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We present the results of a James Webb Space Telescope NIRCam and NIRSpec investigation into the young massive star cluster (YMC) population of NGC 3256, the most cluster-rich luminous infrared galaxy in the Great Observatories All Sky LIRG Survey. We detect 3061 compact YMC candidates with a signal-to-noise ratio ≥3 at F150W, F200W, and F335M. Based on yggdrasil stellar population models, we identify 116/3061 sources with F150W – F200W > 0.47 and F200W – F355M > −1.37 colors, suggesting that they are young ( t ≤ 5 Myr), dusty ( A _V = 5−15), and massive ( M _⊙ > 10 ^5 ). This increases the sample of dust-enshrouded YMCs detected in this system by an order of magnitude relative to previous Hubble Space Telescope studies. With NIRSpec integral field unit pointings centered on the northern and southern nucleus, we extract the Pa α and 3.3 μ m polycyclic aromatic hydrocarbon (PAH) equivalent widths for eight bright and isolated YMCs. Variations in both the F200W – F335M color and 3.3 μ m PAH emission with the Pa α line strength suggest a rapid dust clearing ( 0) correspond to sources with E ( B − V ) > 3, which are typically missed in UV-optical studies. This underscores the importance of deep near-infrared imaging for finding and characterizing these very young and dust-embedded sources.

We present James Webb Space Telescope MIRI data of the inner ∼3 × 2 kpc ^2 of the galaxy IC 5063, in which the jets of a supermassive black hole interact with the gaseous disk they are crossing. Jet-driven outflows were known to be initiated along or near the jet path and to modify the stability of molecular clouds, possibly altering their star formation properties. The MIRI data, of unprecedented resolution and sensitivity in the infrared, now reveal that there are more than 10 discrete regions with outflows, nearly doubling the number of such known regions. Outflows exist near the radio lobes, at the nucleus, in a biconical structure perpendicular to the jet, and in a bubble moving against the disk. In some of them, velocities above escape velocity are observed. Stratification is also observed, with higher ionization or excitation gas attaining higher velocities. More outflows and bow shocks, found further away from the nucleus than the radio lobes, in regions without significant radio emission, reveal the existence of past or weak radio jets that interacted with the interstellar medium. The coincidence of the bow shocks with the optical extended emission line region (EELR) suggests that the jets also contributed to the gas ionization. Maps of the H _2 gas excitation temperature, T _ex , indicate that the molecular gas is most excited in regions with radio emission. There, T _ex is >100 K higher than in the EELR interior. We argue that a combination of jet-related shocks and cosmic rays is likely responsible for this excess molecular gas excitation.

We present an analysis of eight JWST Mid-Infrared Instrument (MIRI) 5.6 μ m images with 5 σ depths of ≈0.1 μ Jy. We detect 2854 sources within our combined area of 18.4 arcmin ^2 . We compute the MIRI 5.6 μ m number counts, including an analysis of the field-to-field variation. Compared to earlier published MIRI 5.6 μ m counts, our counts have a more pronounced knee, at roughly 2 μ Jy. The location and amplitude of the counts at the knee are consistent with the Cowley et al. model predictions, although these models tend to overpredict the counts below the knee. In areas of overlap, 84% of the MIRI sources have a counterpart in the COSMOS2020 catalog. These MIRI sources have redshifts that are mostly in the z ∼ 0.5–2, with a tail out to z ∼ 5. They are predominantly moderate to low stellar masses (10 ^8 –10 ^10 M _⊙ ) main-sequence star-forming galaxies, suggesting that with ≈2 hr exposures, MIRI can reach well below M _* at cosmic noon and reach higher mass systems out to z ∼ 5. Nearly 70% of the COSMOS2020 sources in areas of overlap now have a data point at 5.6 μ m (rest-frame near-IR at cosmic noon), which allows for more accurate stellar population parameter estimates. Finally, we discovered 31 MIRI-bright sources not present in COSMOS2020. A crossmatch with IRAC channel 1 suggests that 10%–20% of these are likely lower mass ( M _* ≈ 10 ^9 M _⊙ ), z ∼ 1 dusty galaxies. The rest (80%–90%) are consistent with more massive but still very dusty galaxies at z > 3.

