Illustris TNG壳层星系并合定年中的投影效应
Projection Effects in Merger Dating for Illustris TNG Shell Galaxies
AI总结：
本研究以Illustris TNG50模拟为基础，探究壳层星系并合定年中的投影效应，发现视线方向会显著影响由壳层半径推导的并合时间估计。
AI中文摘要：
恒星壳层是表面亮度较低的结构，通常呈现为同心弧状，在许多巨椭圆星系、透镜星系，以及部分旋涡星系和矮星系中被观测到，它们被认为源于星系的小质量并合以及接近径向的中等质量并合。确定并合时间的关键因素是壳层到星系中心的距离，因此如果部分壳层因投影效应未被探测到，会显著影响并合时间的估计。本研究首次系统探究了测量的壳层半径如何依赖于星系相对于观测者的取向，利用Illustris TNG50模拟，从9个选定的视线方向对壳层星系进行观测并测量壳层半径，通过建模壳层演化计算每个观测角度对应的并合时间，量化取向对推断的并合年龄的影响。结果表明，视线方向会对由壳层半径推导的并合时间估计产生显著影响。
英文摘要：
Stellar shells are low-surface-brightness structures that typically appear as concentric arcs. They are observed in many giant elliptical and lenticular galaxies, as well as in some spiral and dwarf galaxies. They presumably result from minor and intermediate close-to-radial mergers of galaxies. An essential factor in determining the merger time are the distances of shells from the centre of the galaxy. Consequently, estimates of the merger time can be significantly affected if some shells remain undetected due to projection effects. In this study, we present the first systematic investigation of how measured shell radii depend on the orientation of a galaxy relative to the observer. Using the Illustris TNG50 simulation, we examine shell galaxies from nine selected lines of sight and measure the shell radii. We model shell evolution and calculate the merger time accordingly for each viewing angle and quantify the impact of orientation on the inferred merger age. Our results indicate that the line of sight can have a substantial effect on merger-time estimates derived from shell radii.
