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| Main Authors: | , , , , , , , , , , |
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| Format: | Preprint |
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2026
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2603.06785 |
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| _version_ | 1866915840359661568 |
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| author | White, Laurel McDonald, Michael Allen, Steven W. Bautz, Marshall W. Calzadilla, Michael Garmire, Gordon P. Hlavacek-Larrondo, Julie Kraft, Ralph Mantz, Adam B. Somboonpanyakul, Taweewat Vikhlinin, Alexey |
| author_facet | White, Laurel McDonald, Michael Allen, Steven W. Bautz, Marshall W. Calzadilla, Michael Garmire, Gordon P. Hlavacek-Larrondo, Julie Kraft, Ralph Mantz, Adam B. Somboonpanyakul, Taweewat Vikhlinin, Alexey |
| contents | With rapid improvements in the assembly of large samples of galaxy clusters, we are approaching the ability to study clusters at $z\gtrsim2$. Evolutionary studies comparing these distant clusters to the clusters in our local universe depend heavily on the reliability of low-redshift cluster samples, most of which are subject to X-ray selection effects, biasing them to relaxed, cool core clusters. Here, we introduce the Cluster Evolutionary Reference Ensemble At Low-$z$ (CEREAL) sample, composed of Chandra X-ray observations of 169 galaxy clusters that have been selected from the Planck Sunyaev-Zel'dovich catalog. CEREAL has a simple and well-understood selection function, spans an order of magnitude in mass at $z\sim0.15$, and has uniform, high-resolution X-ray follow-up. We present the full sample and provide results based on X-ray surface brightness properties, finding significantly more non-cool core systems than in X-ray-selected samples. We use surface brightness concentration (c$_\mathrm{SB}$) as a proxy for cool core strength and centroid shift ($w$) to measure dynamical state. Over the full sample, we find a cool core (c$_\mathrm{SB} > 0.075$) fraction of $0.39_{-0.04}^{+0.04}$, a strong cool core (c$_\mathrm{SB} > 0.155$) fraction of $0.13_{-0.03}^{+0.03}$, and a dynamically relaxed ($w<0.01$) fraction of $0.42_{-0.04}^{+0.04}$. We find no mass dependence in the fraction of clusters that appear relaxed or have cool cores. We quantify the rarity of X-ray-bright central point sources (L$_\mathrm{nuc,~2-10~keV} > 10^{43}$ erg s$^{-1}$), finding them to be intrinsically rare ($0.7_{-0.5}^{+1.2}$\% of massive, low-z clusters) with a notable increase in occurrence rate at the centers of cool cores. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_06785 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | The Cluster Evolutionary Reference Ensemble at Low-$z$ (CEREAL) Sample of Galaxy Clusters I: X-ray Morphological Properties and Demographics White, Laurel McDonald, Michael Allen, Steven W. Bautz, Marshall W. Calzadilla, Michael Garmire, Gordon P. Hlavacek-Larrondo, Julie Kraft, Ralph Mantz, Adam B. Somboonpanyakul, Taweewat Vikhlinin, Alexey Cosmology and Nongalactic Astrophysics With rapid improvements in the assembly of large samples of galaxy clusters, we are approaching the ability to study clusters at $z\gtrsim2$. Evolutionary studies comparing these distant clusters to the clusters in our local universe depend heavily on the reliability of low-redshift cluster samples, most of which are subject to X-ray selection effects, biasing them to relaxed, cool core clusters. Here, we introduce the Cluster Evolutionary Reference Ensemble At Low-$z$ (CEREAL) sample, composed of Chandra X-ray observations of 169 galaxy clusters that have been selected from the Planck Sunyaev-Zel'dovich catalog. CEREAL has a simple and well-understood selection function, spans an order of magnitude in mass at $z\sim0.15$, and has uniform, high-resolution X-ray follow-up. We present the full sample and provide results based on X-ray surface brightness properties, finding significantly more non-cool core systems than in X-ray-selected samples. We use surface brightness concentration (c$_\mathrm{SB}$) as a proxy for cool core strength and centroid shift ($w$) to measure dynamical state. Over the full sample, we find a cool core (c$_\mathrm{SB} > 0.075$) fraction of $0.39_{-0.04}^{+0.04}$, a strong cool core (c$_\mathrm{SB} > 0.155$) fraction of $0.13_{-0.03}^{+0.03}$, and a dynamically relaxed ($w<0.01$) fraction of $0.42_{-0.04}^{+0.04}$. We find no mass dependence in the fraction of clusters that appear relaxed or have cool cores. We quantify the rarity of X-ray-bright central point sources (L$_\mathrm{nuc,~2-10~keV} > 10^{43}$ erg s$^{-1}$), finding them to be intrinsically rare ($0.7_{-0.5}^{+1.2}$\% of massive, low-z clusters) with a notable increase in occurrence rate at the centers of cool cores. |
| title | The Cluster Evolutionary Reference Ensemble at Low-$z$ (CEREAL) Sample of Galaxy Clusters I: X-ray Morphological Properties and Demographics |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2603.06785 |