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26 April 2024 |
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Stellar Dynamics in the Galactic centre: Proper Motions and Anisotropy | | R. Genzel
; C. Pichon
; A. Eckart
; O.E. Gerhard
; T. Ott
; | | Date: |
25 Dec 1999 | | Journal: | Mon.Not.Roy.Astron.Soc. 317 (2000) 348 | | Subject: | astro-ph | | Affiliation: | 2 and 3), A. Eckart , O.E. Gerhard , T. Ott ( MPE, Univ. Basel, Obs. de Strasbourg | | Abstract: | We report a new analysis of stellar dynamics in the Galactic centre, based on improved sky and LOS velocities for >100 stars within a few arcsec of SgrA*. Overall the motions do not deviate strongly from isotropy. For 32 stars with all 3 components determined the absolute, LOS and sky velocities agree well, as for a spherical cluster. The projected radial and tangential motions of all 104 pm stars are also consistent with overall isotropy. However, the projected velocities of the young, early type stars have a strong radial dependence. Most of the bright HeI stars 1-10" from SgrA* are on tangential orbits. This anisotropy of the HeI stars and most of the brighter IRS16 complex members is largely caused by a CW and counter-rotating, coherent rotation pattern. The overall rotation of the young star cluster probably is a remnant of the angular momentum in the cloud these stars formed from. The fainter, fast stars within ~1" of SgrA* appear to be largely moving on radial or very elliptical orbits. We have not detected nonlinear motion for any of them. Most of the SgrA* cluster members also are on CW orbits. Spectroscopy shows them to be early type stars. We propose that the SgrA* cluster stars are those members of the early type cluster with small angular momentum which can plunge to the vicinity of SgrA*. Our anisotropy-independent estimate of the Sun-GC distance is 7.8-8.2 kpc (+/- 0.9 kpc). We include velocity anisotropy in estimating the central mass distribution. We confirm previous conclusions that a compact central mass concentration is present and dominates the potential from 0.01-1 pc. The central mass ranges from 2.6-3.3E6 M_sun. (abridged) | | Source: | arXiv, astro-ph/0001428 | | Services: | Forum | Review | PDF | Favorites | |
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