%0 Generic %1 Strader2011 %A Strader, Jay %A Caldwell, Nelson %A Seth, Anil %D 2011 %K clusters imf star %T Star Clusters in M31: V. Internal Dynamical Trends: Some Troublesome, Some Reassuring %U http://arxiv.org/abs/1104.4649 %X We present internal velocity dispersions and precise radial velocities for 200 globular clusters (GCs) in M31 that are derived using new high-resolution spectra from MMT/Hectochelle. Of these, 163 also have King model structural parameters that allow us to estimate their mass-to-light ratios. This is, by far, the largest such dataset available for any galaxy, including the Milky Way. These data strongly confirm earlier suggestions that the optical and near-infrared mass-to-light ratios of M31 GCs decline with increasing metallicity. This behavior is the opposite of that predicted by stellar population models for a standard initial mass function. We show that this phenomenon does not appear to be caused by standard dynamical evolution. A shallower mass function for metal-rich GCs (with dN/dM ~ M^-0.8 to M^-1.3 below one solar mass) can explain the bulk of extant observations. We also observe a consistent, monotonic correlation between mass-to-light ratio and cluster mass. This correlation, in contrast to the correlation with metallicity, is well-explained by the accepted model of dynamical evolution of GCs through mass segregation and the preferential loss of low-mass stars, and these data are among the best available to constrain this process.

@misc{Strader2011, abstract = { We present internal velocity dispersions and precise radial velocities for 200 globular clusters (GCs) in M31 that are derived using new high-resolution spectra from MMT/Hectochelle. Of these, 163 also have King model structural parameters that allow us to estimate their mass-to-light ratios. This is, by far, the largest such dataset available for any galaxy, including the Milky Way. These data strongly confirm earlier suggestions that the optical and near-infrared mass-to-light ratios of M31 GCs decline with increasing metallicity. This behavior is the opposite of that predicted by stellar population models for a standard initial mass function. We show that this phenomenon does not appear to be caused by standard dynamical evolution. A shallower mass function for metal-rich GCs (with dN/dM ~ M^-0.8 to M^-1.3 below one solar mass) can explain the bulk of extant observations. We also observe a consistent, monotonic correlation between mass-to-light ratio and cluster mass. This correlation, in contrast to the correlation with metallicity, is well-explained by the accepted model of dynamical evolution of GCs through mass segregation and the preferential loss of low-mass stars, and these data are among the best available to constrain this process. }, added-at = {2011-04-26T13:56:05.000+0200}, author = {Strader, Jay and Caldwell, Nelson and Seth, Anil}, biburl = {https://www.bibsonomy.org/bibtex/2a2dc649daa0d0804819da36c2dfa4d3d/miki}, description = {[1104.4649] Star Clusters in M31: V. Internal Dynamical Trends: Some Troublesome, Some Reassuring}, interhash = {c0aacdd4f6bd6b8986ec24e776f45743}, intrahash = {a2dc649daa0d0804819da36c2dfa4d3d}, keywords = {clusters imf star}, note = {cite arxiv:1104.4649 Comment: AJ in press. 11 pages, 7 figures (not including tables) in emulate format}, timestamp = {2011-04-26T13:56:05.000+0200}, title = {Star Clusters in M31: V. Internal Dynamical Trends: Some Troublesome, Some Reassuring}, url = {http://arxiv.org/abs/1104.4649}, year = 2011 }