| Issue |
A&A
Volume 473, Number 2, October II 2007
|
|
|---|---|---|
| Page(s) | 429 - 436 | |
| Section | Galactic structure, stellar clusters, and populations | |
| DOI | https://doi.org/10.1051/0004-6361:20077122 | |
| Published online | 23 July 2007 | |
The extended structure of the remote cluster B514 in M 31*,**,***
Detection of extra-tidal stars
INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy e-mail: [luciana.federici;michele.bellazzini;flavio.fusipecci;alberto.buzzoni; gianluigi.parmeggiani]@oabo.inaf.it; silvia.galleti2@unibo.it
Received:
18
January
2007
Accepted:
6
June
2007
Aims.We present a study of the density profile of the remote M 31 globular cluster B514, obtained from HST/ACS observations.
Methods.By coupling analysis of the distribution of the integrated light with star counts, we
are able to reliably follow the profile of the cluster out to r ~
35″, corresponding to 
130 pc. The profile is well-fitted
out to ~15 core radii by a King Model having 
. With an
estimated core radius rc = 0.38″, this corresponds to a tidal radius
of rt~ 17″ (~65 pc). The analysis of the light profile
also allows an estimate of the ellipticity and position angle of the
isophotes within r ≤ 20″.
Results.We find that both the light and the star-count profiles show a departure from the
best-fit King model for r 
8″ – as a surface brightness excess at
large radii, and the star-count profile shows a clear break in the
correspondence of the estimated tidal radius. Both features are interpreted
as the signature of the presence of extra tidal stars around the cluster. It
is also shown that B514 has a significantly larger half-light radius than
ordinary globular clusters of the same luminosity. In the MV vs. log rh plane, B514 lies in a region inhabited by peculiar clusters, like ω Cen, G1, NGC 2419 and others, as well as by the nuclei of dwarf elliptical galaxies.
Key words: galaxies: individual: M 31 / galaxies: star clusters / catalogs / galaxies: local group / stellar dynamics
Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute (STScI), which is operated by AURA, Inc., under NASA contract NAS 5-26555.
© ESO, 2007
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