银河系中心氨的ATCA巡天：SgrA * 和SgrB2之间致密气体团的温度
ATCA Survey of Ammonia in the Galactic Center: The Temperatures of Dense Gas Clumps between SgrA* and SgrB2
摘要：
我们提出了一个大规模的，氨（1，1）和（2，2）朝向银河系中心的观测与澳大利亚望远镜紧凑阵列（ATCA）的干涉测量。这次巡天覆盖了Delta l ~ 1度（约150秒差距，假设距离为8.5千秒差距）和Delta b ~ 0.2度（约30秒差距），它们横跨超大质量黑洞SgrA* 和大质量恒星形成区SgrB 2之间的区域。分辨率为~ 20“（~0.8pc），由于缺少干涉短间距，尺度>~2”（>~3.2pc）的发射被滤除。因此，这些数据代表了密度更大、更紧凑的云，而忽略了大尺度的扩散气体。许多团块与100 pc尘埃环对齐，大多与1.2 cm连续辐射反相关。我们提出了一个稠密气体的动力学温度图。温度分布峰值在~ 38 K，半峰宽在18 K和61 K之间（测量灵敏度在Tkin~10- 80 K内）。较大的团块平均比较小的团块温暖，这表明内部热源。我们的观测结果表明，SgrA ~* 周围约1.5pc的环核盘由20 km/s的分子云提供气体。该气体比距离SgrA* 约3- 15 pc的气体冷得多。我们发现SgrB 2上有很强的温度梯度。氨柱密度与SCUBA 850 um通量相关性很好，但这种关系偏离了原点，这可能表明需要最小量的灰尘来形成和屏蔽氨。在拱和五重星系团周围，我们发现在它们的中心有受紫外线影响的气体的壳形态，其次是氨和无线电连续层。
英文摘要：
We present a large-scale, interferometric survey of ammonia (1,1) and (2,2) toward the Galactic Center observed with the Australia Telescope Compact Array (ATCA). The survey covers Delta l ~1degree (~150pc) at an assumed distance of 8.5 kpc) and Delta b ~0.2degree (~30pc) which spans the region between the supermassive black hole SgrA* and the massive star forming region SgrB2. The resolution is ~20'' (~0.8pc) and emission at scales >~2' (>~3.2pc) is filtered out due to missing interferometric short spacings. Consequently, the data represent the denser, compact clouds and disregards the large scale, diffuse gas. Many of the clumps align with the 100 pc dust ring and mostly anti-correlate with 1.2cm continuum emission. We present a kinetic temperature map of the dense gas. The temperature distribution peaks at ~38K with a width at half maximum between 18K and 61K (measurements sensitive within Tkin~10-80K). Larger clumps are on average warmer than smaller clumps which suggests internal heating sources. Our observations indicate that the circumnuclear disk ~1.5 pc around SgrA* is supplied with gas by the 20km/s molecular cloud. This gas is substantially cooler than gas ~3-15pc away from SgrA*. We find a strong temperature gradient across SgrB2. Ammonia column densities correlate well with SCUBA 850um fluxes, but the relation is shifted from the origin, which may indicate a requirement for a minimum amount of dust to form and shield ammonia. Around the Arches and Quintuplet clusters we find shell morphologies with UV-influenced gas in their centers, followed by ammonia and radio continuum layers.
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