We present James Webb Space Telescope (JWST) integral-field spectrograph observations of NGC 3256, a local infrared-luminous late-stage merging system with two nuclei roughly 1 kpc apart, both of which have evidence of cold molecular outflows. Using JWST/NIRSpec and Mid-Infrared Instrument data sets, we investigate this morphologically complex system on spatial scales of

Measurements of oxygen abundance throughout galaxies provide insight to the formation histories and ongoing processes. Here we present a study of the gas-phase oxygen abundance in the H ii regions and diffuse gas of the nearby starburst dwarf galaxy, IC 10. Using the Keck Cosmic Web Imager at W. M. Keck Observatory, we map the central region of IC 10 from 3500 to 5500 Å. The auroral [O III ] 4363 Å line is detected with a high signal-to-noise ratio in 12 of 46 H II regions observed, allowing for direct measurement of the oxygen abundance, yielding a median and standard deviation of $12+\mathrm{log}({\rm{O}}/{\rm{H}})=8.37\pm 0.25$ . We investigate trends between these directly measured oxygen abundances and other H II region properties, finding weak negative correlations with the radius, velocity dispersion, and luminosity. We also find weak negative correlations between the oxygen abundance and the derived quantities of turbulent pressure and ionized gas mass, and a moderate correlation with the derived dynamical mass. Strong line, R _23 abundance estimates are used in the remainder of the H II regions and on a resolved spaxel-by-spaxel basis. There is a large offset between the abundances measured with R _23 and the auroral line method. We find that the R _23 method is unable to capture the large range of abundances observed via the auroral line measurements. The extent of this variation in the measured abundances further indicates a poorly mixed interstellar medium in IC 10, which is not typical of dwarf galaxies and may be partly due to the ongoing starburst, accretion of pristine gas, or a late stage merger.

We present the CO(1–0) maps of 28 infrared-bright galaxies from the Great Observatories All-Sky Luminous Infrared Galaxy Survey (GOALS) taken with the Combined Array for Research in Millimeter Astronomy (CARMA). We detect 100 GHz continuum in 16 of the 28 CARMA GOALS galaxies, which trace both active galactic nuclei (AGNs) and compact star-forming cores. The GOALS galaxies show a variety of molecular gas morphologies, though in the majority of cases the average velocity fields show a gradient consistent with rotation. We fit the full continuum spectral energy distributions (SEDs) of each of the sources using either magphys or SED3FIT (if there are signs of an AGN) to derive the total stellar mass, dust mass, and SFRs of each object. We adopt a value determined from luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) of α _CO = ${1.5}_{-0.8}^{+1.3}$ M _⊙ (K km s ^−1 pc ^2 ) ^−1 , which leads to more physical values for f _mol and the gas-to-dust ratio. Mergers tend to have the highest gas-to-dust ratios. We assume the cospatiality of the molecular gas and star formation and plot the CARMA GOALS sample on the Schmidt–Kennicutt relation, where we find that they preferentially lie above the line set by normal star-forming galaxies. This hyper-efficiency is likely due to the increased turbulence in these systems, which decreases the freefall time compared to star-forming galaxies, leading to “enhanced” star formation efficiency. Line wings are present in a non-negligible subsample (11/28) of the CARMA GOALS sources and are likely due to outflows driven by AGNs or star formation, gas inflows, or additional decoupled gas components.

We use deep Spitzer mid-infrared spectroscopic maps of radial strips across three nearby galaxies with well-studied metallicity gradients (M101, NGC 628, and NGC 2403) to explore the physical origins of the observed deficit of polycyclic aromatic hydrocarbons (PAHs) at subsolar metallicity (i.e., the PAH–metallicity relation or PZR). These maps allow us to trace the evolution of all PAH features from 5–18 μ m as metallicity decreases continuously from solar ( Z _⊙ ) to 0.2 Z _⊙ . The total PAH-to-dust luminosity ratio remains relatively constant until reaching a threshold of ∼ 2/3 Z _⊙ , below which it declines smoothly but rapidly. The PZR has been attributed to preferential destruction of the smallest grains in the hard radiation environments found at low metallicity. In this scenario, a decrease in emission from the shortest-wavelength PAH features is expected. In contrast, we find a steep decline in long-wavelength power below Z _⊙ , especially in the 17 μ m feature, with the shorter-wavelength PAH bands carrying an increasingly large fraction of power at low metallicity. We use newly developed grain models to reproduce the observed PZR trends, including these variations in fractional PAH feature strengths. The model that best reproduces the data employs an evolving grain size distribution that shifts to smaller sizes as metallicity declines. We interpret this as a result of inhibited grain growth at low metallicity, suggesting continuous replenishment in the interstellar medium is the dominant process shaping the PAH grain population in galaxies.

