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Search for dark matter around intermediate mass black holes with the H.E.S.S. experiment

Jann Aschersleben, Dieter Horns, Emmanuel Moulin, Manuela Vecchi

TL;DR

The paper investigates indirect dark matter detection around intermediate-mass black holes by modeling dark matter spikes and computing the expected gamma-ray flux from annihilation. It analyzes 6200 hours of H.E.S.S. observations (HGPS, HEGS, and satellites) to search for DM-like point sources and derives 90% CL upper limits on the velocity-averaged cross section for DM masses in the range 0.8–100 TeV, finding signals that do not rise above background. The results, which approach or fall below the thermal relic cross section for $m_\chi \gtrsim 10$ TeV, rely on mock IMBH distributions from cosmological simulations and are subject to systematic uncertainties linked to IMBH formation and spike evolution. Overall, the work demonstrates the feasibility of probing IMBH-associated DM with current TeV gamma-ray data, while highlighting key astrophysical uncertainties that shape sensitivity.

Abstract

Intermediate mass black holes (IMBHs), with masses ranging from a hundred and a million solar masses, are hypothesised to be surrounded by dense regions of dark matter known as dark matter spikes, where the annihilation of dark matter particles could produce detectable gamma rays. The detection of dark matter annihilation around IMBHs therefore offers a promising approach for probing the nature of dark matter. In this work, we search for dark matter annihilation around IMBHs using data from the Galactic Plane Survey, the Extragalactic Survey and a selection of satellite galaxies observed by the H.E.S.S. gamma-ray experiment in Namibia. Since no evidence for a gamma-ray signal from dark matter annihilation around IMBHs has been found, we set upper limits on the velocity-weighted annihilation cross section for dark matter masses between 800 GeV and 100 TeV. Our analysis obtains limits on the velocity-weighted annihilation cross section below the thermal relic cross section for dark matter masses between 10 and 100 TeV.

Search for dark matter around intermediate mass black holes with the H.E.S.S. experiment

TL;DR

The paper investigates indirect dark matter detection around intermediate-mass black holes by modeling dark matter spikes and computing the expected gamma-ray flux from annihilation. It analyzes 6200 hours of H.E.S.S. observations (HGPS, HEGS, and satellites) to search for DM-like point sources and derives 90% CL upper limits on the velocity-averaged cross section for DM masses in the range 0.8–100 TeV, finding signals that do not rise above background. The results, which approach or fall below the thermal relic cross section for TeV, rely on mock IMBH distributions from cosmological simulations and are subject to systematic uncertainties linked to IMBH formation and spike evolution. Overall, the work demonstrates the feasibility of probing IMBH-associated DM with current TeV gamma-ray data, while highlighting key astrophysical uncertainties that shape sensitivity.

Abstract

Intermediate mass black holes (IMBHs), with masses ranging from a hundred and a million solar masses, are hypothesised to be surrounded by dense regions of dark matter known as dark matter spikes, where the annihilation of dark matter particles could produce detectable gamma rays. The detection of dark matter annihilation around IMBHs therefore offers a promising approach for probing the nature of dark matter. In this work, we search for dark matter annihilation around IMBHs using data from the Galactic Plane Survey, the Extragalactic Survey and a selection of satellite galaxies observed by the H.E.S.S. gamma-ray experiment in Namibia. Since no evidence for a gamma-ray signal from dark matter annihilation around IMBHs has been found, we set upper limits on the velocity-weighted annihilation cross section for dark matter masses between 800 GeV and 100 TeV. Our analysis obtains limits on the velocity-weighted annihilation cross section below the thermal relic cross section for dark matter masses between 10 and 100 TeV.

Paper Structure

This paper contains 6 sections, 3 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Expected signal
  3. Analysis of H.E.S.S. data
  4. Statistical analysis
  5. Results
  6. Conclusions

Figures (3)

  • Figure 1: Dark matter density profile around an IMBH assuming a black hole mass of $1.6~10^5 M_{\odot}$. Figure taken from Aschersleben:2024xsb.
  • Figure 2: Flux sensitivity map for the HGPS in Galactic Coordinates for a DM mass of $m_\chi = 30~TeV$, the $b \overline{b}$-channel.
  • Figure 3: Upper limits on velocity averaged DM annihilation cross section $\langle \sigma v \rangle$ as a function of DM mass $m_\chi$ on a $90 \%$ C.L. The grey dashed line corresponds to the thermal relic cross section of $\langle \sigma v \rangle = 3~10^{-26}~cm^{-3}s^{-1}$, for the $b \overline{b}$ annihilation channel.