Diffuse gamma-ray emission from the vicinity of young massive star cluster RSGC 1

Abstract

We report the Fermi Large Area Telescope (Fermi-LAT) detection of the gamma-ray emission towards the young massive star cluster RSGC 1. Using the latest source catalog and diffuse background models, we found that the diffuse gamma-ray emission in this region can be resolved into three different components. The GeV gamma-ray emission from the region HESS J1837-069 has a photon index of 1.83 $\pm$ 0.08. Combining with the HESS and MAGIC data, we argue that the gamma-ray emission in this region likely originate from a pulsar wind nebula (PWN). The gamma-ray emission from the northwest part (region A) can be modelled by an ellipse with the semimajor and semiminor axis of 0.5${}^{\circ }$ and 0.25${}^{\circ }$, respectively. The GeV emission has a hard spectrum with a photon index of 2.05 $\pm$ 0.02 and is partially coincide with the TeV source MAGIC J1835-069. The possible origin of the gamma-ray emission in this region is the interaction of the cosmic rays (CRs) accelerated by SNR G24.7+0.6 or/and the OB cluster G25.18+0.26 with the surrounding gas clouds. The GeV gamma-ray emission from the southeast region (region B) can be modeled as an ellipse with the semimajor and semiminor axis of 0.9${}^{\circ }$ and 0.5${}^{\circ }$, respectively, and also reveals a hard gamma-ray spectrum. We argue that the most probable origin is the interaction of the accelerated protons in the young massive star cluster RSGC 1 with ambient gas clouds, and the total cosmic-ray (CR) proton energy is estimated to be as high as $\sim$ 1x10${}^{50}$ erg.

8 pages, 11 figures, 2 tables. published in MNRAS

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• Diffuse $\gamma$-ray emission around the massive star forming region of Carina Nebula Complex
• A hard spectrum diffuse gamma-ray component associated with HII gas in the Galactic plane
• Diffuse gamma-ray emission around the Rosette Nebula
• Detection of diffuse gamma-ray emission towards a massive star forming region hosting Wolf-Rayet stars
• An interacting molecular cloud scenario for production of gamma-rays and neutrinos from MAGIC J1835-069, and MAGIC J1837-073
• A cosmic-ray loaded nascent outflow driven by a massive star cluster
• Direct simulations of very high energy cosmic ray acceleration in 3D MHD model of a compact star cluster