Mass Variance from Archival X-ray Properties of Dark Energy Survey Year-1 Galaxy Clusters
Using archival X-ray observations and a log-normal population model, we estimate constraints on the intrinsic scatter in halo mass at fixed optical richness for a galaxy cluster sample identified in Dark Energy Survey Year-One (DES-Y1) data with the redMaPPer algorithm. We examine the scaling behavior of X-ray temperatures, $$T_X$$, with optical richness, $$\lambda_{RM}$$, for clusters in the redshift range $0.2<0.7$. X-ray temperatures are obtained from Chandra and XMM observations for 58 and 110 redMaPPer systems, respectively. Despite non-uniform sky coverage, the $$T_X$$ measurements are $$> 50\%$$ complete for clusters with $$\lambda_{RM} > 130$$. Regression analysis on the two samples produces consistent posterior scaling parameters, from which we derive a combined constraint on the residual scatter, $$\sigma_{\ln Tx | \lambda} = 0.275 \pm 0.019$$. Joined with constraints for $$T_X$$ scaling with halo mass from the Weighing the Giants program and richness--temperature covariance estimates from the LoCuSS sample, we derive the richness-conditioned scatter in mass, $$\sigma_{\ln M | \lambda} = 0.30 \pm 0.04\, _{({\rm stat})} \pm 0.09\, _{({\rm sys})}$$, at an optical richness of approximately 70. Uncertainties in external parameters, particularly the slope and variance of the $$T_X$$--mass relation and the covariance of $$T_X$$ and $$\lambda_{RM}$$ at fixed mass, dominate the systematic error. The $$95\%$$ confidence region from joint sample analysis is relatively broad, $$\sigma_{\ln M | \lambda} \in [0.14, \, 0.55]$$, or a factor ten in variance.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- Contributing Organization:
- DES
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 1545112
- Report Number(s):
- arXiv:1903.08042; FERMILAB-PUB-19-162-AD-AE-CD; 1725779
- Journal Information:
- Mon.Not.Roy.Astron.Soc., Journal Name: Mon.Not.Roy.Astron.Soc.
- Country of Publication:
- United States
- Language:
- English
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