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We present JWST/MIRI MRS spatially resolved ∼5 − 28 μm observations of the central ∼4 − 8 kpc of the ultraluminous infrared galaxy and broad absorption line quasar Mrk 231. These are part of the Mid-Infrared Characterization of Nearby Iconic galaxy Centers (MICONIC) program of the MIRI European Consortium guaranteed time observations. No high excitation lines (i.e., [Mg V] at 5.61 μm or [Ne V] at 14.32 μm) typically associated with the presence of an active galactic nucleus (AGN) are detected in the nuclear region of Mrk 231. This is likely due to the intrinsically X-ray weak nature of its quasar. Some intermediate ionization potential lines, for instance, [Ar III] at 8.99 μm and [S IV] at 10.51 μm, are not detected either, even though they are clearly observed in a star-forming region ∼920 pc south-east of the AGN. Thus, the strong nuclear mid-infrared (mid-IR) continuum is also in part hampering the detection of faint lines in the nuclear region. The nuclear [Ne III]/[Ne II] line ratio is consistent with values observed in star-forming galaxies. Moreover, we resolve for the first time the nuclear starburst in the mid-IR low-excitation line emission (size of ∼400 pc, FWHM). Several pieces of evidence also indicate that it is partly obscured even at these wavelengths. At the AGN position, the ionized and warm molecular gas emission lines have modest widths (W80 ∼ 300 km s−1). There are, however, weak blueshifted wings reaching velocities v02 ≃ − 400 km s−1 in [Ne II]. The nuclear starburst is at the center of a large (∼8 kpc), massive rotating disk with widely-spread, low velocity outflows. Given the high star formation rate of Mrk 231, we speculate that part of the nuclear outflows and the large-scale non-circular motions observed in the mid-IR are driven by its powerful nuclear starburst. [ABSTRACT FROM AUTHOR]

Dusty star-forming galaxies emit most of their light at far-infrared to millimeter wavelengths as their star formation is highly obscured. Far-infrared and millimeter observations have revealed their dust, neutral and molecular gas properties. The sensitivity of JWST at rest-frame optical and near-infrared wavelengths now allows the study of the stellar and ionized gas content. We investigate the spatially resolved distribution and kinematics of the ionized gas in GN20, a dusty star-forming galaxy at z = 4.0548. We present deep MIRI/MRS integral field spectroscopy of the near-infrared rest-frame emission of GN20. We detect spatially resolved Paα, out to a radius of 6 kpc, distributed in a clumpy morphology. The star formation rate derived from Paα (144 ± 9 M⊙ yr−1) is only 7.7 ± 0.5% of the infrared star formation rate (1860 ± 90 M⊙ yr−1). We attribute this to very high extinction (AV = 17.2 ± 0.4 mag, or AV, mixed = 44 ± 3 mag), especially in the nucleus of GN20, where only faint Paα is detected, suggesting a deeply buried starburst. We identify four, spatially unresolved, clumps in the Paα emission. Based on the double peaked Paα profile, we find that each clump consists of at least two sub-clumps. We find mass upper limits consistent with them being formed in a gravitationally unstable gaseous disk. The ultraviolet bright region of GN20 does not have any detected Paα emission, suggesting an age of more than 10 Myr for this region of the galaxy. From the rotation profile of Paα, we conclude that the gas kinematics are rotationally dominated and the vrot/σm = 3.8 ± 1.4 is similar to low-redshift luminous infrared galaxies. From the Paα kinematics, we cannot distinguish between a rotational profile of a large disk and a late stage merger mimicking a disk. We speculate that GN20 is in the late stage of a major merger, where the clumps in a large gas-rich disk are created by the major merger, while the central starburst is driven by the merger event. [ABSTRACT FROM AUTHOR]

