Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/37194

Title

Stellar populations of globular clusters in the elliptical galaxy NGC 1407

Author(s)

Cenarro, A. Javier;  Beasley, Michael A.;  Strader, Jay;  Brodie, Jean P.;  Forbes, Duncan A.

Abstract

We present high-quality Keck spectroscopic data for a sample of 20 globular clusters (GCs) in the massive E0 galaxy NGC 1407. A subset of 20 line-strength indices of the Lick/IDS system has been measured for both the GC system and the central integrated starlight of the galaxy. Ages, metallicities, and [α/Fe] ratios have been derived using several different approaches. The majority of GCs in NGC 1407 studied are old, follow a tight metallicity sequence reaching values slightly above solar, and exhibit mean [α/Fe] ratios of ~0.3 dex. In addition, three GCs are formally derived to be young (~4 Gyr), but we argue that they are actually old GCs hosting blue horizontal branches. We report, for the first time, evidence for the existence of two chemically distinct subpopulations of metal-rich (MR) GCs. We find that some MR GCs exhibit significantly larger [Mg/Fe] and [C/Fe] ratios. Different star formation timescales are proposed to explain the correlation between Mg and C abundances. We also find striking CN overabundances over the entire GC metallicity range. It is interesting to note that the behavior of C and N in metal-poor GCs clearly deviates from that in MR GCs. In particular, for MR GCs, N increases dramatically while C essentially saturates. This may be interpreted as a consequence of the increasing importance of the CNO cycle with increasing metallicity.

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. 134 (Aug 2007), p. 391-410

Publication year

2007

Keyword(s)

Galactic clusters;  Galaxy formation;  GCs;  Globular clusters;  Star clusters

Publisher

University of Chicago Press

ISSN

0004-6256

Publisher URL

http://dx.doi.org/10.1086/518504

Copyright

Copyright © 2007 The American Astronomical Society. All rights reserved.

Peer reviewed