Studying the interstellar medium (ISM) in merging high-redshift galaxies is crucial for understanding early galaxy assembly, star formation, and black hole growth, predicted by hierarchical ΛCDM models. Deep imaging and spatially resolved spectroscopy with JWST enable unprecedented insight into these processes, even for galaxies in the Epoch of Reionization. We present NIRSpec and MIRI integral field spectroscopy and MIRI imaging of the merging galaxy Gz9p3 at z=9.3 of the UV and optical rest-frame showing a clumpy morphology in the continuum as well as line emission covering the entire galaxy over a range of 5 kpc from the central clump to the tail region. We analyze the integrated spectrum as well as different apertures in the galaxy allowing a spatially resolved characterization of the ionized ISM of this galaxy. We compare our measurements with archival NIRCam imaging and ALMA data. We measure a total star formation rate of 13.4 ± 1.8 Msun yr^-1, a metallicity of 12+log(O/H) = 7.84 ± 0.05 and ξ_ion= 25.4 ± 0.1 erg^-1 Hz and a burstiness parameter of 0.9 ± 0.1 for the integrated spectrum. We find large spatial differences in these parameters between the central clump and the tail region. The optical [OIII] emission peaks in the main galaxy, the far-infrared [OIII] emission peaks towards the tail, indicating different physical conditions in the ISM of the tail and main galaxy. This study presents the spatially resolved ISM analyses of a galaxy at z>9, revealing nebular line emission and strong spatial variations in star formation, metallicity, physical conditions, and ionizing efficiency. The results indicate a recent, metal-poor starburst in a tail alongside a more evolved, enriched central clump with evidence for extreme excitation. This demonstrates the power of spatially resolved JWST spectroscopy of galaxies in the Epoch of Reionization.

Context. The recently launched James Webb Space Telescope (JWST) is opening new observing windows on the distant Universe. Among JWST's instruments, the Mid Infrared Instrument (MIRI) offers the unique capability of imaging observations at wavelengths of lambda > 5 mu m. This enables unique access to the rest frame near-infrared (NIR, lambda >= 1 mu m) emission from galaxies at redshifts of z > 4 and the visual (lambda greater than or similar to 5000 & Aring;) rest frame for z > 9. We report here on the guaranteed time observations (GTO), from the MIRI European Consortium, of the Hubble Ultra Deep Field (HUDF), forming the MIRI Deep Imaging Survey (MIDIS), consisting of an on source integration time of similar to 41 hours in the MIRI/F560W (5.6 mu m) filter. The F560W filter was selected since it would produce the deepest data in terms of AB magnitudes in a given time. To our knowledge, this constitutes the longest single filter exposure obtained with JWST of an extragalactic field as of yet. Aims. The HUDF is one of the most observed extragalactic fields, with extensive multi-wavelength coverage, where (before JWST) galaxies up to z similar to 7 have been confirmed, and at z > 10 suggested, from HST photometry. We aim to characterise the galaxy population in HUDF at 5.6 mu m, enabling studies such as: the rest frame NIR morphologies for galaxies at z less than or similar to 4.6, probing mature stellar populations and emission lines in z > 6 sources, intrinsically red and dusty galaxies, and active galactic nuclei (AGNs) and their host galaxies at intermediate redshifts. Methods. We reduced the MIRI data using the official JWST pipeline, augmented by in-house custom scripts. We measured the noise characteristics of the resulting image. Galaxy photometry was obtained, and photometric redshifts were estimated for sources with available multi-wavelength photometry (and compared to spectroscopic redshifts when available). Results. Over the deepest part of our image, the 5 sigma point source limit is 28.65 mag AB (12.6 nJy), similar to 0.35 mag better than predicted by the JWST exposure time calculator. We find similar to 2500 sources, the overwhelming majority of which are distant galaxies, but we note that spurious sources likely remain at faint magnitudes due to imperfect cosmic ray rejection in the JWST pipeline. More than 500 galaxies with available spectroscopic redshifts, up to z approximate to 11, have been identified, the majority of which are at z < 6. More than 1000 galaxies have reliable photometric redshift estimates, of which similar to 25 are at 6 < z < 12. The point spread function in the F560W filter has a full width at half maximum (FWHM) of approximate to 0.2 '' (corresponding to 1.4 kpc at z = 4), allowing the NIR rest frame morphologies and stellar mass distributions to be resolved for z < 4.5. Moreover, > 100 objects with very red NIRCam vs MIRI (3.6-5.6 mu m > 1 mag) colours have been found, suggestive of dusty or old stellar populations at high redshifts. Conclusions. We conclude that MIDIS surpasses preflight expectations and that deep MIRI imaging has great potential to characterise the galaxy population from cosmic noon to dawn.