Context. Lyman-α (Lyα) is the brightest emission line in star-forming galaxies. However, its interpretation in terms of physical properties is hampered by the resonant nature of Lyα photons. In order to remedy this complicated situation, the Lyman Alpha Reference Sample (LARS) was defined, enabling the study of Lyα production and escape mechanisms in 14 local star-forming galaxies. Aims. With this paper, we complement our efforts and study the global dust and (molecular) gas content as well as the properties of gas associated with photon-dominated regions. We aim to characterize the interstellar medium of LARS galaxies, allowing us to relate these newly derived properties to quantities relevant for Lyα escape. Methods. We observed LARS galaxies with Herschel, SOFIA, the IRAM 30m telescope, and APEX, targeting far-infrared (FIR) continuum and emission lines of [C II]158 μm, [O I]63 μm, [O III]88 μm, and low-J CO lines. Using Bayesian methods we derived dust model parameters and estimated the total gas masses for all LARS galaxies, taking into account a metallicity-dependent gas-to-dust ratio. Star formation rates were estimated from FIR, [C II]158 μm, and [O I]63 μm luminosities. Results. LARS covers a wide dynamic range in the derived properties, with FIR-based star formation rates from ∼0.5−100 M⊙ yr−1, gas fractions between ∼15−80%, and gas depletion times ranging from a few hundred megayears up to more than ten gigayears. The distribution of LARS galaxies in the Σgas versus ΣSFR (Kennicutt–Schmidt plane) is thus quite heterogeneous. However, we find that LARS galaxies with the longest gas depletion times, that is, relatively high gas surface densities (Σgas) and low star formation rate densities (ΣSFR), have by far the highest Lyα escape fraction. A strong approximately linear relation is found between the Lyα escape fraction and the total gas (HI+H2) depletion time. We argue that the Lyα escape in those galaxies is driven by turbulence in the star-forming gas that shifts the Lyα photons out of resonance close to the places where they originate. We further report on an extreme [C II]158 μm excess in LARS 5, corresponding to ∼14 ± 3% of the FIR luminosity, which probably is the most extreme [C II]-to-FIR ratio observed in a galaxy (without active nucleus) to date. [ABSTRACT FROM AUTHOR]

We have used the capability of the Multi-Unit Spectroscopic Explorer (MUSE) instrument to explore the impact of stellar feedback at large scales in Haro 11, a galaxy under extreme starburst condition and one of the first galaxies where Lyman continuum (LyC) has been detected. Using H α, [O  iii ] λ5007, and [O  i ] λ6300 emission lines from deep MUSE observations, we have constructed a sequence of velocity-dependent maps of the H α emission, the state of the ionized gas, and a tracer of fast shocks. These allowed us to investigate the ionization structure of the galaxy in 50 km s−1 bins over a velocity range of −400 to 350 km s−1. The ionized gas in Haro 11 is assembled by a rich arrangement of structures, such as superbubbles, filaments, arcs, and galactic ionized channels, whose appearances change drastically with velocity. The central star-forming knots and the star-forming dusty arm are the main engines that power the strong mechanical feedback in this galaxy, although with different impact on the ionization structure. Haro 11 appears to leak LyC radiation in many directions. We found evidence of a kpc-scale fragmented superbubble that may have cleared galactic-scale channels in the ISM. Additionally, the Southwestern hemisphere is highly ionized in all velocities, hinting at a density bound scenario. A compact kpc-scale structure of lowly ionized gas coincides with the diffuse Lyα emission and the presence of fast shocks. Finally, we find evidence that a significant fraction of the ionized gas mass may escape the gravitational potential of the galaxy. [ABSTRACT FROM AUTHOR]

The stellar content of young massive star clusters emit large amounts of Lyman continuum photons and inject momentum into the inter stellar medium (ISM) by the strong stellar winds of the most massive stars in the cluster. When the most massive stars explode as supernovae, large amounts of mechanical energy are injected in the ISM. A detailed study of the ISM around these massive cluster provides insights on the effect of cluster feedback.We present high quality integral field spectroscopy taken with VLT/MUSE of two starburst galaxies: ESO 338-IG04 and Haro 11. Both galaxies contain a significant number of super star clusters. The MUSE data provide us with an unprecedented view of the state and kinematics of the ionized gas in the galaxy allowing us to study the effect of stellar feedback on small and large spatial scales. We present our recent results on studying the ISM state of these two galaxies. The data of both galaxies show that the mechanical and ionization feedback of the super star clusters in the galaxy modify the state and kinematics of the ISM substancially by creating highly ionized bubbles around the cluster, making the central part of the galaxy highly ionized. This shows that the HII regions around the individual clusters are density bounded, allowing the ionizing photons to escape and ionize the ISM further out. [ABSTRACT FROM PUBLISHER]

