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arXiv 0804.4136astro-ph
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八个邻近星系水脉泽辐射的发现

The Discovery of Water Maser Emission from Eight Nearby Galaxies

J. A. Braatz, N. E. Gugliucci

摘要:

使用绿岸望远镜,我们进行了一个“快照”的调查水脉泽发射到611个星系的核,并发现了8个新的来源。样本由附近的(v < 5000 km/s)和发光的(M_B < -19.5)星系组成,其中一些星系有已知的核活动,但大多数以前不知道有活动星系核。我们的探测包括与活动星系核有关的超脉泽和可能与恒星形成有关的相对低光度脉泽。在UGC 3789中的探测特别有趣,因为光谱显示了系统性和高速线,表明从AGN吸积盘的边缘看到的排放。基于六个月的监测,我们检测到的系统性特征之间的加速度范围从2到8公里/秒/年,较大的值属于最红移的系统组件。UGC 3789中的高速脉泽线在同一时期没有可探测到的漂移。尽管在这次调查之前还不知道UGC 3789是活动星系核,但盘脉泽的存在是核活动的有力证据,后来获得的光谱也证实了这一点。通过后续观测,有可能测量到UGC 3789的几何距离。

英文摘要:

Using the Green Bank Telescope, we conducted a ``snapshot'' survey for water maser emission toward the nuclei of 611 galaxies and detected eight new sources. The sample consisted of nearby (v < 5000 km/s) and luminous (M_B < -19.5) galaxies, some with known nuclear activity but most not previously known to host AGNs. Our detections include both megamasers associated with AGNs and relatively low luminosity masers probably associated with star formation. The detection in UGC 3789 is particularly intriguing because the spectrum shows both systemic and high-velocity lines indicative of emission from an AGN accretion disk seen edge-on. Based on six months of monitoring, we detected accelerations among the systemic features ranging from 2 to 8 km/s/yr, the larger values belonging to the most redshifted systemic components. High-velocity maser lines in UGC 3789 show no detectable drift over the same period. Although UGC 3789 was not known to be an AGN prior to this survey, the presence of a disk maser is strong evidence for nuclear activity, and an optical spectrum obtained later has confirmed it. With follow up observations, it may be possible to measure a geometric distance to UGC 3789.

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