Lensing, reddening and extinction effects of Mg ii absorbers from z= 0.4 to 2
Lensing, reddening and extinction effects of Mg ii absorbers from z= 0.4 to 2
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DOI：
10.1111/j.1365-2966.2008.12909.x
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发表时间：
2007-06
影响因子：
4.8
通讯作者：
B. M'enard;D. Nestor;D. Turnshek;A. Quider;G. Richards;D. Chelouche;Sandhya Rao Cita;I. Cambridge;U. Pittsburgh;D. Univ.;Ias
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文献类型：
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作者：
B. M'enard;D. Nestor;D. Turnshek;A. Quider;G. Richards;D. Chelouche;Sandhya Rao Cita;I. Cambridge;U. Pittsburgh;D. Univ.;Ias
利用SDSS DR4数据集中探测到的近7000个具有W0和1 A、0.4和2.2的强镁II吸收体，我们研究了它们对背景类星体的引力透镜效应和尘埃消光效应。在仔细量化了几种选择偏向后，我们分离出红移和吸收峰静止等效宽度W0的红化效应。我们发现，随着宇宙恒星密度或积分恒星形成率的演化，尘埃数量随宇宙时间的增加而增加，其公式为τ(Z)α(1i+z)-1.1±0.4。我们测量了E(B-V)中30倍以上的红化效应，得到了rα(W0)1.9+0.1，为金属吸收材料的理论模拟提供了一个重要的标度。我们还测量了尘埃与金属的比率，发现它与银河系相似。与以前的研究不同，我们没有探测到镁II系统的任何引力放大。我们测量了上限μ<；1.10，并讨论了差异的根源。最后，我们估计了由于消光效应而丢失的吸收峰的比例，并表明它在1<；W0<；6A范围内从1%上升到50%。我们对这种影响进行了参数化，并为恢复本征∂N/BW0分布提供了一个修正。
Using a sample of almost 7000 strong Mg II absorbers with W 0 > 1 A and 0.4 < z < 2.2 detected in the SDSS DR4 data set, we investigate the gravitational lensing and dust extinction effects they induce on background quasars. After carefully quantifying several selection biases, we isolate the reddening effects as a function of redshift and absorber rest equivalent width, W 0 . We find the amount of dust to increase with cosmic time as τ(z) α(1 I + z)- 1.1± 0.4, following the evolution of cosmic star density or integrated star formation rate. We measure the reddening effects over a factor of 30 in E(B - V) and we find that r α (W 0 ) 1.9+0.1 , providing us with an important scaling for theoretical modelling of metal absorbers. We also measure the dust-to-metal ratio and find it similar to that of the Milky Way. In contrast to previous studies, we do not detect any gravitational magnification by Mg II systems. We measure the upper limit μ < 1.10 and discuss the origin of the discrepancy. Finally, we estimate the fraction of absorbers missed due to extinction effects and show that it rises from 1 to 50 per cent in the range 1 < W 0 < 6 A. We parametrize this effect and provide a correction for recovering the intrinsic ∂N/bw 0 distribution.