Context. Though Lyα emission is one of the most used tracers of massive star formation at high redshift, it is strongly affected by neutral gas radiation transfer effects. A correct understanding of these effects is required to properly quantify the star formation rate along the history of the Universe. Aims. We aim to parameterize the escape of Lyα photons as a function of the galaxy properties, in order to properly calibrate the Lyα luminosity as a tracer of star formation intensity at any age of the Universe. Methods. We have embarked on a program to study the properties of the Lyα emission (spectral profile, spatial distribution, relation to Balmer lines intensity,...) in a number of starburst galaxies in the Local Universe. The study is based on Hubble Space Telescope spectroscopic and imaging observations at various wavelengths, X-ray data, and ground-based spectroscopy, complemented with the use of evolutionary population synthesis models. Results. We present here the results obtained for one of those sources, IRAS 08339+6517, a strong Lyα emitter in the Local Universe, which is undergoing an intense episode of massive star formation. We have characterized the properties of the starburst, which transformed 1.4 × 108 M⊙ of gas into stars around 5−6 Myr ago. The mechanical energy released by the central super stellar cluster (SSC), located in the core of the starburst, has created a cavity devoid of gas and dust around it, leaving a clean path through which the UV continuum of the SSC is observed, with almost no extinction. While the average extinction affecting the stellar continuum is significantly larger out of the cavity, with E(B − V) = 0.15 on average, we have not found any evidence for regions with very large extinctions, which could be hiding some young, massive stars not contributing to the global UV continuum. The observed soft and hard X-ray emissions are consistent with this scenario, being originated by the interstellar medium heated by the release of mechanical energy in the first case, and by a large number of active high-mass X-ray binaries (HMXBs) in the second. In addition to the central compact emission blob, we have identified a diffuse Lyα emission component smoothly distributed over the whole central area of IRAS 08339+6517. This diffuse emission is spatially decoupled from the UV continuum, the Hα emission, or the Hα/Hβ ratio. Both locally and globally, the Lyα/Hα ratio is lower than the Case B predictions, even after reddening correction, with an overall Lyα escape fraction of only 4%. Conclusions. We conclude that in IRAS 08339+6517 the Lyα photons resonantly scattered by an outflowing shell of neutral gas are being smoothly redistributed over the whole central area of the galaxy. Their increased probability of being destroyed by dust would explain the low Lyα escape fraction measured. In any case, in the regions where the diffuse Lyα emission shows the largest Lyα/Hα ratios, no additional sources of Lyα emission are required, like ionization by hot plasma as proposed for Haro 2, another galaxy in our sample. These results stress again the importance of a proper correction of scattering and transfer effects when using Lyα to derive the star formation rate in high-redshift galaxies. [ABSTRACT FROM AUTHOR]

Aims. We study the effects of an inhomogeneous interstellar medium (ISM) on the strength and the shape of the Lyman alpha (Lyα) line in starburst galaxies. Methods. Using our 3D Monte Carlo Lyα radiation transfer code, we have studied the radiative transfer of Lyα, UV, and optical continuum photons in homogeneous and clumpy shells of neutral hydrogen and dust surrounding a central source. Our simulations predict the Lyα and continuum escape fraction, the Lyα equivalent width EW(Lyα), the Lyα line profile, and their dependence on the geometry of the gas distribution and the main input physical parameters. Results. The ISM clumpiness is found to have a strong impact on the Lyα line radiative transfer, leading to a strong dependence of the emergent features of the Lyα line (escape fraction, EW(Lyα)) on the ISM morphology. Although a clumpy and dusty ISM appears more transparent to radiation (both line and continuum) compared to an equivalent homogeneous ISM of equal dust optical depth, we find that the Lyα photons are, in general, still more attenuated than UV continuum radiation. As a consequence, the observed equivalent width of the Lyα line (EWobs(Lyα)) is lower than the intrinsic one (EWint(Lyα)) for nearly all clumpy ISM configurations being considered. There are, however, special conditions under which Lyα photons escape more easily than the continuum, resulting in an enhanced EWobs(Lyα). The requirement for this to happen is that the ISM is almost static (galactic outflows ⩽200 km s-1), extremely clumpy (with density contrasts >107 in HI between clumps and the interclump medium), and very dusty (E(B-V) > 0:30). When these conditions are fulfilled, the emergent Lyα line profile generally shows no velocity shift and little asymmetry. Otherwise, the Lyα line profile is very similar to the one expected for homogeneous media. Conclusions. Given the asymmetry and velocity shifts generally observed in star-forming galaxies with Lyα emission, we therefore conclude that clumping is unlikely to significantly enhance their relative Lyα/UV transmission. [ABSTRACT FROM AUTHOR]

