MILLIMETER OBSERVATIONS OF CS, HCO+, AND CO TOWARD FIVE PLANETARY NEBULAE: FOLLOWING MOLECULAR ABUNDANCES WITH NEBULAR AGE
MILLIMETER OBSERVATIONS OF CS, HCO+, AND CO TOWARD FIVE PLANETARY NEBULAE: FOLLOWING MOLECULAR ABUNDANCES WITH NEBULAR AGE
复制标题
对五个行星状星云的 CS、HCO 和 CO 的毫米观测：跟踪分子丰度与星云年龄
DOI：
10.1088/0004-637x/791/2/79
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
L. Ziurys
中科院分区：
文献类型：
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作者：
J. L. Edwards;E. Cox;L. Ziurys
使用亚毫米望远镜和亚利桑那射电天文台的12米天线，对五个行星状星云（PNe：K4-47、NGC 6537（红蜘蛛）、M2-48、NGC 6720（环形）和NGC 6853（哑铃））进行了CO、CS和HCO+的毫米和亚毫米观测，年龄范围为900- 10，000年。CS在245、147和98 GHz处的J = 5 → 4、J = 3 → 2和J = 2 → 1跃迁，以及HCO+在268和89 GHz处的J = 3 → 2和J = 1 → 0谱线都被探测到。在691和461 GHz处还观察到CO的至少三个转动跃迁，包括J = 6 → 5和J = 4 → 3谱线。CS以前在PNe中没有被确定，在五个星云中的四个中发现了新的HCO+。通过对CO和CS数据的辐射传递分析，确定了这些源中分子物质的动力学温度TK为10-80 K，气体密度n（H2）为0.1-1 × 106 cm−3。CO、CS和HCO+的柱密度分别为Ntot = 0.2-5 × 1016 cm−2、Ntot = 0.4-9 × 1012 cm−2和Ntot = 0.3-5 × 1012 cm−2，相对于H2的丰度分数分别为f = 0.4-2 × 10−4、f = 1-4 × 10−8和f = 1 × 10 − 8，M2-48除外，它的f（HCO+）= 10−7。总体而言，分子丰度在10，000年的持续时间内没有显着变化，与化学模型的预测相反。丰度反映了残留的渐近巨分支壳材料，加上光化学在早期PN阶段。这些观测结果还表明，PNe喷射大量的分子物质进入弥漫的星际介质。
Millimeter and sub-millimeter observations of CO, CS, and HCO+ have been conducted toward five planetary nebulae (PNe: K4-47, NGC 6537 (Red Spider), M2-48, NGC 6720 (Ring), and NGC 6853 (Dumbbell)), spanning an age range of 900–10,000 yr, using the Sub-Millimeter Telescope and the 12 m antenna of the Arizona Radio Observatory. The J = 5 → 4, J = 3 → 2, and J = 2 → 1 transitions of CS at 245, 147, and 98 GHz, as well as the J = 3 → 2 and J = 1 → 0 lines of HCO+ at 268 and 89 GHz, were detected toward each source. At least three rotational transitions of CO have also been observed, including the J = 6 → 5 and J = 4 → 3 lines at 691 and 461 GHz. CS had not been definitively identified previously in PNe, and new detections of HCO+ were made in four of the five nebulae. From a radiative transfer analysis of the CO and CS data, kinetic temperatures of TK ∼ 10–80 K and gas densities of n(H2) ∼ 0.1–1 × 106 cm−3 were determined for the molecular material in these sources. Column densities for CO, CS, and HCO+ were Ntot ∼ 0.2–5 × 1016 cm−2, Ntot ∼ 0.4–9 × 1012 cm−2, and Ntot ∼ 0.3–5 × 1012 cm−2, respectively, with fractional abundances, relative to H2, of f ∼ 0.4–2 × 10−4, f ∼ 1–4 × 10−8, and f ∼ 1 × 10−8, with the exception of M2-48, which had f(HCO+) ∼ 10−7. Overall, the molecular abundances do not significantly vary over a duration of 10,000 yr, in contrast to predictions of chemical models. The abundances reflect the remnant asymptotic giant branch shell material, coupled with photochemistry in the early PN phase. These observations also suggest that PNe eject substantial amounts of molecular material into the diffuse interstellar medium.