Globular Clusters as Probes of the Virgo gE NGC 4472

We present radial velocities for 144 globular clusters (GCs) around the Virgo gE NGC 4472 (M49), and ages and metallicities from co-added spectra of 131 GCs. We confirm our earlier finding that the metal-poor GCs have a significantly higher velocity dispersion than the metal-rich GCs, and we find little or no rotation in the metal-rich GCs. The velocity dispersion profile is consistent with isotropic orbits for the GCs and the NGC 4472 mass distribution inferred from X-ray data. Our sample of GCs spans a metallicity range of −1.6 ≤ [Fe/H] ≤ 0 dex. The metal-poor and metal-rich GC populations are coeval within the errors, and all GCs older than 6 Gyr at 95% confidence. Our findings are consistent with a merger origin for NGC 4472, but other elliptical formation models cannot be ruled out.