The Position of Sagittarius A*: Accurate Alignment of the Radio and Infrared Reference Frames at the Galactic Center
The Position of Sagittarius A*: Accurate Alignment of the Radio and Infrared Reference Frames at the Galactic Center
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人马座 A* 的位置：无线电和红外参考系在银河系中心的精确对准
DOI：
10.1086/310472
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
R. Genzel
中科院分区：
文献类型：
--
作者：
K. Menten;M. Reid;A. Eckart;R. Genzel
我们提出了一种新的方法来定位银河系中心区域的红外图像上的紧凑的非热射电源Sgr A* 的位置的长期存在的问题。利用甚大天线阵，我们已经探测到SiO和H2O脉泽发射对几个源内的中央秒差距的银河系。这些脉泽产生于核星星团成员巨星和超巨星的星周包层的最内部，在衍射极限的2.2 μm红外图像中表现为紧凑的红外源。其中一个SiO脉泽与M型超巨星IRS 7有关，IRS 7是银河系中心区域最突出的2.2 μm点源。无线电数据允许测量微波激射器的位置相对于紧凑的非热无线电连续源Sgr A* 与毫角秒精度。由于银河系中心附近的恒星SiO脉泽可以在几毫角秒内追踪其宿主恒星，这些相对位置可以用来校准红外图像的板块尺度和旋转。我们的方法允许注册的无线电相对于红外参考系的估计精度为0.“03。利用改进的位置精度，我们对Sgr A* 的2.2 μm通量密度设置了严格的上限，该上限明显低于最近理论模型计算预测的值。
We present a novel approach to the long-standing problem of locating the position of the compact nonthermal radio source Sgr A* on infrared images of the Galactic center region. Using the Very Large Array, we have detected SiO and H2O maser emission toward several sources within the central parsec of our Galaxy. These masers arise from the innermost parts of circumstellar envelopes of giant and supergiant stars that are members of the nuclear star cluster and appear as compact infrared sources in a diffraction-limited 2.2 μm infrared image. One of the SiO masers is associated with the M-type supergiant IRS 7, the most prominent 2.2 μm point source in the Galactic center region. The radio data allow measurements of the maser positions relative to the compact nonthermal radio continuum source Sgr A* with milliarcsecond accuracy. Because stellar SiO masers near the Galactic center trace their host stars to within a few milliarcseconds, these relative positions can be used to calibrate the plate scale and rotation of the infrared image. Our method allows registration of the radio relative to the infrared reference frame with an estimated accuracy of 0.″03. Using the improved position accuracy we put a stringent upper limit on the 2.2 μm flux density of Sgr A* that is significantly lower than values predicted by recent theoretical model calculations.