ChandraX‐Ray Spectroscopy and Imaging of the Galaxy Cluster PKS 0745−191

Abstract

We present a detailed spectral and spatial analysis of the galaxy cluster PKS 0745À191, using recent observations from the Chandra X-Ray Observatory. The data provide information on the temperature and metallicity of the intracluster medium, the distribution of emission throughout the cluster, morphology of the cluster core, and an independent mass estimate that can be compared to that from gravitational lensing. X-ray spectra extracted from the central 300 kpc ($2 0 ) are well described by a two-temperature plasma, and the mean cluster temperature is consistent with previously determined values. The distribution of both temperature and metallicity within the inner 360 kpc (2<3) of PKS 0745À191 is probed on scales of 8 00 ($20 kpc), yielding a relatively constant abundance throughout the region and a strong temperature gradient (down to $4-5 keV) within the central 215 kpc. -model fits to the surface brightness profile of PKS 0745À191 indicate that a second -model component is required to fit the inner $10 kpc. Imaging analysis of the cluster core reveals an irregular morphology within the inner 50 kpc and confirms that the X-ray emission peak lies within 0>5 (the spatial resolution of Chandra) of both the optical and radio central cD positions. The cluster mass, based on both two-temperature and multiphase fits to the X-ray spectrum, is in close agreement with lensing mass estimates of PKS 0745À191.

The peculiar small-scale X-ray morphology of NGC 5846 observed with $\vec{Chandra}$

“…It is 3 The spectral matrixes for each region do not take into account the extended nature of the sources. While formally incorrect, the errors introduced by this assumption are very small on the scale of the sources analyzed here, and are also not very significant throughout the S3 chip (J. McDowell, private communication, see also Hicks et al 2002). evident from the figure that the distributions are not the same, both in shape and in the position of the peak. The average distribution at the same radial distance also appears to have a broader shape than for example the S region (open squares).…”

LX‐TRelation and Related Properties of Galaxy Clusters

“…However, for some of them, the results have already been published with the Chandra and XMM-Newton data. As for the doubleclusters or the small-core clusters with very short cooling times of À1:3 P log (t cool /t age ) P À0:7, A2204, PKS 0745À191, A2390, and A1835, the gradual temperature declines within the central region of roughly r < 100 200 kpc were reported Hicks et al 2002;Allen et al 2001a;Majerowicz et al 2002). For the other double-cluster, A1689, with slightly longer log t cool /t age ¼ À0:56, a nearly isothermal profile was found with Chandra (Xue & Wu 2002), and a complex temperature structure was further reported with XMM-Newton (Andersson & Madejski 2004).…”

“…Therefore, with the cooling rate in the form q A ffiffiffi ffi T p n 2 e0 , we define the cooling time for a cluster as t cool ¼ 3k ffiffiffi ffi T p /q A n e0 , where n e0 is the gas density at the cluster center. On the other hand, recent higher resolution observations of clusters with a cooling core pointed out that the conventional -model does not sufficiently fit overall profiles (e.g., Lewis et al 2003;Hicks et al 2002). In addition, if the central temperature drop by a factor of $2 exists, as observed in many cooling-flow clusters, it might cause an overestimation of t cool .…”

Thermal conduction and reduced cooling flows in galaxy clusters

“… Previous papers covering the X‐ray spectra of these objects include: (1) Mazzotta, Edge & Markevitch (2003); (2) Johnstone et al (1992); (3) Sun et al (2003); (4) De Grandi & Molendi (1999); (5) Hicks et al (2002); (6) David et al (2001); (7) McNamara et al (2000); (8) Matsushita et al (2002); (9) Molendi (2002); (10) Böhringer et al (2001); (11) Young, Wilson & Mundell (2002); (12) Allen, Schmidt & Fabian (2002); (13) Ettori, Allen & Fabian (2001); (14) Ettori et al (2002); (15) Tamura et al (2001); (16) Schmidt et al (2001); (17) Johnstone, Fabian & Taylor (1998); (18) Allen et al (2001b); (19) Lewis, Stocke & Buote (2002); (20) Smith et al (2002); (21) Allen, Ettori & Fabian (2001a); (22) Kaastra et al (2001); (23) McNamara et al (2001). …”