JADES and BlackTHUNDER: rest-frame Balmer-line absorption and the local environment in a Little Red Dot at z = 5

Journal article

We present a ‘Little Red Dot’ (LRD) broad-line active galactic nucleus (AGN) at , observed with NIRSpec/MSA (micro-shutter assembly) and NIRSpec/IFU (integral-field unit) by the JADES (JWST Advanced Deep Extragalactic Survey) and BlackTHUNDER (Black holes in THe early Universe aNd their DensE surRoundings) surveys. Combining spatially resolved and high-resolution spectroscopy, we characterize its central engine, host, and environment. H has multiple components, including two broad Gaussians, yielding a black-hole mass , while [O iii]5007 gives a galaxy dynamical mass , suggesting an overmassive black hole relative to the host galaxy. The target is immersed in a 7-kpc wide pool of ionized gas and has three neighbours: a satellite galaxy, a possible satellite/gas cloud, and a tentatively detected spatially detached outflow. H shows strong, rest-frame absorption, deeper than the continuum, ruling out a stellar origin. The velocity and velocity dispersion are and . There is tentative evidence (2.6σ) of temporal variability in the equivalent width of the H absorber over two rest-frame months, suggesting a highly dynamic nucleus. Notably, while the H absorber is clearly visible and even dominant in the high-resolution G395H observations, it is not detected in the medium-resolution G395M data of the same epoch. This implies that the current incidence rate of absorbers in LRDs – and especially of rest-frame absorbers – may be severely underestimated, because most LRDs rely on lower resolution spectroscopy. The high incidence rate of rest-frame absorbers in LRDs may indicate a configuration that is either intrinsically stationary, such as a rotating disc, or that exhibits time-averaged stability, such as an oscillatory ‘breathing mode’ accretion with cyclic expansion and contraction of the gas around the supermassive black hole.

Authors: D’Eugenio, F; Juodžbalis, I; Ji, X; Scholtz, J; Maiolino, R

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 545
• Issue: 3
• Pages: staf2117
• Article number: staf2117
• Publication date: 2025-11-28
• Acceptance date: 2025-11-14
• DOI: 10.1093/mnras/staf2117
• EISSN: 1365-2966
• ISSN: 0035-8711
• Language: English
• Keywords: galaxies: active; quasars: supermassive black holes; galaxies: Seyfert