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The segregation of baryons and dark matter during halo assembly

Liao, Shihong; Gao, Liang; Frenk, Carlos S.; Guo, Qi; Wang, Jie

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Authors

Shihong Liao

Liang Gao

Qi Guo

Jie Wang



Abstract

The standard galaxy formation theory assumes that baryons and dark matter are initially well mixed before becoming segregated due to radiative cooling. We use non-radiative hydrodynamical simulations to explicitly examine this assumption and find that baryons and dark matter can also be segregated due to different characteristics of gas and dark matter during the buildup of the halo. As a result, baryons in many haloes do not originate from the same Lagrangian region as the dark matter. When using the fraction of corresponding dark matter and gas particles in the initial conditions (the ‘paired fraction’) as a proxy of the dark matter and gas segregation strength of a halo, on average about 25 per cent of the baryonic and dark matter of the final halo are segregated in the initial conditions. This is at odds with the assumption of the standard galaxy formation model. A consequence of this effect is that the baryons and dark matter of the same halo initially experience different tidal torques and thus their angular momentum vectors are often misaligned. The degree of the misalignment is largely preserved during later halo assembly and can be understood with the tidal torque theory. The result challenges the precision of some semi-analytical approaches that utilize dark matter halo merger trees to infer properties of gas associated with dark matter haloes.

Citation

Liao, S., Gao, L., Frenk, C. S., Guo, Q., & Wang, J. (2017). The segregation of baryons and dark matter during halo assembly. Monthly Notices of the Royal Astronomical Society, 470(2), 2262-2269. https://doi.org/10.1093/mnras/stx1391

Journal Article Type Article
Acceptance Date Jun 3, 2017
Online Publication Date Jun 7, 2017
Publication Date Sep 11, 2017
Deposit Date Aug 4, 2017
Publicly Available Date Mar 28, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 470
Issue 2
Pages 2262-2269
DOI https://doi.org/10.1093/mnras/stx1391

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Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.





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