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arXiv 0902.0122astro-ph.CO
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HCO +和HCN J=3-2吸收朝向半人马座A的中心

HCO+ and HCN J=3-2 absorption toward the center of Centaurus A

Sebastien Muller, Dinh-V-Trung

备注：
Accepted for publication in ApJ
发表信息：
Astrophys.J.696:176-181,2009
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摘要：

我们用亚毫米波阵观测了射电源Cen A前HCO ~+和HCN（3-2）线的吸收，研究了射电源Cen A附近稠密气体的存在。我们检测到窄的HCO+（3-2）吸收，并暂时HCN（3-2），接近系统速度。对于这两种分子，J=3-2吸收比J=1-0线弱得多。通过简单的激发分析，我们得出结论，当柱密度N（HCO+）/dV为3 × 10^12 cm^-2 km^-1 s，动力学温度为10 K时，气体密度约为10^4 cm^-3。特别是，我们没有发现任何证据表明，在连续谱源的视线范围内，分子气体的密度高于几个10^4 cm^-3。我们讨论的影响，我们的发现的性质的分子气体负责的吸收向Cen A。

英文摘要：

We have investigated the presence of dense gas toward the radio source Cen A by looking at the absorption of the HCO+ and HCN (3-2) lines in front of the bright continuum source with the Submillimeter Array. We detect narrow HCO+ (3-2) absorption, and tentatively HCN (3-2), close to the systemic velocity. For both molecules, the J=3-2 absorption is much weaker than for the J=1-0 line. From simple excitation analysis, we conclude that the gas density is on the order of a few 10^4 cm^-3 for a column density N(HCO+)/dV of 3x10^12 cm^-2 km^-1 s and a kinetic temperature of 10 K. In particular, we find no evidence for molecular gas density higher than a few 10^4 cm^-3 on the line of sight to the continuum source. We discuss the implications of our finding on the nature of the molecular gas responsible for the absorption toward Cen A.

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