The study of the atmosphere of exoplanets orbiting white dwarfs is a largely unexplored field. With WD 0806-661 b, we present the first deep dive into the atmospheric physics and chemistry of a cold exoplanet around a white dwarf. We observed WD 0806-661 b using JWST’s Mid-InfraRed Instrument Low-Resolution Spectrometer, covering the wavelength range from 5 to 12 μ m, and the Imager, providing us with 12.8, 15, 18, and 21 μ m photometric measurements. We carried the data reduction of those data sets, tackling second-order effects to ensure a reliable retrieval analysis. Using the T au RE x retrieval code, we inferred the pressure–temperature structure, atmospheric chemistry, mass, and radius of the planet. The spectrum of WD 0806-661 b is shaped by molecular absorption of water, ammonia, and methane, consistent with a cold Jupiter atmosphere, allowing us to retrieve their abundances. From the mixing ratio of water, ammonia, and methane we derive C/O = 0.34 ± 0.06, C / N = 14 . 4 − 1.8 + 2.5 , and N/O = 0.023 ± 0.004 and the ratio of detected metals as a proxy for metallicity. We also derive upper limits for the abundance of CO and CO 2 (1.2 × 10 −6 and 1.6 × 10 −7 , respectively), which were not detected by our retrieval models. While our interpretation of WD 0806-661 b’s atmosphere is mostly consistent with our theoretical understanding, some results—such as the lack of evidence for water clouds, an apparent increase in the mixing ratio of ammonia at low pressure, or the retrieved mass at odds with the supposed age—remain surprising and require follow-up observational and theoretical studies to be confirmed.

Context . We report MIRI-JWST coronagraphic observations at 11.3 and 15.5 μm of the debris disk around the young star HD 106906. The wavelength range is sensitive to the thermal emission of the dust heated by the central star. Aims . The observations were made to characterize the structure of the disk through the thermal emission, to search for clues to the presence of a central void of dust particles, and to derive the mass of the dust and the temperature distribution. Another goal was also to constrain the size distribution of the grains. Methods . The data were reduced and calibrated using the JWST pipeline. The analysis was based on a forward-modeling of the images using a multiparameter radiative transfer model coupled to an optical code for coronagraphy processing. Results . The disk is clearly detected at both wavelengths. The slight asymmetry is geometrically consistent with the asymmetry observed in the near-IR, but it is inconsistent the brightness distribution. The observed structure is well reproduced with a model of a disk (or belt) with a critical radius 70 au, a mildly inward-increasing density (index 2) and a steeper decrease outward (index −6). This indication of a filled disk inside the critical radius is inconsistent with sculpting from an inner massive planet. The size distribution of the grains that cause the mid-IR emission is well constrained by the flux ratio at the two wavelengths : 0.45–10 and 0.65–10 μm for silicate and graphite grains, respectively. The minimum size is consistent with predictions of blowout through radiative pressure. Conclusions . We derive a mass of the dust that causes the mid-IR emission of 3.3–5.0 10 −3 M ⊕ . When the larger grains (up to 1 cm) that cause the millimeter emission are included, we extrapolate this mass to 0.10–0.16 M ⊕ . We point out to that this is fully consistent with ALMA observations of the disk in terms of dust mass and of its millimeter flux. We estimate the average dust temperature in the planetesimal belt to be 74 K, but the temperature range within the whole disk is rather wide: from 40 to 130 K.

