IONIZATION NEAR ZONES ASSOCIATED WITH QUASARS AT z ∼ 6
IONIZATION NEAR ZONES ASSOCIATED WITH QUASARS AT z ∼ 6
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DOI：
10.1088/0004-637x/714/1/834
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发表时间：
2010-02
期刊：
影响因子：
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通讯作者：
C. Carilli;Ran Wang;X. Fan;F. Walter;J. Kurk;D. Riechers;J. Wagg;J. Hennawi;L. Jiang;K.M.Menten;F. Bertoldi;M. Strauss;P. Cox
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文献类型：
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作者：
C. Carilli;Ran Wang;X. Fan;F. Walter;J. Kurk;D. Riechers;J. Wagg;J. Hennawi;L. Jiang;K.M.Menten;F. Bertoldi;M. Strauss;P. Cox
我们分析了在z=5.7到6.4之间的27个类星体(“类星体近区”或NZ)附近HⅡ区的尺寸演化。与以前的研究相比，我们包括了更多的源，我们对宿主星系使用了更准确的红移，有8个CO分子线红移和9个MG II红移。我们证实了NZ尺寸随红移减小而增大的趋势，亮度归一化的合适尺寸演化为RNZ，修正后为(7.4±0.3)−(8.0±1.1)×(z−6)Mpc。虽然用这种技术得出绝对中性分数仍然很困难，但从NZ大小的演变可以看出，在最简单的解释中，星系间氢的中性分数减少了一个因子∼9.4，从z=6.4降到了5.7。或者，最近的数值模拟表明，NZ尺寸从z=6.4迅速增加到5.7是由于渗流或重叠阶段结束时背景光电离速率的快速增加，此时电离光子的平均平均自由路径急剧增加。在任何一种情况下，结果都与z∼6-7对应于宇宙再电离的尾端的观点一致。由于测量误差，归一化新西兰大小的散布比预期的要大，很可能反映了类星体或它们所处环境的内在差异。我们发现NZ尺寸随着类星体UV光度的增加而增大，正如类星体辐射主导的光致电离所预期的那样。
We analyze the size evolution of H ii regions around 27 quasars between z = 5.7 and 6.4 (“quasar near zones” or NZs). We include more sources than previous studies, and we use more accurate redshifts for the host galaxies, with eight CO molecular line redshifts and nine Mg ii redshifts. We confirm the trend for an increase in NZ size with decreasing redshift, with the luminosity-normalized proper size evolving as RNZ,corrected = (7.4 ± 0.3) − (8.0 ± 1.1) × (z − 6) Mpc. While derivation of the absolute neutral fraction remains difficult with this technique, the evolution of the NZ sizes suggests a decrease in the neutral fraction of intergalactic hydrogen by a factor ∼9.4 from z = 6.4 to 5.7, in its simplest interpretation. Alternatively, recent numerical simulations suggest that this rapid increase in NZ size from z = 6.4 to 5.7 is due to the rapid increase in the background photo-ionization rate at the end of the percolation or overlap phase, when the average mean-free path of ionizing photons increases dramatically. In either case, the results are consistent with the idea that z ∼ 6–7 corresponds to the tail end of cosmic reionization. The scatter in the normalized NZ sizes is larger than expected simply from measurement errors, and likely reflects intrinsic differences in the quasars or their environments. We find that the NZ sizes increase with quasar UV luminosity, as expected for photo-ionization dominated by quasar radiation.