# Low X-Ray Luminosity Galaxy Clusters. IV. SDSS galaxy clusters at z < 0.2

## TL;DR

This study analyzes low X-ray luminosity galaxy clusters from SDSS at z < 0.2, examining their galaxy populations, red sequence, and luminosity functions to compare with groups and poor clusters.

## Contribution

It provides a detailed analysis of galaxy clusters with low X-ray luminosity, including spectroscopic and photometric member selection, red sequence fitting, and luminosity function estimation.

## Key findings

- Red sequence parameters are similar to those of groups and poor clusters.
- Luminosity functions fit well with Schechter functions, consistent with low-luminosity cluster properties.
- Stacked cluster analysis reveals consistent galaxy population characteristics across redshift bins.

## Abstract

This is the fourth of a series of papers on low X-ray luminosity galaxy clusters. The sample comprises 45 galaxy clusters with X-ray luminosities fainter than 0.7 10$^{44}$ erg s$^{-1}$ at redshifts lower than 0.2 in the regions of the Sloan Digital Sky Survey. The sample of spectroscopic members of the galaxy clusters was obtained with the criteria: r$_p$ $\le$ 1 Mpc and $\Delta V \leq \sigma$ using our $\sigma$ estimates containing 21 galaxy clusters with more than 6 spectroscopic members. We have also defined a sample of photometric members with galaxies that satisfy r$_p \le $ 1 Mpc, and $\Delta V \leq $ 6000 \kms including 45 galaxy clusters with more than 6 cluster members. We have divided the redshift range in three bins: $z \leq 0.065$; 0.065 $<$ z $<$ 0.10; and z $\ge$ 0.10. We have stacked the galaxy clusters using the spectroscopic sub-sample and we have computed the best RS linear fit within 1$\sigma$ dispersion. With the photometric sub-sample, we have added more data to the RS obtaining the photometric 1$\sigma$ dispersion relative to the spectroscopic RS fit. We have computed the luminosity function using the $1/V_{max}$ method fitting it with a Schechter function. The obtained parameters for these galaxy clusters with low X-ray luminosities are remarkably similar to those for groups and poor galaxy clusters at these lower redshifts.