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Cold streams in early massive hot haloes as the main mode of galaxy formation


Dekel, A; Birnboim, Y; Engel, G; Freundlich, J; Goerdt, T; Mumcuoglu, M; Neistein, E; Pichon, C; Teyssier, R; Zinger, E (2009). Cold streams in early massive hot haloes as the main mode of galaxy formation. Nature, 457(7228):451-454.

Abstract

Massive galaxies in the young Universe, ten billion years ago, formed stars at surprising intensities1, 2. Although this is commonly attributed to violent mergers, the properties of many of these galaxies are incompatible with such events, showing gas-rich, clumpy, extended rotating disks not dominated by spheroids1, 2, 3, 4, 5. Cosmological simulations6 and clustering theory6, 7 are used to explore how these galaxies acquired their gas. Here we report that they are 'stream-fed galaxies', formed from steady, narrow, cold gas streams that penetrate the shock-heated media of massive dark matter haloes8, 9. A comparison with the observed abundance of star-forming galaxies implies that most of the input gas must rapidly convert to stars. One-third of the stream mass is in gas clumps leading to mergers of mass ratio greater than 1:10, and the rest is in smoother flows. With a merger duty cycle of 0.1, three-quarters of the galaxies forming stars at a given rate are fed by smooth streams. The rarer, submillimetre galaxies that form stars even more intensely2, 12, 13 are largely merger-induced starbursts. Unlike destructive mergers, the streams are likely to keep the rotating disk configuration intact, although turbulent and broken into giant star-forming clumps that merge into a central spheroid4, 10, 11. This stream-driven scenario for the formation of discs and spheroids is an alternative to the merger picture.

Abstract

Massive galaxies in the young Universe, ten billion years ago, formed stars at surprising intensities1, 2. Although this is commonly attributed to violent mergers, the properties of many of these galaxies are incompatible with such events, showing gas-rich, clumpy, extended rotating disks not dominated by spheroids1, 2, 3, 4, 5. Cosmological simulations6 and clustering theory6, 7 are used to explore how these galaxies acquired their gas. Here we report that they are 'stream-fed galaxies', formed from steady, narrow, cold gas streams that penetrate the shock-heated media of massive dark matter haloes8, 9. A comparison with the observed abundance of star-forming galaxies implies that most of the input gas must rapidly convert to stars. One-third of the stream mass is in gas clumps leading to mergers of mass ratio greater than 1:10, and the rest is in smoother flows. With a merger duty cycle of 0.1, three-quarters of the galaxies forming stars at a given rate are fed by smooth streams. The rarer, submillimetre galaxies that form stars even more intensely2, 12, 13 are largely merger-induced starbursts. Unlike destructive mergers, the streams are likely to keep the rotating disk configuration intact, although turbulent and broken into giant star-forming clumps that merge into a central spheroid4, 10, 11. This stream-driven scenario for the formation of discs and spheroids is an alternative to the merger picture.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute for Computational Science
Dewey Decimal Classification:530 Physics
Language:English
Date:January 2009
Deposited On:27 Feb 2010 16:01
Last Modified:05 Apr 2016 13:56
Publisher:Nature Publishing Group
ISSN:0028-0836
Funders:France-Israel Teamwork in Sciences, German-Israel Science Foundation, Israel Science Foundation, NASA Theory Program at UCSC, Minerva fellowship
Publisher DOI:https://doi.org/10.1038/nature07648
Related URLs:http://arxiv.org/abs/0808.0553

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Download PDF  'Cold streams in early massive hot haloes as the main mode of galaxy formation'.
Preview
Content: Accepted Version
Filetype: PDF (Accepted manuscript, Version 1)
Size: 1MB