A deep optical luminosity function of NGC 6712 with the VLT: Evidence for severe tidal disruption
Abstract
The VLT on Cerro Paranal was used to observe four fields located at ~ 2farcm3 from the center of the Galactic globular cluster NGC 6712 in the V and R bands. The resulting color-magnitude diagram shows a well defined main sequence reaching down to the 5 sigma detection limit at V =~ 25, R =~ 23.5 or approximately 4 magnitudes below the main sequence turn-off, the deepest obtained so far on this cluster. This yields a main sequence luminosity function that peaks at M_R =~ 4.5 and drops down to the 50% completeness limit at M_R =~ 8.5. Transformation to a mass function via the latest mass-luminosity relation appropriate to this object indicates that the peak of the luminosity function corresponds to ~ 0.75 M_sun, a value significantly higher than the ~ 0.25 M_sun, measured for most other clusters observed so far. Since this object, in its Galactic orbit, penetrates very deeply into the Galactic bulge with perigalactic distance of ~ 0.3 kpc, this result is the first strong evidence that tidal forces have stripped this cluster of a substantial portion of its lower mass star population all the way down to its half-light radius and possibly beyond. Based on observations collected at the European Southern Observatory, Paranal, Chile (VLT-UT1 Science Verification Program)
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 1999
- DOI:
- 10.48550/arXiv.astro-ph/9811173
- arXiv:
- arXiv:astro-ph/9811173
- Bibcode:
- 1999A&A...343L...9D
- Keywords:
-
- STARS: LUMINOSITY FUNCTION;
- MASS FUNCTION;
- STARS: LOW-MASS;
- BROWN DWARFS;
- STARS: POPULATION II;
- GALAXY: GLOBULAR CLUSTERS: GENERAL;
- GALAXY: GLOBULAR CLUSTERS: INDIVIDUAL: NGC 6712;
- Astrophysics
- E-Print:
- 6 pages, 3 figures, to appear as a Letter in the special VLT issue of Astronomy &