利用JWST光度学识别本超星系团中的红超巨星。I. NGC 6822、 Sextans A、 NGC 300、 WLM和IC 1613
Identifying Red Supergiants in the Local Group Using JWST Photometry. I. NGC 6822, Sextans A, NGC 300, WLM, and IC 1613
AI总结：
本研究利用JWST光度学数据，通过优化颜色-颜色图识别本超星系团中红超巨星，并提供了新的RSG候选星列表及O-AGBs和C-AGBs目录。
摘要：
红超巨星（RSGs）对于研究大质量恒星的性质和演化至关重要。在本超星系团内进行RSGs普查是有代表性的，因为该区域涵盖了广泛的金属丰度范围。然而，识别遥远且金属贫乏的星系中的RSGs仍然具有挑战性，主要是由于前景矮星的污染和观测限制。在本工作中，我们使用DOLPHOT NIRCam模块对五颗本超星系团内的星系，即NGC 6822、Sextans A、NGC 300、WLM和IC 1613的公开发布的JWST/NIRCam图像进行了PSF光度学分析。我们发现了一个最佳的颜色-颜色图（CCD），即F115W - F200W相对于F356W - F444W，这能清晰地区分RSGs与前景矮星。通过使用该CCD，我们在NGC 6822、Sextans A和NGC 300中分别识别出208、135和22个RSG候选星，这些候选星不受前景矮星和富含氧的渐近巨星分支星（O-AGBs）的污染。此外，在WLM和IC 1613中，分别有40和14个RSG候选星直接在CMD上被选中。与之前的工作相比，相同光度范围和天空区域内的RSG候选星数量显著增加，这表明JWST在本超星系团中构建更完整的RSG样本方面具有优势，得益于其高空间分辨率和光度学质量。此外，还提供了O-AGBs和碳丰富的AGBs（C-AGBs）的目录作为副产品。
英文摘要：
Red supergiants (RSGs) are crucial for studying the properties and evolution of massive stars. It is representative to conduct a census of RSGs across the Local Group, which spans a broad metallicity range. However, identifying RSGs in distant and metal-poor galaxies remains challenging mainly due to contamination of foreground dwarfs and observational limitations. In this work, we perform PSF photometry on publicly released JWST/NIRCam images of five Local Group galaxies: NGC 6822, Sextans~A, NGC 300, WLM, and IC 1613 using the DOLPHOT NIRCam module. We find an optimal color-color diagram (CCD) for metal-poor environments, that is F115W $-$ F200W versus F356W $-$ F444W, which clearly separates RSGs from foreground dwarfs. By using the CCD, we identify 208, 135, and 22 RSG candidates in NGC 6822, Sextans A, and NGC 300, respectively, free from contamination by foreground dwarfs and oxygen-rich asymptotic giant branch stars (O-AGBs). In addition, 40 and 14 RSG candidates are directly selected on the CMD in WLM and IC 1613, respectively. Compared with previous works, the number of RSG candidates within the same luminosity range and sky region increases significantly, demonstrating the advantages of JWST in constructing a more complete RSG sample in the Local Group thanks to its high spatial resolution and photometric quality. In addition, catalogs of O-AGBs and carbon-rich AGBs (C-AGBs) are provided as by-products.
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