A redshift survey of the nearby galaxy cluster Abell 2199 : No upturn of the faint-end slope of galaxy luminosity function

TL;DR

This study measures the galaxy luminosity function in Abell 2199, finding a faint-end slope similar to other clusters and challenging previous claims of a steep upturn, suggesting environmental effects suppress low-mass galaxy formation.

Contribution

The paper provides a detailed measurement of the faint-end slope of the luminosity function in Abell 2199 using enhanced spectroscopic data, showing no steep upturn as previously claimed.

Findings

Faint-end slope $eta = -1.23$ in Abell 2199.

No evidence of a steep upturn in the luminosity function.

Environmental processes may suppress low-mass galaxy formation.

Abstract

We determine the galaxy luminosity function of cluster galaxies in the nearby galaxy cluster Abell 2199 (A2199), focusing on the faint-end slope down to $M_r \sim -14.5$. To achieve this, we augment the existing dataset by adding redshift data from our deep MMT/Hectospec survey and from the Dark Energy Spectroscopic Instrument (DESI), significantly improving the spectroscopic completeness down to $r_{\mathrm{petro},0} = 20.8$ within the central $30^\prime$ region. The resulting luminosity function is well described by a Schechter function with a characteristic magnitude $M^* = -21.30 \pm 0.27$ and a faint-end slope $\alpha = -1.23 \pm 0.05$. This faint-end slope is consistent with those measured in the nearby Coma and Virgo clusters and in a cluster from the TNG50 cosmological simulation, and is slightly shallower than that of field galaxies. These findings indicate that the previously claimed steep faint-end upturn (with $\alpha \sim -2$) in nearby galaxy clusters is not supported. Instead, they indicate that environmental processes in dense cluster cores does not seem to trigger the formation or survival of low-mass galaxies, thereby preventing a steep faint-end upturn in the luminosity function.