Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userConstraints on dark matter annihilation by radio observations of M31
138
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We used radio observations of the neighbour galaxy M31 in order to put constraints on dark matter particle mass and annihilation cross section. Dark matter annihilation in M31 halo produces highly energetic leptons, which emit synchrotron radiation on radio frequencies in the galactic magnetic field. We predicted expected radio fluxes for the two annihilation channels: chichi -> bb* and chichi -> tau^+tau^-. We then compared them with available data on the central radio emission of M31 as observed by four radio surveys: VLSS (74 MHz), WENSS (325 MHz), NVSS (1400 MHz) and GB6 (4850 MHz). Assuming a standard NFW dark matter density profile and a conservative magnetic field distribution inside the Andromeda galaxy, we find that the thermal relic annihilation cross section <sigma v> = 3*10^{-26} cm^3/s or higher are only allowed for WIMP masses greater than 100 GeV and 55 GeV for annihilation into bb* and tau^+tau^- respectively. Taking into account potential uncertainties in the distributions of DM density and magnetic field, the mentioned WIMP limiting masses can be as low as 23 GeV for both channels, and as high as 280 and 130 GeV for annihilation into bb* and tau^+tau^- respectively. These mass values exceed the best up-to-day known constraints from Fermi gamma observations: 40 GeV and 19 GeV respectively [A.Geringer-Sameth and S.M.Koushiappas, Phys. Rev. Lett. 107, 241303 (2011)]. Precise measurements of the magnetic field in the relevant region and better reconstruction of the DM density profile of M31 will be able to reduce the uncertainties of our exclusion limits.
rate research
Read More
Fast Radio Bursts (FRBs) are bright radio transients with millisecond duration at cosmological distances. Since compact dark matter/objects (COs) could act as lenses and cause split of this kind of very short duration signals, Mu$rm{tilde{n}}$oz et al. (2016) has proposed a novel method to probe COs with lensing of FRBs. In this Letter, we for the first time apply this method to real data and give constraints of the nature of COs with currently available FRB observations. We emphasize the information from dynamic spectra of FRBs is quite necessary for identifying any lensed signals and find no echoes in the existing data. The null search gives a constraint comparable to that from galactic wide binaries, though the methods of redshift inference from dispersion measure would impact a little. Furthermore, we make an improved forecast basing on the distributions of real data for the ongoing and upcoming telescopes. Finally, we discuss the situation where one or more lensed signals will be detected. In such a case, the parameter space of COs can be pinned down very well since the lens mass can be directly determined through the observed flux ratio and time delay between split images.
We present the first observational limits on the predicted synchrotron signals from particle Dark Matter annihilation models in dwarf spheroidal galaxies at radio frequencies below 1 GHz. We use a combination of survey data from the Murchison Widefield Array (MWA) and the Giant Metre-wave Radio Telescope (GMRT) to search for diffuse radio emission from 14 dwarf spheroidal galaxies. For in-situ magnetic fields of 1 $mu G$ and any plausible value for the diffusion coefficient, our limits do not constrain any Dark Matter models. However, for stronger magnetic fields our data might provide constraints comparable to existing limits from gamma-ray and cosmic ray observations. Predictions for the sensitivity of the upgraded MWA show that models with Dark Matter particle mass up to $sim$ 1.6 TeV (1 TeV) may be constrained for magnetic field of 2 $mu G$ (1 $mu G$). While much deeper limits from the future low frequency Square Kilometre Array (SKA) will challenge the LHC in searches for Dark Matter particles, the MWA provides a valuable first step toward the SKA at low frequencies.
The injection of secondary particles produced by Dark Matter (DM) annihilation at redshift 100<z<1000 affects the process of recombination, leaving an imprint on Cosmic Microwave Background (CMB) anisotropies. Here we provide a new assessment of the constraints set by CMB data on the mass and self-annihilation cross-section of DM particles. Our new analysis includes the most recent WMAP (7-year) and ACT data, as well as an improved treatment of the time-dependent coupling between the DM annihilation energy with the thermal gas. We show in particular that the improved measurement of the polarization signal places already stringent constraints on light DM particles, ruling out thermal WIMPs with mass less then about 10 GeV.
We use a combined 1.2 Ms of $NuSTAR$ observations of M31 to search for X-ray lines from sterile neutrino dark matter decay. For the first time in a $NuSTAR$ analysis, we consistently take into account the signal contribution from both the focused and unfocused fields of view. We also reduce the modeling systematic uncertainty by performing spectral fits to each observation individually and statistically combining the results, instead of stacking the spectra. We find no evidence of unknown lines, and thus derive limits on the sterile neutrino parameters. Our results place stringent constraints for dark matter masses $gtrsim 12$ keV, which reduces the available parameter space for sterile neutrino dark matter produced via neutrino mixing ($e.g.$, in the $ u$MSM) by approximately one-third. Additional $NuSTAR$ observations, together with improved low-energy background modeling, could probe the remaining parameter space in the future. Lastly, we also report model-independent limits on generic dark matter decay rates and annihilation cross sections.
Galaxy clusters are dominated by dark matter, and may have a larger proportion of surviving substructure than, e.g, field galaxies. Due to the presence of galaxy clusters in relative proximity and their high dark matter content, they are promising targets for the indirect detection of dark matter via Gamma-rays. Indeed, dedicated studies of sets of up to 100 clusters have been made previously, so far with no clear indication of a dark matter signal. Here we report on Gamma-ray observations of some 26,000 galaxy clusters based on Pass-7 Fermi Large Area Telescope (LAT) data, with clusters selected from the Tully 2MASS Groups catalog. None of these clusters is significantly detected in Gamma-rays, and we present Gamma-ray flux upper limits between 20 GeV and 500 GeV. We estimate the dark matter content of each of the clusters in these catalogs, and constrain the dark matter annihilation cross section, by analyzing Fermi-LAT data from the directions of the clusters. We set some of the tightest cluster-based constraints to date on the annihilation of dark matter particles with masses between 20 GeV and 500 GeV for annihilation to a gamma-ray line. Our cluster based constraints are not yet as strong as bounds placed using the Galactic Center, although an uncertainty still exists regarding the boost factor from cluster substructure, where we have chosen a rather conservative value. Our analysis, given this choice of possible boost, is not yet sensitive enough to fully rule out typical realistic DM candidates, especially if the gamma-ray line is not a dominant annihilation mode.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
