High Excitation Molecular Gas in the Galactic Center Loops; 12CO(J =2-1 and J =3-2) Observations
High Excitation Molecular Gas in the Galactic Center Loops; 12CO(J =2-1 and J =3-2) Observations
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DOI：
10.1093/pasj/63.1.171
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发表时间：
2010-11
期刊：
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通讯作者：
N. Kudo;K. Torii;M. Machida;T. Davis;Kazuki Tsutsumi;M. Fujishita;N. Moribe;H. Yamamoto;T. Okuda;A. Kawamura;N. Mizuno;T. Onishi;H. Maezawa;A. Mizuno;Kunihiko Tanaka;N. Yamaguchi;H. Ezawa;Kunio Takahashi;S. Nozawa;R. Matsumoto;Y. Fukui
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作者：
N. Kudo;K. Torii;M. Machida;T. Davis;Kazuki Tsutsumi;M. Fujishita;N. Moribe;H. Yamamoto;T. Okuda;A. Kawamura;N. Mizuno;T. Onishi;H. Maezawa;A. Mizuno;Kunihiko Tanaka;N. Yamaguchi;H. Ezawa;Kunio Takahashi;S. Nozawa;R. Matsumoto;Y. Fukui
我们在1.0-3.8pC的空间分辨率下，用NANTEN和ASTE对银河系中心环1、2和部分环3进行了12co(J=2-1)和12co(J=3-2)的观测。这些新的结果揭示了分子气体的详细分布和两个跃迁的谱线强度比R3-2/2-1。在三个环中，R3-2/2-1在0.1-2.5的范围内，峰值在~0.7，而盘状分子气中的R3-2/2-1在0.1-1.2的范围内，峰值在0.4。这支持了环比圆盘分子气体更高的激发。12co J=3-2和2-1和13co J=2-1向环1和2的6个位置的三个跃迁的左旋群分析表明，密度和温度分别在102.2-104.7 cm-3和15-100K或更高的范围内。环路中延伸50-100pC的三个区域倾向于具有更高的激发条件，其特征是R3-2/2-1大于1.2。在环1和环2之间最发达的足点上的比值最高，为2.5.从S-1的50-100公里的大线宽推断，脚点表示强烈震荡条件，证实了Torii等人的观点.(2010b)。脚点之外的另外两个区域表明，分子气体被一些额外的加热机制加热，可能包括磁重联。对四个足点的详细分析表明，b-v分布呈U形、L形或镜面L形。结果表明，一个简单的运动学模型能够解释这些特征形状，该模型包含了环路的整体旋转和扩展。
We have carried out 12CO(J =2-1) and 12CO(J =3-2) observations at spatial resolutions of 1.0-3.8 pc toward the entirety of loops 1 and 2 and part of loop 3 in the Galactic center with NANTEN2 and ASTE. These new results revealed detailed distributions of the molecular gas and the line intensity ratio of the two transitions, R3-2/2-1. In the three loops, R3-2/2-1 is in a range from 0.1 to 2.5 with a peak at ~ 0.7 while that in the disk molecular gas is in a range from 0.1 to 1.2 with a peak at 0.4. This supports that the loops are more highly excited than the disk molecular gas. An LVG analysis of three transitions, 12CO J =3-2 and 2-1 and 13CO J =2-1, toward six positions in loops 1 and 2 shows density and temperature are in a range 102.2 - 104.7 cm-3 and 15-100 K or higher, respectively. Three regions extended by 50-100 pc in the loops tend to have higher excitation conditions as characterized by R3-2/2-1 greater than 1.2. The highest ratio of 2.5 is found in the most developed foot points between loops 1 and 2. This is interpreted that the foot points indicate strongly shocked conditions as inferred from their large linewidths of 50-100 km s-1, confirming the suggestion by Torii et al. (2010b). The other two regions outside the foot points suggest that the molecular gas is heated up by some additional heating mechanisms possibly including magnetic reconnection. A detailed analysis of four foot points have shown a U shape, an L shape or a mirrored-L shape in the b-v distribution. It is shown that a simple kinematical model which incorporates global rotation and expansion of the loops is able to explain these characteristic shapes.