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

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 × 10⁴⁴ 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 ≤ 1 Mpc and ΔV ≤ σ using our σ estimates containing 21 galaxy clusters with more than six spectroscopic members. We have also defined a sample of photometric members with galaxies that satisfy r_p ≤ 1 Mpc, and ΔV ≤ 6000 km s^-1 including 45 galaxy clusters with more than six cluster members. We have divided the redshift range in three bins: z ≤ 0.065; 0.065 < z < 0.10; and z ≥ 0.10. We have stacked the galaxy clusters using the spectroscopic sub-sample and we have computed the best RS linear fit within 1σ dispersion. With the photometric sub-sample we have added more data to the RS obtaining the photometric 1σ 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.