Discovery of two little red dots transitioning into quasars

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.

Figures (12)

• Figure 1: SEDs and multi-band images of the Forges. Upper: The X-ray to radio SEDs of the Forges. For reference, we also show the SEDs of other sources: a typical $z = 3.1$ LRD (RUBIES-BLAGN-1Wang2025), a local LRD counterpart (the EggLin2025_locallrd), the stacked maximal COSMOS-Web LRD SED where the dotted line represents upper limitsAkins2024a_cos, another X-ray detected $z=4.66$ LRD in COSMOS fieldKocevski2025, and a highly obscured Type II AGN2006ApJ...642..673P. Lower: Cutout images of the Forge I (left) and Forge II (right) spanning from X-ray to far-IR, including Chandra X-ray (0.5–7 keV), CFHT $U$, Subaru $grizy$, HST ACS F814W, JWST NIRCam F115W, F150W, F200W, F277W, F356W, F444W, JWST MIRI F770W, F1000W, F2100W, and Spitzer MIPS 24, 70, and 160 µm bands. All cutouts are centered on the Forges.
• Figure 1: Two-dimensional image decomposition of the Forge I with galfitM. For each JWST/NIRCam band (F115W–F444W), panels from left to right show the surface-brightness ($\mu$, in the units of $\rm mag\,arcsec^{-2}$) profiles, data, best-fit model, individual Sérsic components, data - PSF, and residuals/error that are stretched linearly from $-$5 to 5. The reduced $\chi^2$ values and the PSF flux fractions ($f_{\rm PSF}$) are indicated for each band. The $\chi^2$ value for all eight bands is given in the lower-left corner of the panel for F356M.
• Figure 2: JWST NIRCam F444W slitless spectra of the Forges. We also show the best-fit results and associated residuals. Prominent emission features (e.g., He i, O i$\lambda11287$, Pa$\gamma$, Pa$\delta$) are labeled. Short vertical lines at the top, labeled with line names, mark the theoretical positions of the emission lines. For Forge II, A zoom-in on the Pa$\delta$ absorption feature is shown in the subpanel, and additional spectroscopic coverage from DESI (covering the wavelength ranges of Ly$\alpha$, N v, O i$\lambda1304$, C iv, He ii, and C iii]) and HST G141 (Mg ii) is also displayed. The gray-shaded regions indicate the wavelength ranges masked during the fitting process due to contamination from neighboring sources in the NIRCam spectra.
• Figure 2: Same as Figure above, but for the Forge II.
• Figure 3: Left:$M_*$ versus $M_{\mathrm{BH}}$ for the Forges, shown as red stars. For comparison, we include a few high-redshift LRD and AGN samples (brown symbols)2023ApJ...959...39HMaiolino2024_diverse2025ApJ...983...60C, a $z=2.26$ LRD (blue dot)2024MNRAS.535..853J, as well as local scaling relations: inactive galaxies (light blue dots and dashed line)2020ARAA..58..257G, AGN with early-type hosts (blue dashed line), and AGNs with late-type hosts (pink dashed line)2023NatAs...7.1376Z. The grey dashed lines denote constant $M_{\mathrm{BH}}$–to–$M_*$ ratios. Right:$L_{\mathrm{bol}}$ versus $M_{\mathrm{BH}}$. For comparison, we include high-redshift quasar (blue open circles)2023ARAA..61..373F and LRD/AGN samples (brown symbols)2023ApJ...959...39HMaiolino2024_diverseGreene2024. The SDSS quasars with z $\leq$3 are shown in the black contour2025ApJ...988..204C. The grey dashed lines indicate constant Eddington ratios.