skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Heating of galactic gas by dark matter annihilation in ultracompact minihalos

Abstract

The existence of substructure in halos of annihilating dark matter would be expected to substantially boost the rate at which annihilation occurs. Ultracompact minihalos of dark matter (UCMHs) are one of the more extreme examples of this. The boosted annihilation can inject significant amounts of energy into the gas of a galaxy over its lifetime. Here we determine the impact of the boost factor from UCMH substructure on the heating of galactic gas in a Milky Way-type galaxy, by means of N-body simulation. If 1% of the dark matter exists as UCMHs, the corresponding boost factor can be of order 10{sup 5}. For reasonable values of the relevant parameters (annihilation cross section 3×10{sup −26} cm{sup 3} s{sup −1}, dark matter mass 100 GeV, 10% heating efficiency), we show that the presence of UCMHs at the 0.1% level would inject enough energy to eject significant amounts of gas from the halo, potentially preventing star formation within ∼1 kpc of the halo centre.

Authors:
; ;  [1];  [2];  [3]
  1. Sydney Institute for Astronomy, School of Physics A28, The University of Sydney, NSW 2006 (Australia)
  2. International Centre for Radio Astronomy Research, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia)
  3. Department of Physics, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom)
Publication Date:
OSTI Identifier:
22676192
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2017; Journal Issue: 05; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANNIHILATION; COSMIC GASES; CROSS SECTIONS; EFFICIENCY; GEV RANGE; HEATING; LIFETIME; MANY-BODY PROBLEM; MASS; MILKY WAY; NONLUMINOUS MATTER; SIMULATION; STARS