We present new observations of the central 1 kpc of the M82 starburst obtained with the James Webb Space Telescope near-infrared camera instrument at a resolution θ ∼ 0.″05–0.″1 (∼1–2 pc). The data comprises images in three mostly continuum filters (F140M, F250M, and F360M), and filters that contain [Fe ii ] (F164N), H _2 v = 1 → 0 (F212N), and the 3.3 μ m polycyclic aromatic hydrocarbon (PAH) feature (F335M). We find prominent plumes of PAH emission extending outward from the central starburst region, together with a network of complex filamentary substructures and edge-brightened bubble-like features. The structure of the PAH emission closely resembles that of the ionized gas, as revealed in Paschen α and free–free radio emission. We discuss the origin of the structure, and suggest the PAHs are embedded in a combination of neutral, molecular, and photoionized gas.

The enormous increase in mid-IR sensitivity and spatial and spectral resolution provided by the JWST spectrographs enables, for the first time, detailed extragalactic studies of molecular vibrational bands. This opens an entirely new window for the study of the molecular interstellar medium in luminous infrared galaxies (LIRGs). We present a detailed analysis of rovibrational bands of gas-phase CO, H _2 O, C _2 H _2 , and HCN toward the heavily obscured eastern nucleus of the LIRG VV 114, as observed by NIRSpec and the medium resolution spectrograph on the Mid-InfraRed Instrument (MIRI MRS). Spectra extracted from apertures of 130 pc in radius show a clear dichotomy between the obscured active galactic nucleus (AGN) and two intense starburst regions. We detect the 2.3 μ m CO bandheads, characteristic of cool stellar atmospheres, in the star-forming regions, but not toward the AGN. Surprisingly, at 4.7 μ m, we find highly excited CO ( T _ex ≈ 700–800 K out to at least rotational level J = 27) toward the star-forming regions, but only cooler gas ( T _ex ≈ 200 K) toward the AGN. We conclude that only mid-infrared pumping through the rovibrational lines can account for the equilibrium conditions found for CO and H _2 O in the deeply embedded starbursts. Here, the CO bands probe regions with an intense local radiation field inside dusty young massive star clusters or near the most massive young stars. The lack of high-excitation molecular gas toward the AGN is attributed to geometric dilution of the intense radiation from the bright point source. An overview of the relevant excitation and radiative transfer physics is provided in an appendix.

We present new JWST NIRSpec integral field spectroscopy (IFS) data for the luminous infrared galaxy NGC 7469, a nearby (70.6 Mpc) active galaxy with a Seyfert 1.5 nucleus that drives a highly ionized gas outflow and a prominent nuclear star-forming ring. Using the superb sensitivity and high spatial resolution of the JWST instrument NIRSpec IFS, we investigate the role of the Seyfert nucleus in the excitation and dynamics of the circumnuclear gas. Our analysis focuses on the [Fe ii ], H _2 , and hydrogen recombination lines that trace the radiation/shocked-excited molecular and ionized interstellar medium around the active galactic nucleus (AGN). We investigate gas excitation through H _2 /Br γ and [Fe ii ]/Pa β emission line ratios and find that photoionization by the AGN dominates within the central 300 pc of the galaxy except in a small region that shows signatures of shock-heated gas; these shock-heated regions are likely associated with a compact radio jet. In addition, the velocity field and velocity dispersion maps reveal complex gas kinematics. Rotation is the dominant feature, but we also identify noncircular motions consistent with gas inflows as traced by the velocity residuals and the spiral pattern in the Pa α velocity dispersion map. The inflow is 2 orders of magnitude higher than the AGN accretion rate. The compact nuclear radio jet has enough power to drive the highly ionized outflow. This scenario suggests that the inflow and outflow are in a self-regulating feeding–feedback process, with a contribution from the radio jet helping to drive the outflow.

