Stronger Constraints on Primordial Black Holes as Dark Matter Derived from the Thermal Evolution of the Intergalactic Medium over the Last Twelve Billion Years

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Main Authors: Khan, Nabendu Kumar, Ray, Anupam, Kulkarni, Girish, Dasgupta, Basudeb
Format: Preprint
Published: 2025
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author Khan, Nabendu Kumar
Ray, Anupam
Kulkarni, Girish
Dasgupta, Basudeb
author_facet Khan, Nabendu Kumar
Ray, Anupam
Kulkarni, Girish
Dasgupta, Basudeb
contents Primordial black holes (PBHs) have been explored as potential dark matter candidates, with various astrophysical observations placing upper limits on the fraction $f_\mathrm{PBH}$ of dark matter in the form of PBHs. However, a largely underutilized probe of PBH abundance is the temperature of the intergalactic medium (IGM), inferred from the thermal broadening of absorption lines in the Lyman-$α$ forest of quasar spectra. PBHs inject energy into the IGM via Hawking radiation, altering its thermal evolution. In this work, we constrain this energy injection by self-consistently modeling its interplay with the cosmological ultraviolet background from galaxies and supermassive black holes. Leveraging IGM temperature measurements spanning the past twelve billion years ($z \sim 0$ to $6$), we derive one of the most stringent constraints on PBH-induced heating from light PBHs within the mass range $10^{15}$-$10^{17}$ g. Specifically, for $M_\mathrm{PBH} = 10^{16}$ g, we find $f_\mathrm{PBH} < 5 \times 10^{-5}$ at 95\% confidence, with the bound scaling approximately as $M_\mathrm{PBH}^{4}$ at other masses. Our inclusion of helium reionization and low-redshift temperature measurements strengthens previous IGM-based PBH constraints by an order of magnitude or more. Compared to other existing limits, our result is among the strongest, second only to the constraints from the 511 keV line from the Galactic Center, but with distinct systematics. More broadly, this study highlights the IGM thermal history as a powerful and independent probe of beyond-standard model physics.
format Preprint
id arxiv_https___arxiv_org_abs_2503_15595
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Stronger Constraints on Primordial Black Holes as Dark Matter Derived from the Thermal Evolution of the Intergalactic Medium over the Last Twelve Billion Years
Khan, Nabendu Kumar
Ray, Anupam
Kulkarni, Girish
Dasgupta, Basudeb
Cosmology and Nongalactic Astrophysics
High Energy Astrophysical Phenomena
High Energy Physics - Phenomenology
Primordial black holes (PBHs) have been explored as potential dark matter candidates, with various astrophysical observations placing upper limits on the fraction $f_\mathrm{PBH}$ of dark matter in the form of PBHs. However, a largely underutilized probe of PBH abundance is the temperature of the intergalactic medium (IGM), inferred from the thermal broadening of absorption lines in the Lyman-$α$ forest of quasar spectra. PBHs inject energy into the IGM via Hawking radiation, altering its thermal evolution. In this work, we constrain this energy injection by self-consistently modeling its interplay with the cosmological ultraviolet background from galaxies and supermassive black holes. Leveraging IGM temperature measurements spanning the past twelve billion years ($z \sim 0$ to $6$), we derive one of the most stringent constraints on PBH-induced heating from light PBHs within the mass range $10^{15}$-$10^{17}$ g. Specifically, for $M_\mathrm{PBH} = 10^{16}$ g, we find $f_\mathrm{PBH} < 5 \times 10^{-5}$ at 95\% confidence, with the bound scaling approximately as $M_\mathrm{PBH}^{4}$ at other masses. Our inclusion of helium reionization and low-redshift temperature measurements strengthens previous IGM-based PBH constraints by an order of magnitude or more. Compared to other existing limits, our result is among the strongest, second only to the constraints from the 511 keV line from the Galactic Center, but with distinct systematics. More broadly, this study highlights the IGM thermal history as a powerful and independent probe of beyond-standard model physics.
title Stronger Constraints on Primordial Black Holes as Dark Matter Derived from the Thermal Evolution of the Intergalactic Medium over the Last Twelve Billion Years
topic Cosmology and Nongalactic Astrophysics
High Energy Astrophysical Phenomena
High Energy Physics - Phenomenology
url https://arxiv.org/abs/2503.15595