On the formation and stability of fermionic dark matter haloes in a cosmological framework

Argüelles, Carlos R.; Díaz, Manuel I.; Krut, Andreas; Yunis, Rafael

doi:10.1093/mnras/staa3986

On the formation and stability of fermionic dark matter haloes in a cosmological framework

Carlos R. Argüelles
(
- UNLP, La Plata (main)
)
,
Manuel I. Díaz
(
- LPENS, Paris and
- Buenos Aires U.
)
,
Andreas Krut
(
- LPENS, Paris and
- Buenos Aires U.
)
,
Rafael Yunis
(
- ICRA, Pescara and
- Rome U.
)

Dec 21, 2020

20 pages

Published in:

Mon.Not.Roy.Astron.Soc. 502 (2021) 3, 4227-4246

Published: Mar 2, 2021

e-Print:

2012.11709 [astro-ph.GA]

DOI:

10.1093/mnras/staa3986 (publication)

View in:

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Abstract: (Oxford University Press)

The formation and stability of collisionless self-gravitating systems are long-standing problems, which date back to the work of D. Lynden-Bell on violent relaxation and extends to the issue of virialization of dark matter (DM) haloes. An important prediction of such a relaxation process is that spherical equilibrium states can be described by a Fermi–Dirac phase-space distribution, when the extremization of a coarse-grained entropy is reached. In the case of DM fermions, the most general solution develops a degenerate compact core surrounded by a diluted halo. As shown recently, the latter is able to explain the galaxy rotation curves, while the DM core can mimic the central black hole. A yet open problem is whether these kinds of astrophysical core–halo configurations can form at all, and whether they remain stable within cosmological time-scales. We assess these issues by performing a thermodynamic stability analysis in the microcanonical ensemble for solutions with a given particle number at halo virialization in a cosmological framework. For the first time, we demonstrate that the above core–halo DM profiles are stable (i.e. maxima of entropy) and extremely long-lived. We find the existence of a critical point at the onset of instability of the core–halo solutions, where the fermion-core collapses towards a supermassive black hole. For particle masses in the keV range, the core-collapse can only occur for |

M_{\rm vir} \gtrsim 10^{9}{\, \mathrm{M}_\odot}

| starting at z_vir ≈ 10 in the given cosmological framework. Our results prove that DM haloes with a core–halo morphology are a very plausible outcome within non-linear stages of structure formation.

Note:

16+4 pages, 20 figures. This version matches the MNRAS published version

methods: numerical
galaxies: haloes
galaxies: nuclei
galaxies: formation
galaxies: structure
dark matter

References(81)

Figures(20)

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