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Title: Dwarf spheroidal galaxies as degenerate gas of free fermions

In this paper we analyze a simple scenario in which Dark Matter (DM) consists of free fermions with mass m{sub f}. 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 con figuration 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 m{sub f}. 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 m{sub f}≅ 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, itsmore » branching ratio into DM and the reheating temperature.« less
Authors:
;  [1]
  1. SISSA - International School for Advanced Studies, via Bonomea 256, Trieste, 34136 Italy (Italy)
Publication Date:
OSTI Identifier:
22382040
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2015; Journal Issue: 01; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; COSMOLOGICAL INFLATION; DECAY; DENSITY; EQUATIONS; FERMI GAS; FERMIONS; FORECASTING; GRAVITATIONAL COLLAPSE; LENGTH; MASS; MILKY WAY; NONLUMINOUS MATTER; PAULI PRINCIPLE; RELATIVISTIC RANGE; REVIEWS; VELOCITY