Digest
From the first 10% (≈127 arcmin²) of COSMOS-3D NIRCam grism WFSS, the team identifies 13 broad-line AGNs at z=5–8 via Hα/Hβ, including a z=7.646 Hβ source at F444W=23.6, among the brightest z>7.5 BL AGN. Most (10/13) show reddened optical continua with β_opt>0, while three have quasar-like SEDs that are less blue than unobscured QSOs; two objects have 7.7–18 μm MIRI points constraining rest-NIR, and no significant F115W UV variability is seen over Δt_rest≈60 days. The Hα luminosity functions at z≈5–6 hint at evolution relative to z≈4–5. An Hβ LF at z∼8 implies number densities ~100× above UV-selected quasar LFs, pointing to a populous bridge between UV-bright quasars and LRD-like BL AGN.
Key figures to inspect
- Figure 1: Use the LW magnitude–redshift plane to locate the z=7.646 Hβ emitter (F444W=23.6) and compare COSMOS-3D WFSS-selected points to NIRSpec literature samples; note that Greene et al. (2024) are uncorrected for lensing, affecting the bright end.
- Figure 2: Inspect where the 13 spectroscopic BL AGNs fall relative to the Akins et al. LRD color cuts in F277W–F444W vs F444W; identify which objects land outside the dashed selection and how this maps onto the reported β_opt>0 reddened continua.
- Figure 3: For the eight broad-Hα emitters, examine the 2D+1D spectra and the Gaussian decompositions to read off FWHM and the presence/absence of narrow components; check line shapes and continuum visibility source by source.
- Figure 4: Focus on ID18221 and ID27974 with detected continua to gauge continuum slopes and Balmer-line widths directly; these illustrate how continuum detection informs the β_opt and SED classification within the sample.