Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/210021

Title

The relationships among compact stellar systems: a fresh view of ultracompact dwarfs

Author(s)

Brodie, Jean P.;  Romanowsky, Aaron J.;  Strader, Jay;  Forbes, Duncan A.

Abstract

We use a combined imaging and spectroscopic survey of the nearby central cluster galaxy, M87, to assemble a sample of 34 confirmed ultra compact dwarfs (UCDs) with half-light radii of >~ 10 pc measured from Hubble Space Telescope images. This doubles the existing sample in M87, making it the largest such sample for any galaxy, while extending the detection of UCDs to unprecedentedly low luminosities (MV = -9). With this expanded sample, we find no correlation between size and luminosity, in contrast to previous suggestions, and no general correlation between size and galactocentric distance. We explore the relationships between UCDs, less luminous extended clusters (including faint fuzzies), globular clusters (GCs), as well as early-type galaxies and their nuclei, assembling an extensive new catalog of sizes and luminosities for stellar systems. Most of the M87 UCDs follow a tight color-magnitude relation, offset from the metal-poor GCs. This, along with kinematical differences, demonstrates that most UCDs are a distinct population from normal GCs, and not simply a continuation to larger sizes and higher luminosities. The UCD color-magnitude trend couples closely with that for Virgo dwarf elliptical nuclei. We conclude that the M87 UCDs are predominantly stripped nuclei. The brightest and reddest UCDs may be the remnant nuclei of more massive galaxies while a subset of the faintest UCDs may be tidally limited and related to more compact star clusters. In the broader context of galaxy assembly, blue UCDs may trace halo build-up by accretion of low-mass satellites, while red UCDs may be markers of metal-rich bulge formation in larger galaxies.

Publication type

Journal article

Research centre

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

Source

Astronomical Journal, Vol. 142, no. 6 (Dec 2011), article no. 199

Publication year

2011

FOR Code(s)

0201 Astronomical and Space Sciences

Keyword(s)

Dwarf galaxies;  Galaxy structure;  Globular clusters;  M87;  Nuclei;  Star cluster

Publisher

Institute of Physics Publishing

ISSN

0004-6256

Publisher URL

http://dx.doi.org/10.1088/0004-6256/142/6/199

Copyright

Copyright © 2011 The American Astronomical Society. All rights reserved. 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/1109.5696.

Peer reviewed