Diffuse gamma-ray emission around the Rosette Nebula

TL;DR

This study revisits gamma-ray emission around the Rosette Nebula using 13 years of Fermi-LAT data, revealing a harder spectrum than previously thought, suggesting it is a gamma-ray emitting young star cluster.

Contribution

It introduces improved spatial modeling with HII gas templates and provides new spectral analysis of gamma-ray emission around the Rosette Nebula.

Findings

Gamma-ray emission is significantly better modeled with HII gas templates.

The gamma-ray spectrum is substantially harder than earlier reports.

Rosette Nebula may be classified as a gamma-ray emitting young massive star cluster.

Abstract

The Rosette Nebula is a young stellar cluster and molecular cloud complex, located at the edge of the southern shell of a middle-aged SNR Monoceros Loop (G205.5+0.5). We revisited the GeV gamma-ray emission towards the Rosette Nebula using more than 13 years of Fermi-LAT data. We tested several spatial models and found that compared to the result using the CO gas template only, the inclusion of the HII gas template can significantly improve the likelihood fit. We performed spectral analysis using the new spatial template. With both the gamma-ray observation and CO+HII gas data, we derived the cosmic ray spectrum of different components in the vicinity of the Rosette Nebula. We found the gamma-ray emissions from Rosette Nebula are substantially harder than previously reported, which may imply that Rosette Nebula is another example of a gamma-ray emitting young massive star cluster.