We present results from the Quasar hosts Unveiled by high Angular Resolution Techniques survey studying the circumgalactic medium (CGM) by observing rest-frame UV emission lines Ly α , C iv , and He ii around two radio-loud quasars, 3C 9 ( z = 2.02) and 4C 05.84 ( z = 2.32), using the Keck Cosmic Web Imager. We detect large-scale Ly α nebulae around both quasars with projected diameters ∼100 kpc, with spatially resolved, embedded 15–30 kpc He ii and C iv nebulae around both quasars as well as kinematically distinct He ii and C iv nebulae at a physical separation of ∼15 kpc from both quasars. Observations of H α , H β , and [O iii ] emission using Keck MOSFIRE spectroscopically confirm that the Ly α nebulae extend to companion galaxies and that these quasars are in a protogroup/protocluster environment. We confirm that the He ii and C iv emission is kinematically and spatially coincident with the companion galaxies. We estimate the virial masses of the companion galaxies, their metallicities, and star formation rates, and investigate the sources of ionization. We measure the dynamical mass of the host dark matter halos and estimate that the dark matter halos of these systems will grow to a mass of 2 × 10 ^14 M _⊙ (3C 9) and 2 × 10 ^13 M _⊙ (4C 05.84) by z = 0. The combined CGM and companion galaxies observations indicate Ly α substructure can indicate the presence of companion galaxies in the CGM.

We present JWST Mid-InfraRed Instrument/Medium-Resolution Spectrometer (MIRI/MRS) observations of an infrared luminous disk galaxy, FLS1, at z ∼ 0.54. With a lookback time of 5 Gyr, FLS1 is chronologically at the midpoint between the peak epoch of star formation and the present day. The MRS data provide maps of the atomic fine structure lines [Ar ii ]6.99, [Ar iii ]8.99, [Ne ii ]12.81, and [Ne iii ]15.55 μ m, polycyclic aromatic hydrocarbon (PAH) features at 3.3, 6.2, and 11.3 μ m, and the warm molecular gas indicators H _2 S(5) and H _2 S(3); all these emission features are spatially resolved. We find that the PAH emission is more extended along the northern side of the galaxy when compared to the well-studied star formation tracer [Ne ii ]. The H _2 rotational lines, which are shock indicators, are strongest and most extended on the southern side of the galaxy. [Ar ii ] is the second brightest fine structure line detected in FLS1 and we show that it is a useful kinematic probe that can be detected with JWST out to z ∼ 3. Velocity maps of [Ar ii ] show a rotating disk with signs of turbulence. Our results provide an example of how spatially resolved mid-infrared spectroscopy can allow us to better understand the star formation and interstellar medium conditions in a galaxy halfway back to the peak epoch of galaxy evolution.

We present James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec) integral field spectroscopy of the nearby luminous infrared galaxy NGC 7469. We take advantage of the high spatial/spectral resolution and wavelength coverage of JWST/NIRSpec to study the 3.3 μ m neutral polycyclic aromatic hydrocarbon (PAH) grain emission on ∼200 pc scales. A clear change in the average grain properties between the star-forming ring and the central AGN is found. Regions in the vicinity of the AGN, with [Ne iii ]/[Ne ii ] > 0.25, tend to have larger grain sizes and lower aliphatic-to-aromatic (3.4/3.3) ratios, indicating that smaller grains are preferentially removed by photodestruction in the vicinity of the AGN. PAH emission at the nucleus is weak and shows a low 11.3/3.3 PAH ratio. We find an overall suppression of the total PAH emission relative to the ionized gas in the central 1 kpc region of the AGN in NGC 7469 compared to what has been observed with Spitzer on 3 kpc scales. However, the fractional 3.3 μ m–to–total PAH power is enhanced in the starburst ring, possibly due to a variety of physical effects on subkiloparsec scales, including recurrent fluorescence of small grains or multiple photon absorption by large grains. Finally, the IFU data show that while the 3.3 μ m PAH-derived star formation rate (SFR) in the ring is 27% higher than that inferred from the [Ne ii ] and [Ne iii ] emission lines, the integrated SFR derived from the 3.3 μ m feature would be underestimated by a factor of 2 due to the deficit of PAHs around the AGN, as might occur if a composite system like NGC 7469 were to be observed at high redshift.

