Dark matter implications of the WMAP-Planck Haze

Abstract

Gamma rays and microwave observations of the Galactic Center and surrounding areas indicate the presence of anomalous emission, whose origin remains ambiguous. The possibility of dark matter (DM) annihilation explaining both signals through prompt emission at gamma-rays and secondary emission at microwave frequencies from interactions of high-energy electrons produced in annihilation with the Galactic magnetic fields has attracted much interest in recent years. We investigate the DM interpretation of the Galactic Center gamma-ray excess by searching for the associated synchrotron in the WMAP-Planck data. Considering various magnetic field and cosmic-ray propagation models, we predict the synchrotron emission due to DM annihilation in our Galaxy, and compare it with the WMAP-Planck data at 23-70GHz. In addition to standard microwave foregrounds, we separately model the microwave counterpart to the Fermi Bubbles and the signal due to DM, and use component separation techniques to extract the signal associated with each template from the total emission. We confirm the presence of the Haze at the level of 7% of the total sky intensity at 23GHz in our chosen region of interest, with a harder spectrum $I\sim {\nu }^{-0.8}$ than the synchrotron from regular cosmic-ray electrons. The data do not show a strong preference towards fitting the Haze by either the Bubbles or DM emission only. Inclusion of both components provides a better fit with a DM contribution to the Haze emission of 20% at 23GHz, however, due to significant uncertainties in foreground modeling, we do not consider this a clear detection of a DM signal. We set robust upper limits on the annihilation cross section by ignoring foregrounds, and also report best-fit DM annihilation parameters obtained from a complete template analysis. We conclude that the WMAP-Planck data are consistent with a DM interpretation of the gamma-ray excess.

34 pages, 9 figures

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