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arXiv 1305.0076astro-ph.GAastro-ph.CO
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圆规星系亚毫米波H2O脉泽--活动星系核环核区的新探测

Submillimeter H2O Maser in Circinus Galaxy - A New Probe for the Circumnuclear Region of Active Galactic Nuclei

Yoshiaki Hagiwara, Makoto Miyoshi, Akihiro Doi, Shinji Horiuchi

摘要:

利用阿塔卡玛大型毫米波/亚毫米波阵首次在321 GHz向Circinus星系中心(附近的2型Seyfert)过渡的区域探测到河外亚毫米波H2O脉泽。我们发现,多普勒特征的检测到的321 GHz的H2O脉泽跨越星系的系统速度中看到的光谱中的已知的22 GHz的H2O脉泽在星系。通过比较两个跃迁中脉泽特征的速度,可以推断出321 GHz脉泽发生在与22 GHz脉泽相似的区域中,其中22 GHz脉泽的亚秒差距尺度分布由早期的甚长基线干涉测量观测揭示。在~0”.66(~15 pc)的合成光束处,所探测到的脉泽特征仍然无法分辨,并且在很小的不确定度内与321 GHz连续谱峰相吻合。我们还提出了一个试探性的检测的最高速度功能(红移高达~635公里/秒)的星系。如果这个高速特征来自于这个星系中的开普勒旋转盘,那么它的半径约为0.018 pc(约1.2 x 10^5史瓦西半径),这可能是最接近中央引擎的分子物质。

英文摘要:

We present the first detection of extragalactic submillimeter H2O maser in the 321 GHz transition toward the center of Circinus galaxy, the nearby Type 2 Seyfert using the Atacama Large Millimeter/Submillimeter Array. We find that Doppler features of the detected 321 GHz H2O maser straddle the systemic velocity of the galaxy as seen in the spectrum of the known 22 GHz H2O maser in the galaxy. By comparing the velocities of the maser features in both transitions, it can be deduced that the 321 GHz maser occurs in a region similar to that of the 22 GHz maser, where the sub-parsec-scale distribution of the 22 GHz maser was revealed by earlier very long baseline interferometry observations. The detected maser features remain unresolved at the synthesized beam of ~0".66 (~15 pc) and coincide with the 321 GHz continuum peak within small uncertainties. We also present a tentative detection of the highest velocity feature (redshifts up to ~635 km/s) in the galaxy. If this high-velocity feature arises from a Keplerian rotating disk well established in this galaxy, it is located at a radius of ~0.018 pc (~1.2 x 10^5 Schwarzschild radii), which might probe molecular material closest to the central engine.

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