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MEDIUM-RESOLUTION FAR-ULTRAVIOLET SPECTROSCOPY OF PKS 2155-304

机译:PKS 2155-304的中等分辨率远紫外光谱

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摘要

Using the Berkeley spectrometer of the Orbiting Retrievable Far and Extreme Ultraviolet Spectrometer (ORFEUS) we observed the 87-117 nm UV spectrum of the BL Lac object PKS 2155-304 with about 0.5 A resolution. In addition to the expected interstellar lines we detected higher quantum number counterparts of the intergalactic Lyα lines discovered earlier with IUE and the HST in the direction of PKS 2155-304. The Lyman discontinuities indicate for three of the redshifted clouds a combined H I column density of 2-5 x 10~(16) cm~(-2), while the column density for another cloud appears to be well below 5 x 10~(15) cm~(-2). No significant O VI absorption in the galactic halo toward PKS 2155-304 could be detected from our data. Assuming that saturation effects are negligible for these weak features, we obtain for the O VI column density toward PKS 2155-304 a 3 σ upper limit of 2.7 x 10~(14) cm~(-2).
机译:使用轨道可检索远和极紫外光谱仪(ORFEUS)的伯克利光谱仪,我们观察到BL Lac物体PKS 2155-304的87-117 nm紫外光谱,分辨率约为0.5A。除了预期的星际线,我们还检测到了较早发现的IUE和HST在PKS 2155-304方向上的银河系Lyα线的更高量子数对应物。莱曼不连续性表明,对于三个红移云,组合的HI柱密度为2-5 x 10〜(16)cm〜(-2),而另一朵云的柱密度似乎大大低于5 x 10〜(15 )cm〜(-2)。从我们的数据中,未检测到银河晕朝PKS 2155-304的显着O VI吸收。假设这些弱特征的饱和效应可忽略不计,我们获得的O VI色谱柱密度朝向PKS 2155-304的3σ上限为2.7 x 10〜(14)cm〜(-2)。

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