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An X-ray Detected Group of Quiescent Early-type Galaxies at z=1.6 in the Chandra Deep Field South | Masayuki Tanaka
; Alexis Finoguenov
; Mohammad Mirkazemi
; David J. Wilman
; John S. Mulchaey
; Yoshihiro Ueda
; Yongquan Xue
; William N. Brandt
; Nico Cappelluti
; | Date: |
1 Oct 2012 | Abstract: | (Abridged) We report the discovery of an X-ray group of galaxies located at a
high redshift of z=1.61 in the Chandra Deep Field South. The group is first
identified as an extended X-ray source. We use a wealth of deep
multi-wavelength data to identify the optical counterpart -- our red sequence
finder detects a significant over-density of galaxies at z~1.6 and the
brightest group galaxy is spectroscopically confirmed at z=1.61. We measure an
X-ray luminosity of L_{0.1-2.4 keV}= 1.8pm0.6 imes 10^{43} erg/s, which then
translates into a group mass of 3.2pm0.8 imes 10^{13} M_sun. This is the
lowest mass group ever confirmed at z>1.5. The deep optical-nearIR images from
CANDELS reveal that the group exhibits a surprisingly prominent red sequence. A
detailed analysis of the spectral energy distributions of the group member
candidates confirms that most of them are indeed passive galaxies. Furthermore,
their structural parameters measured from the near-IR CANDELS images show that
they are morphologically early-type. The newly identified group at z=1.61 is
dominated by quiescent early-type galaxies and the group appears similar to
those in the local Universe. One possible difference is the high fraction of
AGN (38^{+23}_{-20}%), which might indicate a role for AGN in quenching. But, a
statistical sample of high-z groups is needed to draw a general picture of
groups at this redshift. Such a sample will hopefully be available in near
future surveys. | Source: | arXiv, 1210.0302 | Services: | Forum | Review | PDF | Favorites |
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