Discovery of two little red dots transitioning into quasars

TL;DR

This paper reports the discovery of two transitional red dots with hybrid properties that suggest they are evolving into typical active galactic nuclei or quasars, providing new insights into their nature and evolution.

Contribution

It presents the first observations of LRDs exhibiting strong X-ray, radio, and mid-IR emissions, indicating a transitional phase in their evolution into AGNs.

Findings

LRDs can evolve into typical AGNs or quasars.

Hybrid properties reveal dispersing gas envelopes around black holes.

Evidence of forming dust tori in transitional LRDs.

Abstract

James Webb Space Telescope (JWST) has uncovered a new population of compact objects that show a unique V-shaped spectral energy distribution (SED) in the UV and optical wavelength range. These so-called "little red dots" (LRDs) often exhibit broad Balmer emission lines, indicative of the presence of active galactic nuclei (AGNs). They generally lack detection of X-ray, radio, and mid-IR radiation, which is fundamentally different from typical AGNs. Various models, including super-Eddington-accreting black holes enshrouded in dense and dust-poor gas, have been proposed to explain these features. However, the nature of LRDs remains debated, and their evolutionary fate is unclear. Here we report two unusual LRDs at redshift z = 2.868 and 2.925 that are in a transitional phase towards typical AGNs. Their V-shaped SEDs, compact optical morphology, and broad emission lines satisfy the defining criteria of LRDs. On the other hand, they exhibit intense X-ray, radio, and mid-IR radiation that is much stronger than previously known LRDs. These hybrid properties suggest that the dense gas envelope around their central black holes is dispersing, allowing high-energy photons and radio emission to escape. Meanwhile, a dust torus is forming. This finding provides a direct insight into the nature of LRDs and indicates that at least some LRDs will evolve into AGNs or quasars at later times.