A High-Resolution Survey of Low-Redshift QSO Absorption Lines: Statistics and Physical Conditions of O VI Absorbers
A High-Resolution Survey of Low-Redshift QSO Absorption Lines: Statistics and Physical Conditions of O VI Absorbers
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DOI：
10.1086/587486
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发表时间：
2007-06
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通讯作者：
T. Tripp;K. Sembach;D. Bowen;B. Savage;E. Jenkins;N. Lehner;P. Richter
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作者：
T. Tripp;K. Sembach;D. Bowen;B. Savage;E. Jenkins;N. Lehner;P. Richter
利用空间望远镜成像光谱仪E140M梯形模获得的16个低z类星体的高分辨率紫外光谱，研究了星系际介质在z30 mä的O VI吸收的物理条件和统计性质，得到单位红移Dn/dz=15.6−2.4+2.9(21.0−2.8+3.2)，WR>；30 0 mä的单位红移Dn/Dz=0.9−0.5+1.0(0.3−0.3+0.7)。随着zABS接近zQSO，每个红移的数目急剧增加，我们发现在zQSO的2500公里范围内，dN/dz是≈的3-10倍，S−1。中间系统和近端系统之间最显著的区别是，一些近端吸收体的H I/O VI比要低得多。近邻系统中较低的比率可能部分是由于电离效应，但这些近邻吸收体也必须具有明显更高的金属活性。我们发现，37%的中间O-VI吸收体具有与相应的H-I吸收相一致的速度质心。如果OVI和HI跟踪相同的气体，线宽的相对较小的差异意味着吸收体是冷的，温度为105K，光电离气体是冷的。
Using high-resolution ultraviolet spectra of 16 low-z QSOs obtained with the E140M echelle mode of the Space Telescope Imaging Spectrograph, we study the physical conditions and statistics of O VI absorption in the intergalactic medium (IGM) at z 30 mÅ, the number of O VI absorbers per unit redshift dN/dz = 15.6−2.4+2.9 (21.0−2.8+3.2) , and this decreases to dN/dz = 0.9−0.5+1.0 (0.3−0.3+0.7) for Wr > 300 mÅ. The number per redshift increases steeply as zabs approaches zQSO; we find that dN/dz is ≈3-10 times higher within 2500 km s−1 of zQSO. The most striking difference between intervening and proximate systems is that some proximate absorbers have substantially lower H I/O VI ratios. The lower ratios in proximate systems could be partially due to ionization effects, but these proximate absorbers must also have significantly higher metallicities. We find that 37% of the intervening O VI absorbers have velocity centroids that are well aligned with corresponding H I absorption. If the O VI and the H I trace the same gas, the relatively small differences in line widths imply that the absorbers are cool, with T 105 K and cold photoionzed gas.