Mass-to-light ratios for globular clusters. III. M107 (NGC 6171; GC1629-129)

Slawomir Piatek, Carlton Pryor, Robert D. Mcclure, J. M. Fletcher, James E. Hesser

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Abstract

We have measured radial velocities accurate to about 1 km s-1 for 76 stars located within 7 arcmin of the center of the globular cluster M107 (NGC 6171; GC1629-129). Nine of these stars are probably nonmembers and are excluded from the subsequent analysis. We find no signature of rotation greater than our 2 km s-1 detection threshold. The velocity dispersion decreases with radius, but this change is only about 1.3 times its uncertainty. We have fitted single- and multicomponent King models to our velocity data and to existing surface-brightness profiles. The multicomponent models have a power law or the galactic disk mass function. The single-component models imply that M107 has a mass-to-light ratio, Script M sign/LV, of 1.8±0.4, in solar units. The best-fitting multicomponent King models have an isotropic or anisotropic (ra=10) velocity dispersion tensor and x=0.67. These models yield a projected central mass-to-light ratio, (Script M sign/LV)0, of 2.0±0.4 and a global Script M sign/LV of 1.8±0.4. The isotropic model with x =1.35 is also an acceptable, though poorer, fit and yields (Script M sign/LV)0 of 1.6±0.3 and Script M sign/LV of 2.7±0.5. We have rejected models with the galactic disk initial mass function because their dynamical and population Script M sign/L's disagree. This suggests that the galactic disk and M107 initial mass functions were different.

Original languageEnglish (US)
Pages (from-to)1397-1407
Number of pages11
JournalAstronomical Journal
Volume107
Issue number4
DOIs
StatePublished - Apr 1994
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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