Cosmic vorticity and the origin halo spins
Entity
UAM. Departamento de Física TeóricaPublisher
The American Astronomical Society. All rights reserved. Printed in the U.S.A.Date
2013-04-01Citation
10.1088/2041-8205/766/2/L15
The Astrophysical Journal Letters 766.2 (2013): L15
ISSN
2041-8205 (print); 2041-8213 (online)DOI
10.1088/2041-8205/766/2/L15Editor's Version
http://iopscience.iop.org/2041-8205/766/2/L15/Subjects
Dark matter; Large-scale structure of universe; Cosmology; Galaxies; FísicaNote
Astrophysical Journal Letters 766.2 (2013) L15 reproduced by permission of the AASRights
© 2013. The American Astronomical Society. All rights reserved. Printed in the U.S.A.Abstract
In the standard model of cosmology, structure emerges out of a non-rotational flow and the angular momentum of collapsing halos is induced by tidal torques. The growth of angular momentum in the linear and quasi-linear phases is associated with a shear, curl-free, flow and it is well described within the linear framework of tidal torque theory (TTT). However, TTT ceases to be applicable as halos approach turnaround when their ambient flow field becomes rotational. Subsequently, halos become embedded in a vortical flow field and the growth of their angular momentum is affected by the vorticity of their ambient velocity field. Using a cosmological simulation, we have examined the importance of the curl of the velocity field in determining halo spin, finding a significant alignment between the two: the vorticity tends to be perpendicular to the axis of the fastest collapse of the velocity shear tensor (e 1). This is independent of halo masses and cosmic web environment. Our results agree with previous findings on the tendency of halo spin to be perpendicular to e 1, and of the spin of (simulated) halos and (observed) galaxies to be aligned with the large-scale structure. It follows that angular momentum growth proceeds in two distinct phases. First, the angular momentum emerges out of a shear, curl-free, potential flow, as described by TTT. In the second phase, in which halos approach virialization, the angular momentum emerges out of a vortical flow and halo spin becomes partially aligned with the vorticity of the ambient flow field.
Files in this item
Google Scholar:Libeskind, Noam I.
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Hoffman, Yehuda
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Steinmetz, Matthias
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Gottlöber, Stefan
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Knebe, Alexander
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Hess, Steffen
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