Constraints on MeV dark matter and primordial black holes: Inverse Compton signals at the SKA

Abstract

We investigate the possibilities for probing MeV dark matter (DM) particles and primordial black holes (PBHs) (for masses ~ 1015–1017 g) at the upcoming radio telescope SKA, using photon signals from the Inverse Compton (IC) effect within a galactic halo. Pair-annihilation or decay of MeV DM particles (into e+ e- pairs) or Hawking radiation from a population of PBHs generates mildly relativistic e± which can lead to radio signals through the IC scattering on low energy cosmic microwave background (CMB) photons. We study the ability of SKA to detect such signals coming from nearby ultra-faint dwarf galaxies Segue I and Ursa Major II as well as the globular cluster ω-cen and the Coma cluster. We find that with ~ 100 hours of observation, the SKA improves the Planck constraints on the DM annihilation/decay rate and the PBH abundance for masses in the range ~ 1 to few tens of MeV and above 1015 to 1017 g, respectively. Importantly, the SKA limits are independent of the assumed magnetic fields within the galaxies. Previously allowed regions of diffusion parameters of MeV electrons inside a dwarf galaxy that give rise to observable signals at the SKA are also excluded. For objects like dwarf galaxies, predicted SKA constraints depend on both the DM and diffusion parameters. Independent observations in different frequency bands, e.g., radio and γ-ray frequencies, may break this degeneracy and thus enable one to constrain the combined parameter space of DM and diffusion. However, the constraints are independent of diffusion parameters for galaxy clusters such as Coma.

Background of radio photons from primordial black holes

“…For this assess-ment we calculate the specific intensity of very low energy (frequencies ∼ 1 GHz) photons from PBHs of representative mass ∼ 10 14 and 10 25 kg. The former case is interesting as PBHs of mass ∼ 10 14 kg can actually be constrained as dark matter candidate via non-observation of their Hawkingevaporated products (Carr et al 2010;Boudaud & Cirelli 2019;DeRocco & Graham 2019;Laha 2019;Arbey et al 2020;Ballesteros et al 2020;Laha et al 2020;Dasgupta et al 2020;Coogan et al 2021;Iguaz et al 2021;Cai et al 2021), by observation from upcoming X-ray, gamma-ray, gravitationalwave experiments (Ray et al 2021;Wang et al 2021;Calabrese et al 2021;De Romeri et al 2021;Ghosh et al 2021) or their effect on the thermal properties of the intergalactic medium (Clark et al 2017;Stöcker et al 2018;Acharya & Khatri 2020;Chan & Lee 2020;Cang et al 2021;Kim 2021;Laha et al 2021;Dutta et al 2021). The latter mass is not constrained by evaporation but via lensing effects such as those reported by Subaru Hyper Suprime-Cam (HSC, Niikura et al 2019a;Smyth et al 2020), Kepler satellite (Griest et al 2013(Griest et al , 2014, Optical Gravitational Lensing Experiment (OGLE, Niikura et al 2019b), Expérience de Recherche d'Objets Sombres (EROS, Tisserand et al 2007), Massive Compact Halo Object (MACHO, Alcock et al 2001, Icarus (Oguri et al 2018) and type Ia supernovae (Zumalacárregui & Seljak 2018).…”

Limits on primordial black holes detectability with Isatis: A BlackHawk tool

“…to the change in the re-ionization history at the cosmic microwave background [21,22]. Other studies are based on the direct [23] or indirect detection of electrons-positrons [22,[24][25][26][27][28][29][30][31][32][33][34][35][36][37]; and finally there are some papers that focus on neutrino constraints [25,[38][39][40]. Most of the more recent studies now take into account the effect of having a non-zero PBH spin, which enhances the photon emission and thus results in more stringent constraints for Kerr (rotating) PBHs [9,13,18,19,25,28,32,37,40], or an extended PBH mass distribution, that should be more realistic regarding the channels of PBH formation [13,15,16,18,24,25,29,32,40].…”

Baryogenesis from ultra-slow-roll inflation

“…Nevertheless, despite the fact that the USR transition provides a quantitative connection between baryon and PBH densities with a viable answer to the cosmic coincidence problem independent of the statistical uncertainties, the existing fine-tuning problem for the inflaton potential to realize PBH dark matter inevitably enters the story of cosmology. On the other hand, the asteroid-mass window for PBH dark matter, one of the fundamental assumption in this work, could be tested by near future astrophysical or gravitational-wave experiments [106][107][108][109][110][111][112][113][114][115][116][117][118].…”