Upper limits on the VHE gamma-ray emission from the Willman 1 satellite galaxy with the Magic telescope

© The American Astronomical Society. We thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, and Spanish MCINN is gratefully acknowledged. This work was also supported by ETH Research grant TH 34/043, by the Polish MNiSzW grant N N203 390834, and by the YIP of the Helmholtz Gemeinschaft. Finally, we thank the anonymous referees for useful comments.
We present the result of the observation of the ultrafaint dwarf galaxy Willman 1 performed with the 17 m MAGIC telescope during 15.5 hr between March and May 2008. No significant gamma-ray emission was found. We derived upper limits of the order of 10(-12) ph cm(-2) s(-1) on the integral flux above 100 GeV, which we compare with predictions from several of the established neutralino benchmark models in the mSUGRA parameter space. The neutralino annihilation spectra are defined after including the recently quantified contribution of internal bremsstrahlung from the virtual sparticles that mediate the annihilation. Flux boost factors of three orders of magnitude are required even in the most optimistic scenario to match our upper limits. However, uncertainties in the dark matter intrinsic and extrinsic properties (e.g., presence of substructures, Sommerfeld effect) may significantly reduce this gap.
ETH Research
Polish MNiSzW
German BMBF
MPG
Italian INFN
Spanish MCINN
Depto. de Estructura de la Materia, Física Térmica y Electrónica
Fac. de Ciencias Físicas
TRUE
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