Constraints on primordial black holes from the Galactic gamma-ray background
By Bernard Carr, K. Kohri, Y. Sendouda, Jun'ichi Yokoyama. 2016
133 citations recorded by the source corpus.
The fraction of the Universe going into primordial black holes (PBHs) with initial mass M_* \approx 5 \times 10^{14} g, such that they are evaporating at the present epoch, is strongly constrained by observations of both the extragalactic and Galactic gamma-ray backgrounds. However, while the dominant contribution to the extragalactic background comes from the time-integrated emission of PBHs with initial mass M_*, the Galactic background is dominated by the instantaneous emission of those with initial mass slightly larger than M_* and current mass below M_*. Also, the instantaneous emission of PBHs smaller than 0.4 M_* mostly comprises secondary particles produced by the decay of directly emitted quark and gluon jets. These points were missed in the earlier analysis by Lehoucq et al. using EGRET data. For a monochromatic PBH mass function, with initial mass (1+\mu) M_* and \mu << 1, the current mass is (3\mu)^{1/3} M_* and the Galactic background constrains the fraction of the Universe going into PBHs as a function of \mu. However, the initial mass function cannot be precisely monochromatic and even a tiny spread of mass around M_* would generate a current low-mass tail of PBHs below M_*. This tail would be the main contributor to the Galactic background, so we consider its form and the associated constraints for a variety of scenarios with both extended and nearly-monochromatic initial mass functions. In particular, we consider a scenario in which the PBHs form from critical collapse and have a mass function which peaks well above M_*. In this case, the largest PBHs could provide the dark matter without the M_* ones exceeding the gamma-ray background limits.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/d632346787d07794439251bfba35658f17c3da61
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Citations in the corpus
- Primordial Black Holes as Dark Matter: Recent Developments (2020, background): “The Galactic γ-ray background constraint could give a stronger limit [146] but this depends sensitively on the form of the PBH mass function, so we do not discuss it here.”
- Primordial black holes from α-attractors (2018, background): “In the late universe, the PBH evaporation rate is constrained from the extra galactic gamma-ray background [90] (the area in green) and in the early universe from the big-bang nucleosynthesis [92].”
- Primordial black holes as dark matter candidates (2021, background): “1 Evaporation Constraints A PBH of initial mass M will evaporate through the emission of Hawking radiation on a timescale τ∝ M3 which is less than the present age of the Universe for M below M∗ ≈ 5×1014 g [107].”
- PRIMORDIAL BLACK HOLE FORMATION IN THE MATTER-DOMINATED PHASE OF THE UNIVERSE (2016, background): “The abundance of primordial black holes is severely constrained observationally (Carr 1975; Carr et al. 2010, 2016) and this fact has rich implications on the early universe and other relevant fields of physics.”