Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...211.2607h&link_type=abstract
American Astronomical Society, AAS Meeting #211, #26.07; Bulletin of the American Astronomical Society, Vol. 39, p.777
Astronomy and Astrophysics
Astronomy
Scientific paper
NGC205, a close satellite of the M31 galaxy, is our nearest example of a dwarf elliptical galaxy. Photometric and kinematic observations strongly suggest NGC205 is currently undergoing tidal distortion from its interaction with M31. Despite earlier attempts, the orbit and progenitor properties of NGC205 are not well known. We perform an optimized search for these unknowns by combining a genetic algorithm with restricted N-body simulations of the interaction. This approach, coupled with photometric and kinematic constraints, allows for an effective exploration of the parameter space. We represent the gravitational potential of M31 as a static analytic bulge-disk-halo model. NGC205 is modeled as a static Hernquist potential with embedded massless test particles that serve as tracers of surface brightness. We explore three distinct, initially stable configurations of test particles: a cold rotating disk, a warm rotating disk, and a hot, pressure-supported spheroid. Each model reproduces some, but not all, of NGC205's observed features. This leads us to speculate that a rotating progenitor with substantial pressure support could match all of the observables. We find that NGC205's line-of-sight distance and proper motion are well constrained by its kinematic profile and surface brightness distribution. Orbits best matching the observables place the satellite 11? kpc behind M31 moving at very large velocities: 300-500 km/s on primarily radial orbits. Given that the observed radial component is only 54 km/s, this implies a large tangential motion for NGC205, moving from the northwest towards the southeast, that translates into a predicted proper motion of ˜40.1 mas/yr. This suggests that NGC205 is not associated with the stellar arc observed north of M31 and northeast of NGC205. Furthermore, NGC205's velocity appears to be near or greater than its escape velocity, signifying that the satellite is likely on its first M31 passage.
This research was supported by NSF grant AST-0607852.
Geha Marla
Guhathakurta Puraga
Howley Kirsten
Johnston Kathryn V.
Laughlin Greg
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