Letter to the Editor

Radio detection of a local little red dot

¹ Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Apdo. Postal 3-72 Morelia, Michoacán 58089, Mexico
² Instituto de Astronomía y Física del Espacio (IAFE) CONICET-Universidad de Buenos Aires, C1428 Buenos Aires, Argentina

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 30 November 2025
Accepted: 2 February 2026

Abstract

Context. One of the most important discoveries by the James Webb Space Telescope (JWST) is the unexpected existence of very large quantities of so-called little red dots (LRDs) in the early Universe (z > 4). These are compact luminous red galaxies with intriguing physical properties, one of which is the absence of radio detections.

Aims. We wish to know if LRDs give off radio emission produced by accreting intermediate-mass or supermassive black holes (IMBHs or SMBHs) or by frequent supernovae from a cluster of massive stars.

Methods. Assuming that LRDs at high redshifts have not been detected at radio wavelengths because they reside at large distances and/or the observational capabilities are limited, we present images made from archive Very Large Array (VLA) radio observations of J1047+0739 and J1025+1402. These are two analog candidate LRDs in the Local Universe at redshifts z = 0.1−0.2.

Results. The source J1047+0739 at z = 0.1682 is detected at 6.0 GHz in 2018 with the VLA-A as a compact source with a radius smaller than 0.2 arcsec (< 700 pc at d ≃ 750 Mpc). Its flux density was 117 ± 8 μJy and its in-band spectral index was −0.85 ± 0.24, which is typical of optically thin synchrotron emission. It was also detected at 5.0 GHz in 2010 with the VLA-C, showing a flux density of 130 ± 9 μJy. We also detect a compact source very near J1025+1402 (≃2″) with a flux density of 45 ± 10 μJy that might be tracing a kiloparsec-scale jet emanating from an IMBH or SMBH.

Conclusions. The observed flux densities can be provided by either a radio luminous supernova or an accreting IMBH or SMBH. However, the lack of significant variation in the flux density over eight years favors the IMBH–SMBH hypothesis. Radio time monitoring of this and other Local Little Red Dots (LLRDs) might help us solve the mystery of the radio silence of its cosmological counterparts.