Christopher Packham

This Letter presents JWST MIRI/Medium-Resolution Spectrometer (MRS) observations of the central r ≈ 40–240 pc regions of five active galactic nuclei (AGN) spanning a wide range of luminosities (log L _bol /erg s ⁻¹ ≈ 39.8–43.8). Combining multiphase diagnostics from polycyclic aromatic hydrocarbons (PAHs), molecular hydrogen (H ₂ ), and ionized gas at spatial scales of ∼4–24 pc, this study presents a spatially resolved investigation into the effects of the two distinct AGN feedback modes—radiative and kinetic—on the surrounding medium. The results indicate that these two feedback modes, associated with AGN irradiation and shock processing, respectively, collectively drive the relative suppression of PAH emission in the nuclear regions of the targets studied here. Moreover, the coexistence of these two AGN feedback modes, especially the shock processing associated with either jets or outflows, in the central regions of AGN naturally explains both the bimodal distribution of PAH band ratios observed in the targets studied here and the seemingly disparate results reported in the literature. Although based on a limited sample, these findings provide new insights into calibrating star formation rates from PAH emission in AGN and, more importantly, lay the groundwork for a practical framework to diagnose and quantify AGN feedback in the JWST era.

The Habitable Worlds Observatory (HWO) mission concept is anticipated as NASA’s next astronomical flagship observatory after Roman and the top large, space-based mission recommendation in the 2020 US Astronomy and Astrophysics Decadal Survey. HWO, which combines leaps in scientific discovery space relative to the Hubble Space Telescope with the ability to find and characterize Earth-like exoplanets, is currently being matured by NASA and its potential international partners. The worldwide astronomical community is developing the scientific framework for this mission concept, and it has become widely recognized that most of the cosmic ecosystem, exoplanet, and stellar science goals of HWO require high-throughput imaging and/or spectroscopy at ultraviolet (UV) wavelengths. This paper summarizes current progress by the HWO Community Science and Instrumentation Team to identify and quantify the potential driving science cases that motivate the capabilities of the UV instrument suite for HWO. Key topics currently include the regulation of star formation over cosmic time through galactic feedback, the intergalactic ionizing radiation field, the properties of local analogs of early universe massive stars, and the evolution of chemical complexity in stars and galaxies. We will describe the current driving science cases relevant to UV observations and the measurement goals they imply for the HWO, ranging from UV high-resolution point-source spectroscopy, multi-object and integral field spectroscopy, and far-UV imaging capabilities.

Jet–cloud interactions are a key manifestation of active galactic nucleus (AGN) feedback on nuclear scales, which is distinct from the large-scale radio-mode feedback that suppresses gas cooling in galaxy halos. On these smaller scales, radio jets can inject energy and momentum into the interstellar medium (ISM), shaping the physical and kinematic properties of the nuclear and circumnuclear regions of galaxies. Using JWST MIRI/MRS observations of seven nearby radio-loud AGNs (3C 293, 3C 305, Centaurus A, Cygnus A, IC 5063, NGC 1052, and M 87), we investigated jet-driven turbulence in both the warm molecular and ionized gas phases. By combining spatially resolved H ₂ /polycyclic aromatic hydrocarbon flux ratios with diagnostic line ratios of the ionized gas, we constrained the dominant H ₂ excitation processes and assessed the impact of radio jet–ISM interactions on the multiphase gas. We find that radio jets drive increased turbulence in both molecular and ionized (traced by [Fe II ], [Ne II ], and [Ne III ] lines) gas, not only along but also perpendicular to the jet axis, indicating that jet–ISM interactions extend beyond the collimated jet channel and affect the nuclear environment. Strong correlations between the H ₂ /polycyclic aromatic hydrocarbon ratio, the H ₂ excitation temperature, and shock-sensitive ionized-gas tracers indicate that jet-driven shocks dominate the excitation of the H ₂ rotational lines in most sources. These results indicate that radio jets are a key driver of multiphase ISM kinematics and excitation in nearby radio-loud galaxies.