We present James Webb Space Telescope (JWST) imaging of NGC 7469 with the Near-Infrared Camera and the Mid-InfraRed Instrument. NGC 7469 is a nearby, z = 0.01627, luminous infrared galaxy that hosts both a Seyfert Type-1.5 nucleus and a circumnuclear starburst ring with a radius of ∼0.5 kpc. The new near-infrared (NIR) JWST imaging reveals 66 star-forming regions, 37 of which were not detected by Hubble Space Telescope (HST) observations. Twenty-eight of the 37 sources have very red NIR colors that indicate obscurations up to A _v ∼ 7 and a contribution of at least 25% from hot dust emission to the 4.4 μ m band. Their NIR colors are also consistent with young (

We present the results of a James Webb Space Telescope NIRCam investigation into the young massive star cluster (YMC) population in the luminous infrared galaxy VV 114. We identify 374 compact YMC candidates with signal-to-noise ratios ≥ 3, 5, and 5 at F150W, F200W, and F356W, respectively. A direct comparison with our HST cluster catalog reveals that ∼20% of these sources are undetected at optical wavelengths. Based on yggdrasil stellar population models, we identify 17 YMC candidates in our JWST imaging alone with F150W – F200W and F200W – F356W colors suggesting they are all very young, dusty ( A _V = 5–15), and massive (10 ^5.8 < M _⊙ < 10 ^6.1 ). The discovery of these “hidden” sources, many of which are found in the “overlap” region between the two nuclei, quadruples the number of t < 3 Myr clusters and nearly doubles the number of t < 6 Myr clusters detected in VV 114. Now extending the cluster age distribution ( ${dN}/d\tau \propto {\tau }^{\gamma }$ ) to the youngest ages, we find a slope of γ = −1.30 ± 0.39 for 10 ^6 < τ (yr) < 10 ^7 , which is consistent with the previously determined value from 10 ^7 < τ (yr) < 10 ^8.5 , and confirms that VV 114 has a steep age distribution slope for all massive star clusters across the entire range of cluster ages observed. Finally, the consistency between our JWST- and HST-derived age distribution slopes indicates that the balance between cluster formation and destruction has not been significantly altered in VV 114 over the last 0.5 Gyr.

Selecting the first galaxies at z > 7 − 10 from JWST surveys is complicated by z < 6 contaminants with degenerate photometry. For example, strong optical nebular emission lines at z < 6 may mimic JWST/NIRCam photometry of z > 7–10 Lyman-break galaxies (LBGs). Dust-obscured 3 < z < 6 galaxies in particular are potentially important contaminants, and their faint rest-optical spectra have been historically difficult to observe. A lack of optical emission line and continuum measures for 3 < z < 6 dusty galaxies now makes it difficult to test their expected JWST/NIRCam photometry for degenerate solutions with NIRCam dropouts. Toward this end, we quantify the contribution by strong emission lines to NIRCam photometry in a physically motivated manner by stacking 21 Keck II/NIRES spectra of hot, dust-obscured, massive ( $\mathrm{log}{M}_{* }/{M}_{\odot }\gtrsim 10\mbox{--}11$ ) and infrared (IR) luminous galaxies at z ∼ 1–4. We derive an average spectrum and measure strong narrow (broad) [O iii ] _5007 and H α features with equivalent widths of 130 ± 20 Å (150 ± 50 Å) and 220 ± 30 Å (540 ± 80 Å), respectively. These features can increase broadband NIRCam fluxes by factors of 1.2 − 1.7 (0.2–0.6 mag). Due to significant dust attenuation ( A _V ∼ 6), we find H α +[N ii ] to be significantly brighter than [O iii ]+H β and therefore find that emission-line dominated contaminants of high − z galaxy searches can only reproduce moderately blue perceived UV continua of S _λ ∝ λ ^β with β > − 1.5 and z > 4. While there are some redshifts ( z ∼ 3.75) where our stack is more degenerate with the photometry of z > 10 LBGs at λ _rest ∼ 0.3–0.8 μ m , redder filter coverage beyond λ _obs > 3.5 μ m and far-IR/submillimeter follow-up may be useful for breaking the degeneracy and making a crucial separation between two fairly unconstrained populations, dust-obscured galaxies at z ∼ 3–6 and LBGs at z > 10.

