A Wide-field Photometric Survey of Globular Clusters in the Peculiar Early-type Galaxy M85

Abstract

We survey globular clusters (GCs) in M85 using $ugi$-band images of a $1^{\circ }\times 1^{\circ }$ field obtained with the MegaCam at the 3.6 m Canada-France-Hawaii Telescope. We identify 1318 GC candidates with 20.0 mag $<g_0<$ 23.5 mag in the entire survey region. Their radial number density profile is well fit by a S{é}rsic profile with $n$ = 2.58${}_{-0.33}^{+0.43}$ and effective radius $R_{\mathrm{e},\mathrm{GCS}}$ = 4$\text{.}{}^{\prime }$14 (= 22 kpc), showing that the candidates at $R<20^{\prime }$ are mostly genuine GCs in M85. We estimate the total number of GCs, $N$(total) = $1216_{-50}^{+82}$, and the specific frequency, $S_N=1.41_{-0.06}^{+0.10}$. The overall color distribution of the GCs in M85 is bimodal, but the GCs in the central region at $R<2^{\prime }$ do not show a bimodal distribution clearly. The radial number density profile and surface number density map of the blue GCs (BGCs) show more extended structures than those of the red GCs (RGCs). The spatial distributions of both BGCs and RGCs are elongated, similar to that of the galaxy stellar light. The number fraction of the RGCs in the central region is much smaller compared to those in other early-type galaxies of similar luminosity. The mean $(g-i{)}_0$ color of the RGCs in M85 is about 0.1 mag bluer than typical values for other Virgo early-type galaxies of similar luminosity, indicating that a significant fraction of the RGCs in M85 may be younger than typical GCs. These results indicate that M85 might have undergone a major wet merger recently.

20 pages, 19 figures, 4 tables, accepted for publication in ApJ

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• Tracing the Giant Outer Halo of the Mysterious Massive Disk Galaxy M104 I. Photometry of the Extended Globular Cluster Systems
• Nonlinear Color-Metallicity Relations of Globular Clusters. IX. Different Radial Number Density Profiles between Blue and Red Clusters
• Mysterious Globular Cluster System of the Peculiar Massive Galaxy M85
• The Color Gradients of the Globular Cluster Systems in M87 and M49