Andrew Bunker

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.

Abstract:

Active galactic nuclei (AGNi) are a key ingredient in galaxy evolution and possibly shape galaxy growth through the generation of powerful outflows. Little is known regarding AGN-driven ionized outflows in moderate-luminosity AGNi (log( L bol /erg s −1 )<47) beyond cosmic noon ( z ≳3). In this work we present the first systematic analysis of the ionized outflow properties of a sample of seven X-ray-selected AGNi (log( L X /erg s −1 )>44) from the COSMOS-Legacy field at z ≃3.5 and with log( L bol /erg s −1 ) = 45.2−46.7 by using JWST NIRSpec/IFU near-IR spectroscopic observations as part of the “Galaxy Assembly with NIRSpec IFS” (GA-NIFS) program. We spectrally isolated and spatially resolved the ionized outflows by performing a multi-component kinematic decomposition of the rest-frame optical emission lines. JWST/NIRSpecIFU data also revealed a wealth of close-by companions, of both non-AGN and AGN nature, and ionized gas streams likely tracing tidal structures and large-scale ionized gas nebulae extending up to the circumgalactic medium. Ionized outflows were detected in all COS-AGNi targets, with outflow masses in the range 1.5−11×10 6 M ⊙ , outflow velocities in the range ≃570−3200 km s −1 , and mass outflow rates in the range ≃1.4−40 M ⊙ yr −1 . We compared the outflow properties of AGNi presented in this work with previous results from the literature up to z ≃3, which were opportunely (re-)computed for a coherent comparison. We normalized outflow energetics ( Ṁ out , Ė out ) to the outflow density in order to standardize the various assumptions that were made in the literature. Our choice is equal to assuming that each outflow has the same gas density. We find GA-NIFS AGNi to show outflows consistent with literature results, within the large scatter shown by the collected measurements, thus suggesting no strong evolution with redshift in terms of total mass outflow rate, energy budget, and outflow velocity for fixed bolometric luminosity. Moreover, we find no clear redshift evolution of the ratio of mass outflow rate and kinetic power over AGNi bolometric luminosity beyond z >1. In general, our results indicate no significant evolution of the physics driving outflows beyond z ≃3.

Abstract:

For the first time, we present a systematic search for galaxies with extended emission lines and potential outflow features using JWST medium-band images in the GOODS South field. This is done by comparing the morphology in medium-band images to adjacent continuum and UV bands. We look for galaxies that have a maximum extent 50% larger, an excess area 30% greater, or an axis ratio difference of more than 0.3 in the medium band compared to the reference bands. After visual inspection, we find 326 candidate galaxies at 1.4 < z < 8.4, with a peak in the population near cosmic noon, benefiting from the good coverage of the medium-band filters. By fitting their spectral energy distributions, we find that the candidate galaxies are at least 20% more bursty in their star-forming activity and have 50% more young stellar populations compared to a control sample selected based on the continuum band flux. Additionally, these candidates exhibit a significantly higher production rate of ionizing photons. We further find that candidates hosting known active galactic nuclei (AGN) produce extended emission that is more anisotropic compared to non-AGN candidates. A few of our candidates have been spectroscopically confirmed to have prominent outflow signatures through NIRSpec observations, showcasing the robustness of the photometric selection. Future spectroscopic follow-up will better help verify and characterize the kinematics and chemical properties of these systems.

Abstract:

We present observations of the Lyman-break galaxy HZ10 with the JWST/NIRSpec integral field unit in high and low spectral resolution (G395H, spectral resolving power and PRISM, , respectively), as part of the GA-NIFS programme. By spatially resolving the source (spatial resolution or kpc), we find three spatially and spectrally distinct regions of line emission along with one region of strong continuum emission, all within a projected distance of kpc. The R2700 data features strong detections in H, [O iii] , [N ii] , H, and [S ii] . The R100 data additionally contain a strong detection of the Ly break, rest-frame UV and optical continuum, and [O ii] . None of the detected lines present strong evidence for active galactic nucleus excitation from line diagnostic diagrams, and no high-ionization lines are detected. Using the detected lines, we constrain the electron density and metallicity ( solar) in each component. Spaxel-by-spaxel fits reveal a strong east-west velocity gradient and significant line asymmetries (possibly indicating tidal features or outflows). The western component features a very red UV slope () and significant H emission, suggesting an evolved population and active star formation. A comparison to high-resolution ( or kpc) [] m imaging obtained with the Atacama Large Millimetre/submillimetre Array (ALMA) reveals areas of dust obscuration. Altogether, these data suggest that HZ10 represents an ongoing merger, with a complex distribution of stars, gas, and dust Gyr after the big bang

Abstract:

The unexpectedly high nitrogen-to-oxygen (N/O) ratios observed in high-redshift (z) galaxies have challenged our understanding of early star formation. Notably, many of these nitrogen-rich galaxies show signatures of active galactic nuclei (AGNs), suggesting a possible connection between black hole formation and nitrogen enrichment. To explore this connection, we analyse stacked spectra of broad-line and narrow-line AGNs using deep Near Infrared Spectrograph data from the JWST Advanced Deep Extragalactic Survey. We identify a significant N iii] quintuplet and a high electron density ( cm) only in the broad-line AGN stack, indicating nitrogen-rich (, ) and dense gas similar to the high-z nitrogen-rich galaxies. Our findings suggest that dense nuclear star formation may trap nitrogen-rich gas in proto-globular clusters, in line with the high N/O observed in local globular clusters; associated runaway stellar collisions could produce intermediate-mass black hole seeds, as predicted by some models and simulations, whose accretion results into AGN signatures. These findings support scenarios connecting the early black hole seeding and growth to merging processes within and between proto-globular clusters in primeval galaxies.