Dice Question Streamline Icon: https://streamlinehq.com

Presence of redshifted absorption in non-Hydrogen lines in The Cliff

Ascertain whether redshifted absorption analogous to the Hα absorption is present in other emission lines, specifically He I λ10830 and O I λ8446, in the JWST/NIRSpec spectrum of The Cliff by obtaining higher signal-to-noise and spectral resolution observations to unambiguously detect or rule out such absorbers.

Information Square Streamline Icon: https://streamlinehq.com

Background

The authors identify a complex, broad, and asymmetric Hα profile in The Cliff (RUBIES-UDS-154183) and attribute part of the asymmetry to a redshifted Balmer absorption line, consistent with dense absorbing gas along the line of sight in some Little Red Dots (LRDs).

While similar absorption may exist in other transitions (e.g., He I λ10830 and O I λ8446), the current NIRSpec data quality and resolution prevent a definitive determination, motivating deeper spectroscopic follow-up to clarify whether absorption occurs beyond the Balmer series.

References

It is likely that this absorption is also present in other lines (e.g. or ; \citealt{Wang2024a,Ji2025}), but at the current signal-to-noise of the data ($S/N$) and available spectral resolution we cannot establish whether this is the case.

— A remarkable Ruby: Absorption in dense gas, rather than evolved stars, drives the extreme Balmer break of a Little Red Dot at $z=3.5$ (2503.16600 - Graaff et al., 20 Mar 2025) in Section 3.2 (Emission lines)