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Register a new userCan Primordial Black Holes as all Dark Matter explain Fast Radio Bursts?
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Added by
Enrico Schiappacasse
Publication date
2021
fields
Physics
and research's language is
English
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Primordial black holes (PBHs) are one of the most interesting non-particle dark matter (DM) candidates. They may explain all the DM content in the Universe in the mass regime about $10^{-14}M_{odot}-10^{-11}M_{odot}$. We study PBHs as the source of Fast Radio Bursts via magnetic reconnection in the event of collisions between them and neutron stars (NSs) in galaxies. We investigate the energy-loss of PBHs during PBH-NS encounters to model their capture by NSs. To an order-of-magnitude estimation, we conclude that the parameter space of PBHs being all DM is accidentally consistent with that to produce FRBs with a rate which is the order of the observed FRB rate.
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If primordial black holes with masses of $10^{25},mbox{g}gtrsim m gtrsim 10^{17},mbox{g}$ constitute a non-negligible fraction of the galactic dark-matter haloes, their existence should have observable consequences: they necessarily collide with galactic neutron stars, nest in their centers and accrete the dense matter, eventually converting them to neutron-star mass black holes while releasing the neutron-star magnetic field energy. Such processes may explain the fast radio bursts phenomenology, in particular their millisecond durations, large luminosities ${sim}10^{43}$ erg/s, high rate of occurrence $gtrsim 1000/mbox{day}$, as well as high brightness temperatures, polarized emission and Faraday rotation. Longer than the dynamical timescale of the Bondi-like accretion for light primordial black holes allows for the repeating fast radio bursts. This explanation follows naturally from (assumed) existence of the dark matter primordial black holes and requires no additional unusual phenomena, in particular no unacceptably large magnetic fields of neutron stars. In our model, the observed rate of fast radio bursts throughout the Universe follows from the presently known number of neutron stars in the Galaxy.
Although the dark matter is usually assumed to be some form of elementary particle, primordial black holes (PBHs) could also provide some of it. However, various constraints restrict the possible mass windows to $10^{16}$ - $10^{17},$g, $10^{20}$ - $10^{24},$g and $10$ - $10^{3},M_{odot}$. The last possibility is contentious but of special interest in view of the recent detection of black-hole mergers by LIGO/Virgo. PBHs might have important consequences and resolve various cosmological conundra even if they have only a small fraction of the dark-matter density. In particular, those larger than $10^{3},M_{odot}$ could generate cosmological structures through the seed or Poisson effect, thereby alleviating some problems associated with the standard cold dark-matter scenario, and sufficiently large PBHs might provide seeds for the supermassive black holes in galactic nuclei. More exotically, the Planck-mass relics of PBH evaporations or stupendously large black holes bigger than $10^{12},M_{odot}$ could provide an interesting dark component.
We examine the extent to which primordial black holes (PBHs) can constitute the observed dark matter while also giving rise to the measured matter-antimatter asymmetry and account for the observed baryon abundance through asymmetric Hawking radiation generated by a derivative coupling of curvature to the baryon-lepton current. We consider both broad and monochromatic mass spectra for this purpose. For the monochromatic spectrum we find that the correct dark matter and baryon energy densities are recovered for peak masses of the spectrum of $M_{rm pk} geq 10^{12}$ kg whereas for the broad case the observed energy densities can be reproduced regardless of peak mass. Adopting some simplifications for the early-time expansion history as a first approximation, we also find that the measured baryon asymmetry can be recovered within an order of magnitude. We argue furthermore that the correct value of the baryon-lepton yield can in principle be retrieved for scenarios where a significant amount of the radiation is produced by PBH decay during or after reheating, as is expected when the decaying PBHs also cause reheating, or when an early matter-dominated phase is considered. We conclude from this first analysis that the model merits further investigation.
In this paper we propose the model that the coalescence of primordial black holes (PBHs) binaries with equal mass $M sim 10^{28}$g can emit luminous gigahertz (GHz) radio transient, which may be candidate sources for the observed fast radio bursts (FRBs), if at least one black hole holds appropriate amount of net electric charge $Q$. Using a dimensionless quantity for the charge $q = Q/sqrt{G}M$, our analyses infer that $qsim O(10^{-4.5})$ can explain the FRBs with released energy of order $O(10^{40}) {rm ergs}$. With the current sample of FRBs and assuming a distribution of charge $phi(q)$ for all PBHs, we can deduce that its form is proportional to $q^{-3.0pm0.1}$ for $qgeq 7.2times10^{-5}$ if PBHs are sources of the observed FRBs. Furthermore, with the proposed hypothetical scenario and by estimating the local event rate of FRBs $sim 2.6 times 10^3 {rm Gpc}^{-3} {rm yr}^{-1}$, one derives a lower bound for the fraction of PBHs (at the mass of $10^{28}$g) against that of matter $f_{rm PBH}(10^{28}{rm g})$ $gtrsim 10^{-5}$ needed to explain the rate. With this inspiring estimate, we expect that future observations of FRBs can help to falsify their physical origins from the PBH binaries coalescences. In the future, the gravitational waves produced by mergers of small black holes can be detected by high frequency gravitational wave detectors. We believe that this work would be a useful addition to the current literature on multimessenger astronomy and cosmology.
The LIGO discoveries have rekindled suggestions that primordial black holes (BHs) may constitute part to all of the dark matter (DM) in the Universe. Such suggestions came from 1) the observed merger rate of the BHs, 2) their unusual masses, 3) their low/zero spins, and 4) also from the independently uncovered cosmic infrared background (CIB) fluctuations signal of high amplitude and coherence with unresolved cosmic X-ray background (CXB). Here we summarize the prospects to resolve this important issue with electromagnetic observations using the instruments and tools expected in the 2020s. These prospects appear promising to make significant, and potentially critical, advances. We demonstrate that in the next decade, new space- and ground-borne electromagnetic instruments, combined with concurrent theoretical efforts, should shed critical light on the long-considered link between primordial BHs and DM. Specifically the new data and methodologies under this program will involve: I) Probing with high precision the spatial spectrum of source-subtracted CIB with Euclid and WFIRST, and its coherence with unresolved cosmic X-ray background using eROSITA and Athena, II) Advanced searches for microlensing of Galactic stars by the intervening Galactic Halo BHs with OGLE, Gaia, LSST and WFIRST, III) Supernovae (SNe) lensing in the upcoming surveys with WFIRST, LSST and also potentially with Euclid and JWST, IV) Advanced theoretical work to understand the details of PBH accretion and evolution and their influence on cosmic microwave background (CMB) anisotropies in light of the next generation CMB experiments, V) Better new samples and theoretical understanding involving stability and properties of ultra faint dwarf galaxies, pulsar timing, and cosmological quasar lensing.
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