HIFLUGCS: X-ray luminosity -- dynamical mass relation and its implications for mass calibrations with the SPIDERS and 4MOST surveys

TL;DR

This study establishes the X-ray luminosity versus dynamical mass relation for nearby galaxy clusters, assesses the impact of galaxy redshift sampling on mass estimates, and highlights the potential of upcoming surveys for accurate cluster mass calibration.

Contribution

It provides a detailed analysis of the L-M relation using extensive X-ray and optical data, and evaluates the effectiveness of spectroscopic follow-up strategies for high-redshift cluster mass calibration.

Findings

L-M relation is consistent across disturbed and undisturbed clusters.

Cool-core clusters contribute significantly to scatter, indicating structural formation effects.

Spectroscopic follow-up with limited galaxy redshifts can still achieve within 50% mass estimate accuracy.

Abstract

We present the X-ray luminosity (L) versus dynamical mass (M) relation for 63 nearby clusters in the HIFLUGCS. The luminosity measurements are obtained based on ~1.3 Ms of clean XMM data and ROSAT pointed observations. The masses are estimated using optical spectroscopic redshifts of 13647 cluster galaxies in total. Given sufficient numbers of member galaxies in computing the dynamical masses, the L-M relations agree between the disturbed and undisturbed clusters. The cool-core clusters still dominate the scatter in the L-M relation even when a core corrected X-ray luminosity is used, which indicates that the scatter mainly reflects the structure formation history of the clusters. As shown by the clusters with a small number of redshifts, the dynamical masses can be underestimated leading to a biased scaling relation. To investigate the potential of spectroscopic surveys to follow up high-redshift galaxy clusters/groups observed in X-ray surveys for the identifications and mass calibrations, we carried out Monte-Carlo re-sampling of the cluster galaxy redshifts and calibrated the uncertainties of the redshift and dynamical mass estimates when only reduced numbers of galaxy redshifts per cluster are available. The re-sampling considers the SPIDERS and 4MOST configurations, designed for the follow-up of the eROSITA clusters, and was carried out for each cluster at the actual cluster redshift as well as at z=0.2, 0.4, 0.6, and 0.8. For following up very distant cluster/groups, we carried out the mass calibration based on the re-sampling with only 10zs/cluster, and redshift calibration based on the re-sampling with only 5zs/cluster and 10zs/cluster, respectively. Our results demonstrate the power of combining upcoming X-ray and optical spectroscopic surveys for mass calibration. The scatter in the dynamical mass estimates for the clusters with at least ten members is within 50%.