Kinematics and Metallicities of Globular Clusters in M 104 1 1996

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 ∼ 260 km/sec, and the Projected Mass Estimator gives a mass of 5.0 (3.5,6.7)× 10 M for M104 within a projected radius of ∼ 330′′ (14 kpc for D=8.55 Mpc). Our best estimate for the mass-to-light ratio is M/LVT= 16 +5.5 −5.0 within the same radius. Considering all of the possible sources of uncertainty, we find a lower limit of M/LV= 5.3, which is larger than the M/LV found from rotation curve analyses inside 180′′. 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 ∼ 100′′. Finally, we find a mean cluster metallicity of [Fe/H] = −0.70 ± 0.3, which is more typical of clusters in gE/cD galaxies than it is of clusters in other spirals.