A search for radio signatures of Dark Matter particles in the Draco dwarf galaxy

Dark Matter is a fundamental component of the Universe both on Galactic and cosmological scales, albeit its intrinsic nature is still largely unknown. Weakly interactive massive particles (WIMPs) have been a long standing Dark Matter particle candidate from the theory stand point, although they have not received observational confirmation so far. Theoretical models suggest that WIMPs can annihilate/decay into electron/positron pairs and, in the presence of magnetic fields, such relativistic electrons would generate an observable synchrotron radio emission that would be the footprint of the WIMP particle and its cross section. In this thesis we present a search for the radio signature of Dark Matter particles in the Draco dwarf spheroidal galaxy with Giant Metrewave Radio Telescope observations. We analyzed observations from the GMRT, taken with a large bandwidth around 650 MHz and with full array configuration in order to obtain the maximum sensitivity. We used long baselines to identify and remove compact sources, leading to a final image with 20.5′′ angular resolution and a 230 μJy beam−1 rms noise. We modeled the DM-induced synchrotron emission in Draco in order to place constraints to the annihilation cross section from our observations. We found marginal evidence (σ = 1.97) of a diffuse signal over the whole field of view that is unlikely due to DM but to residual artifacts left in the image after source subtraction. We still present best fits on the annihilation cross section of WIMPs assuming that the signal was due to DM. A best fit cross section of ∼10−23 cm3 s−1 is obtained at 100 GeV for different annihilation channels. We estimate the best noise rms image that we could achieve with improved calibration/subtraction and we use it to place upper limits near 2 ·10−24 cm3 s−1 on the DM cross section for 100 GeV particle mass. We discuss our result in the light of the current literature constraints and explore alternative models for the theoretical emission.