GLOBULAR CLUSTER SYSTEMS IN DWARF ELLIPTICAL GALAXIES. I. THE dE,N GALAXY NGC 3115 DW1

摘要

We present new BV photometry of the globular cluster system (GCS) around the dE1,N dwarf companion galaxy to NGC 3115. Its GCS has a total population of 59 ± 23 clusters and a mean mietallicity < [Fe/H] > approx= -1.2 ± 0.13, which is about 0.5 dex more metal poor (in the mean) than that of the dE halo light. Neither the GCS nor the galaxy halo exhibits a radial color gradient. We derive a distance modulus (m - M)_V = 30.3_(-0.5)~(+0.8) (d ～ 11_(-2.3)~(+5) Mpc) by using the turnover of the globular cluster luminosity function (GCLF); this result is consistent with the dwarf being a physical satellite of NGC 3115. The specific frequency of NGC 3115 DW1 is S_N = 4.9 ± 1.9, considerably larger than that of NGC 3115 itself, but similar to those of dE's in the Local Group, as well as many large ellipticals. Finally, we find that the GCS mass spectrum follows a power law dN/dm ～ m~(-1.8) above the turnover of the GCLF. This slope is similar to those found in many larger elliptical and spiral galaxies and suggests that the mechanisms of globular cluster formation are similar in galaxies of a large range in mass.