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Efficient satellite quenching at z∼1 from the GEEC2 spectroscopic survey of galaxy groups.

Mok, A. and Balogh, M.L. and McGee, S.L. and Wilman, D.J. and Finoguenov, A. and Tanaka, M. and Giodini, S. and Bower, R.G. and Connelly, J.L. and Hou, A. and Mulchaey, J.S. and Parker, L.C. (2013) 'Efficient satellite quenching at z∼1 from the GEEC2 spectroscopic survey of galaxy groups.', Monthly notices of the Royal Astronomical Society., 431 (2). pp. 1090-1106.


We present deep Gemini Multi-Object Spectrograph-South spectroscopy for 11 galaxy groups at 0.8 < z < 1.0, for galaxies with rAB < 24.75. Our sample is highly complete (>66 per cent) for eight of the 11 groups. Using an optical–near-infrared colour–colour diagram, the galaxies in the sample were separated with a dust insensitive method into three categories: passive (red), star-forming (blue) and intermediate (green). The strongest environmental dependence is observed in the fraction of passive galaxies, which make up only ∼20 per cent of the field in the mass range 1010.3 < Mstar/M⊙ < 1011.0, but are the dominant component of groups. If we assume that the properties of the field are similar to those of the ‘pre-accreted’ population, the environment quenching efficiency (ϵρ) is defined as the fraction of field galaxies required to be quenched in order to match the observed red fraction inside groups. The efficiency obtained is ∼0.4, similar to its value in intermediate-density environments locally. While green (intermediate) galaxies represent ∼20 per cent of the star-forming population in both the group and field, at all stellar masses, the average specific star formation rate of the group population is lower by a factor of ∼3. The green population does not show strong Hδ absorption that is characteristic of starburst galaxies. Finally, the high fraction of passive galaxies in groups, when combined with satellite accretion models, require that most accreted galaxies have been affected by their environment. Thus, any delay between accretion and the onset of truncation of star formation (τ) must be ≲ 2 Gyr, shorter than the 3–7 Gyr required to fit data at z = 0. The relatively small fraction of intermediate galaxies require that the actual quenching process occurs quickly, with an exponential decay time-scale of τq ≲ 1 Gyr.

Item Type:Article
Keywords:Galaxies: evolution, Galaxies: general, Galaxies: luminosity function, Mass function.
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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society © 2013 The Authors Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved.
Date accepted:No date available
Date deposited:27 June 2014
Date of first online publication:May 2013
Date first made open access:No date available

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