Kyoko Matsushita

The new emerging model for the structure of cooling cores in clusters of galaxies

New X-ray observations with XMM-Newton show a lack of spectral evidence for large amounts of cooling and condensing gas in the centers of galaxy clusters believed to harbour strong cooling flows. This paper re-explores the cooling flow scenario in the light of the new observations. We explore the diagnostics of the temperature structure of cooling cores with XMM-spectroscopy, tests for intracluster X-ray absorption towards central AGN, the effect of metal abundance inhomogeneities, and the implications of high resolution images in the centers of clusters. We find no evidence of intrinsic absorption in the center of the cooling flows of M 87 and the Perseus cluster. We further consider the effect of cluster rotation in cooling flow regions in the frame of cosmic structure evolution models. Also, the heating of the core regions of clusters by jets from a central AGN is reconsidered. We find that the power of the AGN jets as estimated by their interaction effects with the intracluster medium in several examples is more then sufficient to heat the cooling flows and to reduce the mass deposition rates. We explore in more detail which requirements such a heating model has to fulfill to be consistent with all observations, point out the way such a model could be constructed, and argue that such model building seems to be successful. In summary, it is argued that most observational evidence points towards much lower mass deposition rates than previously inferred in the central region of clusters thought to contain strong cooling flows.

The Representative XMM-Newton Cluster Structure Survey (REXCESS) of an X-ray Luminosity Selected Galaxy Cluster Sample

Context.The largest uncertainty for cosmological studies using clusters of galaxies is introduced by our limited knowledge of the statistics of galaxy cluster structure, and of the scaling relations between observables and cluster mass.

XMM-Newton observation of M 87 - I. Single-phase temperature structure of intracluster medium

We report the results of a detailed analysis of the temperature structure of the X-ray emitting plasma halo of M 87, the cD galaxy of the Virgo Cluster. Using the MEKAL model, the data provide strong indications that the intracluster medium has a single phase structure locally, except the regions associated with the radio structures. The deprojected spectrum at each radius is well tted by a single temperature MEKAL model, except for the very central region (<2 arcmin) which seems to be aected by the jet and radio lobe structure. The temperature of the intracluster plasma is 1 keV at the center and gradually increases to 2.5 keV at 80 kpc. We have also tted spectra using the APEC code. Although the large changes of the strength of K lines causes a discrepancy between the Fe-L and Fe-K lines for the APEC results, the overall temperature structure has not changed. There is no sign of excess absorption in the spectral data. The single-phase nature of the intracluster medium is in conflict with the standard cooling flow model which is based on a multi-phase temperature structure. In addition, the signature of gas cooling below 0.8 keV to zero temperature is not observed as expected for a cooling flow. The gravitational mass prole derived from the temperature and density distribution of the intracluster gas shows two distinct contributions that can be assigned to the gravitational potential of the cD galaxy and the cluster. The central temperature of the intracluster medium agrees well with the potential depth and the velocity dispersion of the cD galaxy. The latter result implies that the central region of the intracluster medium is equivalent to a virialized interstellar medium in M 87.

Implications of the central metal abundance peak in cooling core clusters of galaxies

Recent XMM-Newton observations of clusters of galaxies have provided detailed information on the distribution of heavy elements in the central regions of clusters with cooling cores providing strong evidence that most of these metals come from recent SN type Ia. In this paper we compile information on the cumulative mass profiles of iron, the most important metallicity tracer. We find that long enrichment times (≥5 Gyr) are necessary to produce the central abundance peaks. Classical cooling flows, a strongly convective intracluster medium, and a complete metal mixing by cluster mergers would destroy the observed abundance peaks too rapidly. Thus the observations set strong constraints on cluster evolution models requiring that the cooling cores in clusters are preserved over very long times. We further conclude from the observations that the innermost part of the intracluster medium is most probably dominated by gas originating predominantly from stellar mass loss of the cD galaxy.

