HE 0435-4312的SALT长缝光谱：Mg II发射线的快速位移
SALT long-slit spectroscopy of HE 0435-4312: fast displacement in the Mg II emission line
摘要：
对于中等红移的类星体（0.4 < z < 1.6），Mg II发射线在可见光波段可见，因此它是测量黑洞质量和理解宽线区结构的一个非常重要的工具。我们的目标是确定的子结构和可变性的Mg II线的目的是确定哪一部分的线来自介质中开普勒运动。使用南非大望远镜（SALT）和罗伯特·斯托比光谱仪（RSS），我们在三年内（2012年12月23/24日至2015年12月7/8日）对类星体HE 0435-4312（z = 1.2231）进行了十次光谱观测。Mg II线和Fe II伪连续谱都随时间增加。我们清楚地检测到Mg II线相对于Fe II多年来的系统性移位，对应于类星体静止框架中104 pm 14 km/s/年的加速度。Mg II的线形是明显的非高斯但单组分，并且线等效宽度和线位移的增加并不伴随着线形的显著演变。我们分析了Mg II和Fe II形成区域中的条件，并且我们注意到覆盖因子和湍流速度的非常大的差异也支持这两个区域在空间上分离的结论。测得的线系统位移的加速度太大，无法将其与该源中宽线区（BLR）距离处的轨道运动联系起来。这可能意味着一个旋进的内盘照亮了BLR。仍然需要进一步监测，以更好地限制可变性机制。
英文摘要：
The Mg II emission line is visible in the optical band for intermediate redshift quasars (0.4 < z < 1.6) and it is thus an extremely important tool to measure the black hole mass and to understand the structure of the Broad Line Region. We aim to determine the substructure and the variability of the Mg II line with the aim to identify which part of the line comes from a medium in Keplerian motion. Using the Southern African Large Telescope (SALT) with the Robert Stobie Spectrograph (RSS) we performed ten spectroscopic observations of quasar HE 0435-4312 (z = 1.2231) over a period of three years (Dec 23/24, 2012 to Dec 7/8, 2015). Both the Mg II line and the Fe II pseudo-continuum increase with time. We clearly detect the systematic shift of the Mg II line with respect to the Fe II over the years, corresponding to the acceleration of 104 pm 14 km/s/year in the quasar rest frame. The Mg II line shape is clearly non-Gaussian but single-component, and the increase in line equivalent width and line shift is not accompanied with significant evolution of the line shape. We analyse the conditions in the Mg II and Fe II formation region and we note that the very large difference in the covering factor and the turbulent velocity also support the conclusion that the two regions are spatially separated. The measured acceleration of the line systematic shift is too large to connect it with the orbital motion at a distance of the Broad Line Region (BLR) in this source. It may imply a precessing inner disk illuminating the BLR. Further monitoring is still needed to better constrain the variability mechanism.
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