论文标题
冠状宽莱曼·阿尔法吸收器所追踪的星系光环中的热气
Hot gas in galaxy halos traced by coronal broad Lyman alpha absorbers
论文作者
论文摘要
我们探讨了系统研究具有冠状宽α吸收剂（CBLA）的低红移星系的扩展气体光环的可能性。这些是由于这些星系中碰撞电离的百万度光晕气体中的中性氢的微小比例而产生的弱的，热宽的HI吸收系。使用半分析方法，我们对热冠气的空间密度和温度分布进行建模，以预测CBLA的强度，光谱形状和横截面，这是Galaxy-Halo质量和视线撞击参数的函数。对于范围内的病毒光环质量（M/M_SUN）= 10.6-12.6，特征对数CBLA HI列密度和多普勒参数为log N（HI）= 12.4-13.4 = 12.4-13.4和B（hi）= 70-200 km/s，表明CBLAS代表弱，浅谱谱的较弱的光谱特征。然而，在给定的质量范围内，每单位红移的预期数量密度为DN/DZ（CBLA）〜3，这意味着CBLA具有大量吸收横截面。我们将模型预测与来自HST/COS和HST/STIS的一组紫外线（UV）吸收线光谱进行比较，这些光谱追踪了四个低降射星系的光晕。我们证明了在这些光谱中可能已经检测到的CBLA，但是复杂的多组分结构和有限的信噪比（S/N）使这些CBLA候选系统的解释变得复杂。我们的研究表明，CBLA代表了一个非常有趣的吸收剂类别，可能会使我们能够进一步探索使用紫外光谱数据的星系热冠。
We explore the possibility to systematically study the extended, hot gaseous halos of low-redshift galaxies with Coronal Broad Ly alpha Absorbers (CBLAs). These are weak, thermally broadenend HI absorption lines arising from the tiny fraction of neutral hydrogen that resides in the collisionally ionized, million-degree halo gas in these galaxies. Using a semi-analytic approach, we model the spatial density and temperature distribution of hot coronal gas to predict strength, spectral shape, and cross section of CBLAs as a function of galaxy-halo mass and line-of-sight impact parameter. For virial halo masses in the range log (M/M_sun)=10.6-12.6, the characteristic logarithmic CBLA HI column densities and Doppler parameters are log N(HI)=12.4-13.4 and b(HI)=70-200 km/s, indicating that CBLAs represent weak, shallow spectral features that are difficult to detect. Yet, the expected number density of CBLAs per unit redshift in the above given mass range is dN/dz(CBLA)~3, implying that CBLAs have a substantial absorption cross-section. We compare the model predictions with a combined set of ultraviolet (UV) absorption-line spectra from HST/COS and HST/STIS that trace the halos of four low-redshift galaxies. We demonstrate that CBLAs already might have been detected in these spectra, but the complex multi-component structure and the limited signal-to-noise ratio (S/N) complicate the interpretation of these CBLA candidate systems. Our study suggests that CBLAs represent a very interesting absorber class that potentially will allow us to further explore the hot coronae of galaxies with UV spectral data.
