In this paper we analyze a simple scenario in which Dark Matter (DM) consists of free fermions with mass mf. We assume that on galactic scales these fermions are capable of forming a degenerate Fermi gas, in which stability against gravitational collapse is ensured by the Pauli exclusion principle. The mass density of the resulting configuration is governed by a non-relativistic Lane-Emden equation, thus leading to a universal cored profile that depends only on one free parameter in addition to mf. After reviewing the basic formalism, we test this scenario against experimental data describing the velocity dispersion of the eight classical dwarf spheroidal galaxies of the Milky Way. We find that, despite its extreme simplicity, the model exhibits a good fit to the data and realistic predictions for the size of DM halos providing that mf≃200 eV. Furthermore, we show that in this setup larger galaxies correspond to the non-degenerate limit of the gas. We propose a concrete realization of this model in which DM is produced non-thermally via inflaton decay. We show that imposing the correct relic abundance and the bound on the free-streaming length constrains the inflation model in terms of inflaton mass, its branching ratio into DM and the reheating temperature.

Dwarf spheroidal galaxies as degenerate gas of free fermions / Domcke, V.; Urbano, A.. - In: JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS. - ISSN 1475-7516. - 2015:1(2015). [10.1088/1475-7516/2015/01/002]

Dwarf spheroidal galaxies as degenerate gas of free fermions

Urbano A.
2015

Abstract

In this paper we analyze a simple scenario in which Dark Matter (DM) consists of free fermions with mass mf. We assume that on galactic scales these fermions are capable of forming a degenerate Fermi gas, in which stability against gravitational collapse is ensured by the Pauli exclusion principle. The mass density of the resulting configuration is governed by a non-relativistic Lane-Emden equation, thus leading to a universal cored profile that depends only on one free parameter in addition to mf. After reviewing the basic formalism, we test this scenario against experimental data describing the velocity dispersion of the eight classical dwarf spheroidal galaxies of the Milky Way. We find that, despite its extreme simplicity, the model exhibits a good fit to the data and realistic predictions for the size of DM halos providing that mf≃200 eV. Furthermore, we show that in this setup larger galaxies correspond to the non-degenerate limit of the gas. We propose a concrete realization of this model in which DM is produced non-thermally via inflaton decay. We show that imposing the correct relic abundance and the bound on the free-streaming length constrains the inflation model in terms of inflaton mass, its branching ratio into DM and the reheating temperature.
2015
dark matter theory; dwarfs galaxies; inflation
01 Pubblicazione su rivista::01a Articolo in rivista
Dwarf spheroidal galaxies as degenerate gas of free fermions / Domcke, V.; Urbano, A.. - In: JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS. - ISSN 1475-7516. - 2015:1(2015). [10.1088/1475-7516/2015/01/002]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1645194
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