Diffuse interstellar bands in z < 0.6 Ca II absorbers
Diffuse interstellar bands in z < 0.6 Ca II absorbers
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z < 0.6 Ca II 吸收体中的弥散星际带
DOI：
10.1111/j.1745-3933.2007.00404.x
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
Ellison S
中科院分区：
文献类型：
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作者：
Ellison S
弥散星际带（DIB）可能是由复杂的有机分子产生的，这些分子在本地星系中的强度与中性氢柱密度N（Hi）和尘埃红化E（B−V）相关。由于类星体（QSO）光谱中的CaII吸收体被假定具有高N（Hi）和显著的E（B−V），它们代表了在宇宙学距离上探测DIBs的有希望的地点。在这里，我们给出了在0.07 >zabs> 0.55的九个Caii选择的吸收体中首次搜索DIB的结果。我们在zabs = 0.1556的一条视线中探测到5780- 1000 DIB;这只是第二个探测到DIB的类星体吸收体。与大多数本地DIB视线不同，这两个类星体吸收器与探测到的DIB相比，显示出较弱的6284- 100吸收。这可能表明与本地星系相比，中间红移类星体吸收体的物理条件不同。假设在类星体吸收体中，5780-ψ DI B强度与N（Hi）和E（B−V）之间的局部关系适用，DI B探测和极限可用于推导N（Hi）和E（B−V）。对于本研究中检测到DI B的一个吸收体，我们推导出E（B−V）= 0.23 mag和logN（Hi）≥ 20.9，与之前的结论一致，即CaI系统具有高的Hicolumn密度和显著的变红。对于剩余的八个具有5780-μ DI B未检测的Caii选择的吸收体，我们推导出E（B−V）的上限为0.1-0.3 mag.
The diffuse interstellar bands (DIBs) probably arise from complex organic molecules whose strength in local galaxies correlates with neutral hydrogen column density,N(Hi), and dust reddening,E(B−V). Because Caiiabsorbers in quasar (QSO) spectra are posited to have highN(Hi) and significantE(B−V), they represent promising sites for the detection of DIBs at cosmological distances. Here we present the results from the first search for DIBs in nine Caii-selected absorbers at 0.07 >zabs> 0.55. We detect the 5780-Å DIB in one line of sight atzabs= 0.1556; this is only the second QSO absorber in which a DIB has been detected. Unlike the majority of local DIB sight-lines, both QSO absorbers with detected DIBs show weak 6284-Å absorption compared with the 5780-Å band. This may be indicative of different physical conditions in intermediate redshift QSO absorbers compared with local galaxies. Assuming that local relations between the 5780-Å DIB strength andN(Hi) andE(B−V) apply in QSO absorbers, DIB detections and limits can be used to deriveN(Hi) andE(B−V). For the one absorber in this study with a detected DIB, we deriveE(B−V) = 0.23 mag and logN(Hi) ≥ 20.9, consistent with previous conclusions that Caiisystems have high Hicolumn densities and significant reddening. For the remaining eight Caii-selected absorbers with 5780-Å DIB non-detections, we deriveE(B−V) upper limits of 0.1–0.3 mag.