Bounds on Dark Matter Properties from Radio Observations of Ursa Major II using the Green Bank Telescope

TL;DR

This study uses radio observations of Ursa Major II with the Green Bank Telescope to set bounds on dark matter properties, especially WIMP annihilation parameters, by modeling synchrotron radiation from charged particles.

Contribution

It provides new constraints on WIMP dark matter annihilation cross-section, mass, magnetic field, and diffusion coefficient using radio data and dark matter halo modeling.

Findings

Excluded 10 GeV WIMPs annihilating to e^+ e^- at thermal rate under certain magnetic field conditions.

Constraints are sensitive to dark matter density profile uncertainties.

Limits depend on magnetic field strength and diffusion coefficient assumptions.

Abstract

Radio observations of the Ursa Major II dwarf spheroidal galaxy obtained using the Green Bank Telescope are used to place bounds on WIMP dark matter properties. Dark matter annihilation releases energy in the form of charged particles which emit synchrotron radiation in the magnetic field of the dwarf galaxy. We compute the expected synchrotron radiation intensity from WIMP annihilation to various primary channels. The predicted synchrotron radiation is sensitive to the distribution of dark matter in the halo, the diffusion coefficient D_0, the magnetic field strength B, the particle mass m_\chi, the annihilation rate <\sigma v>, and the annihilation channel. Limits on <\sigma v>, m_\chi, B, and D_0 are obtained for the e^+ e^-, \mu^+ \mu^-, \tau^+ \tau^-, and b \bar b channels. Constraints on these parameters are sensitive to uncertainties in the measurement of the dark matter density profile. For the best fit halo parameters derived from stellar kinematics, we exclude 10 GeV WIMPs annihilating directly to e^+ e^- at the thermal rate <\sigma v> = 2.18 x 10^{-26} cm^3/s at the 2\sigma level, for B > 0.6 microGauss (1.6 microGauss) and D_0 = 0.1 (1.0) x the Milky Way diffusion value.