DISCOVERY OF CANDIDATE H2O DISK MASERS IN ACTIVE GALACTIC NUCLEI AND ESTIMATIONS OF CENTRIPETAL ACCELERATIONS
DISCOVERY OF CANDIDATE H2O DISK MASERS IN ACTIVE GALACTIC NUCLEI AND ESTIMATIONS OF CENTRIPETAL ACCELERATIONS
复制标题
DOI：
10.1088/0004-637x/707/1/787
复制
发表时间：
2009-11
期刊：
影响因子：
--
通讯作者：
L. Greenhill;P. T. Kondratko;J. Moran;A. Tilak
中科院分区：
文献类型：
--
作者：
L. Greenhill;P. T. Kondratko;J. Moran;A. Tilak
根据光谱特征，在活动星系核（agn）中，大约三分之一的已知水脉射源被认为是在中心发动机周围的高倾斜吸积盘中产生的。这些“盘脉泽候选者”之所以引起人们的兴趣，主要是因为角结构和旋转曲线可以用干涉仪分辨，从而进行动力学研究。我们在Green Bank望远镜的研究中发现了5个新的盘脉泽候选者，使发表的总数达到30个。我们在对40个倾斜活动星系（vsys < 20,000 km s - 1）的调查中发现了两个（NGC 1320和NGC 17）。其余三个盘脉泽候选者是在对已知源的监测中确定的：NGC 449、NGC 2979和NGC 3735。我们还确认了UGC 4203中先前的次要案例。对于这里报道的盘脉泽候选者，推断的旋转速度为130-500 km s−1。对三个更快速旋转的候选圆盘（cg211, NGC 6264, VV 340A）的监测已经能够测量可能的轨道向心加速度，并估计中心质量（（2-7）×107 M☉）和平均圆盘半径（0.2-0.4 pc）。当与干涉仪数据结合时，加速度最终可能允许估计距离。这是值得注意的，因为三个agn相对较远（10,000 km s - 1 <vsys < 15,000 km s - 1），并且由于星系的特殊运动，推导出的哈勃常数的分数误差很小。作为银河系中心半径为~ 0.1-1 pc的高度倾斜几何形状的标志，盘脉泽也提供了强大的方向参考，即使没有广泛的干涉测绘，也可以分析agn和周围星系恒星盘之间的（错误）对准。我们发现在已发表的盘脉泽候选者中，没有偏向于位于高倾角星系的现象。这为在晚型星系中，中央发动机吸积盘与星系平面方向不相关的结论提供了独立的支持。
Based on spectroscopic signatures, about one-third of known H2O maser sources in active galactic nuclei (AGNs) are believed to arise in highly inclined accretion disks around central engines. These “disk maser candidates” are of interest primarily because angular structure and rotation curves can be resolved with interferometers, enabling dynamical study. We identify five new disk maser candidates in studies with the Green Bank Telescope, bringing the total number published to 30. We discovered two (NGC 1320, NGC 17) in a survey of 40 inclined active galaxies (vsys < 20, 000 km s−1). The remaining three disk maser candidates were identified in monitoring of known sources: NGC 449, NGC 2979, and NGC 3735. We also confirm a previously marginal case in UGC 4203. For the disk maser candidates reported here, inferred rotation speeds are 130–500 km s−1. Monitoring of three more rapidly rotating candidate disks (CG 211, NGC 6264, VV 340A) has enabled measurement of likely orbital centripetal acceleration, and estimation of central masses ((2–7) ×107 M☉) and mean disk radii (0.2–0.4 pc). Accelerations may ultimately permit estimation of distances when combined with interferometer data. This is notable because the three AGNs are relatively distant (10,000 km s−1 <vsys < 15, 000 km s−1), and fractional error in a derived Hubble constant, due to peculiar motion of the galaxies, would be small. As signposts of highly inclined geometries at galactocentric radii of ∼0.1–1 pc, disk masers also provide robust orientation references that allow analysis of (mis)alignment between AGNs and surrounding galactic stellar disks, even without extensive interferometric mapping. We find no preference among published disk maser candidates to lie in high-inclination galaxies. This provides independent support for conclusions that in late-type galaxies, central engine accretion disks and galactic plane orientations are not correlated.