The galaxy luminosity function in groups and clusters: the faint-end upturn and the connection to the field luminosity function

Understand

We characterize the luminosity functions of galaxies residing in $z\sim0$ groups and clusters over the broadest ranges of luminosity and mass reachable by the Sloan Digital Sky Survey.

• Our measurements cover four orders of magnitude in luminosity, down to about $M_r=-12$ mag or $L=10^7\,L_\odot$, and three orders of magnitude in halo mass, from $10^{12}$ to $10^{15} \, {\rm M}_\odot$.
• We find a characteristic scale, $M_r\sim-18$ mag or $L\sim10^9\, L_\odot$, below which the slope of the luminosity function becomes systematically steeper.
• This trend is present for all halo masses and originates mostly from red satellites.