Kinematics and Metallicities of Globular Clusters in M104

Abstract

We have obtained spectra for globular cluster candidates in M104 with LDSS-2 on the William Herschel Telescope, confirming 34 objects as M104 globular clusters. We find a cluster velocity dispersion of $\sim$ 260 km/sec, and the Projected Mass Estimator gives a mass of 5.0 (3.5,6.7) $\times 10^{11}$ M${}_{\odot }$ for M104 within a projected radius of $\sim 330^{{}^{\prime \prime }}$ (14 kpc for D=8.55 Mpc). Our best estimate for the mass-to-light ratio is M/L${}_{V_T}$= 16${}_{-5.0}^{+5.5}$ within the same radius. Considering all of the possible sources of uncertainty, we find a lower limit of M/L_V= 5.3, which is larger than the M/L${}_V$ found from rotation curve analyses inside 180${}^{{}^{\prime \prime }}$. We thus conclude that the mass-to-light ratio increases with radius, or in other words that M104 possesses a dark matter halo. There is a marginal detection of rotation in the M104 cluster system at the 92.5% confidence level; larger samples will be needed to investigate this possibility. Interestingly, the M104 globular cluster and planetary nebulae (PNe) kinematics are roughly consistent inside $\sim 100^{{}^{\prime \prime }}$. Finally, we find a mean cluster metallicity of [Fe/H] = $-$0.70 $\pm$ 0.3, which is more typical of clusters in gE/cD galaxies than it is of clusters in other spirals.

11 pages, latex, 7 figures. Figures embedded into postscript file. Accepted (August 1996) for publication in MNRAS