期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 451, 期 1, 页码 433-454出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stv989
关键词
galaxies: evolution; galaxies: peculiar; galaxies: star formation
资金
- Missouri Consortium of NASA's National Space Grant College
- Research Corporation for Science Advancement under the Cottrell College Science Award [10777]
- Alfred P. Sloan Foundation
- National Aeronautics and Space Administration
- National Science Foundation
- US Department of Energy
- Japanese Monbukagakusho
- Max Planck Society
- University of Chicago
- Fermi lab
- Institute for Advanced Study
- Japan Participation Group
- Johns Hopkins University
- Los Alamos National Laboratory
- Max-Planck-Institute for Astronomy (MPIA)
- Max-Planck-Institute for Astrophysics (MPA)
- New Mexico State University
- University of Pittsburgh
- Princeton University
- United States Naval Observatory
- University of Washington
- Spanish Ministry of Science [ICTS-2009-10]
- Centro Astroni?oemico Hispano-Aleman
The modern merger hypothesis offers a method of forming a new elliptical galaxy through merging two equal-mass, gas-rich disc galaxies fuelling a nuclear starburst followed by efficient quenching and dynamical stabilization. A key prediction of this scenario is a central concentration of young stars during the brief phase of morphological transformation from highly disturbed remnant to new elliptical galaxy. To test this aspect of the merger hypothesis, we use integral field spectroscopy to track the stellar Balmer absorption and 4000-angstrom break strength indices as a function of galactic radius for 12 massive (M* >= 10(10)M(circle dot)), nearby (z <= 0.03), visually-selected plausible new ellipticals with blue-cloud optical colours and varying degrees of morphological peculiarities. We find that these index values and their radial dependence correlate with specific morphological features such that the most disturbed galaxies have the smallest 4000-angstrom break strengths and the largest Balmer absorption values. Overall, two-thirds of our sample are inconsistent with the predictions of the modern merger hypothesis. Of these eight, half exhibit signatures consistent with recent minor merger interactions. The other half have star formation histories similar to local, quiescent early-type galaxies. Of the remaining four galaxies, three have the strong morphological disturbances and star-forming optical colours consistent with being remnants of recent, gas-rich major mergers, but exhibit a weak, central burst consistent with forming similar to 5 per cent of their stars. The final galaxy possesses spectroscopic signatures of a strong, centrally concentrated starburst and quiescent core optical colours indicative of recent quenching (i.e. a post-starburst signature) as prescribed by the modern merger hypothesis.
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