SUBARU Spectroscopy of the Globular Clusters in the Virgo Giant Elliptical Galaxy M86

TL;DR

This study provides the first spectroscopic analysis of globular clusters in M86, revealing their velocities, metallicities, ages, and evidence for an extended dark matter halo in this Virgo elliptical galaxy.

Contribution

It presents new spectroscopic data for GCs in M86, including velocities, metallicities, ages, and dark matter halo evidence, which were previously unstudied.

Findings

GCs have a mean velocity different from the galaxy nucleus

Evidence suggests the presence of an extended dark matter halo

GCs exhibit a wide range of ages and metallicities

Abstract

We present the first spectroscopic study of the globular clusters (GCs) in the giant elliptical galaxy (gE) M86 in the Virgo cluster. Using spectra obtained in the Multi-Object Spectroscopy (MOS) mode of the Faint Object Camera and Spectrograph (FOCAS) on the Subaru telescope, we measure the radial velocities for 25 GCs in M86. The mean velocity of the GCs is derived to be vp = -354+81 -79 km/s, which is different from the velocity of the M86 nucleus (vgal = -234\pm41 km/s). We estimate the velocity dispersion of the GCs, {\sigma}p = 292+32-32 km/s, and find a hint of rotation of the M86 GC system. A comparison of the observed velocity dispersion profiles of the GCs and stars with a prediction based on the stellar mass profile strongly suggests the existence of an extended dark matter halo in M86. We also estimate the metallicities and ages for 16 and 8 GCs, respectively. The metallicities of M86 GCs are in the range -2.0 < [Fe/H] < -0.2 with a mean value of -1.13\pm0.47. These GCs show a wide age distribution from 4 to 15 Gyr.