JADES and BlackTHUNDER: rest-frame Balmer-line absorption and the local environment in a Little Red Dot at <i>z</i> = 5
Francesco D’Eugenio, Ignas Juodžbalis, Xihan Ji, Jan Scholtz, R. Maiolino, Stefano Carniani, Michele Perna, Giovanni Mazzolari, Hannah Übler, Santiago Arribas, Rachana Bhatawdekar, Andrew J. Bunker, G. Cresci, Emma Curtis-Lake, Kevin Hainline, Kohei Inayoshi, Yuki Isobe, Zhiyuan Ji, Benjamin D. Johnson, Gareth C. Jones, Tobias J. Looser, Erica J. Nelson, Eleonora Parlanti, Dávid Puskás, Pierluigi Rinaldi, Brant Robertson, Bruno Rodríguez Del Pino, Irene Shivaei, Fengwu Sun, Sandro Tacchella, Giacomo Venturi, Marta Volonteri, Christina C. Williams, Christopher N. A. Willmer, Chris J. Willott, Joris Witstok
Abstract
ABSTRACT We present a ‘Little Red Dot’ (LRD) broad-line active galactic nucleus (AGN) at $z=5.077 $, observed with NIRSpec/MSA (micro-shutter assembly) and NIRSpec/IFU (integral-field unit) by the JADES (JWST Advanced Deep Extragalactic Survey) and BlackTHUNDER (Black holes in THe early Universe aNd their DensE surRoundings) surveys. Combining spatially resolved and high-resolution spectroscopy, we characterize its central engine, host, and environment. H$\alpha $ has multiple components, including two broad Gaussians, yielding a black-hole mass $\log (M_{\bullet }/{\rm M}_\odot) = 7.65 $, while [O iii]$\lambda$5007 gives a galaxy dynamical mass $\log (M_\mathrm{dyn}/{\rm M}_\odot) = 9.1 $, suggesting an overmassive black hole relative to the host galaxy. The target is immersed in a 7-kpc wide pool of ionized gas and has three neighbours: a satellite galaxy, a possible satellite/gas cloud, and a tentatively detected spatially detached outflow. H$\alpha $ shows strong, rest-frame absorption, deeper than the continuum, ruling out a stellar origin. The velocity and velocity dispersion are $v_\mathrm{abs} = -13~\mathrm{km\, s^{-1}} $ and $\sigma _\mathrm{abs} = 120~\mathrm{km\, s^{-1}} $. There is tentative evidence (2.6σ) of temporal variability in the equivalent width of the H$\alpha $ absorber over two rest-frame months, suggesting a highly dynamic nucleus. Notably, while the H$\alpha $ 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.