A Black Hole in the Nucleus of M31?

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Session 64 -- Low Luminosity AGNs and Active Galaxies
Oral presentation, Thursday, 2, 1994, 10:00-11:30

[64.03] A Black Hole in the Nucleus of M31?

Y.C.Pei, Z.Tsvetanov, H.C.Ford, G.A. Kriss, \& L.Ferrarese (JHU)

We present HST (pre-costar) observations of the inner nucleus of M31: $V$ and H$\alpha$ band images from the Planetary Camera, and rotational velocity and velocity dispersion measurements from Faint Object Spectrograph spectra. Both raw and deconvolved images show a double-peaked structure, with a separation of $0.49\pm0.02$ arcsec. Our analyses based on the deconvolved images indicate that the bright peak follows a King profile with $c\approx0.5$, while the faint peak follows a $r^{-7/4}$ power law profile, resembling the density cusp of an embedded black hole. The kinematic data show rapid rotation velocities up to 140 km s$^{-1}$ and large velocity dispersions up to 380 km s$^{-1}$. The maximum velocity dispersion occurs roughly at the location of the faint peak. This, combined with the power law density cusp, indicate that the faint peak is very likely to be the site hosting a black hole of $few\times10^6~M_\odot$. The exact nature of the bright companion is still unknown, although it could be the stripped nucleus of a dwarf galaxy captured recently. The rapid rotation may be accounted for by the fast spin of a binary system, consisting of the nuclear black hole and bright companion.

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