Fermi Gamma-ray Space Telescope

Multi-wavelength emission from dark matter pair annihilation in local dwarf spheroidal galaxies

Kamal Tanti

Abstract:

In this paper, we present a study of multi-wavelength emission from dark matter pair annihilation in a few selected local dwarf spheroidal (dSph) galaxies. In WIMP dark matter model, dark matter pair annihilation is expected to yield a significant amount of energetic antimatter and gamma rays, alongwith a population of energetic electrons and positrons. The energetic electron-positron pairs populate dark matter halos in WIMP model, and further help to determine the dark matter density profile and WIMP pair annihilation rate. The electron-positron pair diffuse, loose energy and produce secondary radiation through various mechanisms, such as synchrotron radiation. These radiations finally give rise to a broad spectrum of photons, stretching from extreme ultra-violet up-to gamma-ray band. Thus the study of multi-wavelength emission from dark matter pair annihilation is an important way of indirect dark matter searches. We are considering few local dwarf spheroidal (dSph) galaxies, as dSph are the most dark-matter dominated known systems. In this paper, we present the analysis of archival X-ray and gamma-ray data of local dSph galaxies, hoping to detect a signal from dark matter pair annihilation. We further analyze the diffuse emission from one of the dSph galaxies at gamma-ray frequencies and by studying the spectral features at various wavelengths, we may detect dark matter and determine the WIMP mass and interaction cross-section. Fitting multi-wavelength spectral energy distribution using recent data from Chandra, Fermi-LAT and Cherenkov observations, we analyze different dark matter annihilation scenarios, including a full treatment of Inverse Compton losses from electrons and positrons produced in the annihilation.