The Norma cluster (ACO3627): II. The near infrared K_s-band luminosity function

TL;DR

This study presents a deep near-infrared K_s-band luminosity function for the Norma cluster, extending into the dwarf galaxy regime and comparing its shape to other environments, finding consistent parameters across different settings.

Contribution

The paper provides the first detailed K_s-band luminosity function for the Norma cluster, including dwarf galaxies, and compares it with field LFs to assess environmental effects.

Findings

Luminosity function well-fit by Schechter function with M_Ks* = -25.39 mag

Faint-end slope of alpha = -1.26, consistent with other environments

LF shape similar to optical and near-infrared studies in different environments

Abstract

A deep K_s-band photometric catalogue of galaxies at the core of the rich, nearby Norma cluster (ACO3627) is presented. The survey covers about 45 by 45 square arcmin (slightly less than 1/3 Abell radius), which corresponds to approx. 0.8 Mpc^2 at the adopted distance (v_cmb/H0) of 70 Mpc of this cluster. The survey is estimated to be complete to a magnitude of M_Ks <~ -19.5 mag. This extends into the dwarf regime, 6 magnitudes below M_Ks*. The catalogue contains 390 objects, 235 of which are classified as likely or definite galaxies and 155 as candidate galaxies. The Ks-band luminosity function (LF) is constructed from the photometric sample, using a spectroscopic subsample to correct for fore- and background contamination. We fit a Schechter function with a characteristic magnitude of M_Ks* = -25.39 \pm 0.80 mag and faint-end slope of alpha = -1.26 \pm 0.10 to the data. The shape of the LF is similar to those found in previous determinations of the cluster LF, in both optical and near infrared. The Schechter parameters agree well with those of recent field LFs, suggesting that both the shape of the bright end and the faint end slope are relatively insensitive to environment.