Ionization of the atomic gas in redshifted radio sources
Ionization of the atomic gas in redshifted radio sources
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DOI：
10.1093/mnras/stz038
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发表时间：
2019-01
影响因子：
4.8
通讯作者：
S. Curran;R. Hunstead;Helen M. Johnston;Matthew Whiting;E. Sadler;E. Sadler;J. R. Allison;R. Athreya
中科院分区：
文献类型：
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作者：
S. Curran;R. Hunstead;Helen M. Johnston;Matthew Whiting;E. Sadler;E. Sadler;J. R. Allison;R. Athreya
我们报道了用巨型米波射电望远镜对一种新的射电源样品在z≲0.4时的21厘米吸收率的测量结果。在11个有良好数据的来源中，我们获得了零探测，其中4个来源预计会考虑到电离光子速率和灵敏度。加上之前公布的值，我们确认在高红移的活动源中没有检测到21厘米的吸收是由于气体的光致电离，而不是21厘米光子的激发(分别在6.09σ和2.90σ显著)。我们还证实了吸收强度和光源变红之间的强烈相关性，这表明尘埃在屏蔽气体免受周围紫外线照射方面发挥了重要作用。还发现了21厘米探测率与无线电周转频率之间的反相关关系，这与周转频率越高，震源越紧凑的预期相反。然而，这与周转频率与电子密度有关的假设是一致的，并得到了周转频率与电离光子率之间的相关性的支持。
We report the results of a survey for H I 21-cm absorption at z ≲ 0.4 in a new sample of radio sources with the Giant Metrewave Radio Telescope. Of the 11 sources for which there are good data, we obtain zero detections, where four are expected upon accounting for the ionizing photon rates and sensitivity. Adding these to the previously published values, we confirm that the non-detection of 21-cm absorption in active sources at high redshift is due to photo-ionization of the gas rather than excitation by 21-cm photons (significant at 6.09σ and 2.90σ, respectively). We also confirm a strong correlation between the absorption strength and the reddening of the source, suggesting that dust plays a significant role in shielding the gas from the ambient ultraviolet field. An anticorrelation between the 21-cm detection rate and the radio turnover frequency is also found, which runs contrary to what is expected on the basis that the higher the turnover frequency, the more compact the source. It is, however, consistent with the hypothesis that the turnover frequency is related to the electron density, supported by a correlation between the turnover frequency and ionizing photon rate.