Atomic and Molecular Absorption in Redshifted Radio Sources
Atomic and Molecular Absorption in Redshifted Radio Sources
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DOI：
10.1093/mnras/stx408
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发表时间：
2017-02
期刊：
影响因子：
--
通讯作者：
S. Curran;M. Whiting;J. Allison;A. M. Sadler;R. Athreya
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文献类型：
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作者：
S. Curran;M. Whiting;J. Allison;A. M. Sadler;R. Athreya
本文报道了用巨米波射电望远镜在红移z = 0.2-0.4处对HI 21-cm和OH 18-cm吸收的观测。虽然低红移的选择，确保我们的目标是低于临界紫外线光度，这是假设电离所有的中性气体在宿主星系，我们没有得到任何检测在六个源搜索。分析这些背景下，以前的调查，除了与紫外线光度（电离光子率）的反相关性，我们发现之间的相关性的吸收强度和蓝色-近红外颜色，以及无线电波段的周转频率。我们认为，这是由于中性气体的光电离，一个模糊的视线更有利于冷气体的存在和紧凑的无线电发射被吸收气体更好地拦截，最大限度地扩大通量覆盖范围，分别。关于光电离，以前的调查的汇编增加了临界电离光子速率的重要性，超过该速率，宿主星系中的所有气体都被假设为电离，>5 sigma。这再次证实了这是一种普遍存在的效应，这对Square Kilometer Array探测这些物体中的中性气体具有深远的意义。
We report on a survey for associated HI 21-cm and OH 18-cm absorption with the Giant Metrewave Radio Telescope at redshifts z = 0.2-0.4. Although the low redshift selection ensures that our targets are below the critical ultra-violet luminosity, which is hypothesised to ionise all of the neutral gas in the host galaxy, we do not obtain any detections in the six sources searched. Analysing these in context of the previous surveys, in addition to the anti-correlation with the ultra-violet luminosity (ionising photon rate), we find a correlation between the strength of the absorption and the blue -- near-infrared colour, as well as the radio-band turnover frequency. We believe that these are due to the photo-ionisation of the neutral gas, an obscured sight-line being more conducive to the presence of cold gas and the compact radio emission being better intercepted by the absorbing gas, maximising the flux coverage, respectively. Regarding the photo-ionisation, the compilation of the previous surveys increases the significance of the critical ionising photon rate, above which all of the gas in the host galaxy is hypothesised to be ionised, to >5 sigma. This reaffirms that this is an ubiquitous effect, which has profound implications for the detection of neutral gas in these objects with the Square Kilometre Array.