CHANDRA STUDIES OF THE X-RAY GAS PROPERTIES OF GALAXY GROUPS

By Ming Sun, G. Mark Voit, M. Donahue, C. Jones, W. Forman, A. Vikhlinin. 2008

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We present a systematic analysis of 43 nearby galaxy groups (kT500 = 0.7–2.7 keV or M500 = 1013–1014 h−1 M☉, 0.012 <z< 0.12), based on Chandra archival data. With robust background subtraction and modeling, we trace gas properties to at least r2500 for all 43 groups. For 11 groups, gas properties can be robustly derived to r500. For an additional 12 groups, we derive gas properties to at least r1000 and estimate properties at r500 from extrapolation. We show that in spite of the large variation in temperature profiles inside 0.15 r500, the temperature profiles of these groups are similar at > 0.15 r500 and are consistent with a “universal temperature profile.” We present the K–T relations at six characteristic radii (30 kpc, 0.15 r500, r2500, r1500, r1000, and r500), for 43 groups from this work and 14 clusters from the Vikhlinin et al. () sample. Despite large scatter in the entropy values at 30 kpc and 0.15 r500, the intrinsic scatter at r2500 is much smaller and remains the same (∼ 10%) to r500. The entropy excess at r500 is confirmed, in both groups and clusters, but the magnitude is smaller than previous ROSAT and ASCA results. We also present scaling relations for the gas fraction. It appears that the average gas fraction between r2500 and r500 has no temperature dependence, ∼ 0.12 for 1–10 keV systems. The group gas fractions within r2500 are generally low and have large scatter. This work shows that the difference of groups from hotter clusters stems from the difficulty of compressing group gas inside of r2500. The large scatter of the group gas fraction within r2500 causes large scatter in the group entropy around the center and may be responsible for the large scatter of the group luminosities. Nevertheless, the groups appear more regular and more like clusters beyond r2500 from the results on gas fraction and entropy. Therefore, mass proxies can be extended into low-mass systems. The M500–T500 and M500–YX,500 relations derived in this work are indeed well behaved down to at least 2 ×1013 h−1 M☉.

