Dynamical modeling of the stellar nucleus of M 31

Free access article

Issue		A&A Volume 388, Number 3, June IV 2002


Page(s)		766 - 770
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20020298

A&A 388, 766-770 (2002)
DOI: 10.1051/0004-6361:20020298

Dynamical modeling of the stellar nucleus of M 31

N. Sambhus and S. Sridhar

Inter-University Centre for Astronomy and Astrophysics, Ganeshkhind, Pune 411 007, India

(Received 13 November 2001 / Accepted 27 February 2002 )

Abstract
We present stellar dynamical models of the lopsided, double-peaked nucleus of M 31, derived from Hubble Space Telescope (HST) photometry. A Schwarzschild-type method, in conjunction with Richardson-Lucy deconvolution, was employed to construct steadily rotating, hot, stellar disks. The stars orbit a massive dark object, on prograde and retrograde quasi-periodic loop orbits. Our results support Tremaine's eccentric disk model, extended to include a more massive disk, non zero pattern speed ( $\Omega$ ), and different viewing angle. Most of the disk mass populated prograde orbits, with $\simeq$ 3.4% on retrograde orbits. The best fits to photometric and kinematic maps were disks with $\Omega\simeq 16\mbox{\,km\, s${}^{-1}$\, pc${}^{-1}$ }$ . We speculate on the origins of the lopsidedness, invoking recent work on the linear overstability of nearly Keplerian disks, that possess even a small amount of a counter - rotating component. Accretion of material - no more massive than a globular cluster - onto a preexisting stellar disk, will account for the mass in our retrograde orbits, and could have stimulated the lopsidedness seen in the nucleus of M 31.

Key words: galaxies: individual: M 31 -- galaxies: kinematics and dynamics -- galaxies: nuclei

Offprint request: N. Sambhus, nbs@iucaa.ernet.in

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