We utilize James Webb Space Telescope/Mid Infrared Instrument (JWST/MIRI) Integral Field Unit observations from the Galaxy Activity, Torus and Outflow Survey to investigate the diverse range of ionized outflow rates of obscured active galactic nuclei (AGN) with similar bolometric luminosity and explore potential associations with AGN feedback. We explore spatial correlations between ionized emission potentially associated with fast shocks ([Fe II ] _{5.34 μ m} ) and the excitation of H ₂ . We further constrain our investigation to the inner 400 pc (the nuclear and circumnuclear regions r < 200 pc), and estimate the excitation temperature and column density of H ₂ assuming local thermodynamic equilibrium and using the S(1)–S(8) rotational H ₂ emission lines visible to JWST/MIRI spectroscopy. We report the molecular gas temperature of the deprojected 400 pc nuclear region to correlate with the ionized mass outflow rate. We also observe a stronger degree of spatial correlation between [Fe II ] _{5.34 μ m} emission and H ₂ gas temperature. We observe regions of enhanced [Fe II ] _{5.34 μ m} /[Ar II ] _{6.99 μ m} spatially coincident with the ionization cones of objects with higher ionized outflow rates and [Fe II ] _{5.34 μ m} /[Ar II ] _{6.99 μ m} in the deprojected 400 pc nuclear region to scale positively with both the ionized outflow rate and the estimated molecular gas temperature. We do not observe the estimated jet cavity power within the central 400 pc as strongly correlated with the ionized mass outflow rate or molecular gas temperature of the nuclear region. We take the preceding observations to suggest a higher degree of interaction between AGN outflows and the circumnuclear disk.

Context. With the rise of integral field spectroscopy (IFS), we are currently dealing with large amounts of spatially resolved data, whose analysis has become challenging, especially when observing complex objects such as nearby galaxies. Aims. We aim to develop a method of automatically separating regions with different physical properties (ionisation, kinematics, etc.) within the central parts (1″ ∼ 160 pc, on average) of galaxies. This could allow us to better understand the systems and provide an initial characterisation of the main ionisation sources affecting its evolution. Methods. We developed an unsupervised hierarchical clustering algorithm to analyse data cubes based on spectral similarity. It clusters spaxels together with similar spectra, which is useful to disentangle regions affected by different processes, such as ionisation sources. We applied this method to a sample of 15 nearby (distances < 100 Mpc) galaxies: 7 from the Galaxy Activity, Torus, and Outflow Survey (GATOS) and 8 archival sources, all observed with the medium-resolution spectrometer (MRS) of the Mid-Infrared Instrument (MIRI) on board the James Webb Space Telescope (JWST). The sample spans sources of various morphologies, active galactic nucleus (AGN) types, and/or starbursts. From the clusters, we computed their median spectrum and measured the line and continuum properties. We used these measurements to train random forest models and create several empirical mid-IR diagnostic diagrams for the MRS channel 3 wavelength range, ranging from 11.5 to 18 μm, which includes among others the bright [Ne II], [Ne III], and [Ne V] lines, several H ₂ transitions, and PAH features. Results. The clustering technique allows one to differentiate emission coming from an AGN, a nuclear starburst, the disc and star-forming (SF) regions in the galaxies, and other composite regions, potentially ionised by several sources simultaneously. This is supported by the results from the empirical diagnostic diagrams, which are indeed able to separate physically distinct regions. This innovative method serves as a tool to identify regions of interest in any data cube prior to an in-depth analysis of the sources. In a future work, we shall explore other wavelength ranges and a larger sample that would help us to obtain statistically significant conclusions.

