Spectroscopy of globular clusters out to large radius in the Sombrero Galaxy

We present new velocities for 62 globular clusters in M104 ( NGC 4594, the Sombrero Galaxy), 56 from 2dF on the AAT and 6 from Hydra on WIYN. Combined with previous data, we have a total sample of 108 M104 globular cluster velocities, extending to 20' radius (similar to 60 kpc), along with BVR photometry for each of these. We use this wide-field data set to study the globular cluster kinematics and dark matter content of M104 out to 100 radius ( 30 kpc). We find no rotation in the globular cluster system. The edge-on nature of M104 makes it unlikely that there is strong rotation which is face-on and hence unobserved; thus, the absence of rotation over our large radial range appears to be an intrinsic feature of the globular cluster system in M104. We discuss ways to explain this low rotation, including the possibility that angular momentum has been transferred to even larger radii through galaxy mergers. The cluster velocity dispersion is similar to 230 km s(-1) within several arcminutes of the galaxy center, and drops to similar to 150 km s(-1) at similar to 10' radius. We derive the mass profile of M104 using our velocity dispersion profile, together with the Jeans equation under the assumptions of spherical symmetry and isotropy, and find excellent agreement with the mass inferred from the stellar and gas rotation curve within 30 radius. The M/L-V increases from similar to 4 near the galaxy center to similar to 17 at 7' radius (similar to 20 kpc, or 4 R-e), thus giving strong support for the presence of a dark matter halo in M104. More globular cluster velocities at larger radii are needed to further study the low rotation in the globular cluster system, and to see if the dark matter halo in M104 extends beyond a radius of 30 kpc.