Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/76046

Download PDF (Accepted manuscript) (Adobe Acrobat PDF, -1 bytes)

Title

Diamonds on the Hat: globular clusters in the Sombrero galaxy (M104)

Author(s)

Harris, William E.;  Spitler, Lee R.;  Forbes, Duncan A.;  Bailin, Jeremy

Abstract

Images from the Hubble Space Telescope Advanced Camera for surveys are used to carry out a new photometric study of the globular clusters (GCs) in M104, the Sombrero galaxy. The primary focus of our study is the characteristic distribution function of linear sizes [size distribution function (SDF)] of the GCs. We measure the effective radii for 652 clusters with point spread function-convolved King and Wilson dynamical model fits. The SDF is remarkably similar to those measured for other large galaxies of all types, adding strong support to the view that it is a 'universal' feature of GC systems. We use the Sombrero and Milky Way data and the formation models of Baumgardt & Kroupa (2007) to develop a more general interpretation of the SDF for GCs. We propose that the shape of the SDF that we see today for GCs is strongly influenced by the early rapid mass loss during their star-forming stage, coupled with stochastic differences from cluster to cluster in the star formation efficiency (SFE) and their initial sizes. We find that the observed SDF shape can be accurately predicted by a simple model in which the protocluster clouds had characteristic sizes of 0.9 ± 0.1 pc and SFEs of 0.3 ± 0.07 . The colours and luminosities of the M104 clusters show the clearly defined classic bimodal form. The blue sequence exhibits a mass/metallicity relation, following a scaling of heavy-element abundance with luminosity of Z∼L0.3 very similar to what has been found in most giant elliptical galaxies. A quantitative self-enrichment model provides a good first-order match to the data for the same initial SFE and protocluster size that were required to explain the SDF. We also discuss various forms of the GC Fundamental Plane of structural parameters and show that useful tests of it can be extended to galaxies beyond the Local Group. The M104 clusters strongly resemble those of the Milky Way and other nearby systems in terms of such test quantities as integrated surface density and binding energy.

Publication type

Journal article

Research centre

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

Source

Monthly Notices of the Royal Astronomical Society, Vol. 401, no. 3 (Jan 2010), pp. 1965-1982

Publication year

2010

Keyword(s)

M104 clusters;  Globular clusters;  Sombrero galaxy;  Star clusters

Publisher

Wiley-Blackwell Publishing

ISSN

0035-8711

Publisher URL

http://dx.doi.org/10.1111/j.1365-2966.2009.15783.x

Copyright

Copyright © 2009 The Authors. Journal compilation copyright © 2009 Royal Astronomical Society. The accepted manuscript of the paper is reproduced here in accordance with the copyright policy of the publisher. The definitive publication is available at www.interscience.wiley.com.

Full text

Peer reviewed