This Letter presents an analysis of the infrared (∼3–28 μ m) spectra extracted from the nuclear ( r < 150 pc) regions of four low-luminosity active galactic nuclei (AGN), observed by JWST NIRSpec/integral field unit and MIRI/Medium Resolution Spectroscopy as an extension of the Galaxy Activity, Torus, and Outflow Survey. We find that, compared to higher-luminosity AGN, these low-luminosity AGN exhibit distinct properties in their emission of ionized gas, polycyclic aromatic hydrocarbons (PAHs), and molecular hydrogen (H ₂ ). Specifically, the low-luminosity AGN exhibit relatively weak high ionization potential lines (e.g., [Ne V ] and [O IV ]), and the line ratios suggest that fast radiative shocks (with v _s of ∼100s km s ⁻¹ ) are the primary excitation source of ionized gas therein. Under the low-excitation conditions of their nuclear regions, these low-luminosity AGN generally exhibit a higher fraction of PAHs with large size ( N _C ≳ 200), reflecting the preferential destruction of smaller PAH molecules by AGN feedback. Furthermore, the H ₂ transitions in these low-luminosity AGN are not fully thermalized, with slow, plausibly jet-driven molecular shocks (with v _s ≤ 10 km s ⁻¹ ) likely being the extra excitation source. Taken together with results from the literature, these findings indicate that feedback operates in both low- and high-luminosity AGN, although its impact varies with AGN luminosity. In particular, systematic variations in PAH band ratios are found across AGN, demonstrating the differing influence of feedback in AGN of varying luminosities and highlighting the potential of PAH band ratios as diagnostics for distinguishing kinetic- and radiative-mode AGN feedback.

Active galactic nuclei (AGNs), star formation (SF), and galaxy interactions can drive turbulence in the gas of the interstellar medium (ISM), which, in turn, plays a role in SF taking place within galaxies. The impact on molecular gas is of particular importance, as it serves as the primary fuel for SF. Our goal is to investigate the origin of turbulence and the emission of molecular gas, as well as low-and-intermediate-ionisation gas, in the inner few kpc of both AGN hosts and star-forming galaxies (SFGs). We used archival JWST MIRI/MRS observations of a sample consisting of 54 galaxies at z < 0.1. We present flux measurements for the H ₂ S(5) λ 6.9091 μm, [Ar II ] λ 6.9853 μm, [Fe II ] λ 5.3403 μm, and [Ar III ] λ 8.9914 μm emission lines along with velocity dispersion estimated by the W ₈₀ parameter. For galaxies with coronal line emission, we included measurements of the [Mg V ] λ 5.6098 μm line. We compared the line ratios to photoionisation and shock models to explore the origin of the gas emission. AGNs exhibit broader emission lines than SFGs, with the largest velocity dispersions observed in radio-strong (RS) AGNs. The H ₂ gas is less turbulent compared to ionised gas, while coronal gas presents higher velocity dispersions. The W ₈₀ values for the ionised gas show a decrease when going from the nucleus out to radii of approximately 0.5–1 kpc, followed by an outward increase up to 2–3 kpc. In contrast, the H ₂ line widths generally display increasing profiles with distance from the center. Correlations between the W ₈₀ parameter and line ratios such as H ₂ S(5)/[Ar II ] and [Fe II ]/[Ar II ] indicate that the most turbulent gas is associated with shocks, enhancing H ₂ and [Fe II ] emissions. Based on the observed line ratios and velocity dispersions, the [Fe II ] emission is consistent with predictions of fast shock models, while the H ₂ emission is likely associated with molecules formed in the post-shock region. We speculate that these shocked gas regions are produced by AGN outflows and jet-cloud interactions in AGN-dominated sources; whereas in SFGs, they might be created through stellar winds and mergers. This shock-induced gas heating may be an important mechanism of AGN (or stellar) feedback, preventing the gas from cooling and forming new stars.

The polar mid-infrared (MIR) emission detected within tens to hundreds of parsecs in some active galactic nuclei (AGN) has been associated with dusty winds driven away by radiation pressure. The physical characterization of this extended polar emission remains uncertain. Here, we combine 10–21 μ m JWST/Mid-InfRared Instrument (MIRI) imaging observations with 7–25 μ m JWST/MIRI MRS integral field spectroscopic observations of six nearby, D ¯ = 35.4 ± 4.6 Mpc, AGN from the GATOS Survey to quantify the nature of the extended MIR emission at ∼75 pc resolution at 21 μ m. These AGN have similar bolometric luminosities, log 10 ( L ¯ bol [ erg s − 1 ] ) = 44.0 ± 0.3 , span a wide range of optical outflow rates, M ̇ = 0.003–0.21 M _⊙ yr ⁻¹ , column densities, log 10 ( N H X − ray [ cm − 2 ] ) = 22.2–24.3, and Eddington ratios, λ _Edd = 0.005–0.06. We cross-correlate the line-only and continuum-only images and find a poor correlation, which indicates that the extended MIR continuum emission is spatially uncorrelated with the warm outflows associated with narrow emission lines within 10–15 μ m. Line emission is resolved along the jet axis, while dust emission is perpendicular to it. The 75–450 pc continuum emission has a fairly constant dust temperature, T d = 13 2 − 7 + 7 K, and mass, M d = 72 8 − 27 + 29 M _⊙ . Using the conditions of energy balance between radiation-pressure and gravity ( λ _Edd versus N _H ), we find that our AGN sample is in the gravitationally bounded regime consistent with no detection of dusty winds. At 10 μ m, the level of extended line emission contribution is correlated with the outflow kinetic energy and mass outflow rates. We find no correlation with the AGN properties. These results indicate that the radio jet may be triggering the gas outflow and line emission, while the extended dust emission is distributed in molecular clouds and/or shocked regions.

