MARKARIAN 6: SHOCKING THE ENVIRONMENT OF AN INTERMEDIATE SEYFERT
- School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom)
- School of Physics and Astronomy, University of Southampton, Southampton SO17 1SJ (United Kingdom)
- Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)
- Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China)
- Department of Physics, Rochester Institute of Technology, Rochester, NY 14623 (United States)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
Markarian 6 is a nearby (D {approx} 78 Mpc) Seyfert 1.5, early-type galaxy, with a double set of radio bubbles. The outer set spans {approx}7.5 kpc and is expanding into the halo regions of the host galaxy. We present an analysis of our new Chandra observation, together with archival XMM-Newton data, to look for evidence of emission from shocked gas around the external radio bubbles, both from spatially resolved regions in Chandra and from spectral analysis of the XMM-Newton data. We also look for evidence of a variable absorbing column along our line of sight to Mrk 6, to explain the evident differences seen in the active galactic nucleus (AGN) spectra from the various, non-contemporaneous, observations. We find that the variable absorption hypothesis explains the differences between the Chandra and XMM-Newton spectra, with the Chandra spectrum being heavily absorbed. The intrinsic N{sub H} varies from {approx}8 x 10{sup 21} atoms cm{sup -2} to {approx}3 x 10{sup 23} atoms cm{sup -2} on short timescales (2-6 years). The past evolution of the source suggests this is probably caused by a clump of gas close to the central AGN, passing in front of us at the moment of the observation. Shells of thermal X-ray emission are detected around the radio bubbles, with a temperature of {approx}0.9 keV. We estimate a temperature of {approx}0.2 keV for the external medium using luminosity constraints from our Chandra image. We analyze these results using the Rankine-Hugoniot shock jump conditions, and obtain a Mach number of {approx}3.9, compatible with a scenario in which the gas in the shells is inducing a strong shock in the surrounding interstellar medium (ISM). This could be the third clear detection of strong shocks produced by a radio-powerful Seyfert galaxy. These results are compatible with previous findings on Centaurus A and NGC 3801, supporting a picture in which these AGN-driven outflows play an important role in the environment and evolution of the host galaxy.
- OSTI ID:
- 21574778
- Journal Information:
- Astrophysical Journal, Vol. 731, Issue 1; Other Information: DOI: 10.1088/0004-637X/731/1/21; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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