Feedback in the dark: a critical examination of CMB bounds on primordial black holes

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Main Authors: Agius, Dominic, Essig, Rouven, Gaggero, Daniele, Scarcella, Francesca, Suczewski, Gregory, Valli, Mauro
Format: Preprint
Published: 2024
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author Agius, Dominic
Essig, Rouven
Gaggero, Daniele
Scarcella, Francesca
Suczewski, Gregory
Valli, Mauro
author_facet Agius, Dominic
Essig, Rouven
Gaggero, Daniele
Scarcella, Francesca
Suczewski, Gregory
Valli, Mauro
contents If present in the early universe, primordial black holes (PBHs) will accrete matter and emit high-energy photons, altering the statistical properties of the {Cosmic Microwave Background (CMB)}. This mechanism has been used to constrain the fraction of dark matter that is in the form of PBHs to be much smaller than unity for PBH masses well above one solar mass. Moreover, the presence of dense dark matter mini-halos around the PBHs has been used to set even more stringent constraints, as these would boost the accretion rates. In this work, we critically revisit CMB constraints on PBHs taking into account the role of the local ionization of the gas around them. We discuss how the local increase in temperature around PBHs can prevent the dark matter mini-halos from strongly enhancing the accretion process, in some cases significantly weakening previously derived CMB constraints. We explore in detail the key ingredients of the CMB bound and derive a conservative limit on the cosmological abundance of massive PBHs.
format Preprint
id arxiv_https___arxiv_org_abs_2403_18895
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Feedback in the dark: a critical examination of CMB bounds on primordial black holes
Agius, Dominic
Essig, Rouven
Gaggero, Daniele
Scarcella, Francesca
Suczewski, Gregory
Valli, Mauro
High Energy Physics - Phenomenology
Cosmology and Nongalactic Astrophysics
High Energy Astrophysical Phenomena
If present in the early universe, primordial black holes (PBHs) will accrete matter and emit high-energy photons, altering the statistical properties of the {Cosmic Microwave Background (CMB)}. This mechanism has been used to constrain the fraction of dark matter that is in the form of PBHs to be much smaller than unity for PBH masses well above one solar mass. Moreover, the presence of dense dark matter mini-halos around the PBHs has been used to set even more stringent constraints, as these would boost the accretion rates. In this work, we critically revisit CMB constraints on PBHs taking into account the role of the local ionization of the gas around them. We discuss how the local increase in temperature around PBHs can prevent the dark matter mini-halos from strongly enhancing the accretion process, in some cases significantly weakening previously derived CMB constraints. We explore in detail the key ingredients of the CMB bound and derive a conservative limit on the cosmological abundance of massive PBHs.
title Feedback in the dark: a critical examination of CMB bounds on primordial black holes
topic High Energy Physics - Phenomenology
Cosmology and Nongalactic Astrophysics
High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2403.18895