Martin J. Ward

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.

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.

We present new Chandra/ACIS-S imaging spectroscopy of two luminous type 2 quasars (QSO2s), FIRST J120041.4+314745 ( z = 0.116) and 2MASX J13003807+5454367 ( z = 0.088), and compare their X-ray emission with Hubble Space Telescope [O III ] λ 5007 morphologies and kinematics. Both systems show kiloparsec-scale soft X-ray emission. In FIRST J120041, the X-ray morphology is clumpy and closely follows the [O III ] structures, with surface-brightness peaks cospatial with the highest [O III ] velocities (600–750 km s ⁻¹ ) and broadest line widths (∼1700 km s ⁻¹ ). In 2MASX J130038, the X-ray emission is centrally concentrated and weakly correlated with rotational [O III ] kinematics. Spectral modeling indicates that photoionization dominates the soft X-rays in both quasars. The inferred hot-gas reservoirs are substantial, M _Xray ∼ 4.5 × 10 ⁸ M _⊙ (FIRST J120041) and M _Xray ∼ 1.8 × 10 ⁸ M _⊙ (2MASX J130038), exceeding the outflowing [O III ] masses by factors of ∼4 and ∼16. In 2MASX J130038, we identify a tentative blueshifted Fe XXVI Ly α line at E _rest = 7.14 ± 0.06 keV ( v ∼ 7600 km s ⁻¹ ), consistent with a hot wind confined to the inner few hundred parsecs. Combining these results with a broader sample of 12 QSO2s, we argue that luminous quasars evolve along a continuous feedback sequence regulated by progressive clearing of circumnuclear gas. As active galactic nucleus radiation and winds pierce the surrounding medium, systems transition from heavily enshrouded, compact configurations to phases where the X-ray and [O III ] components strongly couple and, eventually, to energetically dominant outflows. FIRST J120041 and 2MASX J130038 represent two points along this sequence, tracing the emergence and growth of hot winds as primary drivers of quasar-scale feedback.

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.

The AGN Space Telescope and Optical Reverberation Mapping (STORM) 2 campaign targeted Mrk 817 with intensive multiwavelength monitoring and found its soft X-ray emission to be strongly absorbed. We present results from 157 near-IR spectra with an average cadence of a few days. Whereas the hot dust reverberation signal as tracked by the continuum flux does not have a clear response, we recover a dust reverberation radius of ∼90 lt-days from the blackbody dust temperature light curve. This radius is consistent with previous photometric reverberation mapping results when Mrk 817 was in an unobscured state. The heating/cooling process we observe indicates that the inner limit of the dusty torus is set by a process other than sublimation, rendering it a luminosity-invariant “dusty wall” of a carbonaceous composition. Assuming thermal equilibrium for dust optically thick to the incident radiation, we derive a luminosity of ∼6 × 10 ⁴⁴ erg s ⁻¹ for the source heating it. This luminosity is similar to that of the obscured spectral energy distribution, assuming a disk with an Eddington accretion rate of m ̇ ∼ 0.2 . Alternatively, the dust is illuminated by an unobscured lower luminosity disk with m ̇ ∼ 0.1 , which permits the UV–optical continuum lags in the high-obscuration state to be dominated by diffuse emission from the broad-line region. Finally, we find hot dust extended on scales ≳ 140–350 pc, associated with the rotating disk of ionised gas we observe in spatially resolved [S III ] λ 9531 images. Its likely origin is in the compact bulge of the barred spiral host galaxy, where it is heated by a nuclear starburst.

X-ray and infrared surveys provide efficient, and to some degree complementary, means of detecting and characterising active galactic nuclei (AGNs), with the infrared also providing an important probe of the host galaxies. To this end we combine the deepest X-ray survey from the Chandra Deep Field-South (CDF-S) ‘7-Ms’ survey with the deepest mid-infrared (5.6 μm) image from the JWST/MIRI Deep Imaging Survey (MIDIS) in the Hubble Ultra-Deep Field (HUDF) to study the infrared counterparts and point-source emission of 31 X-ray sources with a median, intrinsic, rest-frame X-ray luminosity of log ₁₀ ( L _Xc ^{0.5−7 keV} ) = 42.04 ± 0.22 erg s ⁻¹ . The sample includes 24 AGNs with a redshift range, set by the X-ray detectability, of z ≃ 0.5−3, with the bulk of the sources lying at z ≃ 1−2, i.e. around the epoch of cosmic noon. Through a multi-wavelength morphological decomposition, employing three separate classifications (visual, parametric, and non-parametric), we separate (where present) the luminosity of the point-like AGN component from the remainder of the host-galaxy emission. The unprecedented mid-infrared sensitivity and imaging resolution of MIRI allows, in many cases, for the direct characterisation of point-like (i.e. unresolved) components in the galaxies’ emission. We establish a broad agreement between the three morphological classifications. At least 70% of the X-ray sources, including some classified as galaxies, show unresolved emission in the MIRI images, with the unresolved-to-total flux fraction at rest-frame 2 μm ranging from ∼0.2 to ∼0.9. At high X-ray luminosities (log ₁₀ ( L _Xc ) > 43 erg s ⁻¹ ), we derive a consistent rest-frame near-infrared 2 μm point-source luminosity to that derived for local AGNs, whilst at lower X-ray luminosities we identify an excess in the 2 μm emission compared to pre-JWST studies. We speculate that this offset may be driven by a combination of Compton-thick AGN components and nuclear starburst, merger-driven activity. Our observations highlight the complex nature of X-ray sources in the distant Universe and demonstrate the power of JWST/MIRI in quantifying their nuclear infrared emission.

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.

Context. Thanks to decades of observations using the Hubble Space Telescope (HST), the structure of galaxies at redshift z>2 has been widely studied in the rest-frame ultraviolet regime, which traces recent star formation from young stellar populations. However, we still have little information about the spatial distribution of the older, more evolved stellar populations, constrained by the rest-frame infrared portion of the galaxies’ spectral energy distribution. Aims. We present the morphological characterization of a sample of 49 massive galaxies (log(M_⋆/M_⊙)>9) at redshift 3<z3 massive galaxies show a smooth distribution of their rest-infrared light, strongly supporting the increasing number of regular disk galaxies already in place at early epochs. These results are further reinforced by the analysis of JWST/NIRCam data at 4.4 μm. On the contrary, the ultraviolet structure obtained from HST/WFC3 and JWST/NIRCam observations at ∼1.5 μm is generally more irregular, catching the most recent episodes of star formation. Importantly, we find a segregation of morphologies across cosmic time, where galaxies at redshift z>3.75 show later-type morphologies compared to z∼3 galaxies. These findings suggest a transition phase in galaxy assembly and central mass build-up, which takes place already at z∼3−4. Conclusions. The combined analysis of NIRCam and MIRI imaging datasets allows us to prove that the rest-frame near-infrared morphology of massive galaxies at cosmic noon is typical of compact disk galaxies with a smooth mass distribution.