Not so-dark: High resolution HI imaging of J0139+4328 and identification of an optical counterpart
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| Main Authors: | , , , , , , |
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| Format: | Preprint |
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2026
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| _version_ | 1866908925839802368 |
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| author | Šiljeg, Barbara Adams, Elizabeth A. K. Oosterloo, Tom A. Fraternali, Filippo Hess, Kelley M. Xu, Jin-Long Zhu, Ming |
| author_facet | Šiljeg, Barbara Adams, Elizabeth A. K. Oosterloo, Tom A. Fraternali, Filippo Hess, Kelley M. Xu, Jin-Long Zhu, Ming |
| contents | Dark galaxies - systems rich in neutral hydrogen (HI) gas but with no stars - are a common prediction of numerous theoretical models and cosmological simulations. However, the unequivocal identification of such sources in current HI surveys has proven challenging. In this work, we present interferometric follow-up observations with the VLA of a former dark galaxy candidate J0139+4328, originally detected with the single-dish FAST telescope. The improved spatial resolution of the VLA data allow us to identify a faint optical counterpart and characterize the galaxy. Located at a distance of about 31 Mpc, J0139+4328 has a stellar mass of 3 x 10^6 M_Sun and a relatively high gas richness of M_HI/M_star = 18. Despite its high ratio, the galaxy is consistent, within the scatter, with the stellar-to-HI mass relation of HI-selected samples in the literature and with the baryonic Tully-Fisher relation (BTFR), although its kinematic measurement is subject to large uncertainties. This case highlights the potential of modern high-sensitivity HI surveys for detecting low surface brightness, gas-rich galaxies, but underscores the need for careful interpretation of low-resolution HI data, with potentially large centroid errors, and for sufficiently deep optical imaging to ensure robust identification. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2601_12513 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Not so-dark: High resolution HI imaging of J0139+4328 and identification of an optical counterpart Šiljeg, Barbara Adams, Elizabeth A. K. Oosterloo, Tom A. Fraternali, Filippo Hess, Kelley M. Xu, Jin-Long Zhu, Ming Astrophysics of Galaxies Dark galaxies - systems rich in neutral hydrogen (HI) gas but with no stars - are a common prediction of numerous theoretical models and cosmological simulations. However, the unequivocal identification of such sources in current HI surveys has proven challenging. In this work, we present interferometric follow-up observations with the VLA of a former dark galaxy candidate J0139+4328, originally detected with the single-dish FAST telescope. The improved spatial resolution of the VLA data allow us to identify a faint optical counterpart and characterize the galaxy. Located at a distance of about 31 Mpc, J0139+4328 has a stellar mass of 3 x 10^6 M_Sun and a relatively high gas richness of M_HI/M_star = 18. Despite its high ratio, the galaxy is consistent, within the scatter, with the stellar-to-HI mass relation of HI-selected samples in the literature and with the baryonic Tully-Fisher relation (BTFR), although its kinematic measurement is subject to large uncertainties. This case highlights the potential of modern high-sensitivity HI surveys for detecting low surface brightness, gas-rich galaxies, but underscores the need for careful interpretation of low-resolution HI data, with potentially large centroid errors, and for sufficiently deep optical imaging to ensure robust identification. |
| title | Not so-dark: High resolution HI imaging of J0139+4328 and identification of an optical counterpart |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2601.12513 |