Robust quantitative measures of cluster X-ray morphology, and comparisons between cluster characteristics

Yasuhiro Hashimoto, H. Böhringer, J. P. Henry, G. Hasinger, G. Szokoly

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Aims. To investigate the possible relationships between dynamical status and other important characteristics of galaxy clusters, we conducted a study of X-ray cluster morphology using a sample of 101 clusters at redshift z ∼ 0.05-1 taken from the Chandra archive. Methods. The X-ray morphology is quantitatively characterized by a series of objectively measured simple statistics of the X-ray surface brightness distribution, which are designed to be robust against variations of image quality caused by various exposure times and various cluster redshifts. Using these measures, we quantitatively investigated the relationships between the cluster X-ray morphology and various other cluster characteristics. Results. We found: (1) Our measures are robust against various image quality effects introduced by exposure time difference, and various cluster redshifts. (2) The distorted and non-distorted clusters occupy well-defined loci in the L - T plane, demonstrating that the measurements of the global luminosity and temperature for distorted clusters should be interpreted with caution, or alternatively, a rigorous morphological characterization is necessary when we use a sample of clusters with heterogeneous morphological characteristics to investigate the L - T or other related scaling relations. (3) Ellipticity and Offcenterness show no evolutionary effects between high and low redshift cluster subsets, while there may be a hint of weak evolution for Concentration and Asymmetry, such that high-z clusters show more distorted morphology. (4) No correlation is found between X-ray morphology and X-ray luminosity or X-ray morphology and X-ray temperature of clusters, implying that interaction of clusters may not enhance or decrease the luminosity or temperature of clusters for extended periods of time. (5) Clusters are scattered and occupy various places in the plane composed of two X-ray morphological measures, showing a wide variety of characteristics. (6) Relatively strong correlations in Asymmetry-Concentration and Offcenter-Concentration plots indicate that low concentration clusters generally show a high degree of asymmetry or skewness, illustrating the fact that there are not many highly-extended smooth symmetric clusters. Similarly, a correlation between Asymmetry and Ellipticity may imply that there are not many highly-elongated but otherwise smooth symmetric clusters.

Original languageEnglish
Pages (from-to)485-499
Number of pages15
JournalAstronomy and Astrophysics
Volume467
Issue number2
DOIs
Publication statusPublished - 2007 May 1

Fingerprint

x rays
asymmetry
comparison
temperature
skewness
luminosity
ellipticity
brightness distribution
loci
set theory
low concentrations
plots
statistics
galaxies
scaling
exposure
effect

Keywords

  • Galaxies: clusters: general
  • Galaxies: evolution
  • Galaxies: high-redshift
  • X-rays: galaxies: clusters

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Robust quantitative measures of cluster X-ray morphology, and comparisons between cluster characteristics. / Hashimoto, Yasuhiro; Böhringer, H.; Henry, J. P.; Hasinger, G.; Szokoly, G.

In: Astronomy and Astrophysics, Vol. 467, No. 2, 01.05.2007, p. 485-499.

Research output: Contribution to journalArticle

Hashimoto, Yasuhiro ; Böhringer, H. ; Henry, J. P. ; Hasinger, G. ; Szokoly, G. / Robust quantitative measures of cluster X-ray morphology, and comparisons between cluster characteristics. In: Astronomy and Astrophysics. 2007 ; Vol. 467, No. 2. pp. 485-499.
@article{5527eeb7f97b4eab8edde1c643c9a586,
title = "Robust quantitative measures of cluster X-ray morphology, and comparisons between cluster characteristics",
abstract = "Aims. To investigate the possible relationships between dynamical status and other important characteristics of galaxy clusters, we conducted a study of X-ray cluster morphology using a sample of 101 clusters at redshift z ∼ 0.05-1 taken from the Chandra archive. Methods. The X-ray morphology is quantitatively characterized by a series of objectively measured simple statistics of the X-ray surface brightness distribution, which are designed to be robust against variations of image quality caused by various exposure times and various cluster redshifts. Using these measures, we quantitatively investigated the relationships between the cluster X-ray morphology and various other cluster characteristics. Results. We found: (1) Our measures are robust against various image quality effects introduced by exposure time difference, and various cluster redshifts. (2) The distorted and non-distorted clusters occupy well-defined loci in the L - T plane, demonstrating that the measurements of the global luminosity and temperature for distorted clusters should be interpreted with caution, or alternatively, a rigorous morphological characterization is necessary when we use a sample of clusters with heterogeneous morphological characteristics to investigate the L - T or other related scaling relations. (3) Ellipticity and Offcenterness show no evolutionary effects between high and low redshift cluster subsets, while there may be a hint of weak evolution for Concentration and Asymmetry, such that high-z clusters show more distorted morphology. (4) No correlation is found between X-ray morphology and X-ray luminosity or X-ray morphology and X-ray temperature of clusters, implying that interaction of clusters may not enhance or decrease the luminosity or temperature of clusters for extended periods of time. (5) Clusters are scattered and occupy various places in the plane composed of two X-ray morphological measures, showing a wide variety of characteristics. (6) Relatively strong correlations in Asymmetry-Concentration and Offcenter-Concentration plots indicate that low concentration clusters generally show a high degree of asymmetry or skewness, illustrating the fact that there are not many highly-extended smooth symmetric clusters. Similarly, a correlation between Asymmetry and Ellipticity may imply that there are not many highly-elongated but otherwise smooth symmetric clusters.",
keywords = "Galaxies: clusters: general, Galaxies: evolution, Galaxies: high-redshift, X-rays: galaxies: clusters",
author = "Yasuhiro Hashimoto and H. B{\"o}hringer and Henry, {J. P.} and G. Hasinger and G. Szokoly",
year = "2007",
month = "5",
day = "1",
doi = "10.1051/0004-6361:20065125",
language = "English",
volume = "467",
pages = "485--499",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",
number = "2",

