Investigating the Radio Continuum - Star Formation Relation in Nearby Galaxies

恒星形成星系的星际介质(ISM)充满了宇宙射线电子。它们以相对论速度运动，在被ISM冻结的磁场中以同步辐射的形式损失能量。最近，射电干涉仪灵敏度的大幅提高提供了利用正常恒星形成星系的射电连续谱(RC)发射作为空间分辨恒星形成率(SFR)的替代指标的前景，几乎绕过了困扰光学/UV观测的任何消光问题。一旦正确校准，非热射电连续体-SFR关系将提供一个稳健的、无偏倚的、无消光的工具，用于表征局部宇宙和高红移的SFR。此外，在电磁光谱的射电部分对多个波长的详细观测可以用来提高我们对同步辐射的物理起源和所涉及的各种能量损失机制的理解。在这个项目中，我们将分析从Things调查中获取的4个附近螺旋星系样本的VLA，对敏感的、多波长的、高分辨率的观测进行分析。这些VLA观测将与包括H-α、24um和FUV在内的辅助数据相结合，将射电连续辐射分离为热和非热分量，并将其与SFR进行比较。这些结果将被用来在200-700pC的尺度上在分辨率的基础上校准RC-SFR关系，探索星系的均分磁场性质，以及RC-SFR关系中的本征散射。

The Interstellar Medium (ISM) of star-forming galaxies is pervaded with cosmic ray electrons. They move at relativistic speeds and lose their energy in the form of synchrotron emission in the ever present magnetic field which is frozen in with the ISM. The recent, vast increase in sensitivity of radio interferometers now offers the prospect of using the radio continuum (RC) emission from normal star forming galaxies as a proxy for the spatially resolved star formation rate (SFR), virtually bypassing any of the extinction issues that plague optical/UV observations. Once properly calibrated, a non-thermal radio continuum - SFR relation will provide a robust, unbiased, extinction free tool for characterising the SFR in both the Local Universe and at high redshift. Moreover, detailed observations at multiple wavelengths across the radio part of the electromagnetic spectrum can be used to to improve our understanding of the physical origin of synchrotron emission and the various energy loss mechanisms involved. In this project, sensitive, multi wavelength, high-resolution observations using the VLA of a sample of 4 nearby spiral galaxies taken from the THINGS survey will be analysed. These VLA observations will be combined with ancillary data including H-alpha, 24um, and the FUV to separate the radio continuum emission into its thermal and non-thermal components and compare these to the SFR. These results will be used to calibrate the RC-SFR relation on a resolved basis on scales from 200 to 700 pc, explore the equipartition magnetic field properties of the galaxies, and the intrinsic scatter in the RC-SFR relation.