Chemical enrichment in the cluster of galaxies Hydra A

Free access article

Issue		A&A Volume 493, Number 2, January II 2009


Page(s)		409 - 424
Section		Cosmology (including clusters of galaxies)
DOI		http://dx.doi.org/10.1051/0004-6361:200810225
Published online		20 November 2008

A&A 493, 409-424 (2009)
DOI: 10.1051/0004-6361:200810225

Chemical enrichment in the cluster of galaxies Hydra A

A. Simionescu¹, N. Werner², H. Böhringer¹, J. S. Kaastra², A. Finoguenov^{1, 3}, M. Brüggen⁴, and P. E. J. Nulsen⁵

¹ Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstr, 85748, Garching, Germany
e-mail: aurora@mpe.mpg.de
² SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
³ University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
⁴ Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
⁵ Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA

Received 20 May 2008 / Accepted 3 November 2008

Abstract
We analyzed global properties, radial profiles, and 2D maps of the metal abundances and temperature in the cool core cluster of galaxies Hydra A using a deep ~120 ks XMM-Newton exposure. The best fit among the available spectral models is provided by a Gaussian distribution of the emission measure (gdem). We can accurately determine abundances for 7 elements in the cluster core with EPIC (O, Si, S, Ar, Ca, Fe, Ni) and 3 elements (O, Ne, Fe) with RGS. The gdem model gives lower Fe abundances than a single-temperature model. Based on this, we explain why simulations show that the best-fit Fe abundance in clusters with intermediate temperatures is overestimated. The abundance profiles for Fe, Si, S, but also O are centrally peaked. Combining the Hydra A results with 5 other clusters for which detailed chemical abundance studies are available, we find a significant decrease in O with radius, while the increase in the O/Fe ratio with radius is small within 0.1 r₂₀₀, where the O abundances can be accurately determined, with d $({\rm O/Fe})/{\rm d}({\rm log}_{10}r/r_{200})=0.25\pm0.09$ . We compare the observed abundance ratios with the mixing of various supernova type Ia and core-collapse yield models in different relative amounts. Producing the estimated O, Si, and S peaks in Hydra A requires either the amount of metals ejected by stellar winds to be 3–8 times higher than predicted by available models or the initial enrichment by core-collapse supernovae in the protocluster phase not to be as well mixed on large scales as previously thought. The temperature map shows cooler gas extending in arm-like structures towards the north and south. These structures, and especially the northern one, appear to be richer in metals than the ambient medium and spatially correlated with the large-scale radio lobes. With different sets of assumptions, we estimate the mass of cool gas, which was probably uplifted by buoyant bubbles of relativistic plasma produced by the AGN, to $1.6{-}6.1\times10^9~M_\odot$ , and the energy associated with this uplift to $3.3{-}12.5\times10^{58}$ erg. The best estimate of the mass of Fe uplifted together with the cool gas is $1.7\times10^7~M_\odot$ , 15% of the total mass of Fe in the central 0.5 $^{\prime}$ region.

Key words: X-rays: galaxies: clusters -- galaxies: clusters: individual: Hydra A -- galaxies: abundances -- galaxies: cooling flows -- galaxies: intergalactic medium

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