We utilize James Webb Space Telescope (JWST) Mid Infrared Instrument (MIRI) integral field unit observations to investigate the behavior and excitation of H ₂ in the nearby Seyfert galaxies NGC 3081 and NGC 5506, both part of the Galactic Activity, Torus, and Outflow Survey (or GATOS). We compare population levels of the S(1) to S(8) rotational H ₂ emission lines visible to JWST/MIRI spectroscopy to models assuming local thermodynamic equilibrium (LTE), in order to estimate the column density and thermal scaling of the molecular gas. For the nuclear regions, we incorporate Very Large Telescope Spectrograph for INtegral Field Observations in the Near Infrared (or VLT/SINFONI) K -band observations to estimate population levels for available rovibrational H ₂ emission lines, and compare the resultant population curves to non-LTE radiative transfer models and shock modeling. We report a differing set of prominent active galactic nuclei (AGN)-driven excitation mechanisms between the two galaxies. For NGC 3081, we find that a non-LTE radiative transfer environment is adequate to explain observations of the nuclear region, indicating that the primary mode in which the AGN transfers excitation energy is likely irradiation. We estimate the extent of AGN photoionization along the ionization bicone to be ≈330 pc. In contrast, for NGC 5506, we find a shock scenario to be a more plausible excitation mechanism, a conclusion bolstered by an observed spatial correlation between higher-energy rotational H ₂ and [Fe II ] _{5.34 μ m} emission. In addition, we identify potential nuclear H ₂ outflows resulting from an interaction between the ionization bicone and the rotational disk. By isolating the outflowing component of the H ₂ emission, we estimate the warm molecular mass outflow rate to be 0.07 M _⊙ yr ⁻¹ .

With excellent spectral and angular resolutions and, especially, sensitivity, the JWST allows us to observe infrared emission lines that were previously inaccessible or barely accessible. These emission lines are promising for evaluating the physical conditions in different galaxies. Based on MAPPINGS V photoionization models, we systematically analyze the dependence of over 20 mid-infrared (mid-IR) emission lines covered by MIRI on board JWST on the physical conditions of different galactic environments, in particular narrow-line regions in active galactic nuclei (AGN). We find that mid-IR emission lines of highly ionized argon (i.e., [Ar V] 7.90 and 13.10 μm) and neon (i.e., [Ne V] 14.32 and 24.32 μm, and [Ne VI] 7.65 μm) are effective in diagnosing the physical conditions in AGN. We accordingly propose new prescriptions to constrain the ionization parameter (U), peak energy of the AGN spectrum (E _peak), metallicity ( 12 + log ( O / H ) ), and gas pressure (P/k) in AGN. These new calibrations are applied to the central regions of six Seyfert galaxies included in the Galaxy Activity, Torus, and Outflow Survey as a proof of concept. We also discuss the similarity and difference in the calibrations of these diagnostics in AGN of different luminosities, highlighting the impact of hard X-ray emission and particularly radiative shocks, as well as the different diagnostics in star-forming regions. Finally, we propose diagnostic diagrams involving [Ar V] 7.90 μm and [Ne VI] 7.65 μm to demonstrate the feasibility of using the results of this study to distinguish galactic regions governed by different excitation sources.