GLIMPSED: Direct evidence for a fast AGN-driven outflow from a z=6.64 Little Red Dot host galaxy

TL;DR

This paper reports the discovery of a high-redshift galaxy with a fast AGN-driven outflow, providing direct evidence of AGN activity in Little Red Dot systems at z=6.64, with detailed spectral analysis from JWST.

Contribution

First direct evidence of a fast AGN-driven outflow in a Little Red Dot galaxy at z=6.64 using JWST spectroscopy.

Findings

Outflow velocity ~5500 km/s observed in [O III] and Hα emissions.

Host galaxy has low oxygen abundance (~18% solar) and slight nitrogen enrichment.

Limited impact of the outflow on star formation indicated by low mass loading factor.

Abstract

We report the discovery of GLIMPSED-329380, a z=6.64 galaxy behind Abell S1063, which shows signs of an extreme ionised outflow driven by an active galactic nucleus (AGN). The deep JWST/NIRSpec medium grating observations show spatially resolved structures of a host galaxy containing the very fast outflow and an AGN, which we analyse separately. The outflow, mainly traced by broad [O III]{\lambda}5008 and H{\alpha} emissions in the host, reaches a full-width half-maximum velocity of ~5500km/s, velocities only observed in AGN-dominated systems. From the Balmer decrement, we observe that while the narrow emission lines show no dust attenuation, the outflowing gas is dusty. We use emission lines diagnostics to infer gas abundances within the host galaxy. The oxygen abundance is 12+log(O/H) ~ 7.95 (~18% solar) and the host is slightly nitrogen-enriched with log(N/O) ~ -0.75. Despite its extreme velocity, the mass loading factor (<0.1) and the kinematic energy of the outflow (~10^43 erg/s) suggest limited impact on star formation. The AGN component shows many similarities with little red dots (LRDs): a characteristic "V-shape", exponential profile in hydrogen lines, numerous detection of forbidden [Fe II] lines, a Balmer break, and a broad absorption feature at ~4550 {\AA}. This detection of a fast outflow in an LRD, rare in surveys dominated by low-resolution (e.g. PRISM) spectra, provides direct evidence of AGN activity in these systems.