Open AccessThe 2dF Galaxy Redshift Survey: luminosity functions by density environment and galaxy type
Author(s) -
Croton Darren J.,
Farrar Glennys R.,
Norberg Peder,
Colless Matthew,
Peacock John A.,
Baldry I. K.,
Baugh C. M.,
BlandHawthorn J.,
Bridges T.,
Can R.,
Cole S.,
Collins C.,
Couch W.,
Dalton G.,
De Propris R.,
Driver S. P.,
Efstathiou G.,
Ellis R. S.,
Frenk C. S.,
Glazebrook K.,
Jackson C.,
Lahav O.,
Lewis I.,
Lumsden S.,
Maddox S.,
Madgwick D.,
Peterson B. A.,
Sutherland W.,
Taylor K.
Publication year - 2005
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 - 10.1111/j.1365-2966.2004.08546.x
Subject(s) - physics , astrophysics , galaxy , density contrast , luminosity function , astronomy , luminosity , galaxy group , galaxy cluster , brightest cluster galaxy , population , surface brightness fluctuation , demography , sociology
We use the 2dF Galaxy Redshift Survey to measure the dependence of the b J ‐band galaxy luminosity function on large‐scale environment, defined by density contrast in spheres of radius 8 h −1 Mpc , and on spectral type, determined from principal component analysis. We find that the galaxy populations at both extremes of density differ significantly from that at the mean density. The population in voids is dominated by late types and shows, relative to the mean, a deficit of galaxies that becomes increasingly pronounced at magnitudes brighter than M b J−5log 10 h ≲−18.5 . In contrast, cluster regions have a relative excess of very bright early‐type galaxies with M b J−5log 10 h ≲−21 . Differences in the mid‐ to faint‐end population between environments are significant: at M b J−5log 10 h =−18 early‐ and late‐type cluster galaxies show comparable abundances, whereas in voids the late types dominate by almost an order of magnitude. We find that the luminosity functions measured in all density environments, from voids to clusters, can be approximated by Schechter functions with parameters that vary smoothly with local density, but in a fashion that differs strikingly for early‐ and late‐type galaxies. These observed variations, combined with our finding that the faint‐end slope of the overall luminosity function depends at most weakly on density environment, may prove to be a significant challenge for models of galaxy formation.