The Study of QSO Absorption Lines using 3D Radiative Transfer

使用 3D 辐射传输研究 QSO 吸收线

基本信息

批准号：
11640225
负责人：
UMEMURA Masayuki
金额：
$ 2.3万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

Recently, it has been considered that the Lya absorption systems in QSO spectra can be accounted for in terms of the absorption by intergalactic overdense fluctuations. However, all of previous works have been based upon optically-thin or local optical-depth approximations. Here, we present 3D radiative transfer calculations on the cosmic reionization and the formation of QSO absorption line systems.The resultant ionization degrees in the universe are different from place to place by more than three orders of magnitude. Due to such inhomogeneous ionization structure, relatively low ionization regions could produce strong absorption in QSO spectra. To make a direct comparison with the observations, we have simulated absorption lines. First, we focus on Lya absorption. It has turned out that the so-called Gunn-Peterson effect appears as the overlapping effect of absorption lines just when low dispersion spectroscopy is made. In order to compare the simulations quantitatively with observa … More tions, we have assessed the continuum depression, D_A. It is found that any model with a constant UV intensity does not match the observed trend that D_A tends to grow quickly at higher redshifts up to 5. This implies that the metagalactic UV intensity must decrease rapidly with z at z > 5 by two orders of magnitude at least. If the well fitted value of UV intensity at z = 5 is unchanged at higher redshifts, the reionization epoch is estimated to be z_<reion> > 7- However, the Lya absorption is not appropriate to determine the reionization epoch more accurately, because Lyα is too strongly depleted even if the mean neutral fraction is less than 10^<-2>.Therefore, three conditions are required for a line in order to investigate the universe at z > 5 : (1) line emission is detectable, (2) it has lower line opacity than Lya, and (3) it has lower extinction against dust because young star-forming galaxies are often dust-enshrouded. The most favorable solution is Ha absorption lines. Actually, we have found that the Ha continuum depression traces the reionization history more accurately. Therefore, it is concluded that Ha forest is a more powerful tool to probe the universe at z > 5. The wavelengths of Ha forest drop on 3μm【less than or similar】λ_<Hα>【less than or similar】7μm at 4【less than or similar】z【less than or similar】10. Thus, the observations can be done with Subaru IRCS. Less

最近，人们认为，可以通过间年间过度密度波动来考虑QSO光谱中的LYA抽象系统。但是，以前的所有作品都基于光学薄或局部光学深度近似。在这里，我们提出了3D辐射转移计算，这些计算是宇宙回离和QSO抽象线系统的形成。宇宙中的结果电离度与位置之间的电离度不同。由于这种不均匀的电离结构，相对低电离区域可能会在QSO光谱中产生强大的抽象。为了与观测值进行直接比较，我们已经模拟了抽象线。首先，我们专注于Lya抽象。事实证明，在制作低分散光谱时，所谓的Gunn-Peterson效应似乎是抽象线的重叠效果。为了将模拟与观察者进行定量进行比较……更多的问题，我们评估了连续的抑郁，D_A。发现任何具有恒定UV强度的模型都与观察到的趋势不符，即D_A倾向于在高达5的较高红移时迅速生长。这意味着Metagalactic UV强度必须在Z> 5的情况下以Z> 5的速度迅速降低，至少至少两个幅度。如果在更高的红移下Z = 5时的紫外线强度的合适值不变，则估计回离时期为z__ <reeion> 7--但是，LYA抽象不合适地确定重新离子时期不准确地确定lilα的含量太强，因为即使在平均值中不太需要进行中性级别的范围。 Z> 5：（1）线排放是可以检测到的，（2）它的不透明度低于LYA，并且（3）由于年轻的星系星系通常是尘埃刺激的，因此对灰尘的延伸较低。最有利的解决方案是HA滥用线。实际上，我们发现HA连续抑郁症更准确地追溯了电离历史。因此，可以得出结论，HA森林是在z> 5处探测宇宙的功能更强大的工具。在3μm上的HA森林降落的波长[小于或类似]λ_<Hα> [小于或相似] 4 [小于或类似]相似的Z Z Z】Z【小于或相似的10。这是可以使用Subaru IRC进行的观察。较少的