MASS OF THE SOUTHERN BLACK HOLE IN NGC 6240 FROM LASER GUIDE STAR ADAPTIVE OPTICS
- Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
- Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
- Max Planck Institut fuer extraterrestrische Physik, Postfach 1312, 85741 Garching (Germany)
- Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States)
NGC 6240 is a pair of colliding disk galaxies, each with a black hole in its core. We have used laser guide star adaptive optics on the Keck II telescope to obtain high-resolution ({approx}0.''06) near-infrared integral-field spectra of the region surrounding the supermassive black hole in the south nucleus of this galaxy merger. We use the K-band CO absorption bandheads to trace stellar kinematics. We obtain a spatial resolution of about 20 pc and thus directly resolve the sphere of gravitational influence of the massive black hole. We explore two different methods to measure the black hole mass. Using a Jeans Axisymmetric Multi-Gaussian mass model, we investigate the limit that a relaxed mass distribution produces all of the measured velocity dispersion, and find an upper limit on the black hole mass at 2.0 {+-} 0.2 Multiplication-Sign 10{sup 9} M{sub Sun }. When assuming the young stars whose spectra we observe remain in a thin disk, we compare Keplerian velocity fields to the measured two-dimensional velocity field and fit for a mass profile containing a black hole point mass plus a radially varying spherical component, which suggests a lower limit for the black hole mass of 8.7 {+-} 0.3 Multiplication-Sign 10{sup 8} M{sub Sun }. Our measurements of the stellar velocity dispersion place this active galactic nucleus within the scatter of the M{sub BH}-{sigma}{sub *} relation. As NGC 6240 is a merging system, this may indicate that the relation is preserved during a merger at least until the final coalescence of the two nuclei.
- OSTI ID:
- 22004540
- Journal Information:
- Astrophysical Journal, Vol. 743, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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