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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 We introduce a prescription for estimating the flux of the 7.7μm and 11.3μm polycyclic aromatic hydrocarbon (PAH) features from broadband JWST/MIRI images. Probing PAH flux with MIRI imaging data has advantages in field of view, spatial resolution, and sensitivity compared with MIRI spectral maps, but comparisons with spectra are needed to calibrate these flux estimations over a wide variety of environments. For 267 MIRI/MRS spectra from independent regions in the four luminous infrared galaxies (LIRGs) in the Great Observatories All-sky LIRG Survey Early Release Science program, we derive synthetic filter photometry and directly compare estimated PAH fluxes to those measured from detailed spectral fits. We find that for probing PAH 7.7μm, the best combination of filters is F560W, F770W, and either F1500W or F2100W, and the best for PAH 11.3μm is F560W, F1000W, F1130W, and F1500W. The prescription with these combinations yields predicted flux densities that typically agree with values from spectral decomposition within ∼7% and ∼5% for PAH 7.7 and 11.3μm, respectively. 

Abstract Low-mass galaxy pair fractions are understudied, and it is unclear whether low-mass pair fractions evolve in the same way as more massive systems over cosmic time. In the era of JWST, Roman, and Rubin, selecting galaxy pairs in a self-consistent way will be critical to connect observed pair fractions to cosmological merger rates across all mass scales and redshifts. Utilizing the Illustris TNG100 simulation, we create a sample of physically associated low-mass (10⁸<M_*< 5 × 10⁹M_⊙) and high-mass (5 × 10⁹<M_*< 10¹¹M_⊙) pairs betweenz= 0 and 4.2. The low-mass pair fraction increases fromz= 0 to 2.5, while the high-mass pair fraction peaks atz= 0 and is constant or slightly decreasing atz> 1. Atz= 0 the low-mass major (1:4 mass ratio) pair fraction is 4× lower than high-mass pairs, consistent with findings for cosmological merger rates. We show that separation limits that vary with the mass and redshift of the system, such as scaling by the virial radius of the host halo (r_sep< 1R_vir), are critical for recovering pair fraction differences between low-mass and high-mass systems. Alternatively, static physical separation limits applied equivalently to all galaxy pairs do not recover the differences between low- and high-mass pair fractions, even up to separations of 300 kpc. Finally, we place isolated mass analogs of Local Group galaxy pairs, i.e., Milky Way (MW)–M31, MW–LMC, LMC–SMC, in a cosmological context, showing that isolated analogs of LMC–SMC-mass pairs and low-separation (<50 kpc) MW–LMC-mass pairs are 2–3× more common atz≳ 2–3. 

Abstract 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 3.3μm 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 [Neiii]/[Neii] > 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 3.3μm–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 3.3μm PAH-derived star formation rate (SFR) in the ring is 27% higher than that inferred from the [Neii] and [Neiii] emission lines, the integrated SFR derived from the 3.3μm 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. 

Abstract 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 [Feii], H₂, 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 H₂/Brγand [Feii]/Paβemission 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 Paαvelocity 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. 

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 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. 

We quantify the frequency of companions of low-redshift (0.013 < z < 0.0252) dwarf galaxies (2 × 108 M⊙ < Mstar < 5 × 109 M⊙) that are isolated from more massive galaxies in SDSS and compare against cosmological expectations using mock observations of the Illustris simulation. Dwarf multiples are defined as two or more dwarfs that have angular separations >55 arcsec, projected separations rp < 150 kpc, and relative line-of-sight velocities ΔVLOS < 150 km s-1. While the mock catalogues predict a factor of two more isolated dwarfs than observed in SDSS, the mean number of observed companions per dwarf is Nc ˜ 0.04, in good agreement with Illustris when accounting for SDSS sensitivity limits. Removing these limits in the mock catalogues predicts Nc ˜ 0.06 for future surveys (LSST, DESI), which will be complete to Mstar = 2 × 108 M⊙. The 3D separations of mock dwarf multiples reveal a contamination fraction of ˜40 per cent in observations from projection effects. Most isolated multiples are pairs; triples are rare and it is cosmologically improbable that bound groups of dwarfs with more than three members exist within the parameter range probed in this study. We find that <1 per cent of LMC-analogues in the field have an SMC-analogue companion. The fraction of dwarf "Major Pairs" (stellar mass ratio >1:4) steadily increases with decreasing Primary stellar mass, whereas the cosmological "Major Merger rate" (per Gyr) has the opposite behaviour. We conclude that cosmological simulations can be reliably used to constrain the fraction of dwarf mergers across cosmic time. 

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. 

Abstract 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 4.9–7.6μm region are examined to study the gas dynamics influenced by the central AGN. The low-ionization [Feii]λ5.34μm and [Arii]λ6.99μm lines are bright on the nucleus and in the starburst ring, as opposed to H₂S(5)λ6.91μm, which is strongly peaked at the center and surrounding ISM. The high-ionization [Mgv] 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 H₂and [Feii] ∼ 180 pc from the AGN that also show highL(H₂)/L(PAH) andL([Feii])/L(Pfα) 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.