The Rising Stellar Velocity Dispersion of M87 from Integrated Starlight

Abstract

We have measured the line-of-sight velocity distribution from integrated stellar light at two points in the outer halo of M87 (NGC 4486), the second-rank galaxy in the Virgo Cluster. The data were taken at R = 480" ($\sim 41.5$ kpc) and R = 526" ($\sim 45.5$ kpc) along the SE major axis. The second moment for a non-parametric estimate of the full velocity distribution is $420\pm 23$ km/s and $577\pm 35$ km/s respectively. There is intriguing evidence in the velocity profiles for two kinematically distinct stellar components at the position of our pointing. Under this assumption we employ a two-Gaussian decomposition and find the primary Gaussian having rest velocities equal to M87 (consistent with zero rotation) and second moments of $383\pm 32$ km/s and $446\pm 43$ km/s respectively. The asymmetry seen in the velocity profiles suggests that the stellar halo of M87 is not in a relaxed state and confuses a clean dynamical interpretation. That said, either measurement (full or two component model) shows a rising velocity dispersion at large radii, consistent with previous integrated light measurements, yet significantly higher than globular cluster measurements at comparable radial positions. These integrated light measurements at large radii, and the stark contrast they make to the measurements of other kinematic tracers, highlight the rich kinematic complexity of environments like the center of the Virgo Cluster and the need for caution when interpreting kinematic measurements from various dynamical tracers.

16 pages, 5 figures; accepted for publication in The Astrophysical Journal

References in corpus (13)

• The hierarchical formation of the brightest cluster galaxies
• Evolutionary Stellar Population Synthesis with MILES. Part I: The Base Models and a New Line Index System
• Size evolution of the most massive galaxies at 1.7<z<3 from GOODS NICMOS survey imaging
• The Black Hole Mass, Stellar M/L, and Dark Halo in M87
• The Importance of Mergers for the Origin of Intracluster Stars in Cosmological Simulations of Galaxy Clusters
• Kinematic properties of early-type galaxy haloes using planetary nebulae
• Dynamical masses of early-type galaxies at z~2: Are they truly superdense?
• The evolution of the brightest cluster galaxies since z~1 from the ESO Distant Cluster Survey (EDisCS)
• Evolution in the structural properties of early-type Brightest Cluster Galaxies at small lookback time and dependence on the environment
• Spectroscopic Determination of the Faint End of the Luminosity Function in the Nearby Galaxy Clusters A2199 and Virgo
• The Kinematics of Intracluster Planetary Nebulae and the On-Going Subcluster Merger in the Coma Cluster Core
• Radial kinematics of brightest cluster galaxies
• Counter-dispersed slitless-spectroscopy technique: planetary nebula velocities in the halo of NGC 1399

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• The MASSIVE Survey - VIII. Stellar Velocity Dispersion Profiles and Environmental Dependence of Early-Type Galaxies
• Photometric dissection of Intracluster Light and its correlations with host cluster properties
• A kinematically distinct core and minor-axis rotation: the MUSE perspective on M87
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• Study of gravitational fields and globular cluster systems of early-type galaxies
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