X-ray spectroscopy of NGC 5548

¹ SRON National Institute for Space Research Sorbonnelaan 2, 3584 CA Utrecht, The Nether lands
² Astronomical Institute “Anton Pannekoek", Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
³ Physics Department, Lawrence Livermore National Laboratory, PO Box 808, L-11, Livermore, CA 94550, USA
⁴ Department of Physics, Columbia University, 550 West 120th Street, New York, NY 10027, USA
⁵ Istituto di Astrofisica Spaziale, CNR, Via del Fosso del Cavaliere 100, Roma 00133, Italy

Corresponding author: J. S. Kaastra, J.Kaastra@sron.nl

Received: 14 December 2001
Accepted: 12 February 2002

Abstract

We analyze the high-resolution X-ray spectrum of the Seyfert 1 galaxy NGC 5548, for the full  keV band, using improved calibration results of the Chandra-LETGS instrument. The warm absorber consists of at least three ionization components, with a low, medium and high ionization parameter. The X-ray absorbing material, from an outflowing wind, covers the full range of velocity components found from UV absorption lines. The presence of redshifted emission components for the strongest blue-shifted resonance absorption lines indicate that the absorber is located at a distance larger than the edge of the accretion disk. We derive an upper limit to the edge of the accretion disk of 1 light year. Absorption lines from ions of at least ten chemical elements have been detected, and in general there are no strong deviations from solar abundances. The narrow emission lines from the and forbidden and intercombination lines probably originate from much larger distances to the black hole. We find evidence for weak relativistically broadened oxygen and nitrogen emission lines from the inner parts of the accretion disk, but at a much smaller flux level than those observed in some other active galactic nuclei. In addition, there is a broad, non-relativistic Lyα emission line that is consistent with emission lines from the inner part of the optical/UV broad line region.