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Title

Spectra of globular clusters in the Sombrero galaxy: evidence for spectroscopic metallicity bimodality

Author(s)

Alves-Brito, Alan;  Hau, George K. T.;  Forbes, Duncan A.;  Spitler, Lee R.;  Strader, Jay;  Brodie, Jean P.;  Rhode, Katherine L.

Abstract

We present a large sample of over 200 integrated-light spectra of confirmed globular clusters (GCs) associated with the Sombrero (M104) galaxy taken with the Deep Imaging Multi-Object Spectrograph (DEIMOS) instrument on the Keck telescope. A significant fraction of the spectra have signal-to-noise ratio levels high enough to allow measurements of GC metallicities using the method of Brodie & Huchra. We find a distribution of spectroscopic metallicities in the range -2.2 < [Fe/H] < +0.1 that is bimodal, with peaks at [Fe/H]---1.4 and -0.6. Thus, the GC system of the Sombrero galaxy, like a few other galaxies now studied in detail, reveals a bimodal spectroscopic metallicity distribution supporting the long-held belief that colour bimodality reflects two metallicity subpopulations. This further suggests that the transformation from optical colour to metallicity for old stellar populations, such as GCs, is not strongly non-linear. We also explore the radial and magnitude distribution with metallicity for GC subpopulations but small number statistics prevent any clear trends in these distributions.

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. 417, no. 3 (Nov 2011), pp. 1823-1838

Publication year

2011

FOR Code(s)

0201 Astronomical and Space Sciences

Keyword(s)

Globular clusters;  M104;  NGC 4594;  Sombrero galaxy;  Star clusters

Publisher

Wiley-Blackwell

ISSN

0035-8711

Publisher URL

http://dx.doi.org/10.1111/j.1365-2966.2011.19368.x

Copyright

Copyright © 2011 The Authors. Journal compilation copyright © 2011 Royal Astronomical Society. The accepted manuscript is reproduced in accordance with the copyright policy of the publisher. The definitive publication is available at www.interscience.wiley.com.

Full text

Peer reviewed