  We use the 2dF Galaxy Redshift Survey to measure the dependence of the
bJ-band galaxy luminosity function on large-scale environment, defined by
density contrast in spheres of radius 8h-1Mpc, 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_bJ-5log10h <-18.5. In contrast, cluster regions have a relative
excess of very bright early-type galaxies with M_bJ-5log10h < -21. Differences
in the mid to faint-end population between environments are significant: at
M_bJ-5log10h=-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 which 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.