We present full 3-28 micron JWST MIRI/MRS and NIRSpec/IFU spectra of the western nucleus of Arp 220, the nearest ultraluminous infrared galaxy. This nucleus has long been suggested to possibly host an embedded Compton-thick AGN. Millimeter observations of the dust continuum suggest the presence of a distinct 20 pc core with a dust temperature of $T_\mathrm{d} \gtrsim 500~\mathrm{K}$, in addition to a 100 pc circumnuclear starburst disk. However, unambiguously identifying the nature of this core is challenging, due to the immense obscuration, the nuclear starburst activity, and the nearby eastern nucleus. With the JWST integral field spectrographs, we can, for the first time, separate the two nuclei across this full wavelength range, revealing a wealth of molecular absorption features towards the western nucleus. We analyse the rovibrational bands detected at 4-22 micron, deriving column densities and rotational temperatures for 10 distinct species. Optically thick features of C$_2$H$_2$, HCN and HNC suggest that this molecular gas is hidden behind a curtain of cooler dust, and indicate that the column densities of C$_2$H$_2$ and HCN are an order of magnitude higher than previously derived from Spitzer observations. We identify a warm HCN component with rotational temperature $T_\mathrm{rot} = 330~\mathrm{K}$, which we associate with radiative excitation by the hot inner nucleus. We propose a geometry where the detected molecular gas is located in the inner regions of the starburst disk, directly surrounding the hot 20 parsec core. The chemical footprint of the western nucleus is reminiscent of that of hot cores, with additional evidence for shocks. No evidence for the presence of an AGN in the form of X-ray-driven chemistry or extreme excitation is found.

Excited by our scientific results and the accessibility of the night sky for everyone, we instinctively think of the public engagement, outreach, and educational opportunities that astronomy and JWST provide when asked about societal impact. All stakeholders in the JWST mission have highly effective programmes in this area. In public talks and school programmes people clearly relate to the inspirational nature of the images and science now being produced and to the team work and international collaboration needed to bring JWST to launch. In this summary to set the scene for discussing the societal impact of JWST and astronomy, I indicate some of the other types of societal impact. For our governmental agencies that invest in missions the interest is very often societal impact in the sense of economic impact and progress. Below some are some examples of different types of such economic impact.

We present full 3-28 mu m JWST MIRI/MRS and NIRSpec/IFU spectra of the western nucleus of Arp 220, the nearest ultraluminous infrared galaxy. This nucleus has long been suggested to possibly host an embedded Compton-thick AGN. Millimetre observations of the dust continuum suggest the presence of a distinct 20 pc core with a dust temperature of T-d greater than or similar to 500 K, in addition to a 100 pc circumnuclear starburst disc. However, unambiguously identifying the nature of this core is challenging, due to the immense obscuration, the nuclear starburst activity, and the nearby eastern nucleus. With the JWST integral field spectrographs, for the first time we can separate the two nuclei across this full wavelength range, revealing a wealth of molecular absorption features towards the western nucleus. We analysed the rovibrational bands detected at 4-22 mu m, deriving column densities and rotational temperatures for ten distinct species. Optically thick features of C2H2, HCN, and HNC suggest that this molecular gas is hidden behind a curtain of cooler dust and indicate that the column densities of C2H2 and HCN are an order of magnitude higher than previously derived from Spitzer observations. We identified a warm HCN component with a rotational temperature of T-rot = 330 K, which we associate with radiative excitation by the hot inner nucleus. We propose a geometry where the detected molecular gas is located in the inner regions of the starburst disc, directly surrounding the hot 20 pc core. The chemical footprint of the western nucleus is reminiscent of that of hot cores, with additional evidence of shocks. Despite the molecular material's close proximity to the central source, no evidence for the presence of an AGN in the form of X-ray-driven chemistry or extreme excitation was found.

