Quantitative Constraint on the Contribution of Resolved Gamma-Ray Sources to the Sub-PeV Galactic Diffuse Gamma-Ray Flux Measured by the Tibet ASγ Experiment
S. Kato, M. Anzorena, D. Chen, K. Fujita, R. Garcia, J. Huang, G. Imaizumi, T. Kawashima, K. Kawata, A. Mizuno, M. Ohnishi, T. Sako, T. K. Sako, F. Sugimoto, M. Takita and Y. Yokoe
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Abstract
Motivated by the difference between the fluxes of sub-PeV Galactic diffuse gamma-ray emission (GDE) measured by the Tibet ASγ experiment and the LHAASO collaboration, our study constrains the contribution to the GDE flux measured by Tibet ASγ from the sub-PeV gamma-ray sources in the first LHAASO catalog plus the Cygnus Cocoon. After removing the gamma-ray emission of the sources masked in the observation by Tibet ASγ, the contribution of the sources to the Tibet diffuse flux is found to be subdominant; in the sky region of 25° < l < 100° and ∣b∣ < 5°, it is less than 26.9% ± 9.9%, 34.8% ± 14.0%, and at 121 TeV, 220 TeV, and 534 TeV, respectively. In the sky region of 50° < l < 200° and ∣b∣ < 5°, the fraction is less than 24.1% ± 9.5%, 27.1% ± 11.1%, and . After subtracting the source contribution, the hadronic diffusive nature of the Tibet diffuse flux is the most natural interpretation although some contributions from very faint unresolved hadronic gamma-ray sources cannot be ruled out. Different source-masking schemes adopted by Tibet ASγ and LHAASO for their diffuse analyses result in different effective Galactic latitudinal ranges of the sky regions observed by the two experiments. Our study concludes that the effect of the different source-masking schemes leads to the observed difference between the Tibet diffuse flux measured in 25° < l < 100° and ∣b∣ < 5° and LHAASO diffuse flux in 15° < l < 125° and ∣b∣ < 5°.
由于西藏ASγ实验测量的亚pev星系漫射伽马射线(GDE)通量与LHAASO合作项目的差异,我们的研究限制了西藏ASγ测量的亚pev星系漫射伽马射线通量对LHAASO第一目录和天鹅座茧的亚pev伽玛射线源的贡献。在去除西藏ASγ遮挡观测的源的伽马射线发射后,发现源对西藏漫射通量的贡献是次要的;在25°< l < 100°和∣b∣< 5°的天区,分别小于26.9%±9.9%、34.8%±14.0%和121 TeV、220 TeV和534 TeV。在50°< l < 200°和∣b∣< 5°的天空区域,该分数小于24.1%±9.5%,27.1%±11.1%,和。在减去源的贡献后,西藏漫射通量的强子扩散性质是最自然的解释,尽管不能排除一些来自非常微弱的未解析强子伽玛射线源的贡献。西藏ASγ和LHAASO在散射分析中采用不同的掩源方案,导致两个实验观测到的天空区域的有效银河纬度范围不同。我们的研究表明,不同源掩蔽方案的影响导致观测到25°< l < 100°和∣b∣< 5°的西藏扩散通量与15°< l < 125°和∣b∣< 5°的LHAASO扩散通量之间的差异。