James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) images of the luminous infrared (IR) galaxy VV 114 are presented. This redshift ∼0.020 merger has a western component (VV 114W) rich in optical star clusters and an eastern component (VV 114E) hosting a luminous mid-IR nucleus hidden at UV and optical wavelengths by dust lanes. With MIRI, the VV 114E nucleus resolves primarily into bright NE and SW cores separated by 630 pc. This nucleus comprises 45% of the 15 μ m light of VV 114, with the NE and SW cores having IR luminosities, L _IR (8 − 1000 μ m) ∼ 8 ± 0.8 × 10 ^10 L _⊙ and ∼ 5 ± 0.5 × 10 ^10 L _⊙ , respectively, and IR densities, Σ _IR ≳ 2 ± 0.2 × 10 ^13 L _⊙ kpc ^−2 and ≳ 7 ± 0.7 × 10 ^12 L _⊙ kpc ^−2 , respectively—in the range of Σ _IR for the Orion star-forming core and the nuclei of Arp 220. The NE core, previously speculated to have an active galactic nucleus (AGN), has starburst-like mid-IR colors. In contrast, the VV 114E SW core has AGN-like colors. Approximately 40 star-forming knots with L _IR ∼ 0.02–5 × 10 ^10 L _⊙ are identified, 28% of which have no optical counterpart. Finally, diffuse emission accounts for 40%–60% of the mid-IR emission. Mostly notably, filamentary polycyclic aromatic hydrocarbon (PAH) emission stochastically excited by UV and optical photons accounts for half of the 7.7 μ m light of VV 114. This study illustrates the ability of JWST to detect obscured compact activity and distributed PAH emission in the most extreme starburst galaxies in the local universe.

We have used the Mid-InfraRed Instrument (MIRI) on the James Webb Space Telescope (JWST) to obtain the first spatially resolved, mid-infrared images of IIZw096, a merging luminous infrared galaxy (LIRG) at z = 0.036. Previous observations with the Spitzer Space Telescope suggested that the vast majority of the total IR luminosity ( L _IR ) of the system originated from a small region outside of the two merging nuclei. New observations with JWST/MIRI now allow an accurate measurement of the location and luminosity density of the source that is responsible for the bulk of the IR emission. We estimate that 40%–70% of the IR bolometric luminosity, or 3–5 × 10 ^11 L _⊙ , arises from a source no larger than 175 pc in radius, suggesting a luminosity density of at least 3–5 × 10 ^12 L _⊙ kpc ^−2 . In addition, we detect 11 other star-forming sources, five of which were previously unknown. The MIRI F1500W/F560W colors of most of these sources, including the source responsible for the bulk of the far-IR emission, are much redder than the nuclei of local LIRGs. These observations reveal the power of JWST to disentangle the complex regions at the hearts of merging, dusty galaxies.

The nearby, luminous infrared galaxy NGC 7469 hosts a Seyfert nucleus with a circumnuclear star-forming ring and is thus the ideal local laboratory for investigating the starburst–AGN (active galactic nucleus) connection in detail. We present integral-field observations of the central 1.3 kpc region in NGC 7469 obtained with the JWST Mid-InfraRed Instrument. Molecular and ionized gas distributions and kinematics at a resolution of ∼100 pc over the 4.9–7.6 μ m region are examined to study the gas dynamics influenced by the central AGN. The low-ionization [Fe ii ] λ 5.34 μ m and [Ar ii ] λ 6.99 μ m lines are bright on the nucleus and in the starburst ring, as opposed to H _2 S(5) λ 6.91 μ m, which is strongly peaked at the center and surrounding ISM. The high-ionization [Mg v ] line is resolved and shows a broad, blueshifted component associated with the outflow. It has a nearly face-on geometry that is strongly peaked on the nucleus, where it reaches a maximum velocity of −650 km s ^−1 , and extends about 400 pc to the east. Regions of enhanced velocity dispersion in H _2 and [Fe ii ] ∼ 180 pc from the AGN that also show high L (H _2 )/ L (PAH) and L ([Fe ii ])/ L (Pf α ) ratios to the W and N of the nucleus pinpoint regions where the ionized outflow is depositing energy, via shocks, into the dense interstellar medium between the nucleus and the starburst ring. These resolved mid-infrared observations of the nuclear gas dynamics demonstrate the power of JWST and its high-sensitivity integral-field spectroscopic capability to resolve feedback processes around supermassive black holes in the dusty cores of nearby luminous infrared galaxies.

