XMM-Newtonobservation of the interacting cluster Abell 3528

Abstract

Abstract.We analyze the XMM-Newton dataset of the interacting cluster of galaxies Abell 3528 located westward in the core of the Shapley Supercluster, the largest concentration of mass in the nearby Universe. A3528 is formed by two interacting clumps (A3528-N at North and A3528-S at South) separated by 0.9 h −1 70 Mpc at redshift 0.053. XMM-Newton data describe these clumps as a relaxed structure with an overall temperature of 4.14 ± 0.09 and 4.29 ± 0.07 keV in A3528-N and A3528-S, respectively, and a core cooler by a factor 1.4-1.5 and super-solar metal abundance in the inner 30 arcsec. These clumps are connected by a X-ray soft, bridge-like emission and present an asymmetric surface brightness with significant excess in the North-West region of A3528-N and in the North-East area of A3528-S. However, we do not observe any evidence of shock heated gas, both in the surface brightness and in the temperature map. Considering also that the optical light distribution is more concentrated around A3528-N and makes A3528-S barely detectable, we do not find support for the originally suggested head-on pre-merging scenario and conclude that A3528 is in an off-axis post-merging phase, where the closest core encounter happened about 1-2 Gyrs ago.

Simulations of galactic winds and starbursts in galaxy clusters

“…Following our simulations, these results would suggest that A3528-N and A3528-S are in reality in a pre-merger phase, with a collision axis along the SE/NW direction, in agreement with the first hypothesis about the dynamical state of A3528 Baldi et al 2001;Donnelly et al 2001;Venturi et al 2001). It is however clear that, due to the large errors in the abundance determination (Gastaldello et al 2003), a higher statistics in the iron line would be useful to confirm the pre-merger scenario.…”

“…the two clumps cannot be in a pre-merger phase. By combining this result with: a) the absence of any strong merging signatures in the X-ray data, despite the relatively small separation of the two clusters, and b) the optical light distribution mostly concentrated in the northern clump, Gastaldello et al (2003) suggest that the closest core encounter between A3528-N and A3528-S happened about 1−2 Gyr ago, with a high impact parameter. In agreement with the previous X-ray studies (ROSAT and ASCA data, Donnelly et al 2001), their analysis confirms that the two main clumps in X-ray have a relaxed structure, a centrally peaked surface brightness, and cooler cores.…”

“…Through XMM observations of A3528, Gastaldello et al (2003) reached different conclusions on the dynamical state of this cluster, assessing that in fact A3528 is an off-axis postmerging system. They conclude that the absence of any evidence of shock heated gas both in their temperature and in their density map is due to a wrong initial hypothesis, i.e.…”

“…Iso-density contours (black) of the projected distributions of galaxies (13 ≤ B ≤ 19.5) in the A3528 central field. The abundances in the annuli surrounding the two main sub-clusters (A3528-N and A3528-S) and in the region between them are shown in color (Gastaldello et al 2003). shown. The isodensity map has been built from the APM catalogue (13 ≤ B ≤ 19.5) on the basis of a multi-scale approach (see Ferrari et al 2005, for more details).…”

Probing the Dark Matter and Gas Fraction in Relaxed Galaxy Groups with X‐Ray Observations fromChandraandXMM‐Newton

“…Appropriate flux weighting was performed for RMFs, using our own dedicated software, and for ARFs, using exposure-corrected images of the source as detector maps (with pixel size of 1 0 , the minimum scale modeled by arfgen) to sample the variation in emission, following the prescription of Saxton & Siddiqui (2002). Spectral results obtained using ARFs are completely consistent with the other frequently employed method (e.g., Arnaud et al 2001) of correcting directly the spectra for vignetting (Gastaldello et al 2003;Morris & Fabian 2005). …”