Keck Cosmic Web Imager (KCWI) Spectra of Globular Clusters and Ultra Compact Dwarfs in the Halo of M87

Abstract

Using the Keck Cosmic Web Imager we obtain spectra of several globular clusters (GCs), ultra compact dwarfs (UCDs) and the inner halo starlight of M87, at a similar projected galactocentric radius of $\sim$5 kpc. This enables us, for the first time, to apply the same stellar population analysis to the GCs, UCDs and starlight consistently to derive ages, metallicities and alpha-element abundances in M87. We find evidence for a dual stellar population in the M87 halo light, i.e an $\sim$80\% component by mass which is old and metal-rich and a $\sim$20\% component which is old but metal-poor. Two red GCs share similar stellar populations to the halo light suggesting they may have formed contemporaneously with the dominant halo component. Three UCDs, and one blue GC, have similar stellar populations, with younger mean ages, lower metallicities and near solar alpha-element abundances. Combined with literature data, our findings are consistent with the scenario that UCDs are the remnant nucleus of a stripped galaxy. We further investigate the discrepancy in the literature for M87's kinematics at large radii, favouring a declining velocity dispersion profile. This work has highlighted the need for more self-consistent studies of galaxy halos.

12 pages, 10 figures, accepted for publication in MNRAS

References in corpus (23)

• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• Evolutionary Stellar Population Synthesis with MILES. Part I: The Base Models and a New Line Index System
• UV-extended E-MILES stellar population models: young components in massive early-type galaxies
• Evolutionary stellar population synthesis with MILES - II. Scaled-solar and α-enhanced models
• A Supermassive Black Hole in an Ultracompact Dwarf Galaxy
• The AIMSS Project I: Bridging the Star Cluster - Galaxy Divide
• The SAGES Legacy Unifying Globulars and GalaxieS Survey (SLUGGS): Sample definition, methods, and initial results
• Halo Mass and Assembly History Exposed in the Faint Outskirts: the Stellar and Dark Matter Haloes of Illustris Galaxies
• The Next Generation Virgo Cluster Survey. VI. The Kinematics of Ultra-compact Dwarfs and Globular Clusters in M87
• The MASSIVE Survey - VIII. Stellar Velocity Dispersion Profiles and Environmental Dependence of Early-Type Galaxies
• The Age, Metallicity and Alpha-Element Abundance of Galactic Globular Clusters from Single Stellar Population Models
• The SLUGGS Survey: stellar masses and effective radii of early-type galaxies from Spitzer Space Telescope 3.6$\mu$m imaging
• The Distribution of Ultra-Diffuse and Ultra-Compact Galaxies in the Frontier Fields
• A kinematically distinct core and minor-axis rotation: the MUSE perspective on M87
• The AIMSS Project II: Dynamical-to-Stellar Mass Ratios Across the Star Cluster - Galaxy Divide
• Searches for Ultra-Compact Dwarf Galaxies in Galaxy Groups
• Compact Stellar Systems around NGC 1399
• Detection of a distinct metal-poor stellar halo in the early-type galaxy NGC 3115
• How elevated is the dynamical-to-stellar mass ratio of the ultra-compact dwarf S999?
• A metal-poor ultra compact dwarf galaxy at a kiloparsec distance from the low-mass elliptical galaxy FCC47
• The Strikingly Metal-Rich Halo of the Sombrero Galaxy
• An expanded catalogue of low surface brightness galaxies in the Coma cluster using Subaru/Suprime-Cam
• Spatially-resolved stellar populations and kinematics with KCWI: probing the assembly history of the massive early-type galaxy NGC 1407