X-ray narrow line region variability as a geometry probe: The case of NGC 5548

Abstract

We study the long time scale variability of the gas responsible for the X-ray narrow emission lines in the Seyfert 1 galaxy NGC 5548, in order to constrain the location and geometry of the emitting gas. Using X-ray spectra taken with the Chandra-LETGS and HETGS instruments and with XMM-Newton RGS and combining them with long-term monitoring observations of the Rossi X-ray Timing Explorer (RXTE), we perform a correlation analysis in order to try constrain the time scale on which the narrow line emitting gas responds to variations of the continuum flux. With the inclusion of the 2007 Chandra-LETGS observation we have an additional observation at an historically low flux level. We conclude that the NLR in NGC 5548 is in the form of an ionization cone, compact in size, and located between 1 and 15 pc from the central source, depending on the exact geometry of the NLR.

6 pages, 4 figures, accepted for publication in A&A

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• Anatomy of the AGN in NGC 5548 IX. Photoionized emission features in the soft X-ray spectra
• Anatomy of the AGN in NGC 5548: V. A clear view of the X-ray narrow emission lines
• Intermediate-line Emission in AGNs: The Effect of Prescription of the Gas Density
• Strong variability of the coronal line region in NGC 5548
• Simultaneous XMM-Newton and HST-COS observation of 1H0419-577: the absorbing and emitting ionized gas
• Multi-wavelength Campaign on NGC 7469 VI. Photoionisation Modelling of the Emission Line Regions and the Warm Absorber
• Chandra imaging of the $\sim$kpc extended outflow in 1H 0419-577
• A systematic study of photoionized emission and warm absorption signatures of the NLS1 Mrk 335
• Detection of an Unidentified Soft X-ray Emission Feature in NGC 5548
• Density constraint of the warm absorber in NGC 5548