The warm outer layer of a Little Red Dot as the source of [Fe II] and collisional Balmer lines with scattering wings

Understand

The population of the Little Red Dots (LRDs) may represent a key phase of supermassive black hole (SMBH) growth.

• A cocoon of dense excited gas is emerging as key component to explain the most striking properties of LRDs, such as strong Balmer breaks and Balmer absorption, as well as the weak IR emission.
• To dissect the structure of LRDs, we analyze new deep JWST/NIRSpec PRISM and G395H spectra of FRESCO-GN-9771, one of the most luminous known LRDs at $z=5.5$.
• These reveal a strong Balmer break, broad Balmer lines and very narrow [O III] emission.