Digest
JWST reveals BiRD, a luminous little red dot at z=2.33 in the J1030 field, flagged as a bright outlier in the F200W−F356W vs F356W diagram. NIRCam/WFSS detects He I λ10830 and Paγ with both narrow and broad components (FWHM ≳ 2000 km s−1), plus a blueshifted He I absorption indicating dense outflowing gas with N(He I*, 2^3S) ≈ 0.5–1.2×10^14 cm−2 at Δv ≈ −830 km s−1; the source lacks X-ray and radio emission. The Paγ broad component implies MBH ≈ 10^8 M⊙ and Lbol ≈ 2.9×10^45 erg s−1, echoing GN-28074 and RUBIES-BLAGN-1 where similar He I absorption is seen. A first JWST-based census places the LRD space density at z<3 within a factor ∼2–3 of UV-selected quasars at comparable Lbol and MBH, arguing that LRDs contribute meaningfully to AGN demographics at cosmic noon and may trace rapid seed growth.
Key figures to inspect
- Figure 1: Verify BiRD’s placement above the stellar locus in F200W−F356W versus F356W, its redshift track, and its proximity to the Rosetta Stone and RUBIES-BLAGN-1 points; this sets the color-based selection used for the space-density estimate.
- Figure 2: Inspect the optical–IR cutouts to confirm the compact, point-like morphology and the increasingly red continuum across NIRCam bands that underpin the LRD classification.
- Figure 3: Use the 2D/1D WFSS spectra to confirm z from He I λ10830 and Paγ, note the additional O I emission, and check the red-end contamination flagged in the panel.
- Figure 4: Read off the multi-component fits—narrow+broad Paγ (for MBH, Lbol) and He I emission plus the blueshifted He I absorption—to assess the ≳2000 km s−1 widths and the absorption kinematics and depth.