Context. The Lyman alpha emission line of neutral hydrogen is an important tool for finding galaxies at high redshift, thus for probing the structure of the early universe. However, the resonance nature of the line and its sensitivity to dust and neutral gas is still not fully understood. Aims. We present measurements of the velocity, covering fraction and optical depth of neutral gas in front of two well-known, local blue compact galaxies that show Lyman alpha in emission: ESO 338-IG 04 and Haro 11. We thus observationally test the hypothesis that Lyman alpha can escape through neutral gas by being Doppler shifted out of resonance. Methods. We present integral field spectroscopy, obtained with the GIRAFFE/Argus spectrograph at VLT/FLAMES in Paranal, Chile. The excellent wavelength resolution allowed us to accurately measure the velocity of the ionized and neutral gas through the Ha emission and Na D absorption, which trace the ionized medium and cold interstellar gas, respectively. We also present independent measurements from the VLT/X-shooter spectrograph that confirm our results. Results. For ESO 338-1004 we measure no significant shift of neutral gas: the best fit velocity offset is -15 ± 1 6km s-1. For Haro 11, we see an outflow from knot B at 44 ± 13 km s-1, and infalling gas towards knot C with 32 ± 12 km s-1. Based on the relative strength of the Na D absorption lines, we estimate low covering fractions of neutral gas (down to 10%) in all three cases. Conclusions. The Na D absorption most likely occurs in dense clumps with higher column densities than the medium in which the bulk of the Ly α scattering takes place. Still, we find no strong correlation between outfiowing neutral gas and strong Ly α emission. The Ly α photons from these two galaxies are therefore likely to be escaping due to a low column density and/or covering fraction. [ABSTRACT FROM AUTHOR]

We have initiated a survey using the newly commissioned X-shooter spectrograph to target candidate relatively metal-rich damped Lyα absorbers (DLAs). Our rationale is that high-metallicity DLAs due to the luminosity-metallicity relation likely will have the most luminous galaxy counterparts. In addition, the spectral coverage of X-shooter allows us to search for not only Lyα emission, but also rest-frame optical emission lines. We have chosen DLAs where the strongest rest-frame optical lines ([O ], [O ], Hβ and Hα) fall in the near-infrared atmospheric transmission bands. In this first paper resulting from the survey, we report on the discovery of the galaxy counterpart of the DLA towards the quasar Q 0946. This DLA is amongst the most metal-rich DLAs studied so far at comparable redshifts and there is evidence for substantial depletion of refractory elements on to dust grains. We measure metallicities from Zn , Si , Ni , Mn and Fe of and , respectively. The galaxy is detected in the Lyα, [O ]λλ4959, 5007 and Hα emission lines at an impact parameter of about 0.8 arcsec (6 kpc at ). Based on the Hα line, we infer a star formation rate of 10 M yr, which is a lower limit due to the possibility of slit loss. Compared to the recently determined Hα luminosity function for galaxies, the DLA-galaxy counterpart has a luminosity of . The emission-line ratios are 4.0 (Lyα/Hα) and 1.2 ([O ]/Hα). In particular, the Lyα line shows clear evidence for resonant scattering effects, namely an asymmetric, redshifted (relative to the systemic redshift) component and a much weaker blueshifted component. The fact that the blueshifted component is relatively weak indicates the presence of a galactic wind. The properties of the galaxy counterpart of this DLA are consistent with the prediction that metal-rich DLAs are associated with the most luminous of the DLA-galaxy counterparts. [ABSTRACT FROM AUTHOR]