Alma X. Gonzalez-Morales

Effect of Black Holes in Local Dwarf Spheroidal Galaxies on Gamma-Ray Constraints on Dark Matter Annihilation

Recent discoveries of optical signatures of black holes in dwarf galaxies indicates that low-mass galaxies can indeed host intermediate massive black holes. This motivates the assessment of the resulting effect on the host dark matter density profile, and the consequences for the constraints on the plane of the dark matter annihilation cross section versus mass, stemming from the non-observation of gamma rays from local dwarf spheroidals with the Fermi Large Area Telescope. We compute the density profile using three different prescriptions for the black hole mass associated with a given spheroidal galaxy, and taking into account the cutoff to the density from dark matter pair-annihilation. We find that the limits on the dark matter annihilation rate from observations of individual dwarfs are enhanced by factors of a few up to

Dwarf spheroidal galaxies and Bose-Einstein condensate dark matter

10^6

Towards accurate cosmological predictions for rapidly oscillating scalar fields as dark matter

, depending on the specific galaxy, on the black hole mass prescription, and on the dark matter particle mass. We estimate limits from combined observations of a sample of 15 dwarfs, for a variety of assumptions on the dwarf black hole mass and on the dark matter density profile prior to adiabatic contraction. We find that if black holes are indeed present in local dwarf spheroidals, then, independent of assumptions, (i) the dark matter interpretation of the Galactic center gamma-ray excess would be conclusively ruled out, (ii) wino dark matter would be excluded up to masses of about 3 TeV, and (iii) vanilla thermal relic WIMPs must be heavier than 100 GeV.

No-go theorem for static scalar field dark matter halos with no Noether charges

We constrain the parameters of a self-interacting massive dark matter scalar particle in a condensate using the kinematics of the eight brightest dwarf spheroidal satellites of the Milky Way. For the case of a repulsive self-interaction the condensate develops a mass density profile with a characteristic scale radius that is closely related to the fundamental parameters of the theory. We find that the velocity dispersion of dwarf spheroidal galaxies suggests a scale radius of the order of 1 kpc, in tension with previous results found using the rotational curve of low-surface-brightness and dwarf galaxies. The new value is however favored marginally by the constraints coming from the number of relativistic species at Big-Bang nucleosynthesis. We discuss the implications of our findings for the particle dark matter model and argue that while a single classical coherent state can correctly describe the dark matter in dwarf spheroidal galaxies, it cannot play, in general, a relevant role for the description of dark matter in bigger objects.

Verlinde’s emergent gravity versus MOND and the case of dwarf spheroidals

As we are entering the era of precision cosmology, it is necessary to count on accurate cosmological predictions from any proposed model of dark matter. In this paper we present a novel approach to the cosmological evolution of scalar fields that eases their analytic and numerical analysis at the background and at the linear order of perturbations. We apply the method to a scalar field endowed with a quadratic potential and revisit its properties as dark matter. Some of the results known in the literature are recovered, and a better understanding of the physical properties of the model is provided. It is shown that the Jeans wavenumber defined as

Cosmological signatures of ultralight dark matter with an axionlike potential

k_J = a \sqrt{mH}

Prospects for indirect MeV dark matter detection with gamma rays in light of cosmic microwave background constraints

is directly related to the suppression of linear perturbations at wavenumbers

Unbiased constraints on ultralight axion mass from dwarf spheroidal galaxies

k>k_J

New general parametrization of quintessence fields and its observational constraints

. We also discuss some semi-analytical results that are well satisfied by the full numerical solutions obtained from an amended version of the CMB code CLASS. Finally we draw some of the implications that this new treatment of the equations of motion may have in the prediction for cosmological observables.

Towards a calculation of the halo mass function of a scalar field dark matter

Instituto de Ciencias Nucleares, Universidad Nacional Auto´noma de M´exico,Circuito Exterior, C.U., A.P. 70-543, M´exico D.F. 04510, M´exico(Dated: January 11, 2014)Classical scalar fields have been considered as a possible effective description of dark matter.We show that, for any metric theory of gravity, no static, spherically symmetric, regular, spatiallylocalized, attractive, stable spacetime configuration can be sourced by the coherent excitation of ascalar field with positive definite energy density and no Noether charges. In the weak-field regime theresult also applies for configurations with a repulsive gravitational potential. This extends Derrick’stheorem to the case of a general (non-canonical) scalar field, including the self-gravitational effects.Some possible ways out are briefly discussed.