The Environmental Dependence of the Infrared Luminosity and Stellar Mass Functions

We investigate the dependence of the galaxy infrared luminosity function (LF) and the associated stellar mass function (SMF) on environment and spectral type using photometry from the Two Micron All Sky Survey and redshifts from the Las Campanas Redshift Survey for galaxies brighter than M J < -19 + 5 log h . In the field environment, the LFs of galaxies with emission lines have much steeper faint-end slopes (α J = -1.39) than those of galaxies without emission lines (α J = -0.59). In the cluster environment, however, even the non-emission-line galaxies have a steep faint-end LF (α J = -1.22). There is also a significant (95%) difference between the overall cluster and field LFs, Δα J = -0.34 and Δ M * J = -0.54. All these variations are more pronounced in the SMFs, which we compute by relating the strength of the 4000 Å break in the optical spectra to a stellar mass-to-light ratio.