A Deep Optical Luminosity Function of NGC 6712 with the VLT: Evidence for Severe Tidal Disruption
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The VLT on Cerro Paranal was used to observe four fields located at 2.3' 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 mag 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 Msolar, a value significantly higher than the ~0.25 Msolar 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.
6 pages, 3 figures, to appear as a Letter in the special VLT issue of Astronomy & Astrophysics (March 1999)
6 pages, 3 figures, to appear as a Letter in the special VLT issue of Astronomy & Astrophysics (March 1999)