ACCRETION-DRIVEN TURBULENCE AND THE TRANSITION TO GLOBAL INSTABILITY IN YOUNG GALAXY DISKS
- IBM Research Division, T.J. Watson Research Center, P.O. Box 218, Yorktown Heights, NY 10598 (United States)
- University Observatory Munich (USM), Scheinerstrasse 1, 81679 Munich (Germany)
A simple model of gas accretion in young galaxy disks suggests that fast turbulent motions can be driven by accretion energy for a time t{sub acc} {approx} 2(epsilon{sup 0.5} GM {sup 2}/xiV {sup 3}){sup 0.5} where epsilon is the fraction of the accretion energy going into disk turbulence, M and V are the galaxy mass and rotation speed, and xi is the accretion rate. After t{sub acc}, accretion is replaced by disk instabilities as a source of turbulence driving, and shortly after that, energetic feedback by young stars should become important. The star formation rate equilibrates at the accretion rate after 1 to 2 t{sub acc}, depending on the star formation efficiency per dynamical time. The fast turbulence that is observed in high-redshift starburst disks is not likely to be driven by accretion because the initial t{sub acc} phase is over by the time the starburst is present. However, the high turbulent speeds that must have been present earlier, when the observed massive clumps first formed, could have been driven by accretion energy. The combined observations of a high relative velocity dispersion in the gas of z {approx} 2 clumpy galaxies and a gas mass comparable to the stellar mass suggest that either the star formation efficiency is fairly high, perhaps 10x higher than in local galaxies, or the observed turbulence is powered by young stars.
- OSTI ID:
- 21394275
- Journal Information:
- Astrophysical Journal, Vol. 712, Issue 1; Other Information: DOI: 10.1088/0004-637X/712/1/294; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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