}

TY - JOUR

T1 - Robust quantitative measures of cluster X-ray morphology, and comparisons between cluster characteristics

AU - Hashimoto, Yasuhiro

AU - Böhringer, H.

AU - Henry, J. P.

AU - Hasinger, G.

AU - Szokoly, G.

PY - 2007/5/1

Y1 - 2007/5/1

N2 - Aims. To investigate the possible relationships between dynamical status and other important characteristics of galaxy clusters, we conducted a study of X-ray cluster morphology using a sample of 101 clusters at redshift z ∼ 0.05-1 taken from the Chandra archive. Methods. The X-ray morphology is quantitatively characterized by a series of objectively measured simple statistics of the X-ray surface brightness distribution, which are designed to be robust against variations of image quality caused by various exposure times and various cluster redshifts. Using these measures, we quantitatively investigated the relationships between the cluster X-ray morphology and various other cluster characteristics. Results. We found: (1) Our measures are robust against various image quality effects introduced by exposure time difference, and various cluster redshifts. (2) The distorted and non-distorted clusters occupy well-defined loci in the L - T plane, demonstrating that the measurements of the global luminosity and temperature for distorted clusters should be interpreted with caution, or alternatively, a rigorous morphological characterization is necessary when we use a sample of clusters with heterogeneous morphological characteristics to investigate the L - T or other related scaling relations. (3) Ellipticity and Offcenterness show no evolutionary effects between high and low redshift cluster subsets, while there may be a hint of weak evolution for Concentration and Asymmetry, such that high-z clusters show more distorted morphology. (4) No correlation is found between X-ray morphology and X-ray luminosity or X-ray morphology and X-ray temperature of clusters, implying that interaction of clusters may not enhance or decrease the luminosity or temperature of clusters for extended periods of time. (5) Clusters are scattered and occupy various places in the plane composed of two X-ray morphological measures, showing a wide variety of characteristics. (6) Relatively strong correlations in Asymmetry-Concentration and Offcenter-Concentration plots indicate that low concentration clusters generally show a high degree of asymmetry or skewness, illustrating the fact that there are not many highly-extended smooth symmetric clusters. Similarly, a correlation between Asymmetry and Ellipticity may imply that there are not many highly-elongated but otherwise smooth symmetric clusters.

AB - Aims. To investigate the possible relationships between dynamical status and other important characteristics of galaxy clusters, we conducted a study of X-ray cluster morphology using a sample of 101 clusters at redshift z ∼ 0.05-1 taken from the Chandra archive. Methods. The X-ray morphology is quantitatively characterized by a series of objectively measured simple statistics of the X-ray surface brightness distribution, which are designed to be robust against variations of image quality caused by various exposure times and various cluster redshifts. Using these measures, we quantitatively investigated the relationships between the cluster X-ray morphology and various other cluster characteristics. Results. We found: (1) Our measures are robust against various image quality effects introduced by exposure time difference, and various cluster redshifts. (2) The distorted and non-distorted clusters occupy well-defined loci in the L - T plane, demonstrating that the measurements of the global luminosity and temperature for distorted clusters should be interpreted with caution, or alternatively, a rigorous morphological characterization is necessary when we use a sample of clusters with heterogeneous morphological characteristics to investigate the L - T or other related scaling relations. (3) Ellipticity and Offcenterness show no evolutionary effects between high and low redshift cluster subsets, while there may be a hint of weak evolution for Concentration and Asymmetry, such that high-z clusters show more distorted morphology. (4) No correlation is found between X-ray morphology and X-ray luminosity or X-ray morphology and X-ray temperature of clusters, implying that interaction of clusters may not enhance or decrease the luminosity or temperature of clusters for extended periods of time. (5) Clusters are scattered and occupy various places in the plane composed of two X-ray morphological measures, showing a wide variety of characteristics. (6) Relatively strong correlations in Asymmetry-Concentration and Offcenter-Concentration plots indicate that low concentration clusters generally show a high degree of asymmetry or skewness, illustrating the fact that there are not many highly-extended smooth symmetric clusters. Similarly, a correlation between Asymmetry and Ellipticity may imply that there are not many highly-elongated but otherwise smooth symmetric clusters.

KW - Galaxies: clusters: general

KW - Galaxies: evolution

KW - Galaxies: high-redshift

KW - X-rays: galaxies: clusters

UR - http://www.scopus.com/inward/record.url?scp=34249334341&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34249334341&partnerID=8YFLogxK

U2 - 10.1051/0004-6361:20065125

DO - 10.1051/0004-6361:20065125

M3 - Article

VL - 467

SP - 485

EP - 499

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

IS - 2

ER -