The recently launched James Webb Space Telescope (JWST) is opening new observing windows on the distant universe. Among JWST's instruments, the Mid Infrared Instrument (MIRI) offers the unique capability of imaging observations at wavelengths λ > 5μm. This enables unique access to the rest frame near infra-red (NIR, λ≥ 1) emission from galaxies at redshifts z>4 and the visual (λ≳ 5000Å) rest frame for z>9. We here report on the guaranteed time observations (GTO) from the MIRI European Consortium, of the Hubble Ultra Deep Field (HUDF), forming the MIRI Deep Imaging Survey (MIDIS), consisting of an on source integration time of ∼41 hours in the MIRI/F560W (5.6 μm) filter. To our knowledge, this constitutes the longest single filter exposure obtained with JWST of an extragalactic field as yet.

We present Virgil, a Mid-Infrared Instrument (MIRI) extremely red object detected with the F1000W filter as part of the MIRI Deep Imaging Survey observations of the Hubble Ultra Deep Field. Virgil is an Ly alpha emitter (LAE) at zspec = 6.6312 +/- 0.0019 (from the Very Large Telescope/MUSE) with a rest-frame UV-to-optical spectral energy distribution (SED) typical of LAEs at similar redshifts. However, MIRI observations reveal an unexpected extremely red color at rest-frame near-infrared (NIR) wavelengths, F444W - F1000W = 2.33 +/- 0.06. Such a steep rise in the NIR, completely missed without MIRI imaging, is poorly reproduced by models including only stellar populations and hints toward the presence of an active galactic nucleus, although alternative explanations such as extreme dust obscuration and strong nebular continuum and emission lines contribution due to young stellar ages cannot be completely ruled out. According to the shape of its overall SED, Virgil belongs to the recently discovered population of little red dots but displays an extended rest-frame UV-optical wavelength morphology following a 2D-S & eacute;rsic profile with an average index of n=0.93-0.31+0.85 and re=0.49-0.11+0.05 pkpc. Only at MIRI wavelengths, Virgil is unresolved due to the coarser point-spread function. This discovery demonstrates the crucial importance of deep MIRI surveys to reveal the true nature and properties of high-z galaxies that otherwise would be misinterpreted and raises the question of how common Virgil-like objects could be in the early Universe.

The newly accessible mid-infrared (MIR) window offered by the James Webb Space Telescope (JWST) for exoplanet imaging is expected to provide valuable information to characterize their atmospheres. In particular, coronagraphs on board the JWST Mid-InfraRed instrument (MIRI) are capable of imaging the coldest directly imaged giant planets at the wavelengths where they emit most of their flux. The MIRI coronagraphs have been specially designed to detect the NH3 absorption around 10.5 microns, which has been predicted by atmospheric models. We aim to assess the presence of NH3 while refining the atmospheric parameters of one of the coldest companions detected by directly imaging GJ 504 b. Its mass is still a matter of debate and depending on the host star age estimate, the companion could either be placed in the brown dwarf regime or in the young Jovian planet regime. We present an analysis of MIRI coronagraphic observations of the GJ 504 system. We took advantage of previous observations of reference stars to build a library of images and to perform a more efficient subtraction of the stellar diffraction pattern. We detected the presence of NH3 at 12.5 sigma in the atmosphere, in line with atmospheric model expectations for a planetary-mass object and observed in brown dwarfs within a similar temperature range. The best-fit model with Exo-REM provides updated values of its atmospheric parameters, yielding a temperature of Teff = 512 K and radius of R = 1.08 RJup. These observations demonstrate the capability of MIRI coronagraphs to detect NH3 and to provide the first MIR observations of one of the coldest directly imaged companions. Overall, NH3 is a key molecule for characterizing the atmospheres of cold planets, offering valuable insights into their surface gravity. These observations provide valuable information for spectroscopic observations planned with JWST.

