Ultra-light Dark Matter Is Incompatible with the Milky Way’s Dwarf Satellites

Abstract

The density profiles of dwarf galaxies are a highly varied set. If the dark matter is an Ultra-light particle such as axions, then simulations predict a distinctive and unique profile. If the axion mass is large enough to fit the ultra-faint dwarf (UFD) satellites(m 10 −21 eV), then the models do not fit the density profile of Fornax and Sculptor and are ruled out by more than 3 − σ confidence. If the axion mass is in the mass range that can fit mass profiles of Fornax and Sculptor dwarf spheroidals, then its extended profile implies enormous masses (≈ 10 11 − 10 12 M ) for the UFDs. These large masses for the UFDS are ruled out by more than 3 − σ confidence by dynamical friction arguments. The tension would increase further considering star formation histories and stellar masses of the UFDs. Moreover, light mass axions are inconsistent with the sub-halo mass function in the Milky Way.

Dynamical friction in a Fuzzy Dark Matter universe

“…1 The presence of quantum mechanical pressure and 'quasi-particles' arising in velocity-dispersed media in the FDM paradigm alters the formation of the dark matter wake and therefore warrants a detailed investigation of all relevant cases, including finite-size effects for the infalling objects. Dynamical interactions may also reshape the structure of the dark matter subhalos and reduce the tension between the predicted profiles of isolated halos [18] and the observed dwarf galaxy profiles [32]. A key achievement of this paper is the comparison of analytic perturbation theory results to fully non-linear numerical simulations in order to clearly identify where the perturbation theory results are applicable.…”

Constraints on Dark Matter Properties from Observations of Milky Way Satellite Galaxies

“…In these systems, star formation is highly suppressed by reionization and stellar feedback, leading to mass-to-light ratios that are hundreds of times larger than the universal average [7,8]. Ultrafaint satellite galaxies are, thus, pristine laboratories for studying DM; in particular, the abundance of these systems is a sensitive probe of any DM physics that suppresses the formation or present-day abundance of small halos [9][10][11][12][13][14][15][16].…”

Secular effects of ultralight dark matter on binary pulsars

“…Current constraints from observations of the cosmic microwave background and large scale structure on linear scales robustly exclude m Φ 10 −24 eV [7] (with a factor of 10 improvement in m Φ expected in the future [8]). The analysis of the Lyman-α forest [9][10][11] and galactic dynamics [12][13][14] further excludes m Φ 10 −22 eV and shows a tension between the data and predictions of ULDM models with m Φ ∼ 10 −22 − 10 −21 eV. Complementary constraints in this mass range can come from pulsar-timing arrays [15,16].…”

“…The equations of motion for the binary are conveniently formulated in the Fermi normal coordinates {t F , ξ} associated to the binary barycenter (BB) rest frame. This corresponds to the geodesic motion of a free particle in the metric (14) with the initial conditions x =˙ x = 0 at t = 0. The explicit change of coordinates is:…”

“…Defining r ≡ ξ 1 − ξ 2 , one gets an extra acceleration δr i = −δR i 0j0 r j . Since the perturbation of the Riemann tensor is gauge independent at the linearized level, we can evaluate it in the Newton gauge (14). In this way we arrive aẗ…”