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

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

Abstract

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 Lyα, O VII(f), N VII Lyα, N VI(i) and C VI Lyα 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 , 0.87, 2.56 and column densities  cm^-2 respectively. All three phases show this to be an unusually low velocity outflow ( 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.