EDP Sciences
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Volume 490, Number 1, October IV 2008
Page(s) 103 - 112
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:200810151
Published online 11 September 2008

A&A 490, 103-112 (2008)
DOI: 10.1051/0004-6361:200810151

Exploring the nuclear environment of the NLS1 galaxy Arakelian 564 with XMM-Newton RGS

R. A. N. Smith, M. J. Page, and G. Branduardi-Raymont

Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
    e-mail: rans@mssl.ucl.ac.uk

Received 7 May 2008 / Accepted 27 August 2008

Aims. We present an accurate characterisation of the high-resolution X-ray spectrum of the Narrow Line Seyfert 1 galaxy Arakelian 564 and put it in to context with other objects of its type by making a detailed comparison of their spectra.
Methods. The data are taken from 5 observations with the XMM-Newton Reflection Grating Spectrometer and fitted with various spectral models.
Results. The best fit to the data identifies five significant emission lines at 18.9, 22.1, 24.7, 29.0 and 33.5 Å due to O VIII Ly$\alpha$, O VII(f), N VII Ly$\alpha$, N VI(i) and C VI Ly$\alpha$ respectively. These have an RMS velocity of ~1100 km s-1 and a flow velocity of ~-600 km s-1, except for the O VII(f) emission line, which has a flow velocity consistent with zero. Two separate emitting regions are identified. Three separate phases of photoionized, X-ray absorbing gas are included in the fit with ionization parameters log $\xi=-0.86$, 0.87, 2.56 and column densities $N_{\rm H}=0.89, 2.41, 6.03\times10^{20}$ cm-2 respectively. All three phases show this to be an unusually low velocity outflow ($-10\pm100$ km s-1) for a narrow line Seyfert 1. We present the hypothesis that the BLR is the source of the NLR and warm absorber, and examine optical and UV images from the XMM-Newton Optical Monitor to relate our findings to the characteristics of the host galaxy.

Key words: galaxies: active -- galaxies: Seyfert -- galaxies: individual: Ark 564 -- X-rays: galaxies -- techniques: spectroscopic -- line: identification

© ESO 2008