Dan S. Taranu, Michael J. Hudson, Michael L. Balogh, Russell J. Smith, Chris Power, Brad Krane
In order to understand the processes that quench star formation within rich clusters, we construct a library of subhalo orbits drawn from lambdaCDM cosmological N-body simulations of four rich clusters. The orbits are combined with models of star formation followed by quenching in the cluster environment to predict colours and spectroscopic line indices of satellite galaxies. Simple models with only halo mass-dependent quenching and without environmental (i.e. cluster-dependent) quenching fail to reproduce the observed cluster-centric colour and absorption linestrength gradients. Models in which star formation is instantly quenched at the virial radius also fail to match the observations. Better matches to the data are achieved by more complicated bulge-disc models in which the bulge stellar populations depend only on the galaxy subhalo mass while the disc quenching depends on the cluster environment. In the most successful models quenching begins at pericentre, operating on an exponential timescale of 2 -- 3 Gyr, with the shorter timescale being a better match to disc colours as a function of cluster-centric radius and the longer being a better fit to the radial dependence of stellar absorption line indices. The models thus imply that the environments of rich clusters must impact star formation rates of infalling galaxies on relatively long timescales - several times longer than a typical halo spends within the virial radius of a cluster. This scenario favours gentler quenching mechanisms such as slow "strangulation" over more rapid ram-pressure stripping.
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http://arxiv.org/abs/1211.3411
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