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Abstract:

Stars in galaxies form when baryons radiatively cool down and fall into gravitational wells whose mass is dominated by dark matter. Eventually, star formation quenches as gas is depleted and/or perturbed by feedback processes, no longer being able to collapse and condense. We report the first spatially resolved spectroscopic observations, using the JWST/NIRSpec IFU, of a massive, completely quiescent galaxy (Jekyll) and its neighborhood at z = 3.714, when the Universe age was 10% of today’s. Jekyll resides in a massive dark matter halo (with mass MDM > 1012 M→) and forms a galaxy pair with Hyde, which shows very intense dust-enshrouded star formation (star formation rate → 300 M→ yr↑1). We find large amounts of kinematically perturbed ionized and neutral gas in the circumgalactic medium around the pair. Despite this large gas reservoir, Jekyll, which formed 1011 M→ in stars and chemically enriched early (first billion years of the Universe) and quickly (200–300 Myr), has remained quiescent for over 500 Myr. The properties of the gas found around the two galaxies are consistent with intense, AGN-induced photoionization, or intense shocks. However, with the current data no obscured or unobscured AGN is detected in the central galaxy (Jekyll) nor in the very active and dust rich star-forming galaxy (Hyde).

Abstract:

Early JWST photometric studies discovered a population of UV-faint ( 700 Å) exclude the most metal-poor efficient ionizers and favor (1) more chemically enriched systems with comparable extreme radiation fields and (2) older starbursting systems. In contrast, metallicity degeneracies are reduced in Hα space, enabling the identification of these metal-poor efficient ionizers by their specific star formation rate.

Abstract:

We report the discovery of a remarkably large and luminous line-emitting nebula extending on either side of the Balmer-break galaxy JADES-GS-518794 at , detected with James Webb Space Telescope (JWST)/NIRCam imaging in [O iii]4959, 5007 and H α and spectroscopically confirmed with NIRCam/wide-field slitless spectroscopy, thanks to the pure-parallel programme Slitless Areal Pure Parallel HIgh-Redshift Emission Survey. The end-to-end velocity offset is . Nebulae with such large sizes and high luminosities (25 pkpc diameter, ) are routinely observed around bright quasars, unlike JADES-GS-518794. With a stellar mass of , this galaxy is at the knee of the mass function at . Its star formation rate declined for some time (10–100 Myr prior to observation), followed by a recent (10 Myr) upturn. This system is part of a candidate large-scale galaxy overdensity, with an excess of Balmer-break galaxies compared to the field (3σ). We discuss the possible origin of this nebula as material from a merger or gas expelled by an active galactic nucleus (AGN). The symmetry of the nebula, its bubble-like morphology, kinematics, high luminosity, and the extremely high equivalent width of [O iii] together favour the AGN interpretation. Intriguingly, there may be a physical connection between the presence of such a large, luminous nebula and the possible metamorphosis of the central galaxy towards quenching.

Abstract:

The presence of Active Galactic Nuclei (AGNs) in low mass () galaxies at high redshift has been established, and it is important to characterize these objects and the impact of their feedback on the host galaxies. In this paper, we apply the Spectral Energy Distribution (SED) fitting code beagle-agn to SMACS S06355, a z7.66 Type-II AGN candidate from the JWST NIRSpec Early Release Observations. This object’s spectrum includes a detection of the [Ne iv] line, indicating an obscured AGN due to its high ionization potential energy (63 eV). We use beagle-agn to simultaneously model the Narrow Line Region (NLR) AGN and star-forming galaxy contributions to the observed line fluxes and photometry. Having a high-ionization emission line allows the contribution of the NLR to the remaining lines to be probabilistically disentangled. The H ii region metallicity is derived to be 12 + log(O/H) = . Assuming that the Neon-to-Oxygen abundance is similar to solar we derive a high NLR metallicity of 12 + log(O/H) = , with the 2 lower-limit extending to 12 + log(O/H)8.00, showing the derivation is uncertain. We discuss this result with respect to non-solar Neon abundances that might boost the inferred NLR metallicity. The NLR metallicity places SMACS S06355 in a comparable region of the mass–metallicity plane to intermediate (1.5z3.0) redshift obscured AGN. Our derived accretion disc luminosity, log() = , is moderately high yet still uncertain. We highlight that deviations between bolometric luminosity calibrations and model grid tracks become enhanced at low metallicities.

Abstract:

We present JWST/NIRSpec integral field spectroscopic (IFS) observations of the Lyα emitter CR7 at z ∼ 6.6, observed as part of the GA-NIFS program. Using low-resolution PRISM (R ∼ 100) data, we confirm the observation of a bright Lyα emitter with a diffuse Lyα halo extending up to 3 kpc from the peak of ionised emission. Both features are associated with the most massive UV bright galaxy in the system, CR7-A. We confirm the presence of two additional UV-bright satellites (CR7-B and CR7-C) detected at projected distances of 6.4 and 5.2 kpc from the primary source. We performed a spectral energy distribution fitting of the low-resolution data, and it revealed an inverted star formation history between two satellites at early epochs and a spatially resolved anti-correlation of the gas-phase metallicity and the star formation rate density, likely driven by the gas exchange among the satellites and favouring the merger scenario for CR7. From the high-resolution G395H (R ∼ 2700) data, we discovered at least one additional companion mainly traced by the [O  III ]λ5007 emission line, although it is not detected in continuum emission. We disentangled the kinematics of the system and reveal extended ionised emission linking the main galaxy and the satellite. We spatially resolved the [O  III ]λ5007, [O  III ]4363, and Hγ emission lines and used a diagnostic diagram tailored to high-z systems to reveal tentative evidence of active galactic nucleus ionisation across the main galaxy (CR7-A) and the N-E companion (CR7-B). Moreover, we detected an unresolved blueshifted outflow from one of the satellites and present first evidence for a redshifted outflow from the main galaxy. Finally, we computed the resolved electron temperature (T e ∼1.6×10 4 K) and metallicity maps (log(Z/Z ⊙ ) from –0.8 to –0.5), and we provide insights on how the physical properties of the system evolved at earlier epochs.