Citation Formats

Clark, Hamish A., Iwanus, Nikolas, Lewis, Geraint F., Elahi, Pascal J., and Scott, Pat, E-mail: hamish.clark@sydney.edu.au, E-mail: nikolas.iwanus@sydney.edu.au, E-mail: pascal.elahi@uwa.edu.au, E-mail: geraint.lewis@sydney.edu.au, E-mail: p.scott@imperial.ac.uk. Heating of galactic gas by dark matter annihilation in ultracompact minihalos. United States: N. p., 2017. Web. doi:10.1088/1475-7516/2017/05/048.
Clark, Hamish A., Iwanus, Nikolas, Lewis, Geraint F., Elahi, Pascal J., & Scott, Pat, E-mail: hamish.clark@sydney.edu.au, E-mail: nikolas.iwanus@sydney.edu.au, E-mail: pascal.elahi@uwa.edu.au, E-mail: geraint.lewis@sydney.edu.au, E-mail: p.scott@imperial.ac.uk. Heating of galactic gas by dark matter annihilation in ultracompact minihalos. United States. doi:10.1088/1475-7516/2017/05/048.
Clark, Hamish A., Iwanus, Nikolas, Lewis, Geraint F., Elahi, Pascal J., and Scott, Pat, E-mail: hamish.clark@sydney.edu.au, E-mail: nikolas.iwanus@sydney.edu.au, E-mail: pascal.elahi@uwa.edu.au, E-mail: geraint.lewis@sydney.edu.au, E-mail: p.scott@imperial.ac.uk. Mon . "Heating of galactic gas by dark matter annihilation in ultracompact minihalos". United States. doi:10.1088/1475-7516/2017/05/048.
@article{osti_22676192,
title = {Heating of galactic gas by dark matter annihilation in ultracompact minihalos},
author = {Clark, Hamish A. and Iwanus, Nikolas and Lewis, Geraint F. and Elahi, Pascal J. and Scott, Pat, E-mail: hamish.clark@sydney.edu.au, E-mail: nikolas.iwanus@sydney.edu.au, E-mail: pascal.elahi@uwa.edu.au, E-mail: geraint.lewis@sydney.edu.au, E-mail: p.scott@imperial.ac.uk},
abstractNote = {The existence of substructure in halos of annihilating dark matter would be expected to substantially boost the rate at which annihilation occurs. Ultracompact minihalos of dark matter (UCMHs) are one of the more extreme examples of this. The boosted annihilation can inject significant amounts of energy into the gas of a galaxy over its lifetime. Here we determine the impact of the boost factor from UCMH substructure on the heating of galactic gas in a Milky Way-type galaxy, by means of N-body simulation. If 1% of the dark matter exists as UCMHs, the corresponding boost factor can be of order 10{sup 5}. For reasonable values of the relevant parameters (annihilation cross section 3×10{sup −26} cm{sup 3} s{sup −1}, dark matter mass 100 GeV, 10% heating efficiency), we show that the presence of UCMHs at the 0.1% level would inject enough energy to eject significant amounts of gas from the halo, potentially preventing star formation within ∼1 kpc of the halo centre.},
doi = {10.1088/1475-7516/2017/05/048},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 05,
volume = 2017,
place = {United States},
year = {Mon May 01 00:00:00 EDT 2017},
month = {Mon May 01 00:00:00 EDT 2017}
}
  • Cosmological galaxy formation models predict the existence of dark matter minihalos surrounding galaxies and in filaments connecting groups of galaxies. The more massive of these minihalos are predicted to host H I gas that should be detectable by current radio telescopes such as the Robert C. Byrd Green Bank Telescope (GBT). We observed the region including the M81/M82 and NGC 2403 galaxy groups, searching for observational evidence of an H I component associated with dark matter halos within the 'M81 Filament', using the GBT. The map covers an 8.{sup 0}7 x 21.{sup 0}3 (480 kpc x 1.2 Mpc) region centeredmore » between the M81/M82 and NGC 2403 galaxy groups. Our observations cover a wide velocity range, from -890 to 1320 km s{sup -1}, which spans much of the range predicted by cosmological N-body simulations for dark matter minihalo velocities. Our search is not complete in the velocity range -210 to 85 km s{sup -1}, containing Galactic emission and the HVC Complex A. For an H I cloud at the distance of M81, with a size {<=}10 kpc, our average 5{sigma} mass detection limit is 3.2 x 10{sup 6} M{sub sun}, for a linewidth of 20 km s{sup -1}. We compare our observations to two large cosmological N-body simulations and find that the simulation predicts a significantly greater number of detectable minihalos than are found in our observations, and that the simulated minihalos do not match the phase space of observed H I clouds. These results place strong constraints on the H I gas that can be associated with dark matter halos. Our observations indicate that the majority of extragalactic H I clouds with a mass greater than 10{sup 6} M{sub sun} are likely to be generated through tidal stripping caused by galaxy interactions.« less
  • Warm dark matter (WDM) with mass m{sub WDM} = O(1) keV has long been discussed as a promising solution for discrepancies between cosmic structures observed at small scales and predications of the concordance CDM model. Though several cosmological observations such as the Lyman-alpha forest have already begun to constrain the range of m{sub WDM}, WDM is yet to be fully excluded as a solution for these so-called small-scale problems. In this paper, we study 21 cm line fluctuations from minihalos in a WDM model and evaluate constraints on m{sub WDM} for future cosmological 21 cm surveys, such as SKA andmore » FFTT. We show that, since WDM with mass m{sub WDM}∼>10 keV decreases the abundance of minihalos by suppressing the matter power spectrum on small scales via free-streaming, such WDM can significantly affect the resultant 21 cm line fluctuations from minihalos. We find that if the 21 cm signal from minihalos can be observed above z≥5, SKA and FFTT can give lower bounds m{sub WDM}∼>24 keV and 31 keV, respectively, which are tighter than the current constraint. These future 21 cm surveys might be able to rule out a WDM model as a solution of small-scale problems.« less
  • The nature of the cosmic dark matter is unknown. The most compelling hypothesis is that dark matter consists of weakly interacting massive particles (WIMPs) in the 100 GeV mass range. Such particles would annihilate in the galactic halo, producing high-energy gamma rays which might be detectable in gamma ray telescopes such as the GLAST satellite. We investigate the ability of GLAST to distinguish between the WIMP annihilation spectrum and the spectrum of known astrophysical source classes. Focusing on the emission from the galactic satellite halos predicted by the cold dark matter model, we find that the WIMP gamma-ray spectrum ismore » unique; the separation from known source classes can be done in a convincing way. We discuss the follow-up of possible WIMP sources with Imaging Atmospheric Cerenkov Telescopes. Finally we discuss the impact that Large Hadron Collider data might have on the study of galactic dark matter.« less
  • The GLAST satellite mission will study the gamma ray sky with considerably greater exposure than its predecessor EGRET. In addition, it will be capable of measuring the arrival directions of gamma rays with much greater precision. These features each significantly enhance GLAST's potential for identifying gamma rays produced in the annihilations of dark matter particles. The combined use of spectral and angular information, however, is essential if the full sensitivity of GLAST to dark matter is to be exploited. In this paper, we discuss techniques for separating dark matter annihilation products from astrophysical backgrounds, focusing on the Galactic Center region,more » and perform a forecast for such an analysis. We consider both point-like and diffuse astrophysical backgrounds and model them using a realistic point-spread-function for GLAST. While the results of our study depend on the specific characteristics of the dark matter signal and astrophysical backgrounds, we find that in many scenarios it is possible to successfully identify dark matter annihilation radiation, even in the presence of significant astrophysical backgrounds.« less
  • Although the emission of radiation from dark matter annihilation is expected to be maximized at the Galactic Center, geometric factors and the presence of point-like and diffuse backgrounds make the choice of the angular window size to optimize the chance of a signal detection a non-trivial problem. We find that the best strategy is to focus on an annulus around the Galactic Center of {approx} 1{sup o} to {approx}> 30{sup o}, where the optimal size depends on the angular distribution of the signal and the backgrounds. Although our conclusions are general, we illustrate this point in the particular case ofmore » annihilation into two monochromatic photons in the phenomenologically most interesting range of energy 45 GeV {approx}< E {approx}< 80 GeV, which is of great interest for the GLAST satellite. We find for example that dark matter models with sufficiently strong line annihilation signals, like the Inert Doublet Model, may be detectable without or with reasonable boost factors.« less