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arXiv · 1206.2360

Newborn spheroids at high redshift: when and how did the dominant, old stars in today's massive galaxies form?

S. Kaviraj·S. Cohen·R. S. Ellis·S. Peirani·R. A. Windhorst·R. W. O'Connell·J. Silk·B. C. Whitmore·N. P. Hathi·R. E. Ryan Jr·M. A. Dopita·J. A. Frogel·A. Dekel
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Abstract

We study ~330 massive (M* > 10^9.5 MSun), newborn spheroidal galaxies (SGs) around the epoch of peak star formation (1 10^10.5 MSun, and an age trend becomes evident in this mass regime: SGs with M* > 10^11.5 MSun are ~2 Gyrs older than their counterparts with M* < 10^10.5 MSun. Nevertheless, a smooth downsizing trend with galaxy mass is not observed, and the large scatter in starburst ages indicate that SGs are not a particularly coeval population. Around half of the blue SGs appear not to drive their star formation via major mergers, and those that have experienced a recent major merger, show only modest enhancements (~40%) in their specific star formation rates. Our empirical study indicates that processes other than major mergers (e.g. violent disk instability driven by cold streams and/or minor mergers) likely play a dominant role in building SGs, and creating a significant fraction of the old stellar populations that dominate today's Universe.

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S. Kaviraj, S. Cohen, R. S. Ellis, S. Peirani, R. A. Windhorst, R. W. O'Connell, J. Silk, B. C. Whitmore, N. P. Hathi, R. E. Ryan Jr, M. A. Dopita, J. A. Frogel, A. Dekel. 2012-09-27. Newborn spheroids at high redshift: when and how did the dominant, old stars in today's massive galaxies form?. https://doi.org/10.1093/mnras%2Fsts031

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