论文标题
混乱IV:前四个混乱星系的气相丰度趋势
CHAOS IV: Gas-Phase Abundance Trends From The First Four CHAOS Galaxies
论文作者
论文摘要
HII区域跨磁盘探测的螺旋星系的化学丰度是理解星系在各种环境中的演变的关键。我们介绍了NGC3184中52个HII区域的LBT/MODS光谱,这是螺旋丰度(混乱)项目的一部分。我们使用190个单个HII区域的一个或多个极光线检测量进行的温度测量值,探索了前四个混乱星系的直接使用气相丰度趋势。我们发现Te-Te关系中的分散取决于电离,其特征是F_5007/F_3727,因此建议基于电离的温度优先级以进行丰度计算。我们证实了我们先前的结果,即[NII]和[SIII]在低离子区域中提供了电子温度最强的测量,而[OIII]在高离子化星云中提供了可靠的电子温度。我们测量O,N,S,AR和NE的相对和绝对丰度。这四个混乱星系略符合通用O/H梯度,如经验IFU研究相对于有效半径而发现的。但是,在调整了垂直偏移后,我们发现使用sigma_tot的alpha_n/o = -0.33 dex/re的紧密通用n/o梯度。 RG/RE <2.0 = 0.08,其中N由二次产生主导。尽管具有这种密切的通用N/O梯度,但N/O-O/H关系中的散射很重要。有趣的是,当相对于O/H或S/H绘制N/O时,散射是相似的。 S探针的可观察的离子状态比O低离子化和激发能,这可能更适合表征金属丰富的HII区域的丰度。
The chemical abundances of spiral galaxies, as probed by HII regions across their disks, are key to understanding the evolution of galaxies over a wide range of environments. We present LBT/MODS spectra of 52 HII regions in NGC3184 as part of the CHemical Abundances Of Spirals (CHAOS) project. We explore the direct-method gas-phase abundance trends for the first four CHAOS galaxies, using temperature measurements from one or more auroral line detections in 190 individual HII regions. We find the dispersion in Te-Te relationships is dependent on ionization, as characterized by F_5007/F_3727, and so recommend ionization-based temperature priorities for abundance calculations. We confirm our previous results that [NII] and [SIII] provide the most robust measures of electron temperature in low-ionization zones, while [OIII] provides reliable electron temperatures in high-ionization nebula. We measure relative and absolute abundances for O, N, S, Ar, and Ne. The four CHAOS galaxies marginally conform with a universal O/H gradient, as found by empirical IFU studies when plotted relative to effective radius. However, after adjusting for vertical offsets, we find a tight universal N/O gradient of alpha_N/O = -0.33 dex/Re with sigma_tot. = 0.08 for Rg/Re < 2.0, where N is dominated by secondary production. Despite this tight universal N/O gradient, the scatter in the N/O-O/H relationship is significant. Interestingly, the scatter is similar when N/O is plotted relative to O/H or S/H. The observable ionic states of S probe lower ionization and excitation energies than O, which might be more appropriate for characterizing abundances in metal-rich HII regions.