Astronomy and Astrophysics – Astrophysics
Scientific paper
Jun 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000aipc..515..165g&link_type=abstract
GeV-TeV GAMMA RAY ASTROPHYSICS WORKSHOP: Towards a Major Atmospheric Cherenkov Detector VI. AIP Conference Proceedings, Volume
Astronomy and Astrophysics
Astrophysics
Active And Peculiar Galaxies And Related Systems, Interacting Galaxies, Galaxy Pairs, And Triples, Characteristics And Properties Of External Galaxies And Extragalactic Objects, Visible
Scientific paper
We present Hubble Space Telescope (HST) imagery, and ground-based spectroscopy and CCD photometry of the active galaxy Markarian 421 and its companion galaxy 14 arcsec to the ENE. The HST images indicate that the companion is a morphological spiral rather than elliptical as previous ground-based imaging has concluded. The companion has a bright, compact nucleus, appearing unresolved in the HST images. This is suggestive of Seyfert activity, or possibly a highly luminous compact star cluster. We also report the results of high dynamic range long-slit spectroscopy with the slit placed to extend across both galaxies and nuclei. Velocities derived from a number of absorption lines visible in both galaxies indicate that the two systems are probably tidally bound and thus in close physical proximity. Using the measured relative velocities, we derive a lower limit on the MKN 421 mass within the companion orbit (R~10 kpc) of 5.9×1011 solar masses, and a mass-to-light ratio of >=17. Our spectroscopy also shows for the first time the presence of Hα and [NII] emission lines from the nucleus of MKN 421. We see both broad and narrow line emission, with a velocity dispersion of several thousand km s-1 evident in the broad lines. Based on the imagery and broad-line velocity dispersion we find evidence for a black hole with mass of order 109 Mbeye at the center of MKN 421. .
Gorham Peter. W.
Jacobs Christopher S.
Unwin Stephen C.
van Zee Liese
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