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arXiv 2401.03024astro-ph.GAastro-ph.CO
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探究强引力透镜类星体多重像方向金属吸收的相干性

Probing coherence in metal absorption towards multiple images of strong gravitationally lensed quasars

Rajeshwari Dutta, Ana Acebron, Michele Fumagalli, Claudio Grillo, Gabriel B. Caminha, Matteo Fossati

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9 pages + appendix, 8 figures, accepted in MNRAS
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AI总结：

基于MUSE对强引力透镜类星体多重像的观测，本文层析分析了z~0.5-2星系周介质的金属吸收，发现金属气体相干性随距离减弱（约10 kpc尺度），且高电离CIV比低电离MgII相干度更高，揭示了CGM的团块状结构。

摘要：

我们提出了一项针对z~0.5-2星系周围星系周介质（CGM）中产生的金属吸收线的层析分析。该分析利用了MUSE（Multi Unit Spectroscopic Explorer）对位于z~2.2和2.8的两个背景类星体的观测数据，这两个类星体是目前已知的少数因z~0.6和0.5的星系团强引力透镜效应而形成多重像的类星体。利用基于MUSE观测建立的强引力透镜模型，不同类星体多重像对之间的角分离使我们能够探测横跨约0.4-150 kpc物理分离范围内的吸收特征。MgII、FeII、CIV吸收的静止等效宽度分数差（Delta Wr）平均而言随物理分离增加而增大，表明富金属气体结构的相干性随距离减弱，其相干长度尺度约为10 kpc。然而，所有离子的Delta Wr在约0.08-0.9之间变化显著，表明在所探测的全部长度尺度上CGM均呈团块状。同时，在约100-150 kpc范围内检测到了成对的MgII吸收，且具有相似的视向速度，这可能是在探测同一晕内的冷气体云。未发现Delta Wr对吸收气体的等效宽度、红移以及与吸收相关的星系环境存在显著依赖性。由CIV示踪的高电离气相表现出比由MgII示踪的低电离气相更高的相干度，在<=10 kpc的分离尺度下，约90%的CIV系统Delta Wr <=0.5，而MgII系统仅为约50%。

英文摘要：

We present a tomographic analysis of metal absorption lines arising from the circumgalactic medium (CGM) of galaxies at z~0.5-2, using Multi Unit Spectroscopic Explorer (MUSE) observations of two background quasars at z~2.2 and 2.8, which are two of the few currently known quasars with multiple images due to strong gravitational lensing by galaxy clusters at z~0.6 and 0.5, respectively. The angular separations between different pairs of quasar multiple images enable us to probe the absorption over transverse physical separations of ~0.4-150 kpc, which are based on strong lensing models exploiting MUSE observations. The fractional difference in rest-frame equivalent width (Delta Wr) of MgII, FeII, CIV absorption increases on average with physical separation, indicating that the metal-enriched gaseous structures become less coherent with distance, with a likely coherence length scale of ~10 kpc. However, Delta Wr for all the ions vary considerably over ~0.08-0.9, indicating a clumpy CGM over the full range of length scales probed. At the same time, paired MgII absorption is detected across ~100-150 kpc at similar line-of-sight velocities, which could be probing cool gas clouds within the same halo. No significant dependence of Delta Wr is found on the equivalent width and redshift of the absorbing gas and on the galaxy environment associated with the absorption. The high-ionization gas phase traced by CIV shows a higher degree of coherence than the low-ionization gas phase traced by MgII, with ~90 percent of CIV systems exhibiting Delta Wr <=0.5 at separations <=10 kpc compared to ~50 percent of MgII systems.

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