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arXiv 1201.0336astro-ph.CO
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用HCN（J = 3-2）和HCO +（J = 3-2）谱线探测核周围环境：NGC 1097的情况

Probing Circumnuclear Environments with the HCN(J = 3-2) and HCO+(J = 3-2) lines: Case of NGC 1097

Pei-Ying Hsieh, Paul T. P. Ho, Kotaro Kohno, Chorng-Yuan Hwang, Satoki Matsushita

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accepted for publication in ApJ
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摘要：

本文介绍了用亚毫米波射电望远镜获得的NGC 1097环核区HCN（J = 3-2）和HCO+（J = 3-2）的第一张干涉图。目标是研究与星暴环/塞弗特核有关的致密气体的特性。通过这些跃迁，我们抑制了核区的弥散低密度发射。我们检测和解决个人紧凑的巨分子云协会（GMAs）在1.4千秒差距的环核星暴环和350秒差距的核区域内。在两条谱线中，核比环亮，在中心1.4 kpc内，贡献了总检测到的HCO+（J = 3-2）和HCN（J = 3-2）通量的~20%和~30%。HCN（J = 3-2）/HCO+（J = 3-2）的强度比在星暴环的GMAs中大致为1。然而，在核区域中，该比率高达~2。根据HCN（J = 3-2）/HCN（J = 1-0）比值<0.2，我们推测HCN（J = 3-2）核发射可能是光学薄的。HCO ~+（J = 3-2）和HCN（J = 3-2）与~（12）CO（J = 3-2）和24μm发射有相关性。HCN（J = 3-2）、HCO+（J = 3-2）与星暴环24μm辐射的密切相关表明，致密分子气体与尘埃来自同一恒星形成区。另一方面，HCN（J = 3-2）发射的核显着增强，表明机制以外的恒星形成，如活动星系核活动。通过我们的观测，对原子核的X射线电离化学增强的丰度分数进行自洽检验是可能的。

英文摘要：

We present the first interferometric HCN(J = 3-2) and HCO+(J = 3-2) maps in the circumnuclear region of NGC 1097, obtained with the Submillimeter Array. The goal is to study the characteristics of the dense gas associated with the starburst ring/Seyfert nucleus. With these transitions, we suppress the diffuse low density emission in the nuclear region. We detect and resolve the individual compact giant molecular cloud associations (GMAs) in the 1.4 kpc circumnuclear starburst ring and within the 350 pc nuclear region. The nucleus is brighter than the ring in both lines, and contributes to ~20% and ~30% to the total detected HCO+(J = 3-2) and HCN(J = 3-2) flux, within the central 1.4 kpc. The intensity ratios of HCN(J = 3-2)/HCO+(J = 3-2) are roughly unity in the GMAs of the starburst ring. However, this ratio is up to ~2 in the nuclear region. From the HCN(J = 3-2)/HCN(J = 1-0) ratio of <0.2 in the nucleus, we infer that the nuclear HCN(J = 3-2) emission might be optically thin. The HCO+(J = 3-2) and HCN(J = 3-2) show correlations with 12CO(J = 3-2) and the 24μm emission. The tight correlations of HCN(J = 3-2), HCO+(J = 3-2) and 24μm emission in the starburst ring suggest that the dense molecular gas and the dust are from the same origins of star forming regions. On the other hand, the HCN(J = 3-2) emission of the nucleus is significantly enhanced, indicating mechanisms other than star formation, such as AGN activities. A self-consistent check of the fractional abundance enhanced by X-ray ionization chemistry of the nucleus is possible with our observations.

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