اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدSearch for Gamma-rays from Dark Matter annihilations around Intermediate Mass Black Holes with the H.E.S.S. experiment
49
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The H.E.S.S. array of Cherenkov telescopes has performed, from 2004 to 2007, a survey of the inner Galactic plane at photon energies above 100 GeV. About 400 hours of data have been accumulated in the region between -30 and +60 degrees in Galactic longitude, and between -3 and +3 degrees in Galactic latitude. Assuming that dark matter is composed of Weakly Interacting Massive Particles, we calculate here the H.E.S.S. sensitivity map for dark matter annihilations, and derive the first experimental constraints on the mini-spikes scenario, in which a gamma-ray signal arises from dark matter annihilation around Intermediate Mass Black Holes. The data exclude the proposed scenario at a 90% confidence level for dark matter particles with velocity-weighted annihilation cross section sigma v above 10^28 cm3s^-1 and mass between 800 GeV and 10 TeV.
قيم البحث
اقرأ أيضاً
In this paper, we explore the possibility of a linearly polarized gamma-ray signal from dark matter annihilations in the Galactic center. Considering neutral weakly interacting massive particles, a polarized gamma-ray signal can be realized by a two-
component dark matter model of Majorana fermions with an anapole moment. We discuss the spin alignment of such dark matter fermions in the Galactic center and then estimate the intensity and the polarizability of the final-state electromagnetic radiation in the dark matter annihilations. For low-mass dark matter, the photon flux at sub-GeV energies may be polarized at a level detectable in current X-ray polarimeters. Depending on the mass ratio between the final-state fermion and DM, the degree of polarization at the mass threshold can reach $70%$ or even higher, providing us with a new tool for probing the nature of dark matter in future gamma-ray polarization experiments.
Gamma-ray line signatures can be expected in the very-high-energy (VHE; E_gamma > 100 GeV) domain due to self-annihilation or decay of dark matter (DM) particles in space. Such a signal would be readily distinguishable from astrophysical gamma-ray so
urces that in most cases produce continuous spectra which span over several orders of magnitude in energy. Using data collected with the H.E.S.S. gamma-ray instrument, upper limits on line-like emission are obtained in the energy range between ~500 GeV and ~25 TeV for the central part of the Milky Way halo and for extragalactic observations, complementing recent limits obtained with the Fermi-LAT instrument at lower energies. No statistically significant signal could be found. For monochromatic gamma-ray line emission, flux limits of (2x10^-7 - 2x10^-5) m^-2 s^-1 sr^-1 and (1x10^-8 - 2x10^-6) m^-2 s^-1 sr^-1 are obtained for the central part of the Milky Way halo and extragalactic observations, respectively. For a DM particle mass of 1 TeV, limits on the velocity-averaged DM annihilation cross section < sigma v >(chichi -> gammagamma) reach ~10^-27 cm^3 s^-1, based on the Einasto parametrization of the Galactic DM halo density profile.
Lines in the energy spectrum of gamma rays are a fascinating experimental signal, which are often considered smoking gun evidence of dark matter annihilation. The current generation of gamma ray observatories are currently closing in on parameter spa
ce of great interest in the context of dark matter which is a thermal relic. We consider theories in which the dark matters primary connection to the Standard Model is via the top quark, realizing strong gamma ray lines consistent with a thermal relic through the forbidden channel mechanism proposed in the Higgs in Space Model. We consider realistic UV-completions of the Higgs in Space and related theories, and show that a rich structure of observable gamma ray lines is consistent with a thermal relic as well as constraints from dark matter searches and the LHC. Particular attention is paid to the one loop contributions to the continuum gamma rays, which can easily swamp the line signals in some cases, and have been largely overlooked in previous literature.
Spectral lines are among the most powerful signatures for dark matter (DM) annihilation searches in very-high-energy $gamma$-rays. The central region of the Milky Way halo is one of the most promising targets given its large amount of DM and proximit
y to Earth. We report on a search for a monoenergetic spectral line from self-annihilations of DM particles in the energy range from 300 GeV to 70 TeV using a two-dimensional maximum likelihood method taking advantage of both the spectral and spatial features of signal versus background. The analysis makes use of Galactic Center (GC) observations accumulated over ten years (2004 - 2014) with the H.E.S.S. array of ground-based Cherenkov telescopes. No significant $gamma$-ray excess above the background is found. We derive upper limits on the annihilation cross section $langlesigma vrangle$ for monoenergetic DM lines at the level of $sim4times10^{-28}$ cm$^{3}$s$^{-1}$ at 1 TeV, assuming an Einasto DM profile for the Milky Way halo. For a DM mass of 1 TeV, they improve over the previous ones by a factor of six. The present constraints are the strongest obtained so far for DM particles in the mass range 300 GeV - 70 TeV. Ground-based $gamma$-ray observations have reached sufficient sensitivity to explore relevant velocity-averaged cross sections for DM annihilation into two $gamma$-ray photons at the level expected from the thermal relic density for TeV DM particles.
Recently, it has been shown that electrons and positrons from dark matter (DM) annihilations provide an excellent fit to the Fermi, PAMELA, and HESS data. Using this DM model, which requires an enhancement of the annihilation cross section over its s
tandard value to match the observations, we show that it immediately implies an observable level of gamma-ray emission for the Fermi telescope from nearby galaxy clusters such as Virgo and Fornax. We show that this DM model implies a peculiar feature from final state radiation that is a distinctive signature of DM. Using the EGRET upper limit on the gamma-ray emission from Virgo, we constrain the minimum mass of substructures within DM halos to be > 5x10^-3 M_sun -- about four orders of magnitudes larger than the expectation for cold dark matter. This limits the cutoff scale in the linear matter power spectrum to k < 35/kpc which can be explained by e.g., warm dark matter. Very near future Fermi observations will strongly constrain the minimum mass to be > 10^3 M_sun: if the true substructure cutoff is much smaller than this, the DM interpretation of the Fermi/PAMELA/HESS data must be wrong. To address the problem of astrophysical foregrounds, we performed high-resolution, cosmological simulations of galaxy clusters that include realistic cosmic ray (CR) physics. We compute the dominating gamma-ray emission signal resulting from hadronic CR interactions and find that it follows a universal spectrum and spatial distribution. If we neglect the anomalous enhancement factor and assume standard values for the cross section and minimum subhalo mass, the same model of DM predicts comparable levels of the gamma-ray emission from DM annihilations and CR interactions. This suggests that spectral subtraction techniques could be applied to detect the annihilation signal.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
