DETECTION OF 36 GHz CLASS I METHANOL MASER EMISSION TOWARD NGC 253
DETECTION OF 36 GHz CLASS I METHANOL MASER EMISSION TOWARD NGC 253
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DOI：
10.1088/2041-8205/790/2/l28
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发表时间：
2014-07
期刊：
影响因子：
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通讯作者：
S. Ellingsen;Xi Chen;H. Qiao;W. Baan;T. An;Juan Li;S. Breen
中科院分区：
文献类型：
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作者：
S. Ellingsen;Xi Chen;H. Qiao;W. Baan;T. An;Juan Li;S. Breen
我们使用澳大利亚望远镜紧凑阵列来寻找甲醇（36.2 GHz）4−1 → 30 E跃迁向附近星暴星系NGC 253中心的辐射。探测到两个发射区域，从核沿着与内旋臂相同的位置角偏移。在5“的尺度下，发射的光谱基本上无法分辨，半高宽线宽<30 km s−1，各向同性的光度比在银河系任何星星形成区观测到的都要大几个数量级。这些特征表明，36.2 GHz的甲醇辐射最有可能是一个微波激射器，尽管需要更高的角度和光谱分辨率的观测来证实这一点。如果它是一个脉泽，这代表了第一次在银河系外探测到一类甲醇脉泽。NGC 253中36.2 GHz的甲醇发射比最近在银河系中心检测到的广泛发射的各向同性光度高出一个数量级。如果这种转变的辐射与核星星的形成率成比例，那么在许多星暴星系的中心区域就可以检测到。在超亮红外星系中探测到甲醇的排放，将为在宇宙学尺度上测试基本常数（特别是质子与电子质量比）的变化开辟一个新的工具。
We have used the Australia Telescope Compact Array to search for emission from the 4−1 → 30E transition of methanol (36.2 GHz) toward the center of the nearby starburst galaxy NGC 253. Two regions of emission were detected, offset from the nucleus along the same position angle as the inner spiral arms. The emission is largely unresolved on a scale of 5″, has a FWHM line width of <30 km s−1, and an isotropic luminosity orders of a magnitude larger than that observed in any Galactic star formation region. These characteristics suggest that the 36.2 GHz methanol emission is most likely a maser, although observations with higher angular and spectral resolution are required to confirm this. If it is a maser, this represents the first detection of a class I methanol maser outside the Milky Way. The 36.2 GHz methanol emission in NGC 253 has more than an order of magnitude higher isotropic luminosity than the widespread emission recently detected toward the center of the Milky Way. If emission from this transition scales with the nuclear star formation rate, then it may be detectable in the central regions of many starburst galaxies. Detection of methanol emission in ultra-luminous infrared galaxies would open up a new tool for testing for variations in fundamental constants (particularly the proton-to-electron mass ratio) on cosmological scales.