Open AccessThe galaxy population of Cl 1601+42 at z=0.54
Author(s) -
Dahlén Tomas,
Fransson Claes,
Näslund Magnus
Publication year - 2002
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2002.05054.x
Subject(s) - physics , astrophysics , astronomy , population , elliptical galaxy , dwarf galaxy , galaxy , luminosity function , galaxy cluster , brightest cluster galaxy , redshift , demography , sociology
Photometric redshifts are used to determine the rest‐frame luminosity function (LF) of both early‐ and late‐type galaxies to M B ∼−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 M B ≲−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 f B ∼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.