Dwarf Galaxies Hosting Extreme Star-Forming Regions and (Variable) AGNs at Radio Wavelengths
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| Format: | Preprint |
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2026
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| _version_ | 1866911633465409536 |
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| author | Eberhard, John-Michael Reines, Amy E. |
| author_facet | Eberhard, John-Michael Reines, Amy E. |
| contents | We present a detailed study of radio-detected dwarf galaxies (with stellar masses less than 3 billion solar masses) to characterize extreme star formation and search for (variable) radio AGNs. Our sample comes from Reines et al. (2020) (arXiv:1909.04670), who used the Karl G. Jansky Very Large Array (VLA) with 0.25 arcsecond resolution to observe 111 dwarf galaxies with lower-resolution (5 arcsecond) detections in the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) survey. While that work identified and focused on 13 compact radio AGN candidates in dwarf galaxies, here we focus on 16 compact radio sources consistent with star formation in dwarf galaxies. We find that these objects are dominated by thermal HII regions with ages less than 10 Myr, and the most extreme sources have ionizing luminosities requiring the equivalent of around 10,000 to 100,000 O-type stars. We also investigate the dwarf galaxies detected in FIRST but not detected in the high-resolution follow-up observations. Using the infrared-radio correlation parameter, we identify eight sources consistent with radio-excess AGNs. Five of these objects plus another 15 dwarf galaxies have no corresponding detections in the VLA Sky Survey (VLASS) indicating variability between the FIRST and VLASS observations. The FIRST radio luminosities of these sources are significantly higher than expected for supernova-related emission, suggesting the radio variability is likely associated with AGNs. Together, these results provide new context for the presence of compact star formation and massive black holes in dwarf galaxies, and highlight the utility of radio variability and multi-resolution data for identifying the dominant power sources in low-mass systems. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2604_27065 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Dwarf Galaxies Hosting Extreme Star-Forming Regions and (Variable) AGNs at Radio Wavelengths Eberhard, John-Michael Reines, Amy E. Astrophysics of Galaxies High Energy Astrophysical Phenomena We present a detailed study of radio-detected dwarf galaxies (with stellar masses less than 3 billion solar masses) to characterize extreme star formation and search for (variable) radio AGNs. Our sample comes from Reines et al. (2020) (arXiv:1909.04670), who used the Karl G. Jansky Very Large Array (VLA) with 0.25 arcsecond resolution to observe 111 dwarf galaxies with lower-resolution (5 arcsecond) detections in the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) survey. While that work identified and focused on 13 compact radio AGN candidates in dwarf galaxies, here we focus on 16 compact radio sources consistent with star formation in dwarf galaxies. We find that these objects are dominated by thermal HII regions with ages less than 10 Myr, and the most extreme sources have ionizing luminosities requiring the equivalent of around 10,000 to 100,000 O-type stars. We also investigate the dwarf galaxies detected in FIRST but not detected in the high-resolution follow-up observations. Using the infrared-radio correlation parameter, we identify eight sources consistent with radio-excess AGNs. Five of these objects plus another 15 dwarf galaxies have no corresponding detections in the VLA Sky Survey (VLASS) indicating variability between the FIRST and VLASS observations. The FIRST radio luminosities of these sources are significantly higher than expected for supernova-related emission, suggesting the radio variability is likely associated with AGNs. Together, these results provide new context for the presence of compact star formation and massive black holes in dwarf galaxies, and highlight the utility of radio variability and multi-resolution data for identifying the dominant power sources in low-mass systems. |
| title | Dwarf Galaxies Hosting Extreme Star-Forming Regions and (Variable) AGNs at Radio Wavelengths |
| topic | Astrophysics of Galaxies High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2604.27065 |