Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/201736

Title

The fossil record of two-phase galaxy assembly: kinematics and metallicities in the nearest S0 galaxy

Author(s)

Arnold, Jacob A.;  Romanowsky, Aaron J.;  Brodie, Jean P.;  Chomiuk, Laura;  Spitler, Lee R.;  Strader, Jay;  Benson, Andrew J.;  Forbes, Duncan A.

Abstract

We present a global analysis of kinematics and metallicity in the nearest S0 galaxy, NGC 3115, along with implications for its assembly history. The data include high-quality wide-field imaging from Suprime-Cam on the Subaru telescope, and multi-slit spectra of the field stars and globular clusters (GCs) obtained using Keck-DEIMOS/LRIS and Magellan-IMACS. Within two effective radii, the bulge (as traced by the stars and metal-rich GCs) is flattened and rotates rapidly (v/σ 1.5). At larger radii, the rotation declines dramatically to v σ ~ 0.7, but remains well aligned with the inner regions. The radial decrease in characteristic metallicity of both the metal-rich and metal-poor GC subpopulations produces strong gradients with power-law slopes of –0.17 ± 0.04 and –0.38 ± 0.06 dex dex–1, respectively. We argue that this pattern is not naturally explained by a binary major merger, but instead by a two-phase assembly process where the inner regions have formed in an early violent, dissipative phase, followed by the protracted growth of the outer parts via minor mergers with typical mass ratios of ~15-20:1.

Publication type

Journal article

Research centre

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

Source

Astrophysical Journal Letters, Vol. 736, no. 2 (Aug 2011), article no. L26

Publication year

2011

Keyword(s)

Galaxy bulges;  Galaxy dynamics;  Galaxy formation;  Galaxy kinematics;  Globular clusters;  Halos;  NGC 3115

Publisher

Institute of Physics Publishing

ISSN

2041-8205

Publisher URL

http://dx.doi.org/10.1088/2041-8205/736/2/l26

Copyright

Copyright © 2011 The American Astronomical Society. All rights reserved. The American Astronomical Society does not allow Swinburne Research Bank 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/1106.0745

Peer reviewed