We present James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) integral-field spectroscopy of the nearby merging, luminous infrared galaxy, NGC 7469. This galaxy hosts a Seyfert type-1.5 nucleus, a highly ionized outflow, and a bright, circumnuclear star-forming ring, making it an ideal target to study active galactic nucleus (AGN) feedback in the local universe. We take advantage of the high spatial/spectral resolution of JWST/MIRI to isolate the star-forming regions surrounding the central active nucleus and study the properties of the dust and warm molecular gas on ∼100 pc scales. The starburst ring exhibits prominent polycyclic aromatic hydrocarbon (PAH) emission, with grain sizes and ionization states varying by only ∼30%, and a total star formation rate of 10–30 M _⊙ yr ^−1 derived from fine structure and recombination emission lines. Using pure rotational lines of H _2 we detect 1.2 × 10 ^7 M _⊙ of warm molecular gas at a temperature higher than 200 K in the ring. All PAH bands get significantly weaker toward the central source, where larger and possibly more ionized grains dominate the emission, likely the result of the ionizing radiation and/or the fast wind emerging from the AGN. The small grains and warm molecular gas in the bright regions of the ring however display properties consistent with normal star-forming regions. These observations highlight the power of JWST to probe the inner regions of dusty, rapidly evolving galaxies for signatures of feedback and inform models that seek to explain the coevolution of supermassive black holes and their hosts.

M82 is an archetypal starburst galaxy in the local Universe. The central burst of star formation, thought to be triggered by M82's interaction with other members in the M81 group, is driving a multiphase galaxy-scale wind away from the plane of the disk that has been studied across the electromagnetic spectrum. Here, we present new velocity-resolved observations of the [C ii ] 158 μ m line in the central disk and the southern outflow of M82 using the upGREAT instrument on board SOFIA. We also report the first detections of velocity-resolved (Δ V = 10 km s ^−1 ) [C ii ] emission in the outflow of M82 at projected distances of ≈1–2 kpc south of the galaxy center. We compare the [C ii ] line profiles to observations of CO and H i and find that likely the majority (>55%) of the [C ii ] emission in the outflow is associated with the neutral atomic medium. We find that the fraction of [C ii ] actually outflowing from M82 is small compared to the bulk gas outside the midplane (which may be in a halo or tidal streamers), which has important implications for observations of [C ii ] outflows at higher redshift. Finally, by comparing the observed ratio of the [C ii ] and CO intensities to models of photodissociation regions, we estimate that the far-ultraviolet (FUV) radiation field in the disk is ∼10 ^3.5 G _0 , in agreement with previous estimates. In the outflow, however, the FUV radiation field is 2–3 orders of magnitudes lower, which may explain the high fraction of [C ii ] arising from the neutral medium in the wind.

The surface densities of gas, dust, and stars provide a window into the physics of star formation that, until the advent of high-resolution far-IR/submillimeter observations, has been historically difficult to assess among dusty galaxies. To study the link between IR surface densities and dust properties, we leverage the Atacama Large Millimetre/Submillimetre Array archive to measure the extent of cold dust emission in 15 z ∼ 2 IR-selected galaxies selected on the basis of having available mid-IR spectroscopy from Spitzer. We use the mid-IR spectra to constrain the relative balance between dust heating from star formation and active galactic nuclei (AGNs), and to measure emission from polycylic aromatic hydrocarbons (PAHs), small dust grains that play a key role in the photoelectric heating of gas. In general, we find that dust-obscured star formation at high IR surface densities exhibits similar properties at low and high redshift, namely, local luminous IR galaxies (LIRGs) have comparable PAH luminosity to total dust mass ratios as high- z galaxies, and star formation at z ∼ 0–2 is more efficient at high IR surface densities despite the fact that our sample of high- z galaxies is closer to the main sequence than local LIRGs. High star formation efficiencies are coincident with a decline in the PAH-to-IR luminosity ratio reminiscent of the deficit observed in far-IR fine-structure lines. Changes in the gas and dust conditions arising from high star formation surface densities might help drive the star formation efficiency up. This could help explain the high efficiencies needed to reconcile star formation and gas volume densities in dusty galaxies at cosmic noon.