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Abstract We present high-resolution Keck Cosmic Web Imager and MUSE integral field unit spectroscopy of VV 114, a local IR-luminous merger undergoing a vigorous starburst and showing evidence of galactic-scale feedback. The high-resolution data allow for spectral deblending of the optical emission lines and reveal a broad emission line component (σ_broad ∼ 100–300 km s⁻¹) with line ratios and kinematics consistent with a mixture of ionization by stars and radiative shocks. The shock fraction (percentage of ionization due to shocks) in the high-velocity gas is anticorrelated with the projected surface number density of resolved star clusters, and we find that the radial density profiles around clusters are fit well by models of adiabatically expanding cluster winds driven by massive stellar winds and supernovae (SNe). The total kinetic power estimated from the cluster wind models matches the wind + SN mechanical energy deposition rate estimated from the soft-band X-ray luminosity, indicating that at least 70% of the shock luminosity in the galaxy is driven by the star clusters. Hubble Space Telescope narrowband near-IR imaging reveals embedded shocks in the dust-buried IR nucleus of VV 114E. Most of the shocked gas is blueshifted with respect to the quiescent medium, and there is a close spatial correspondence between the shock map and the Chandra soft-band X-ray image, implying the presence of a galactic superwind. The energy budget of the superwind is in close agreement with the total kinetic power of the cluster winds, confirming the superwind is driven by the starburst. 

Abstract 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, H₂O, C₂H₂, 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 2.3μm CO bandheads, characteristic of cool stellar atmospheres, in the star-forming regions, but not toward the AGN. Surprisingly, at 4.7μm, we find highly excited CO (T_ex≈ 700–800 K out to at least rotational levelJ= 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 H₂O 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. 

Characterizing the physical conditions (density, temperature, ionization state, metallicity, etc) of the interstellar medium is critical to improving our understanding of the formation and evolution of galaxies. In this work, we present a multi-line study of the interstellar medium in the host galaxy of a quasar atz ≈ 6.4, that is, when the universe was 840 Myr old. This galaxy is one of the most active and massive objects emerging from the dark ages and therefore represents a benchmark for models of the early formation of massive galaxies. We used the Atacama Large Millimeter Array to target an ensemble of tracers of ionized, neutral, and molecular gas, namely the following fine-structure lines: [O III] 88 μm, [N II] 122 μm, [C II] 158 μm, and [C I] 370 μm – as well as the rotational transitions of CO(7–6), CO(15–14), CO(16–15), and CO(19–18); OH 163.1 μm and 163.4 μm; along with H₂O 3(0,3)–2(1,2), 3(3,1)–4(0,4), 3(3,1)–3(2,2), 4(0,4)–3(1,3), and 4(3,2)–4(2,3). All the targeted fine-structure lines were detected, along with half of the targeted molecular transitions. By combining the associated line luminosities with the constraints on the dust temperature from the underlying continuum emission and predictions from photoionization models of the interstellar medium, we find that the ionized phase accounts for about one-third of the total gaseous mass budget and is responsible for half of the total [C II] emission. This phase is characterized by a high density (n ∼ 180 cm⁻³) that typical of HII regions. The spectral energy distribution of the photoionizing radiation is comparable to that emitted by B-type stars. Star formation also appears to be driving the excitation of the molecular medium. We find marginal evidence for outflow-related shocks in the dense molecular phase, but not in other gas phases. This study showcases the power of multi-line investigations in unveiling the properties of the star-forming medium in galaxies at cosmic dawn. 

Abstract 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 (<5 Myr) stellar populations and more than half of them are coincident with the mid-infrared (MIR) emission peaks. These younger, dusty star-forming regions account for ∼6% and ∼17% of the total 1.5 and 4.4 μ m luminosity of the starburst ring, respectively. Thanks to JWST, we find a significant number of young dusty sources that were previously unseen due to dust extinction. The newly identified 28 young sources are a significant increase compared to the number of HST-detected young sources (4–5). This makes the total percentage of the young population rise from ∼15% to 48%. These results illustrate the effectiveness of JWST in identifying and characterizing previously hidden star formation in the densest star-forming environments around active galactic nuclei (AGN). 

Abstract We have used the Mid-InfraRed Instrument (MIRI) on the James Webb Space Telescope (JWST) to obtain the first spatially resolved, mid-infrared images ofIIZw096, a merging luminous infrared galaxy (LIRG) atz= 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 × 10¹¹L_⊙, arises from a source no larger than 175 pc in radius, suggesting a luminosity density of at least 3–5 × 10¹²L_⊙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.