scholarly journals Separating astrophysical sources from indirect dark matter signals

2014 ◽  
Vol 112 (40) ◽  
pp. 12272-12277 ◽  
Author(s):  
Jennifer M. Siegal-Gaskins
Keyword(s):  
Dark Matter ◽  
Angular Distribution ◽  
Energy Spectrum ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Dark Matter Annihilation ◽  
Robust Identification ◽  
Analysis Methods ◽  
The Status

Indirect searches for products of dark matter annihilation and decay face the challenge of identifying an uncertain and subdominant signal in the presence of uncertain backgrounds. Two valuable approaches to this problem are (i) using analysis methods which take advantage of different features in the energy spectrum and angular distribution of the signal and backgrounds and (ii) more accurately characterizing backgrounds, which allows for more robust identification of possible signals. These two approaches are complementary and can be significantly strengthened when used together. I review the status of indirect searches with gamma rays using two promising targets, the Inner Galaxy and the isotropic gamma-ray background. For both targets, uncertainties in the properties of backgrounds are a major limitation to the sensitivity of indirect searches. I then highlight approaches which can enhance the sensitivity of indirect searches using these targets.

scholarly journals Constraints to Dark Matter Annihilation from High-Latitude HAWC Unidentified Sources

Galaxies ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 5
Author(s):  
Javier Coronado-Blázquez ◽  
Miguel A. Sánchez-Conde
Keyword(s):  
Dark Matter ◽  
Cross Section ◽  
Gamma Rays ◽  
High Latitude ◽  
Gamma Ray ◽  
Detection Threshold ◽  
Dark Matter Annihilation ◽  
Annihilation Channel ◽  
Dark Matter Search ◽  
Spatially Extended

The Λ CDM cosmological framework predicts the existence of thousands of subhalos in our own Galaxy not massive enough to retain baryons and become visible. Yet, some of them may outshine in gamma rays provided that the dark matter is made of weakly interacting massive particles (WIMPs), which would self-annihilate and would appear as unidentified gamma-ray sources (unIDs) in gamma-ray catalogs. Indeed, unIDs have proven to be competitive targets for dark matter searches with gamma rays. In this work, we focus on the three high-latitude ( | b | ≥ 10 ) sources present in the 2HWC catalog of the High Altitude Water Cherenkov (HAWC) observatory with no clear associations at other wavelengths. Indeed, only one of these sources, 2HWC J1040+308, is found to be above the HAWC detection threshold when considering 760 days of data, i.e., a factor 1.5 more exposure time than in the original 2HWC catalog. Other gamma-ray instruments, such as Fermi-LAT or VERITAS at lower energies, do not detect the source. Also, this unID is reported as spatially extended, making it even more interesting in a dark matter search context. While waiting for more data that may shed further light on the nature of this source, we set competitive upper limits on the annihilation cross section by comparing this HAWC unID to expectations based on state-of-the-art N-body cosmological simulations of the Galactic subhalo population. We find these constraints to be particularly competitive for heavy WIMPs, i.e., masses above ∼25 (40) TeV in the case of the b b ¯ ( τ + τ − ) annihilation channel, reaching velocity-averaged cross section values of 2 × 10 − 25 ( 5 × 10 − 25 ) cm 3 ·s − 1 . Although far from testing the thermal relic cross section value, the obtained limits are independent and nicely complementary to those from radically different DM analyses and targets, demonstrating once again the high potential of this DM search approach.

CONSTRAINING DARK MATTER ANNIHILATION WITH NEUTRINOS AND GAMMA RAYS

2011 ◽  
Vol 01 ◽  
pp. 245-251
Author(s):  
NICOLE F. BELL
Keyword(s):  
Dark Matter ◽  
Total Cross Section ◽  
Cross Section ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Mass Range ◽  
Dark Matter Halo ◽  
Dark Matter Annihilation ◽  
Upper Limits ◽  
Wide Range

We examine dark matter annihilation in galaxy halos. By considering annihilation into all Standard Model particles we show that the least detectable final states, namely neutrinos, define a strong general upper bound on the total cross section. This limit is much stronger than the unitarity bound in the most interesting mass range and implies annihilation cannot significantly modify dark matter halo density profiles. We also calculate conservative upper limits on the self-annihilation cross section to monoenergetic gamma rays over a wide range of dark matter masses, using gamma-ray data from the Milky Way, Andromeda (M31), and the cosmic background. We compare gamma-ray-based and neutrino-based upper limits on the total cross section.

scholarly journals On a Possible Origin of the Gamma-ray Excess around the Galactic Center

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1432
Author(s):  
Dmitry O. Chernyshov ◽  
Andrei E. Egorov ◽  
Vladimir A. Dogiel ◽  
Alexei V. Ivlev
Keyword(s):  
Dark Matter ◽  
Gamma Rays ◽  
Molecular Clouds ◽  
Alternative Explanation ◽  
Gamma Ray ◽  
Galactic Center ◽  
The Self ◽  
Large Area ◽  
Mhd Turbulence ◽  
The Standard Model

Recent observations of gamma rays with the Fermi Large Area Telescope (LAT) in the direction of the inner galaxy revealed a mysterious excess of GeV. Its intensity is significantly above predictions of the standard model of cosmic rays (CRs) generation and propagation with a peak in the spectrum around a few GeV. Popular interpretations of this excess are that it is due to either spherically distributed annihilating dark matter (DM) or an abnormal population of millisecond pulsars. We suggest an alternative explanation of the excess through the CR interactions with molecular clouds in the Galactic Center (GC) region. We assumed that the excess could be imitated by the emission of molecular clouds with depleted density of CRs with energies below ∼10 GeV inside. A novelty of our work is in detailed elaboration of the depletion mechanism of CRs with the mentioned energies through the “barrier” near the cloud edge formed by the self-excited MHD turbulence. This depletion of CRs inside the clouds may be a reason for the deficit of gamma rays from the Central Molecular Zone (CMZ) at energies below a few GeV. This in turn changes the ratio between various emission components at those energies and may potentially absorb the GeV excess by a simple renormalization of key components.

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