, [GSS2010] pBzK.NNNNN, [GSS2010] AGN.NNNN N=18+35. Text: [GSS2010] 7C 1756+6520 cluster N=1.
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