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Deep Chandra Observations of the z = 1.16 Relaxed, Cool-core Galaxy Cluster SPT-CL J2215-3537

Haley R. Stueber, Adam B. Mantz, Steven W. Allen, Anthony M. Flores, R. Glenn Morris, Abigail Y. Pan, Taweewat Somboonpanyakul, Lindsey E. Bleem, Michael Calzadilla, Benjamin Floyd, Julie Hlavacek-Larrondo, Michael McDonald, Arnab Sarkar

TL;DR

This study presents deep Chandra observations of the $z=1.16$ relaxed, cool-core cluster SPT-CL J2215-3537, resolving its cool core and constraining its thermodynamic and cosmological properties. By applying both non-parametric deprojection and hydrostatic-NFW modeling (with a modest inner exclusion) and using SPA morphology metrics to verify relaxation, the authors derive density, temperature, entropy, and metallicity profiles, along with scaling relations for gas mass, temperature, and X-ray luminosity. They also constrain the X-ray gas mass fraction and halo concentration, illustrating that SPT J2215 is consistent with self-similar evolution and serves as a high-redshift benchmark for cooling, feedback, and cluster cosmology. The results illuminate the evolution of massive clusters and provide robust tests of cosmological models using a distant, dynamically relaxed system.

Abstract

Galaxy clusters serve as a unique and valuable laboratory for probing cosmological models and understanding astrophysics at the high-mass limit of structure formation. Clusters that are dynamically relaxed are especially useful targets of study because of their morphological and dynamical simplicity. However, at redshifts z > 1, very few such clusters have been identified. We present results from new Chandra observations of the cluster SPT-CL J2215-3537 (hereafter SPT J2215), at z = 1.16, the second most distant relaxed, cool-core cluster identified to date. We place constraints on the cluster's total mass profile and investigate its thermodynamic profiles, scaling relations (gas mass, average temperature, and X-ray luminosity), and metal enrichment, resolving the cool core and providing essential context for the massive starburst seen in its central galaxy. We contextualize the thermodynamic and cosmological properties of the cluster within a sample of well-studied, lower-redshift relaxed systems. In this way, SPT J2215 serves as a powerful high-redshift benchmark for understanding the formation of cool cores and the evolution of massive clusters of galaxies.

Deep Chandra Observations of the z = 1.16 Relaxed, Cool-core Galaxy Cluster SPT-CL J2215-3537

TL;DR

This study presents deep Chandra observations of the relaxed, cool-core cluster SPT-CL J2215-3537, resolving its cool core and constraining its thermodynamic and cosmological properties. By applying both non-parametric deprojection and hydrostatic-NFW modeling (with a modest inner exclusion) and using SPA morphology metrics to verify relaxation, the authors derive density, temperature, entropy, and metallicity profiles, along with scaling relations for gas mass, temperature, and X-ray luminosity. They also constrain the X-ray gas mass fraction and halo concentration, illustrating that SPT J2215 is consistent with self-similar evolution and serves as a high-redshift benchmark for cooling, feedback, and cluster cosmology. The results illuminate the evolution of massive clusters and provide robust tests of cosmological models using a distant, dynamically relaxed system.

Abstract

Galaxy clusters serve as a unique and valuable laboratory for probing cosmological models and understanding astrophysics at the high-mass limit of structure formation. Clusters that are dynamically relaxed are especially useful targets of study because of their morphological and dynamical simplicity. However, at redshifts z > 1, very few such clusters have been identified. We present results from new Chandra observations of the cluster SPT-CL J2215-3537 (hereafter SPT J2215), at z = 1.16, the second most distant relaxed, cool-core cluster identified to date. We place constraints on the cluster's total mass profile and investigate its thermodynamic profiles, scaling relations (gas mass, average temperature, and X-ray luminosity), and metal enrichment, resolving the cool core and providing essential context for the massive starburst seen in its central galaxy. We contextualize the thermodynamic and cosmological properties of the cluster within a sample of well-studied, lower-redshift relaxed systems. In this way, SPT J2215 serves as a powerful high-redshift benchmark for understanding the formation of cool cores and the evolution of massive clusters of galaxies.
Paper Structure (3 sections, 1 figure, 1 table)

This paper contains 3 sections, 1 figure, 1 table.

Table of Contents

  1. Introduction
  2. Data & Methods
  3. Results and Discussion

Figures (1)

  • Figure 1: Left: Broadband (0.6--7.0 keV) Chandra exposure of SPT J2215 ($z = 1.16$) totaling $\sim 200$ ks. The dashed and solid cyan circles show our estimates of $r_{500}$ and $r_{2500}$, respectively. Right: Zoom-in of the cluster image on the left to the region within $r_{2500}$, where the BCG is indicated by a red 'X'.