The low cosmic-ray density in Polaris Flare

Abstract

We reported the gamma-ray observation towards the giant molecular cloud Polaris Flare. Together with the dust column density map, we derived the cosmic ray density and spectrum in this cloud. Compared with the CR measured locally, the CR density in Polaris Flare is significantly lower and the spectrum is softer. Such a different CR spectrum reveals either a rather large gradient of CR distribution in the direction perpendicular to the Galactic plane or a suppression of CR inside molecular clouds.

7 pages, 5 figures, accepted for publication in Research in Astronomy and Astrophysics (RAA)

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