VLBA25B-349

Confirming the AGN nature of the first radio-detected "Little Red Dot"

Abstract

We request 20 hours of HSA observations (VLBA + phased VLA + GBT) at 1.4 GHz, targeting the only radio-detected "Little Red Dot" (LRD) known to-date. Understanding the nature of LRDs is one of the hottest topic in galaxy evolution. Our proposed target (PRIMER-COS 3866), placed in COSMOS at z=4.66, is detected from low-resolution (arcsec) radio imaging, but the low brightness temperature (Tb~10^3 K) is insufficient to confirm its AGN nature. Our proposed HSA observations at 1.4 GHz are both extremely sensitive (10 uJy/bm at 5sigma) and at high-resolution (20mas x 7mas), in order to reach a limit Tb~10^5 K and undoubtedly assess whether the radio emission of PRIMER-COS 3866 is powered by AGN (if detected) or star-formation (if undetected), or a combination thereof. Our ambitious program, targeting a unique laboratory, will set a benchmark for understanding the origin of radio emission in LRDs and modeling their multi-wavelength emission, thus carrying a huge legacy value in the upcoming of ngVLA and SKA era.

Investigators

Name	Institution
Ivan Delvecchio *	Commissariat à l'Energie Atomique ; Brera, Osservatorio Astronomico di; Sveucilista u Zagrebu; Istituto Nazionale di Astrofisica
Cristiana Spingola	Kapteyn Astronomical Institute; Istituto Nazionale di Astrofisica; Bologna, Universita degli Studi di
Giorgia Peluso	Istituto Nazionale di Astrofisica
Emanuele Daddi	Commissariat à l'Energie Atomique
Jack Radcliffe	Manchester, University of; Pretoria, University of
Vernesa Smolcic	California Institute of Technology; European Southern Observatory; Sveucilista u Zagrebu
Myriam Gitti	Istituto Nazionale di Astrofisica; Bologna, Universita degli Studi di
Isabella Prandoni	Istituto Nazionale di Astrofisica
Francesco Ubertosi	Bologna, Universita degli Studi di
GBT Operator	Green Bank Observatory

* indicates the PI