The Globular Cluster System of NGC4374

Abstract

We study the globular cluster system (GCS) of the giant elliptical NGC4374 (M84) in the Virgo cluster using B and R photometry. The colour distribution is bimodal with peaks at B-R=1.11 and B-R=1.36, fitting well to those found in other early-type galaxies. The radial profile of the cluster number density is flatter than the galaxy light. Using the luminosity function we derive a distance modulus of $\mu=31.61\pm0.2$, which within the uncertainty agrees with the distance from surface brightness fluctuations. Blue and red clusters show similar radial concentrations and azimuthal distributions. The total number of clusters is $N=1775\pm150$, which together with our distance modulus leads to a specific frequency of $S_{N}=1.6\pm0.3$. This value is surprisingly low for a giant elliptical, but resembles the case of merger remnants like NGC1316, where the low specific frequency is probably caused by the luminosity contribution of an intermediate-age population. A further common property is the high rate of type Ia supernovae which also may indicate the existence of a younger population. However, unlike in the case of NGC1316, one cannot find any further evidence that NGC4374 indeed hosts younger populations. The low specific frequency would also fit to a S0 galaxy seen face-on.