Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSearch for $gamma$-ray line signals from dark matter annihilations in the inner Galactic halo from ten years of observations with H.E.S.S
96
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
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 proximity 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.
rate research
Read More
The inner region of the Milky Way halo harbors a large amount of dark matter (DM). Given its proximity, it is one of the most promising targets to look for DM. We report on a search for the annihilations of DM particles using $gamma$-ray observations towards the inner 300 parsecs of the Milky Way, with the H.E.S.S. array of ground-based Cherenkov telescopes. The analysis is based on a 2D maximum likelihood method using Galactic center (GC) data accumulated by H.E.S.S. over the last 10 years (2004-2014), and does not show any significant $gamma$-ray signal above background. Assuming Einasto and Navarro-Frenk-White DM density profiles at the GC, we derive upper limits on the annihilation cross section $langle sigma vrangle$. These constraints are the strongest obtained so far in the TeV DM mass range and improve upon previous limits by a factor 5. For the Einasto profile, the constraints reach $langle sigma vrangle$ values of $rm 6times10^{-26} cm^3s^{-1}$ in the $W^+W^-$ channel for a DM particle mass of 1.5 TeV, and $rm 2times10^{-26} cm^3s^{-1}$ in the $tau^+tau^-$ channel for 1 TeV mass. For the first time, ground-based $gamma$-ray observations have reached sufficient sensitivity to probe $langle sigma vrangle$ values expected from the thermal relic density for TeV DM particles.
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 sources 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.
The presence of dark matter (DM) is suggested by a wealth of astrophysical and cosmological measurements. However, its underlying nature is yet unknown. Among the most promising candidates are weakly interacting massive particles (WIMPs): particles with mass and coupling strength at the electroweak scale and thermally produced in the early universe have a present relic density consistent with that observed today. WIMP self-annihilation would produce Standard Model particles including gamma-rays, which have been long-time recognized as a prime messenger to indirectly detect dark matter signals. The centre of the Milky Way is predicted as the brightest source of DM annihilations. The H.E.S.S. collaboration is currently performing a survey of the inner region of the Milky Way, the Inner Galaxy Survey (IGS), intended to achieve the best sensitivity to faint and diffuse emissions in a region of several degrees around the Galactic Centre. We analyzed 2014-2020 observations taken with the five-telescope array to search for a DM annihilation signal. With the current dataset of about 550 hours, we found no significant excess and therefore derived strong constraints on the velocity-weighted annihilation cross-section. TeV thermal WIMPs can be probed in different annihilation channels.
The presence of dark matter is nowadays widely supported by a large body of astronomical and cosmological observations. A large amount of dark matter is expected to be present in the central region of the Milky Way. Very-high-energy (>100 GeV) {gamma}-rays can be produced in the annihilation of dark matter particles. The H.E.S.S. array of Imaging Atmospheric Cherenkov Telescopes is a powerful tools to observe the Galactic Centre trying to detect {gamma}-rays from dark matter annihilation. A new search for a dark matter signal has been carried out on the full H.E.S.S.-I data set of 2004-2014 observations. A 2D-binned likelihood method has been applied to exploit the spectral and spatial properties of signal and background. Updated constraints are derived on the velocity-weighted annihilation cross section for signals from prompt annihilation of dark matter particles into two photons. The larger statistics from the 10-year Galactic Center dataset of H.E.S.S.-I together with the 2D-analysis technique allows to significantly improve the previous limits.
Cosmological N-body simulations show that Milky-Way-sized galaxies harbor a population of unmerged dark matter subhalos. These subhalos could shine in gamma rays and be eventually detected in gamma-ray surveys as unidentified sources. We search for very-high-energy (VHE, $Egeq 100$ GeV) gamma-ray emission using H.E.S.S. observations carried out from a thorough selection of unidentified Fermi-LAT Objects (UFOs) as dark matter subhalo candidates. Provided that the dark matter mass is higher than a few hundred GeV, the emission of the UFOs can be well described by dark matter annihilation models. No significant VHE gamma-ray emission is detected in any UFO dataset nor in their combination. We, therefore, derive constraints on the product of the velocity-weighted annihilation cross-section $langle sigma vrangle$ by the $J$-factor on dark matter models describing the UFO emissions. Upper limits at 95% confidence level are derived on $langle sigma vrangle J$ in $W^+W^-$ and $tau^+tau^-$ annihilation channels for the TeV dark matter particles. Focusing on thermal WIMPs, strong constraints on the $J$-factors are obtained from H.E.S.S. observations. Adopting model-dependent predictions from cosmological N-body simulations on the $J$-factor distribution function for Milky Way (MW)-sized galaxies, only $lesssim 0.3$ TeV mass dark matter models marginally allow to explain observed UFO emission.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
