论文标题
从类星体中的内部吸收中的元层状电离背景软化
Softening of the Metagalactic Ionizing Background from Internal He II Absorption in Quasars
论文作者
论文摘要
类似物和活跃的银河核（AGN）是红移z <3处的元时间电离背景的重要促进因素。Agn的最新HST/COS复合光谱在lyman continuum，f_nu〜nu^nu^{ - alpha_s}（Alpha_s}（Alpha_s}（Alpha_s = 1.41 = 1.41+0.15）中，agn的HST/cos复合谱分布更加困难。该指数似乎与Lya森林中观察到的II / H I吸收比（ETA）不一致。 We explore effects of internal AGN absorption in the He II (4 ryd) continuum using an analytic source-function model of the ionizing background in which the emissivity (j_nu) arises from quasars, reprocessed by the opacity (kappa_nu) of the intervening Lya forest and distinct AGN escape fractions f_esc(HI) and f_esc(HeII) at 1~ryd and分别为4〜Ryd。我们还检查了从重新加工背景的H I和HE II光电加热，其光谱指数（Alpha_b> alpha_s）取决于Alpha_s，H I列列密度斜率β和比率r = F_ESC（HI） / F_ESC（HEII）。我们将模型与He II和H I的LYA吸收线进行比较，向Quasar He 〜2347-4342进行了比较。使用F_ESC（HEII）= 0.6-0.8的内部AGN吸收，但是F_ESC（HI）= 1将增加索引，而Delta-Alpha_b = 0.3-1.0，与beta = 1.5-1.6的ETA = 60-200相对应，与HST/cos观察一致。观察到的比率范围ETA <200限制了alpha_b <3.4和f_esc（heii）> 0.4。具有柔软光谱，alpha_s> 1.7和更多内部He II吸收的单个AGN可以产生一些具有ETA> 300的吸收剂，距离AGN横向横向视线线。
Quasars and active galactic nuclei (AGN) are significant contributors to the metagalactic ionizing background at redshifts z < 3. Recent HST/COS composite spectra of AGN find a harder flux distribution in the Lyman continuum, F_nu ~ nu^{-alpha_s} (alpha_s = 1.41+/-0.15) compared to previous studies. This index appears to be inconsistent with observed He II / H I absorption ratios (eta) in the Lya forest. We explore effects of internal AGN absorption in the He II (4 ryd) continuum using an analytic source-function model of the ionizing background in which the emissivity (j_nu) arises from quasars, reprocessed by the opacity (kappa_nu) of the intervening Lya forest and distinct AGN escape fractions f_esc(HI) and f_esc(HeII) at 1~ryd and 4~ryd, respectively. We also examine H I and He II photoelectric heating from the reprocessed background, whose spectral index (alpha_b > alpha_s) depends on alpha_s, the H I column density slope beta, and the ratio R = f_esc(HI) / f_esc(HeII). We compare the model to Lya absorption lines of He II and H I toward the quasar HE~2347-4342. Internal AGN absorption with f_esc(HeII) = 0.6-0.8 but f_esc(HI) = 1 would increase the index by Delta-alpha_b = 0.3-1.0, corresponding to eta = 60-200 for beta = 1.5-1.6, in agreement with HST/COS observations at z = 2.5-2.9. The observed range of ratios, eta < 200, constrains alpha_b < 3.4 and f_esc(HeII) > 0.4. Individual AGN with softer spectra, alpha_s > 1.7, and more internal He II absorption could produce a few absorbers with eta > 300 in proximity to AGN transverse to the sight line.