With a temperature of ∼285 K, WISEJ0855–0714 (hereafter, WISE 0855) is the coldest brown dwarf observed thus far. Studying such cold gas giants allows us to probe the atmospheric physics and chemistry of evolved objects that resemble Solar System gas giants. Using James Webb Space Telescope (JWST), we obtained observations to characterize WISE 0855's atmosphere, focusing on vertical variation in the water steam abundance, measuring trace gas abundances, and obtaining the bulk parameters for this cold object. We observed the ultra-cool dwarf WISE 0855 using the Mid-Infrared Instrument Medium Resolution Spectrometer (MIRI/MRS) on board JWST at a spectral resolution of up to 3'750. We combined the observation with published data from the Near-Infrared Spectrograph (NIRSpec) G395M and PRISM modes, yielding a spectrum ranging from 0.8 to 22 µm. We applied atmospheric retrievals using petitRADTRANS to measure the atmospheric abundances, pressure-temperature structure, radius, and gravity of the brown dwarf. We also employed publicly available clear and cloudy self-consistent grid models to estimate the bulk properties of the atmosphere such as the effective temperature, radius, gravity, and metallicity. Atmospheric retrievals have constrained a variable water abundance profile in the atmosphere, as predicted by equilibrium chemistry. We detected the mathrm NH_3 isotopolog and inferred a ratio of volume fraction of mathrm NH_3 /mathrm NH_3 for the clear retrieval. We measured the bolometric luminosity by integrating the presented spectrum, obtaining a value of mathrm log(L/ L _⊙) = -7.291 ± 0.008. The detected water depletion indicates that water condenses out in the upper atmosphere due to the very low effective temperature of WISE 0855. The height in the atmosphere where this occurs is covered by the MIRI/MRS data, thereby demonstrating the potential of MIRI to characterize the atmospheres of cold gas giants. After comparing the data to retrievals and self-consistent grid models, we did not detect any signs of water ice clouds, although their spectral features have been predicted in previous studies.

We report MIRI-JWST coronagraphic observations at 11.3 and 15.5 mic of the debris disk around the young star HD 106906. The observations were made to characterize the structure, temperature and mass of the disk through the thermal emission of the dust heated by the central star. Another goal was also to constrain the size distribution of the grains. The data were reduced and calibrated using the JWST pipeline. The analysis was based on a forward-modeling of the images using a multiparameter radiative transfer model coupled to an optical code for coronagraphy processing. The disk is clearly detected at both wavelengths. The slight asymmetry is geometrically consistent with the asymmetry observed in the near-IR, but it is inconsistent the brightness distribution. The observed structure is well reproduced with a model of a disk (or belt) with a critical radius 70 au, a mildly inward-increasing density (index 2) and a steeper decrease outward (index -6). This indication of a filled disk inside the critical radius is inconsistent with sculpting from an inner massive planet. The size distribution of the grains that cause the mid-IR emission is well constrained by the flux ratio at the two wavelengths : 0.45 10 mic and 0.65 10 mic for silicate and graphite grains, respectively. The minimum size is consistent with predictions of blowout through radiative pressure. We derive a mass of the dust that causes the mid-IR emission of 3.3 5.0 E3 Mearth. When the larger grains (up to 1 cm) that cause the millimeter emission are included, we extrapolate this mass to 0.10 0.16 Mearth. We point out to that this is fully consistent with ALMA observations of the disk in terms of dust mass and of its millimeter flux. We estimate the average dust temperature in the planetesimal belt to be 74 K, and a temperature range within the whole disk from 40 to 130 K.

