Multiwavelength campaign on Mrk 509

VII. Relative abundances of the warm absorber

¹ Instituto de Astronomía, Universidad Católica del Norte, Avenida Angamos 0610, Antofagasta Chile
e-mail: katrien.steenbrugge@gmail.com
² Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK
³ SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
⁴ Astronomical Institute, Utrecht University, P.O. Box 80000, 3508 TA Utrecht, The Netherlands
⁵ School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, UK
⁶ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁷ Department of Physics & Astronomy, John Hopkins University, Baltimore, MD 21218, USA
⁸ Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey, RH5 6NT, UK
⁹ Department of Physics, Technion, Haifa 32000, Israel
¹⁰ Department of Physics, Virginia Tech, Blacksburg, VA 24061, USA
¹¹ INAF-IASF Bologna, via Gobetti 101, 40129 Bologna, Italy
¹² Dipartimento di Fisica, Universitá degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
¹³ UJF-Grenoble 1 / CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Grenoble, 38041, France

Received: 20 May 2011
Accepted: 29 July 2011

Abstract

Context. The study of abundances in the nucleus of active galaxies allows us to investigate the evolution of the abundance by comparing local and higher redshift galaxies. However, the methods used so far have substantial drawbacks or rather large uncertainties. Some of the measurements are at odds with the initial mass function derived from the older stellar population of local elliptical galaxies.

Aims. We determine accurate and reliable abundances of C, N, Ne, and Fe relative to O from the narrow absorption lines observed in the X-ray spectra of Mrk 509.

Methods. We use the stacked 600 ks XMM-Newton RGS and 180 ks Chandra LETGS spectra. Thanks to simultaneous observations with INTEGRAL and the optical monitor on-board XMM-Newton for the RGS observations and HST-COS and Swift for the LETGS observations, we have an individual spectral energy distribution for each dataset. Owing to the excellent quality of the RGS spectrum, the ionisation structure of the absorbing gas is well constrained, allowing for a reliable abundance determination using ions over the whole observed range of ionisation parameters.

Results. We find that the relative abundances are consistent with the proto-solar abundance ratios: C/O = 1.19  ±  0.08, N/O = 0.98  ±  0.08, Ne/O = 1.11  ±  0.10, Mg/O = 0.68  ±  0.16, Si/O = 1.3  ±  0.6, Ca/O = 0.89  ±  0.25, and Fe/O = 0.85  ±  0.06, with the exception of S, which is slightly under-abundant, S/O = 0.57  ±  0.14. Our results, and their implications, are discussed and compared to the results obtained using other techniques to derive abundances in galaxies.