论文标题
外星系中密集气的示踪剂
Tracers of Dense Gas in the Outer Galaxy
论文作者
论文摘要
We have mapped HCN and HCO$^{+}$ (J = 1 $\to$ 0) line emission toward a sample of seven star-forming regions (with 12 + log[O/H] range from 8.34 to 8.69) in the outer Milky Way (Galactocentric distance > 9.5 kpc), using the 14-meter radio telescope of the Taeduk Radio Astronomy Observatory (TRAO).我们将这两条分子线与其他常规的示踪剂，粉尘和灭绝阈值（$ a_ {v} \ geq 8 $ mag）产生的其他常规示踪剂，毫米波连续排放，从$^{13} $ co co Line数据中推断出来。 HCN和HCO $^{+} $与毫米发射的相关性比灭绝标准更好。大量的光度来自以下灭绝标准的区域，以及所有云的毫米块之外。 $ a_ {v} \ geq 8 $ mag的平均HCN光度分数为$ 0.343 \ pm0.225 $;对于毫米排放的地区，它为$ 0.478 \ pm0.149 $。基于与Herschel，HCN和HCO $^{+} $在高柱密度区域中的Trace致密气体的比较，比$^{13} $ CO更好。与内部星系样品相比，HCO $^{+} $对于外星系靶标的HCN浓度较低，这表明金属性可能会影响密集气体示踪剂的解释。当在整个云中集成时，密集的气体质量（$ M_ {浓度} $）与HCN和HCO $^{+} $的线发光性之间的转换因子与外层次研究中使用的因子相当。
We have mapped HCN and HCO$^{+}$ (J = 1 $\to$ 0) line emission toward a sample of seven star-forming regions (with 12 + log[O/H] range from 8.34 to 8.69) in the outer Milky Way (Galactocentric distance > 9.5 kpc), using the 14-meter radio telescope of the Taeduk Radio Astronomy Observatory (TRAO). We compare these two molecular lines with other conventional tracers of dense gas, millimeter-wave continuum emission from dust and extinction thresholds ($A_{V} \geq 8$ mag), inferred from the $^{13}$CO line data. HCN and HCO$^{+}$ correlate better with the millimeter emission than with the extinction criterion. A significant amount of luminosity comes from regions below the extinction criterion and outside the millimeter clump for all the clouds. The average fraction of HCN luminosity from within the regions with $A_{V} \geq 8$ mag is $0.343\pm0.225$; for the regions of millimeter emission, it is $0.478\pm0.149$. Based on a comparison with column density maps from Herschel, HCN and HCO$^{+}$ trace dense gas in high column density regions better than does $^{13}$CO. HCO$^{+}$ is less concentrated than HCN for outer Galaxy targets, in contrast with the inner Galaxy sample, suggesting that metallicity may affect the interpretation of tracers of dense gas. The conversion factor between the dense gas mass ($M_{dense}$) and line luminosities of HCN and HCO$^{+}$, when integrated over the whole cloud, is comparable with factors used in extragalactic studies.
