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首页> 外文期刊>The Astrophysical journal >A NEW PROBE OF DENSE GAS AT HIGH REDSHIFT: DETECTION OF HCO~+ (5-4) LINE EMISSION IN APM 08279+5255
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A NEW PROBE OF DENSE GAS AT HIGH REDSHIFT: DETECTION OF HCO~+ (5-4) LINE EMISSION IN APM 08279+5255

机译：高浓度时的高密度气体新探测：APM 08279 + 5255中HCO〜+（5-4）线发射的检测

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摘要

We report the detection of HCO~+ (5-4) emission from the broad absorption line quasar APM 08279+5255 at z = 3.911 based on observations conducted with the IRAM Plateau de Bure Interferometer. This represents the first detection of this molecular ion at such a high redshift. The inferred line luminosity, uncorrected for lensing, is L′_(HCO~+) = (3.5 ± 0.6) x 10~(10) K km s~(-1) pc~2. The HCO~+ J = 5-4 source position coincides within the errors with that reported from previous HCN J = 5-4 and high-J CO line observations of this quasar. The HCO~+ line profile central velocity and width are consistent with those derived from HCN. This result suggests that HCO~+ (5-4) emission comes roughly from the same circumnuclear region probed by HCN. However, the HCN (5-4)/HCO~+ (5-4) intensity ratio measured in APM 08279+5255 is significantly larger than that predicted by simple radiative transfer models, which assume collisional excitation and equal molecular abundances. This could imply that the [HCN]/[HCO~+] abundance ratio is particularly large in this source, or that the J = 5 rotational levels are predominantly excited by infrared fluorescent radiation.
机译：我们报告了基于IRAM高原德布尔干涉仪进行的观测，从宽吸收线类星体APM 08279 + 5255在z = 3.911处检测到HCO〜+（5-4）发射。这代表了在如此高的红移下对该分子离子的首次检测。推断出的线光度未经透镜校正，为L'_（HCO〜+）=（3.5±0.6）x 10〜（10）K km s〜（-1）pc〜2。 HCO〜+ J = 5-4源位置与先前的HCN J = 5-4和该类星体的高J CO线观测所报告的误差相吻合。 HCO〜+线轮廓中心速度和宽度与从HCN得出的一致。这一结果表明，HCO〜+（5-4）的发射大致来自于HCN探测到的同一核周区域。但是，在APM 08279 + 5255中测得的HCN（5-4）/ HCO〜+（5-4）强度比明显大于简单的辐射传递模型所预测的强度，该模型假设碰撞激发和相等的分子丰度。这可能意味着[HCN] / [HCO〜+]丰度比在此光源中特别大，或者J = 5旋转水平主要由红外荧光辐射激发。

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