{"about":{"site":"https://codewithpapers.app","non_affiliation":"Code with Papers and Syntology are not affiliated with, endorsed by, or sponsored by Papers with Code, Meta, or the pwc-archive mirror.","licence":"CC BY-SA 4.0","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","attribution":"https://codewithpapers.app/attribution","modified":"archive material modified by Syntology; see the attribution page"},"url":"/paper/oxyster-a-circumgalactic-low-ionization","title":"Oxyster: A Circumgalactic Low-ionization Oxygen Nebula next to a Starburst Galaxy at $z\\sim1$","arxiv_id":"2504.11531","date":"2025-04-15","proceeding":null,"authors":["Pengjun Lu","Mingyu Li","Dalya Baron","Minghao Yue","Song Huang","Zheng Cai"],"abstract":"Extended emission line nebulae around galaxies or active galactic nuclei (AGNs) provide a unique window to investigate the galactic ecosystem through the circumgalactic medium (CGM). Using Subaru Hyper-Suprime Cam narrow-band imaging and spectroscopic follow-up, we serendipitously discover \"Oxyster\" - a large ionized nebula next to an interacting starburst galaxy at $z=0.924$. The nebula is traced by extended [OII]3726,3729 ($\\sim 30$ kpc) and [OIII]5007 ($\\sim 20$ kpc) emission lines. On the nebula luminosity-size plane, Oxyster surpasses the extended narrow-line regions around low-$z$ AGNs, resembling a higher-$z$ analog of \"Hanny's Voorwerp\". However, its uniformly low [OIII]/[OII] ratio (O32) sets it apart from typical AGN light echoes. For the host galaxy, HST and JWST images reveal a disturbed red disk galaxy with a single blue spiral \"arm\". Spectral energy distribution (SED) fitting suggests the $2-6\\times 10^{10} ~\\rm M_{\\odot}$ host galaxy sits above the star-forming main sequence with an ongoing starburst, especially in the \"arm\", and have $<5\\%$ luminosity contribution from AGN, consistent with X-ray non-detection and radio continuum. Standard photoionization and shock models struggle to explain simultaneously Oxyster's emission line luminosities, low O32 ratio, and the non-detection of H$\\beta$ line. A plausible explanation could involve the combination of a recent ($<10^8$ yrs) starburst and a low-luminosity AGN ($L_{\\rm{bol}} \\sim 1\\times10^{42}$ erg/s). While Oxyster's nature awaits future investigation, its discovery highlights the potential of ground-based narrow-band imaging to uncover extended emission line nebulae around non-AGN systems, opening new avenues for studying the CGM of normal galaxies in the early Universe.","url_abs":"https://arxiv.org/abs/2504.11531v1","url_pdf":"https://arxiv.org/pdf/2504.11531v1.pdf","source":{"archive":"pwc-archive (Hugging Face), CC BY-SA 4.0","snapshot":"2025-07-28","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","row_kind":"links_only","authors_date_abstract":"arXiv metadata, CC0 1.0 (https://info.arxiv.org/help/license), from the Kaggle arXiv metadata snapshot of 2026-09-12"},"code_links":[{"paper_slug":"oxyster-a-circumgalactic-low-ionization","repo_url":"https://github.com/SunnySco/giant-nebula","is_official":1,"mentioned_in_paper":0,"mentioned_in_github":0,"framework":"none","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"syntology_url":null,"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}