This work aims to measure the mass accretion rate, the accretion luminosity, and more generally the physical conditions of the warm emitting gas in the inner disk of the very low-mass star 2MASS-J16053215-1933159. We investigate the source mid-infrared spectrum for atomic and molecular hydrogen line emission. We present the full James Webb Space Telescope (JWST) Mid-InfraRed Instrument (MIRI) Medium Resolution Spectrometer (MRS) spectrum of the protoplanetary disk around the very low-mass star 2MASS-J16053215-1933159 from the MINDS GTO program, previously shown to be abundant in hydrocarbon molecules. We analyzed the atomic and molecular hydrogen lines in this source by fitting one or multiple Gaussian profiles. We then built a rotational diagram for the H2 lines to constrain the rotational temperature and column density of the gas. Finally, we compared the observed atomic line fluxes to predictions from two standard emission models. We identify five molecular hydrogen pure rotational lines and 16 atomic hydrogen recombination lines. The spectrum indicates optically thin emission for both species. We use the molecular hydrogen lines to constrain the mass and temperature of the warm emitting gas. The HI (7-6) recombination line is used to measure the mass accretion rate and luminosity onto the central source. HI recombination lines can also be used to derive the physical properties of the gas using atomic recombination models. The JWST-MIRI MRS observations for the very low-mass star 2MASS-J16053215-1933159 reveal a large number of emission lines, many originating from atomic and molecular hydrogen because we are able to look into the disk warm molecular layer. Their analysis constrains the physical properties of the emitting gas and showcases the potential of JWST to deepen our understanding of the physical and chemical structure of protoplanetary disks

The first JWST/MIRI photometric observations of TRAPPIST-1 b allowed for the detection of the thermal emission of the planet at 15 μm , suggesting that the planet could be a bare rock with a zero albedo and no redistribution of heat. Here we present five new occultations of TRAPPIST-1 b observed with MIRI in an additional photometric band at 12.8 μm . We perform a joint fit of the 10 eclipses and derive a planet-to-star flux ratio of 452 ± 86 ppm and 775 ± 90 ppm at 12.8 μm and 15 μm , respectively. We test a large range of models and find that the data can be well fitted by either an airless planet model with an unweathered (fresh) ultramafic surface, that could be indicative of relatively recent geological processes, or, more surprisingly, by a thick pure CO 2 atmosphere with photochemical hazes that create a temperature inversion and results in the CO 2 feature being seen in emission. Our results highlight the challenges in accurately determining a planet’s atmospheric or surface nature solely from broadband filter measurements of its emission, but also point towards two very interesting scenarios that will be further investigated with the forthcoming phase curve of TRAPPIST-1 b.

The Mid-Infrared Instrument (MIRI) aboard the James Webb Space Telescope (JWST) provides the observatory with a huge advance in mid-infrared imaging and spectroscopy covering the wavelength range of 5 to 28 microns. This paper describes the performance and characteristics of the MIRI imager as understood during observatory commissioning activities, and through its first year of science operations. We discuss the measurements and results of the imager's point spread function, flux calibration, background, distortion and flat fields as well as results pertaining to best observing practices for MIRI imaging, and discuss known imaging artefacts that may be seen during or after data processing. Overall, we show that the MIRI imager has met or exceeded all its pre-flight requirements, and we expect it to make a significant contribution to mid-infrared science for the astronomy community for years to come.

The multi planet system HR8799 is the first target observed with MIRI's coronagraphs as part of the MIRI-EC Guaranteed Time Observations exoplanets programme in Nov. 2022. We obtained deep observations in three coronagraphic filters from 10 to 15mic (F1065C, F1140C, F1550C), and one standard imaging filter at 20 mic (F2100W), with the goal to extract the photometry of the four planets, as well as to detect and investigate the distribution of circumstellar dust. Using dedicated observations of a reference star, we tested several algorithms to subtract the stellar diffraction pattern while preserving the fluxes of planets, which can be significantly affected by over-subtraction. Measuring correctly the planet's flux values requires accounting for the attenuation by the coronagraphs as a function of their position, and to estimate the normalisation with respect to the central star. We tested several procedures to derive averaged photometric values and error bars. These observations have enabled us to obtain two main results. First of all, the four planets in the system are well recovered, and their mid-IR fluxes, combined with near-IR flux values from the literature, are compared to two exoplanet atmosphere models, ATMO and Exo-REM. As a main outcome, the MIRI photometric data points imply larger radii (0.86 or 1.07 RJ for planet b) and cooler temperatures (950 or 1100 K for planet b), especially for planet b, in better agreement with evolutionary models. Second of all, these JWST/MIRI coronagraphic data also deliver the first spatially resolved detection of the inner warm debris disk, the radius of which is constrained to about 15 au, with flux densities comparable, but lower than former unresolved spectroscopic measurements with Spitzer. abridged...