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Citations in the corpus

GALAXY CLUSTERS SELECTED WITH THE SUNYAEV–ZEL'DOVICH EFFECT FROM 2008 SOUTH POLE TELESCOPE OBSERVATIONS (2010, methodology): “The Bode et al. (2009) gas model is calibrated against X-ray scaling relations measured from low-redshift cluster samples (Vikhlinin et al. 2006; Sun et al. 2009), but assumes an evolving stellar-mass fraction which may drive the stronger redshift evolution.”
Mechanical feedback from active galactic nuclei in galaxies, groups and clusters (2012, background): “At the same time, their central cooling times are often shorter than those in rich clusters (Sun et al 2009, Sun 2012).”
Formation of Galaxy Clusters (2012, background): “For instance, Sun et al. (2009) showed that entropy measured at r500 has a scaling with temperature quite close to the self–similar prediction, yet its level is higher than expected from a simple model in which only gravity determines the evolution of the intra–cluster baryons.”
Cosmology and astrophysics from relaxed galaxy clusters - II. Cosmological constraints (2014, background): “Comparison of fgas values measured for groups and intermediate-mass clusters supports this picture (Sun et al. 2009).”
GALAXY CLUSTER BARYON FRACTIONS REVISITED (2013, methodology): “The two Chandra studies, Sun et al. (2009) and Vikhlinin et al. (2006), together cover the full mass range from groups to clusters.”
What drives the growth of black holes (2011, background): “Observations show that the LX– TX relation is remarkably steep at the low-temperature end, suggesting that small to moderate-mass groups have lower baryon fractions in the centers of their darkmatter halos than higher-mass systems (e.g., Sun et al., 2009; Giodini et al., 2009).”
The Observed Growth of Massive Galaxy Clusters II: X-ray Scaling Relations (2009, result): “E-mail: amantz@slac.stanford.edu The construction of X-ray flux-selected cluster samples out to redshift z = 0.5 and beyond has now enabled investigations of dark energy using these data (Mantz et al. 2008, hereafter M08; Vikhlinin et al. 2009b).”
The accretion of galaxies into groups and clusters (2009, background): “But this scatter is driven by properties of the group and cluster cores, while at the radius of a typical galaxy pericentre (0.2–0.3 times the virial radius), the scatter from system to system is quite small (McCarthy et al. 2008a; Sun et al. 2009).”
Gas entropy in a representative sample of nearby X-ray galaxy clusters (REXCESS): relationship to gas mass fraction (2009, background): “…results were found for a sample of cool core clusters by Nagai et al. (2007), it is important to note that in the group regime, at temperatures lower than 2 keV, the entropy normalisation of morphologically relaxed systems has been found tobe significantly higher than predicted (Sun et al. 2009).”
Thermal instability and the feedback regulation of hot haloes in clusters, groups and galaxies (2011, background): “This can be verified from Figure 9 which shows a relatively constant entropy for c© 2011 RAS, MNRAS 000, 1–26 different halo masses; as a result, the core entropy for groups is larger than the self-similar prediction K ∝ M 2/3 0 , as is ob- served (e.g., Ponman, Cannon, & Navarro 1999; Sun et al. 20”
Gas expulsion by quasar-driven winds as a solution to the overcooling problem in galaxy groups and clusters (2010, methodology): “2 the 16th and 84th percentiles of the Chandra entropy profiles of Sun et al. (2009) [approximately 20 groups with a median mass of log10(M500/M ) ≈ 13.5; note we have used here only the 20 lowest mass groups of Sun et al. so as to achieve a similar median mass to that of the simulated groups].”
Jet-regulated cooling catastrophe (2010, background): “Their gas fraction is the best fit to data from Vikhlinin et al. (2006), Arnaud et al. (2007) and Sun et al. (2009). a modest fraction of the gas is expelled by the AGN outside of the cluster.”
IMPACT OF CLUSTER PHYSICS ON THE SUNYAEV–ZEL'DOVICH POWER SPECTRUM (2010, methodology): “We focus specifically on the M500 − fg relation measured from the cluster samples of Vikhlinin et al. (2006) and Sun et al. (2009) (where the gas fraction fg is defined as the gas mass divided by total mass within R500), and the ‘universal’ electron pressure profile measured by Arnaud et al. (2010)…”
Towards a realistic population of simulated galaxy groups and clusters (2013, methodology): “As we discussed in Section 3.1.1, however, the Sun et al. (2009) sample has a higher mean X-ray luminosity compared to other observational group samples, most likely due to selection.”
INTRACLUSTER MEDIUM ENTROPY PROFILES FOR A CHANDRA ARCHIVAL SAMPLE OF GALAXY CLUSTERS (2009, background): “Additionally, analysis of a diffuse gas temperature structure at large radii, which is spectroscopically dominated by the background, requires a time-consuming, observation-specific analysis of the X-ray background (see Sun et al. 2009, for a detailed discussion on this point).”
Theoretical Challenges in Galaxy Formation (2016, background): “…systems are usually embedded in hot (> 105K) X-ray emitting gas comprising a significant fraction of the total baryonic mass (e.g. Anderson et al. 2015, Dai et al. 2010, Giodini et al. 2009, Kravtsov & Borgani 2012, Mulchaey 2000, Renzini & Andreon 2014, Sun et al. 2009, Vikhlinin et al. 2006).”
Simulating the effect of active galactic nuclei feedback on the metal enrichment of galaxy clusters (2009, methodology): “However, this is obtained at the expense of increasing the ICM entropy in central regions of gr ups above the level indicated by observational results (e.g., Sun et al. 2009; Sanderson et al. 2009b).”
The EAGLE simulations of galaxy formation: the importance of the hydrodynamics scheme (2015, methodology): “For comparison, we show data from Vikhlinin et al. (2006), Maughan et al. (2008), Sun et al. (2009), Pratt et al. (2009) and Lin et al. (2012).”
Quantifying baryon effects on the matter power spectrum and the weak lensing shear correlation (2018, background): “9 provide a measure for the uncertainty of the baryon suppression effect on the matter power spectrum based on the X-ray gas fractions from Refs [57–59] (see Fig.”