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Abstract We present a detailed study of radio-detected dwarf galaxies ( M ⋆ ≲ 3 × 10 9 M ⊙ ) to characterize extreme star formation and search for (variable) radio active galactic nuclei (AGNs). Our sample comes from A. E. Reines et al., who used the Karl G. Jansky Very Large Array (VLA) with ∼0 . ″ 25 resolution to observe 111 dwarf galaxies with lower-resolution (∼5″) 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 (SF) in dwarf galaxies. We find that these objects are dominated by thermal H II regions with ages ≲10 Myr, and the most extreme sources have ionizing luminosities requiring the equivalent of ∼10 4−5 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 SF and massive black holes in dwarf galaxies, and highlight the utility of radio variability and multiresolution data for identifying the dominant power sources in low-mass systems.
Eberhard et al. (Wed,) studied this question.