We study the stellar population properties of 182 spectroscopically-confirmed (MUSE/VLT) Lyman-$\alpha$ emitters (LAEs) and 450 photometrically-selected Lyman-Break galaxies (LBGs) at z = 2.8 - 6.7 in the Hubble eXtreme Deep Field (XDF). Leveraging the combined power of HST and JWST NIRCam and MIRI observations, we analyse their rest-frame UV-through-near-IR spectral energy distributions (SEDs) with MIRI playing a crucial role in robustly assessing the LAE's stellar mass and ages. Our LAEs are low-mass objects (log$_{10}$(M$_\star$[M$_\odot$]) ~ 7.5), with little or no dust extinction (E(B - V) ~ 0.1) and a blue UV continuum slope ($\beta$ ~ -2.2). While 75% of our LAEs are young (< 100 Myr), the remaining 25% have significantly older stellar populations (> 100 Myr). These old LAEs are statistically more massive, less extinct and have lower specific star formation rate (sSFR) compared to young LAEs. Besides, they populate the M$_\star$ - SFR plane along the main-sequence (MS) of star-forming galaxies, while young LAEs populate the starburst region. The comparison between the LAEs properties to those of a stellar-mass matched sample of LBGs shows no statistical difference between these objects, except for the LBGs redder UV continuum slope and marginally larger E(B - V) values. Interestingly, 48% of the LBGs have ages < 10 Myr and are classified as starbursts, but lack detectable Ly$\alpha$ emission. This is likely due to HI resonant scattering and/or selective dust extinction. Overall, we find that JWST observations are crucial in determining the properties of LAEs and shedding light on the properties and similarities between LAEs and LBGs.

Context. Understanding the physical conditions of circumstellar material around young stars is crucial to star and planet formation studies. In particular, very low-mass stars (M★ < 0.2 M⊙) are interesting sources to characterize as they are known to host a diverse population of rocky planets. Molecular and atomic hydrogen lines can probe the properties of the circumstellar gas. Aims. This work aims to measure the mass accretion rate, the accretion luminosity, and more generally the physical conditions of the warm emitting gas in the inner disk of the very low-mass star 2MASS-J16053215-1933159. We investigate the source mid-infrared spectrum for atomic and molecular hydrogen line emission. Methods. We present the full James Webb Space Telescope (JWST) Mid-InfraRed Instrument (MIRI) Medium Resolution Spectrometer (MRS) spectrum of the protoplanetary disk around the very low-mass star 2MASS-J16053215-1933159 from the MINDS GTO program, previously shown to be abundant in hydrocarbon molecules. We analyzed the atomic and molecular hydrogen lines in this source by fitting one or multiple Gaussian profiles. We then built a rotational diagram for the H2 lines to constrain the rotational temperature and column density of the gas. Finally, we compared the observed atomic line fluxes to predictions from two standard emission models. Results. We identify five molecular hydrogen pure rotational lines and 16 atomic hydrogen recombination lines in the 5–20 µm spectral range. The spectrum indicates optically thin emission for both species. We use the molecular hydrogen lines to constrain the mass and temperature of the warm emitting gas. We derive a total gas mass of only 2.3 × 10−5 MJup and a temperature of 635 K for the warm H2 gas component located in the very inner disk (r < 0.033 au), which only accounts for a small fraction of the upper limit for the disk mass from continuum observations (0.2 MJup). The HI (7−6) recombination line is used to measure the mass accretion rate (4.0 × 10−10 M⊙ yr−1) and luminosity (3.1 × 10−3 L⊙) onto the central source. This line falls close to the HI (11−8) line, however at the spectral resolution of JWST MIRI we managed to measure both separately. Previous studies based on Spitzer have measured the combined flux of both lines to measure accretion rates. HI recombination lines can also be used to derive the physical properties of the gas using atomic recombination models. The model predictions of the atomic line relative intensities constrain the atomic hydrogen density to about 109−1010 cm−3 and temperatures up to 5000 K. Conclusions. The JWST-MIRI MRS observations for the very low-mass star 2MASS-J16053215-1933159 reveal a large number of emission lines, many originating from atomic and molecular hydrogen because we are able to look into the disk warm molecular layer. Their analysis constrains the physical properties of the emitting gas and showcases the potential of JWST to deepen our understanding of the physical and chemical structure of protoplanetary disks.

