论文标题
中红外恒星形成率示踪剂及其金属依赖性的比较研究
A Comparative Study of Mid-Infrared Star-Formation Rate Tracers and Their Metallicity Dependence
论文作者
论文摘要
我们介绍了一组基于12.81 $μ$ M [NE II]线，15.56 $μ$ M [NE III]线的一组恒星形成速率示踪剂，以及在5.2和14.7 $ $ $ m之间的15.56 $ $ $ m [NE III]线。我们用在附近星系中观察到的33个核外星形成区域的33 GHz的无线电连续发射的热分组件校准示踪剂。 IR中IR发射特征与热33 GHz恒星形成率（SFR）之间的相关性显示出显着的金属依赖性散射和偏移。我们发现在常用的SFR示踪剂（例如H $α$和24 $μ$ m）中，类似的金属依赖性趋势。如先前的研究所见，由于具有强大的金属依赖性，仅PAH发射是较差的SFR示踪剂：与较高的金属性区域相比，较低的金属性区域相对于其SFR的发射降低。我们构建了PAH频段，霓虹灯发射线及其各自比率的组合，以最大程度地减少金属性趋势。最准确地跟踪具有最小金属性依赖性的SFR的校准涉及12.81 $μ$ m [ne II]线的集成强度和15.56 $μ$ m [nei iii]线的总和，并结合了由粉尘持续发射归一化的任何主要PAH。此中IR校准是测量SFR的有用工具，因为它对金属性的变化至少敏感，并且由明亮的，无处不在的发射特征组成。詹姆斯·韦伯（James Webb）太空望远镜上的中红外仪器（MIRI）将从星系中检测到这些功能，直到红移Z $ \ sim $ 1。我们还研究了PAH带比的行为，发现围绕星形区域的局部背景减少了PAH 11.3 $ $ m $ m至7.7 $ $ $ m $ m的发射的比率。这意味着PAH相对于周围环境而在星形形成区域中更具电离。
We present a comparative study of a set of star-formation rate tracers based on mid-infrared emission in the 12.81$μ$m [Ne II] line, the 15.56$μ$m [Ne III] line, and emission features from polycyclic aromatic hydrocarbons (PAHs) between 5.2 and 14.7$μ$m. We calibrate our tracers with the thermal component of the radio continuum emission at 33 GHz from 33 extranuclear star-forming regions observed in nearby galaxies. Correlations between mid-IR emission features and thermal 33 GHz star-formation rates (SFR) show significant metallicity-dependent scatter and offsets. We find similar metallicity-dependent trends in commonly used SFR tracers such as H$α$ and 24$μ$m. As seen in previous studies, PAH emission alone is a poor SFR tracer due to a strong metallicity dependence: lower metallicity regions show decreased PAH emission relative to their SFR compared to higher metallicity regions. We construct combinations of PAH bands, neon emission lines, and their respective ratios to minimize metallicity trends. The calibrations that most accurately trace SFR with minimal metallicity dependence involve the sum of the integrated intensities of the 12.81$μ$m [Ne II] line and the 15.56$μ$m [Ne III] line combined with any major PAH feature normalized by dust continuum emission. This mid-IR calibration is a useful tool for measuring SFR as it is minimally sensitive to variations in metallicity and it is composed of bright, ubiquitous emission features. The Mid-Infrared Instrument (MIRI) on the James Webb Space Telescope will detect these features from galaxies as far as redshift z$\sim$1. We also investigate the behavior of the PAH band ratios and find that subtracting the local background surrounding a star-forming region decreases the ratio of PAH 11.3$μ$m to 7.7$μ$m emission. This implies PAHs are more ionized in star-forming regions relative to their surroundings.
