The galaxy population of Cl 1601+42 at z=0.54 |
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Authors: | TomasDahlé n,ClaesFransson,MagnusNä slund |
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Affiliation: | Stockholm Observatory, Department of Astronomy, SCFAB, SE-106 91 Stockholm, Sweden |
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Abstract: | Photometric redshifts are used to determine the rest-frame luminosity function (LF) of both early- and late-type galaxies to MB∼−17.6 for the cluster Cl 1601+42 at z=0.54 . The total LF shows a steep faint-end slope α ∼−1.4 , indicating the existence of a population of numerous dwarf galaxies. Luminous galaxies, with MB≲−19.5 are mostly red, early-type galaxies, with a LF best described by a Gaussian. Faint galaxies are predominantly blue, late-type galaxies, well fitted by a Schechter function with α ∼−1.7 . Compared with clusters at lower redshift, the steepening of the faint end starts at brighter magnitudes for Cl 1601+42, which may indicate a brightening of the present-day dwarf population relative to the giant population with increasing redshift. Early-type galaxies are centrally concentrated, and dominate the core region, implying that the radial gradient of early-type galaxies seen in local clusters is already established at z∼0.5 . Bright, late-type galaxies are rare, consistent with a decrease in star formation in field galaxies as they are accreted on to the cluster, while faint, blue galaxies are evenly distributed across the cluster, except for a depletion in the core region. The blue fraction is fB∼0.15 , which is somewhat lower than the Butcher–Oemler average at z∼0.5 . The value of f B is found to increase with limiting magnitude and with radius from the centre. |
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Keywords: | galaxies: clusters: individual: Cl 1601+42 galaxies: distances and redshifts galaxies: luminosity function, mass function cosmology: observations |
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