Using data from the 2 degree Field Galaxy Redshift Survey ( 2dFGRS ) we compute the conditional luminosity functions ( CLFs ) of early- and late-type galaxies .
These functions give the average number of galaxies with luminosities in the range L \pm { d } L / 2 that reside in a halo of mass M , and are a powerful statistical tool to link the distribution of galaxies to that of dark matter haloes .
Although some amount of degeneracy remains , the CLFs are well constrained .
They indicate that the average mass-to-light ratios of dark matter haloes have a minimum of \sim 100 h\ > ( { M } / { L } ) _ { \odot } around a halo mass of \sim 3 \times 10 ^ { 11 } h ^ { -1 } \ > { M _ { \odot } } .
Towards lower masses \langle M / L \rangle increases rapidly , and matching the faint-end slope of the observed luminosity function ( LF ) requires that haloes with M < 10 ^ { 10 } h ^ { -1 } \ > { M _ { \odot } } are virtually devoid of galaxies .
At the high mass end , the observed clustering properties of galaxies require that clusters have b _ { J } -band mass-to-light ratios in the range 500 - 1000 h\ > ( { M } / { L } ) _ { \odot } .
Finally , the fact that early-type galaxies are more strongly clustered than late-type galaxies requires that the fraction of late-type galaxies is a strongly declining function of halo mass .
We compute two-point correlation functions as function of both luminosity and galaxy type .
The agreement with observations , in terms of normalization and power-law slope , is remarkably good .
When including predictions for the correlation functions of faint galaxies we find a weak ( strong ) luminosity dependence for the late ( early ) type galaxies .
We also investigate the inferred halo occupation numbers .
Late-type and faint galaxies reveal a shallower \langle N \rangle ( M ) than bright , early-type galaxies , which explains why \langle N \rangle ( M ) transforms from a single power-law for bright galaxies to a more complicated form when fainter galaxies are included .
Finally we compare our CLFs with predictions from several semi-analytical models for galaxy formation .
As long as these models accurately fit the 2dFGRS luminosity function the agreement with our predictions is remarkably good .
This indicates that the technique used here has recovered a statistical description of how galaxies populate dark matter haloes which is not only in perfect agreement with the data , but which in addition fits nicely within the standard framework for galaxy formation .