An Hα Cloud in the H I Tail: Recent Star Formation in the Outskirts of NGC 4258 Revealed by Nanshan 1 m Telescope

• Published in: The Astronomical journal Vol. 170; no. 3; pp. 145 - 155
• Main Authors: Cheng, Cheng, Huang, Jia-Sheng, Wei, Peng, Esamdin, Ali, Feng, Guojie, Zhang, Zhi-Xiang, Yan, Haojing, Du, Wei, Zuo, Pei, Li, Zijian, Orellana-González, Gustavo, Wang, Letian, Wang, Yong, Iskandar, Abdusamatjan, Yaqup, Shahidin
• Format: Journal Article
• Language: English
• Published: The American Astronomical Society 01.09.2025; IOP Publishing
• Subjects: Narrow band photometry
• ISSN: 0004-6256; 1538-3881
• DOI: 10.3847/1538-3881/adeb53

We present first-light deep H α imaging taken with the Nanshan 1 m wide-field telescope on the local galaxy NGC 4258, alongside archival data from Hubble Space telescope (HST), Westerbork Synthesis Radio Telescope, and The Dark Energy Camera Legacy Survey. The H α image shows ongoing star formation not only inside the galaxy but also in an H I cloud in the eastern H I tail, which is roughly 16 kpc away from the main galaxy. The HST images reveal several ultrablue compact objects (F555W − F814W < −0.5 mag,  FWHM ∼ 0 . ″ 2) in the H α bright region, aligned with the H I tail, suggesting the presence of young open cluster candidate in the H I tail. Our results suggest that wide field H α imaging is a valuable tool for investigating recent star formation in the extended regions of NGC 4258. Furthermore, the star formation in diffuse H I tails could highlight an potential aspect of galaxy stellar halo formation, warranting further investigation of the impact of star formation in halos on galaxy evolution.