CCD PHOTOMETRY OF THE GLOBULAR-CLUSTER SYSTEMS IN NGC-4494 AND NGC-4565

NGC 4494, a large elliptical galaxy, and NGC 4565, an edge-on Sb spiral similar in size to M31 and the Milky Way, have usually been regarded as members of the Coma I group of galaxies at d∼10 Mpc. We present new V-band CCD photometry of the globular cluster systems around both of these galaxies, and use these data to test whether or not the two galaxies are indeed in the same group. Our photometry of the cluster luminosity function (GCLF) yields distance moduli for the two systems of (m-M)0=30.8±0.4 (NGC 4494) and (m-M)0=30.00±0.30 (NGC 4565), which suggest that they are not in the same physical group (NGC 4565 is in Coma I, while NGC 4494 is in the background). We use these galaxies along with several others in the literature to review the calibration of the GCLF turnover luminosity as a function of Hubble type: for large spiral galaxies, we find 〈M0V〉=-7.4±0.2, and for large ellipticals, 〈M0V〉=-7.2±0.1 (although the latter mean depends strongly on an assumed Virgo distance modulus of 31.0). For both NGC 4494 and 4565, we also derive the structural parameters of the two globular cluster systems, including their radial distributions and specific frequencies.