Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/211879

Title

Wide-field precision kinematics of the M87 globular cluster system

Author(s)

Strader, Jay;  Romanowsky, Aaron J.;  Brodie, Jean P.;  Spitler, Lee R.;  Beasley, Michael A.;  Arnold, Jacob A.;  Tamura, Naoyuki;  Sharples, Ray M.;  Arimoto, Nobuo

Abstract

We present the most extensive combined photometric and spectroscopic study to date of the enormous globular cluster (GC) system around M87, the central giant elliptical galaxy in the nearby Virgo Cluster. Using observations from DEIMOS and the Low Resolution Imaging Spectrometer at Keck, and Hectospec on the Multiple Mirror Telescope, we derive new, precise radial velocities for 451 GCs around M87, with projected radii from 5 to 185kpc. We combine these measurements with literature data for a total sample of 737 objects, which we use for a re-examination of the kinematics of the GC system of M87. The velocities are analyzed in the context of archival wide-field photometry and a novel Hubble Space Telescope catalog of half-light radii, which includes sizes for 344 spectroscopically confirmed clusters. We use this unique catalog to identify 18 new candidate ultracompact dwarfs and to help clarify the relationship between these objects and true GCs. We find much lower values for the outer velocity dispersion and rotation of the GC system than in earlier papers and also differ from previous work in seeing no evidence for a transition in the inner halo to a potential dominated by the Virgo Cluster, nor for a truncation of the stellar halo. We find little kinematical evidence for an intergalactic GC population. Aided by the precision of the new velocity measurements, we see significant evidence for kinematical substructure over a wide range of radii, indicating that M87 is in active assembly. A simple, scale-free analysis finds less dark matter within 85kpc than in other recent work, reducing the tension between X-ray and optical results. In general, out to a projected radius of 150kpc, our data are consistent with the notion that M87 is not dynamically coupled to the Virgo Cluster; the core of Virgo may be in the earliest stages of assembly.

Publication type

Journal article

Research centre

Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Astrophysics and Supercomputing

Source

Astrophysical Journal Supplement Series, Vol. 197, no. 2 (Dec 2011), article no. 33

Publication year

2011

FOR Code(s)

0201 Astronomical and Space Sciences;  0305 Organic Chemistry;  0306 Physical Chemistry (Incl. Structural)

Keyword(s)

cD;  Dark matter;  Dynamics;  Elliptical galaxies;  Globular clusters;  Kinematics;  Lenticular galaxies;  M87;  Star clusters

Publisher

Institute of Physics Publishing

ISSN

0067-0049

Publisher URL

http://dx.doi.org/10.1088/0067-0049/197/2/33

Copyright

Copyright © 2011 The American Astronomical Society. All rights reserved. The American Astronomical Society does not allow institutions to archive either the accepted manuscript or the published version of the article. However, you can find an earlier version of the full text here: http://arxiv.org/abs/1110.2778

Peer reviewed