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arXiv 1704.06110astro-ph.HE
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来自G25 .0+0.0区域的扩展Gamma-ray发射:由新发现的OB协会提供动力的恒星形成区域?

Extended Gamma-ray Emission from the G25.0+0.0 Region: A Star Forming Region Powered by the Newly Found OB Association?

Junichiro Katsuta, Yasunobu Uchiyama, Stefan Funk

摘要:

我们报告了费米伽马射线太空望远镜上的大面积望远镜(LAT)的扩展$γ$射线发射的研究,这很可能是我们银河系恒星形成区(SFR)的$γ$射线探测的第二种情况。LAT源位于G25区,$(l, b) = (25.0^{\circ}, 0.0^{\circ})$周围的$1.7^{\circ} \times 2.1^{\circ}$。发现$γ$射线辐射由两个扩展源和一个点状源组成。扩展源具有大约$1.4^{\circ} \times 0.6^{\circ}$的类似大小。$\sim 0.4^{\circ}$直径为1的子区域的光子指数为$Γ= 1.53 \pm 0.15$,在空间上与HESS J1837 $-$ 069重合,可能是一个脉冲星风星云。扩展源的其他部分具有$Γ= 2.1 \pm 0.2$的光子指数,而没有显著的光谱曲率。鉴于它们的空间和光谱特性,它们与其他波长的光源没有明确的联系。它们的$γ$射线特性与天鹅座茧状SFR相似,天鹅座茧状SFR是银河系中唯一确定的SFR的$γ$射线探测。事实上,我们在G25中发现了原子和分子气体的气泡状结构,这可能是由假定的OB协会/集群产生的。$γ$射线的发射区域似乎局限在气泡状结构中;在天鹅座茧中也发现了类似的特性。此外,利用XMM-牛顿的观测,我们在G25区域发现了一个候选的年轻大质量OB星协/星团G25.18+0.26。我们认为G25中的扩展$γ$射线发射与G25.18+0.26驱动的SFR有关。基于这种情况下,我们讨论了可能的加速过程中的SFR和比较它们与天鹅座茧。

英文摘要:

We report a study of extended $γ$-ray emission with the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope, which is likely to be the second case of a $γ$-ray detection from a star-forming region (SFR) in our Galaxy. The LAT source is located in the G25 region, $1.7^{\circ} \times 2.1^{\circ}$ around $(l, b) = (25.0^{\circ}, 0.0^{\circ})$. The $γ$-ray emission is found to be composed of two extended sources and one point-like source. The extended sources have a similar sizes of about $1.4^{\circ} \times 0.6^{\circ}$. An $\sim 0.4^{\circ}$ diameter sub-region of one has a photon index of $Γ= 1.53 \pm 0.15$; and is spatially coincident with HESS J1837$-$069, likely a pulsar wind nebula. The other parts of the extended sources have a photon index of $Γ= 2.1 \pm 0.2$ without significant spectral curvature. Given their spatial and spectral properties, they have no clear associations with sources at other wavelengths. Their $γ$-ray properties are similar to those of the Cygnus cocoon SFR, the only firmly established $γ$-ray detection of an SFR in the Galaxy. Indeed, we find bubble-like structures of atomic and molecular gas in G25, which may be created by a putative OB association/cluster. The $γ$-ray emitting regions appear confined in the bubble-like structure; similar properties are also found in the Cygnus cocoon. In addition, using observations with the the XMM-Newton we find a candidate young massive OB association/cluster G25.18+0.26 in the G25 region. We propose that the extended $γ$-ray emission in G25 is associated with an SFR driven by G25.18+0.26. Based on this scenario, we discuss possible acceleration processes in the SFR and compare them with the Cygnus cocoon.

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