【作者】 蒋耀妹；

【导师】 黄克谅；

【作者基本信息】 南京师范大学 ， 天体物理， 2003， 硕士

【摘要】 以往对Lyα森林的研究大多是基于中低分辨率光谱，谱线混合较严重，所以进行高分辨率光谱的研究很有必要。本文采用19个中高红移类星体的高分辨率光谱数据来研究Lyα森林的接近效应。我们发现所选样本中确实存在接近效应，特别在z_abs≈z_em附近距类星体4h^-1Mpc范围内，Lyα森林的线数相对演化规律估计得到的线数缺少很显著，并且与谱线的静止等值宽度有关，弱线的接近效应较弱。对接近效应的传统解释一般采用Bajtlik,Duncan和Ostriker（BDO）提出的光致电离模型，认为是由于类星体附近吸收云中的中性氢被类星体辐射的紫外光子高度电离，导致Lyα吸收减少而产生该效应。假设该模型是正确的，就可以用来估算Lyman限处的紫外背景辐射的平均强度。假设背景辐射强度在目前可观测的红移范围内是常数，那么我们得到的J（ν_o）的最佳拟合值为：（1）对W≥0.32（?）的Lyα吸收线，logJ（ν_o）=-21.20，（2）对W≥0.16（?）的Lyα吸收线，logJ（ν_o）=-21.63，（3）对0.16（?）<W<0.32（?）的弱线，logJ（ν_o）=-21.85。若以J_-21×10^-（21）erg·S^-1·Hz^-1·Sr^-1来表示J（ν_o），则J_-21，在（0，1）之间，比以往不同样本得到的结果略小。但若考虑我们样本中数据来源的不统一性，及发射线红移的误差等因素，则可以认为该结果与以往的结果基本保持一致。我们的工作再次验证了BDO的光致电离模型，明确了在所观测的红移区间内J（ν_o）的大致范围。更多还原

【Abstract】 Previous work about Ly a Forest was on the basis of low- or moderate-resolution data, where lines blending is severe. So more research with high-resolution data is necessary. We form a Ly a line sample from spectra of 19 QSOs in the literature. In this analysis , we demonstrate that a proximity effect is present in thedata; i.e., there exists a significant deficit of lines at zabs=zem, within 4h-1 Mpc ofthe QSO emission redshift. And the deficit depends on the rest equivalent width of the lines, with weak lines showing a relatively weaker effect. The simplest explanation for this effect is enhanced ionization of H I in the vicinity of the QSO by ultraviolet photons from the QSO itself presented by Bajtlik, Duncan, & Ostriker(BDO). If the "Photoionization Model" is correct ,it permits an estimate of the mean intensity of the extragalactic background radiation at the Lyman limit. If this background is assumed to be constant over the redshift range which can be exploredat present, then the best-fit values for J(vo) are: (1) for W>0.32A,logJ(vo)=-21.20; (2) for W>0.16A , logJ(vo)=-21.63; (3)for0.16A <W<0.32A (weak lines), logJ(vo) =-21.85 . The values are a little smallerthan previous work. But if the inconsistent of the origin of the data and the uncertainty of the redshift are considered, the results are agreement with them.更多还原