Observations of the Large Magellanic Cloud with Fermi
Observations of the Large Magellanic Cloud with Fermi
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DOI：
10.1051/0004-6361/200913474
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发表时间：
2010-01
影响因子：
6.5
通讯作者：
The Fermi-LAT Collaboration;A. Abdo;et al.
中科院分区：
文献类型：
--
作者：
The Fermi-LAT Collaboration;A. Abdo;et al.
大麦哲伦星云（LMC）是迄今为止唯一一个在高能伽马射线中被探测到的正常外部星系。高能伽马射线追踪粒子加速过程和伽马射线观测允许研究加速的性质和地点。目的：通过对大麦哲伦星云γ射线观测资料的分析，揭示大麦哲伦星云中宇宙线的分布和来源。研究方法：我们分析了11个月的连续巡天观测与费米伽马射线太空望远镜上的大面积望远镜，并将其与星际介质的示踪剂和大麦哲伦星系中的伽马射线源模型进行比较。结果：LMC在33 sigma显著性下被检测到。LMC的积分>100 MeV光子通量为（2.6 +/- 0.2）* 10^-7 ph/cm 2/s，对应的能通量为（1.6 +/- 0.1）* 10^-10 erg/cm 2/s，系统不确定度约为16%。分析显示，除了在星系北方发现的较暗的发射区外，剑鱼座30号大质量星星形成区也是大麦哲伦星云中伽马射线的明亮发射源。大麦哲伦星系的伽马射线辐射与气体密度的相关性很小，而与大质量星星形成区的示踪物相关。伽马射线发射到星星形成区域的紧密限制表明宇宙射线质子扩散长度相对较短。结论：宇宙射线密度和大质量星星示踪物之间的密切相关性支持了这样一种观点，即宇宙射线在大质量星星形成区被加速，这是由于大质量恒星的恒星风和超新星爆炸输入星际介质的大量动能。
Context: The Large Magellanic Cloud (LMC) is to date the only normal external galaxy that has been detected in high-energy gamma rays. High-energy gamma rays trace particle acceleration processes and gamma-ray observations allow the nature and sites of acceleration to be studied. Aims: We characterise the distribution and sources of cosmic rays in the LMC from analysis of gamma-ray observations. Methods: We analyse 11 months of continuous sky-survey observations obtained with the Large Area Telescope aboard the Fermi Gamma-Ray Space Telescope and compare it to tracers of the interstellar medium and models of the gamma-ray sources in the LMC. Results: The LMC is detected at 33 sigma significance. The integrated >100 MeV photon flux of the LMC amounts to (2.6 +/- 0.2) * 10^-7 ph/cm2/s which corresponds to an energy flux of (1.6 +/- 0.1) * 10^-10 erg/cm2/s, with additional systematic uncertainties of ~16%. The analysis reveals the massive star forming region 30 Doradus as a bright source of gamma-ray emission in the LMC in addition to fainter emission regions found in the northern part of the galaxy. The gamma-ray emission from the LMC shows very little correlation with gas density and is rather correlated to tracers of massive star forming regions. The close confinement of gamma-ray emission to star forming regions suggests a relatively short GeV cosmic-ray proton diffusion length. Conclusions: The close correlation between cosmic-ray density and massive star tracers supports the idea that cosmic rays are accelerated in massive star forming regions as a result of the large amounts of kinetic energy that are input by the stellar winds and supernova explosions of massive stars into the interstellar medium.