WASHINGTON PHOTOMETRY OF THE GLOBULAR-CLUSTER SYSTEM AROUND NGC-3311 .2. SPATIAL STRUCTURE AND MASS-SPECTRUM

We present Washington T1 photometry of globular clusters around NGC 3311, the central cD in the A1060 (Hydra I) galaxy cluster. The surface density profile of the globular cluster system (GCS) is traced over galactocentric radii 0′.4≲R≲3′.5 (5≲R≲45 kpc); we find σcl∼R-1.4, which follows the radial profile of the galaxy's halo light very closely in this region. The balance of current observational evidence suggests that the only places in D/cD systems where such halo-GCS congruities exist are the envelopes of cD galaxies. The shape of the GCS at R≳0.′9 is found to be at least E3 (and possibly even E4), which, in turn, is at least as elliptical as the galaxy itself at these radii. The mass spectrum of the most luminous globular clusters is also investigated; it follows a power law of logarithmic slope -2.9±0.2 for MV≲-9, which is identical to the value (-3.2±0.5) appropriate for a similar (but narrower) mass range in the GCSs of early-type galaxies in Virgo. The specific frequency of the NGC 3311 GCS is calculated as 15±6; this is somewhat lower than previous investigations had indicated, but is almost identical to the value for M87, and thus still firmly in the "high-SN" regime.