ATCA SURVEY OF AMMONIA IN THE GALACTIC CENTER: THE TEMPERATURES OF DENSE GAS CLUMPS BETWEEN Sgr A* AND Sgr B2
ATCA SURVEY OF AMMONIA IN THE GALACTIC CENTER: THE TEMPERATURES OF DENSE GAS CLUMPS BETWEEN Sgr A* AND Sgr B2
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DOI：
10.1088/0004-637x/785/1/55
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发表时间：
2014-02
期刊：
影响因子：
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通讯作者：
J. Ott;A. Weiss;L. Staveley-Smith;C. Henkel;D. Meier
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作者：
J. Ott;A. Weiss;L. Staveley-Smith;C. Henkel;D. Meier
我们提出了一个大规模的，干涉测量氨（1，1）和（2，2）对银河系中心观察与澳大利亚望远镜紧凑阵列。该巡天覆盖了Δ b = 1 °（假设距离为8.5 kpc时为150 pc）和Δ b = 0. ° 2（130 pc），跨越了超大质量黑洞Sgr A * 和大质量恒星形成区Sgr B2之间的区域。分辨率为20 ″（20.8 pc），由于缺少干涉短间距，尺度为20 ′（20.3 pc）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。温度分布的峰值在1038 K，半高宽在18 K和61 K之间（测量灵敏度在Tkin 10 - 80 K之间）。较大的团块平均比较小的团块温暖，这表明内部热源。我们的观测表明，围绕Sgr A * 的1.5 pc的环核盘由20 km s − 1分子云提供气体。该气体比距离Sgr A * 0.3 - 15 pc的气体冷得多。我们发现一个强大的温度梯度跨越Sgr B2。氨柱密度与SCUBA 850 μ m通量具有良好的相关性，但该关系偏离了原点，这可能表明需要最低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。
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. The survey covers Δℓ ∼ 1° (∼150 pc at an assumed distance of 8.5 kpc) and Δb ∼ 0.°2 (∼30 pc) which spans the region between the supermassive black hole Sgr A* and the massive star forming region Sgr B2. The resolution is ∼20″ (∼0.8 pc) and emission at scales ≳ 2′ (≳ 3.2 pc) 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 1.2 cm continuum emission. We present a kinetic temperature map of the dense gas. The temperature distribution peaks at ∼38 K with a width at half maximum between 18 K and 61 K (measurements sensitive within Tkin ∼ 10–80 K). 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 Sgr A* is supplied with gas from the 20 km s−1 molecular cloud. This gas is substantially cooler than gas ∼3–15 pc away from Sgr A*. We find a strong temperature gradient across Sgr B2. Ammonia column densities correlate well with SCUBA 850 μm 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.