Temperature Profiles of Nearby Clusters of Galaxies

By S. Grandi, S. Brera, Milan, Italy., I. D. F. Cosmica, Cnr - Milan. 2001

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We report results from the analysis of 21 nearby galaxy clusters, 11 with cooling flow (CF) and 10 without cooling flow, observed with BeppoSAX. The temperature profiles of both CF and non-CF systems are characterized by an isothermal core extending out to ~0.2r180; beyond this radius both CF and non-CF cluster profiles rapidly decline. Our results differ from those derived by other authors, who found either continuously declining profiles or substantially flat profiles. Neither the CF nor the non-CF profiles can be modeled by a polytropic temperature profile, the reason being that the radius at which the profiles break is much larger than the core radius characterizing the gas density profiles. For r > 0.2r180, where the gas can be treated as a polytrope, the polytropic indexes derived for CF and non-CF systems are respectively 1.20 ± 0.06 and 1.46 ± 0.06. The former index is closer to the isothermal value, 1, and the latter to the adiabatic value, . Published hydrodynamic simulations do not reproduce the peculiar shape of the observed temperature profile, probably suggesting that a fundamental ingredient is missing.

Subfields: Astronomy and Astrophysics

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THE EVOLUTION OF X-RAY CLUSTERS OF GALAXIES (2002, background): “De Grandi & Molendi (2002) analyzed a set of 21 clusters with Beppo–SAX data and found the gas to be isothermal out to ∼ 0.2Rvir, with a significant temperature decline at larger radii.”
The structural and scaling properties of nearby galaxy clusters. I. The universal mass profile (2005, background): “…(Vikhlinin et al. 1999; Neumann & Arnaud 2001; Arnaud et al. 2002a), and of the temperature profiles of hot clusters observed withASCA andBeppoSAX (Markevitch et al. 1998; Irwin & Bregman 2000; De Grandi & Molendi 2002) provided indirect evidence of a universal underlying dark matter distribution.”
Simulating the effect of active galactic nuclei feedback on the metal enrichment of galaxy clusters (2009, background): “…have negative gradients outside core regions, a trend that extends out to the largest radii covered so far by observations(e.g., De Grandi & Molendi 2002; Vikhlinin et al. 2005; Zhang et al. 2006; Baldi et al. 2007; Pratt et al. 2007; Leccardi & Molendi 2008b); gas entropy is…”
What is a cool-core cluster? a detailed analysis of the cores of the X-ray flux-limited HIFLUGCS cluster sample (2009, methodology): “Additionally we removed the outer annuli where accurate subtraction of the blank sky backgrounds (BSB) becomes critical and where clusters may have a decreasing temperature profile (Markevitch et al. 1998; De Grandi & Molendi 2002; Vikhlinin et al. 2005; Burns et al. 2008).”
CHANDRA CLUSTER COSMOLOGY PROJECT. II. SAMPLES AND X-RAY DATA REDUCTION (2008, background): “Usually, T is overestimated because the observed T (r) decreases at large radii (Markevitch et al. 1998; de Grandi & Molendi 2002; Vikhlinin et al. 2005; Pratt et al. 2007).”
The impact of mergers on relaxed X-ray clusters – I. Dynamical evolution and emergent transient structures (2006, result): “This also approximately matches cosmological simulations (Lewis et al. 2000; Loken et al. 2002) and observations (De Grandi & Molendi 2002).”
Determination of the Cosmic Distance Scale from Sunyaev-Zel’dovich Effect and Chandra X-Ray Measurements of High-Redshift Galaxy Clusters (2005, background): “4 and Table 2 of De Grandi and Molendi 2002).”
ERRATUM: “CHANDRA SAMPLE OF NEARBY RELAXED GALAXY CLUSTERS: MASS, GAS FRACTION, AND MASS–TEMPERATURE RELATION” (2006, ApJ, 640, 691) (2005, result): “The temperature has a broad peak near 0.1–0.2 of r200 and decreases at larger radii in a manner consistent with the results of earlier ASCA and BeppoSAX observations (Markevitch et al. 1998; De Grandi & Molendi 2002), reaching approximately 50% of the peak value near 0.5r200.”
The morgana model for the rise of galaxies and active nuclei (2006, methodology): “…from a cooling radius rcool to the virial radius rH, (iv) pressure-balanced both at rcool and rH, (v) described by a polytropic equation of state with index γ p, a parameter that is observed to take a value of about 1.2 (see e.g. De Grandi & Molendi 2002); we use the best-fitting value of 1.15.”
IMPACT OF CLUSTER PHYSICS ON THE SUNYAEV–ZEL'DOVICH POWER SPECTRUM (2010, background): “X-ray observations of clusters (Vikhlinin et al. 2006; De Grandi & Molendi 2002) as well as hydrodynamical simulations (Battaglia et al. 2010) indicate that the ICM thermal pressure and density profiles do not adhere to a polytrope with constant index.”
A dynamical model for the distribution of dark matter and gas in galaxy clusters (2003, unknown): “…good agreement with previous numerical works (Navarro et al. 1995; Eke et al. 1998; Bryan & Norman 1998; Frenk et al. 1999; Thomas et al. 2001; see, however, Loken et al. 2002; AYMG03) and also with the temperature profile found from the analysis of the Beppo-SAX data by De Grandi & Molendi (2002).”
Heating Hot Atmospheres with Active Galactic Nuclei (2007, background): “There are disagreements between researchers about the normalization constant and temperature profile shapes, resulting in discrepancies in mass by a few tens of percent (e.g., Markevitch et al. 1998; Irwin & Bregman 2000; Allen et al. 2001; De Grandi & Molendi 2002; Vikhlinin et al. 2006).”
Galaxies in a simulated ΛCDM Universe – I. Cold mode and hot cores (2008, background): “The density and temperature profiles of these two halos are reminiscent of the gas profiles in observed cooling flow and non-cooling flow clusters (e.g. De Grandi & Molendi 2002; Morandi & Ettori 2007).”
CHANDRA STUDIES OF THE X-RAY GAS PROPERTIES OF GALAXY GROUPS (2008, methodology): “This result was later confirmed by De Grandi & Molendi (2002) with the BeppoSAX data, and by V05 with the Chandra data, and by Piffaretti et al. (2005), Pratt et al. (2007) and Leccardi & Molendi (2008, LM08 hereafter) with the XMM-Newton data.”
X-ray spectroscopy of galaxy clusters: studying astrophysical processes in the largest celestial laboratories (2009, background): “…means of the Italian-Dutch X-ray missionBeppoSAX some overview on the temperature structure of clusters was obtained, with decreasing temperature profiles outside∼ 0.2r500 and a diversity of the behaviour in the core region depending on the thermal history of the cluster (De Grandi & Molendi 2002).”
A unified model for AGN feedback in cosmological simulations of structure formation (2007, background): “Indeed, a number of observational studies (e.g. De Grandi & Molendi, 2002; Vikhlinin et al., 2005; Dunn & Fabian, 2006; Pratt et al., 2007) have shown that the central temperature profiles of relaxed, cool core clusters decrease with decreasing radius, while at the same time these systems require…”
On the Origin of Intracluster Entropy (2003, background): “Observations indicate that eff 1:1 1:2 in hot clusters (Markevitch et al. 1998, 1999; Ettori & Fabian 1999; De Grandi & Molendi 2002), supporting the idea that K / Mg when gravitationally driven processes dominate the production of intracluster entropy.”