Context . The Medium Resolution integral field Spectrometer (MRS) of the Mid-Infrared Instrument (MIRI) on board the James Webb Space Telescope (JWST) performs spectroscopy between 5 and 28 µm, with a field of view varying from ~13 to ~56 sq. arcsec. The optics of the MRS introduce substantial distortion and this needs to be rectified in order to reconstruct the observed astrophysical scenario. Aims . We aim to use data from the JWST/MIRI commissioning and cycle 1 calibration phase to derive the MRS geometric distortion and astrometric solution, a critical step in the calibration of MRS data. These solutions come in the form of transform matrices that map the detector pixels to spatial coordinates of a local MRS coordinate system called α / β , to the global JWST observatory coordinates V 2 and V 3 ( V 2+ V 3). Methods . For every MRS spectral band and each slice dispersed on the detector, we fit the transform of detector pixels to α / β by a two-dimensional (2D) polynomial, using a raster of point source observations. The dispersed trace of the point source on the detector was initially estimated by fitting a one-dimensional (1D) empirical function and then iterating on the first distortion solution using forward modelling of the point spread function model based on the webbpsf python package. A polynomial transform was used to map the coordinates from α/ β to V 2+ V 3. Results . We calibrated the distortion of all 198 discrete slices of the MIRI/MRS integral field units and derived an updated field of view (FoV) for each MRS spectral band. The precision of the distortion solution is estimated to be better than one-tenth of a spatial resolution element, with a root mean square (rms) of 10 milli-arc-second (mas) at 5 µm, to 23 mas at 27 µm. Finally, we found that the wheel positioning repeatability causes an additional astrometric rms error of 30 mas. Conclusions . We demonstrate the application of the MRS astrometric calibration strategy and analysis for all four integral field units and all spectral bands of the MRS that enable the calibration of MRS spectra. This is a critical step in the data pipeline of every MRS observation. The distortion calibration was folded into the JWST pipeline in the Calibration Reference Data System (CRDS) context (jwst_1094.pmap), meeting the pre-launch requirement, with an estimated total astrometric uncertainty of 50 mas.

The rapid assembly of the first supermassive black holes is an enduring mystery. Until now, it was not known whether quasar 'feeding' structures (the 'hot torus') could assemble as fast as the smaller-scale quasar structures. We present JWST/MRS (rest-frame infrared) spectroscopic observations of the quasar J1120+0641 at z = 7.0848 (well within the epoch of reionization). The hot torus dust was clearly detected at lambda rest similar or equal to 1.3 mu m, with a black-body temperature of Tdust=1,413.5-7.4+5.7\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${T}_{{{{\rm{dust}}}}}=\text{1,413.5}_{-7.4}<^>{+5.7}$$\end{document} K, slightly elevated compared to similarly luminous quasars at lower redshifts. Importantly, the supermassive black hole mass of J1120+0641 based on the H alpha line (accessible only with JWST), MBH = 1.52 +/- 0.17 x 109 M circle dot, is in good agreement with previous ground-based rest-frame ultraviolet Mg ii measurements. Comparing the ratios of the H alpha, Pa alpha and Pa beta emission lines to predictions from a simple one-phase Cloudy model, we find that they are consistent with originating from a common broad-line region with physical parameters that are consistent with lower-redshift quasars. Together, this implies that J1120+0641's accretion structures must have assembled very quickly, as they appear fully 'mature' less than 760 Myr after the Big Bang. A JWST/MIRI spectrum of an early quasar in the mid-infrared indicates that J1120+0641 had a mature feeding structure 760 Myr after the Big Bang. This finding suggests that supermassive black holes and their torii build up surprisingly quickly.