X-ray properties in massive galaxy clusters: XMM-Newton observations of the REFLEX-DXL sample

We selected an unbiased, flux-limited and almost volume-com plete sample of 13 distant, X-ray luminous (DXL, z ∼ 0.3) clusters and one supplementary cluster at z = 0.2578 from the REFLEX Survey (the REFLEX-DXL sample). We performed a detailed study to explore their X-ray properties using XMM-Newton observations. Based on the precise radial distributions of the gas density and temperature, we obtained robust cluster masses and gas mass fractions. The average gas mass fraction of the REFLEX-DXL sample at r500, 0.116± 0.007, agrees with the previous cluster studies and the WMAP baryon fraction measurement. The scaled profiles of the surf ace brightness, temperature, entropy, gas mass and total mass are characterized by a self-similar behaviour at radii above 0. 2-0.3 r500. The REFLEX-DXL sample confirms the previous studies of the normalization of the scaling relations ( L-T , L-M, M-T and Mgas-T ) when the redshift evolution of the scaling relations is accounted for. We investigated the scatter of the scaling relations of the REFLEX-DXL sample. This gives the correlative scatter of (0.20,0.10) for variable of ( M,T ) of the M500-T relation, for example.

Origin of the Scatter in the X-Ray Luminosity of Early-Type Galaxies Observed with ROSAT

Statistical properties of X-ray luminosity and temperature are studied for 52 early-type galaxies based on the ROSAT PSPC data. All of the X-ray luminous galaxies show largely extended emission with a radius of a few times 10re, while X-ray faint galaxies do not show such a component. This leads to a division of early-type galaxies into two categories: X-ray extended and X-ray compact galaxies. Except for a few galaxies in dense cluster environments, the luminosity and temperature of X-ray compact galaxies are well explained by a kinematical heating of the gas supplied by stellar mass loss. In contrast, X-ray extended galaxies indicate large scatter in the X-ray luminosity. We discuss the notion that X-ray extended galaxies are the central objects of large potential structures and that the presence or absence of this potential is the main origin of the large scatter in the X-ray luminosity.

X-Ray Probing of the Central Regions of Clusters of Galaxies

The results on ASCA X-ray study of the central regions of medium-richness clusters of galaxies are summarized, while emphasizing the differences between cD and non-cD clusters. The intra-cluster medium (ICM) is likely to consist of two (hot and cool) phases within ∼ 100kpc of a cD galaxy, where the ICM metallicity is also enhanced. In contrast, the ICM in non-cD clusters appears to be isothermal with a small metallicity gradient right of the center. The gravitational potential exhibits a hierarchical nesting around cD galaxies, while a total mass-density profile with a central cusp is indicated for a non-cD cluster, Abell 1060. The iron-mass-to-light ratio of the ICM decreases toward the center in both types of clusters, although it is radially constant in peripheral regions. The silicon-toiron abundance ratio in the ICM increases with the cluster richness, but remains close to the solar ratio around cD galaxies. These overall results are interpreted without appealing to the popular cooling-flow hypothesis. Instead, an emphasis is put on the halo-in-halo structure formed around cD galaxies.

Temperature gradients in XMM-Newton observed REFLEX-DXL galaxy clusters at z - 0.3

We present XMM-Newton results on the temperature profiles of a volume-limited sample of galaxy clusters at redshifts z ∼ 0.3, selected from the REFLEX survey (REFLEX-DXL sample). In the spectral analysis, where only the energies above I keV were considered, we obtained consistent results for the temperature derived from the pn, MOS1 and MOS2 data. Useful temperature measurements could be performed out to radii with overdensity 500 (r 5 0 0 ) for all nine clusters. We discovered a diversity in the temperature gradients at the outer cluster radii with examples of both flat and strongly decreasing profiles. Using the total mass and the gas mass profiles for the cluster RXCJ0307.0-2840 we demonstrate that the errors on the mass estimates for the REFLEX-DXL clusters are within 25% up to r 5 0 0 .

Metal Abundances in the Hot Interstellar Medium in Early-Type Galaxies Observed with ASCA

We have analyzed ASCA data of 27 early-type galaxies, and studied the properties of their X-ray emitting ISM (Inter Stellar Medium) in detail. We found that overlapping lines and free-bound continuum cause strong coupling in the derived abundances of various elements. The abundance determination is also difficult due to the uncertainties in the Fe-L atomic physics, because Fe-L lines couple with O and Ne K-lines. However, when abundances of

An XMM-Newton study of the sub-structure in M 87's halo

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