Stellar bow shocks form when an outflow interacts with the interstellar medium. In white dwarfs accreting from a binary companion, outflows are associated with strong winds from the donor star, the accretion disk or a thermonuclear runaway explosion on the white dwarf surface. To date, only six accreting white dwarfs are known to harbour disk-wind-driven bow shocks that are not associated with thermonuclear explosions. Here we report the discovery of a bow shock associated with a high-proper-motion diskless accreting white dwarf, 1RXS J052832.5+283824. We show that the white dwarf has a strong magnetic field in the range B ≈ 42–45 MG, making RXJ0528+2838 a bona fide known polar-type cataclysmic variable harbouring a bow shock. The resolved bow shock is shown to be inconsistent with a past thermonuclear explosion or with being inflated by a donor wind, ruling out all accepted scenarios for inflating a bow shock around this system. Modelling of the energetics reveals that the observed bow shock requires a persistent power source with a luminosity significantly exceeding the system accretion energy output. This implies the presence of a powerful, previously unrecognized energy-loss mechanism—potentially tied to magnetic activity—that may operate over sufficiently long timescales to influence the course of binary evolution. The study reports the discovery of a persistent bow shock around a diskless magnetic accreting white dwarf, revealing a powerful energy-loss mechanism that challenges current models of accretion and compact binary evolution.

We present a Bayesian analysis of star clusters in the dwarf starburst galaxy NGC 1569 based on high-resolution Hubble Space Telescope (HST) imaging combined with integral-field spectroscopy from the Keck Cosmic Web Imager, obtained as part of the DUVET survey. For each cluster identified, we infer posterior probability distributions for mass and age using a forward modelling method that properly accounts for uncertainties due to stochastic sampling of the initial mass function (IMF). We investigate how the inferred properties depend on photometric coverage by repeating the analysis with different filter combinations, including mock extensions to the ultraviolet (UV) and near-infrared that emulate the addition of HST UV bands and James Webb Space Telescope imaging. We find that, while inclusion of these wavelength regimes further breaks age and mass degeneracies, the currently available data yield reasonably strong constraints on cluster parameters. We compare inferred cluster properties to the conditions of the local interstellar medium, and find evidence for multiple interesting correlations. The truncation mass of the cluster mass function varies with galactocentric distance, particularly moving off the disc, consistent with a dependence on the density of the interstellar medium. Cluster mass positively correlates with metallicity, suggesting that massive clusters preferentially form in pre-enriched gas, and the ionization state of the gas, reflecting the increased prevalence of high-mass stars in high-mass clusters. These results demonstrate the power of Bayesian, IMF-aware modelling for resolving cluster populations in nearby starburst dwarfs and provide new insight into how cluster formation and feedback respond to local galactic conditions.

Stellar clusters often host massive stars that heat up and ionize the gas surrounding low-mass stars. The large amounts of far-ultraviolet radiation produced by these stars can deplete the gas from the outer layers of the disk around a low-mass star, an effect known as external photoevaporation. We have chosen to study this effect in Trumpler 14 (Tr14), a young stellar cluster in the Carina Nebula Complex. Specifically, we focus on the center of Tr14 and introduce a new, more robust methodology to extract stellar spectra from previously obtained VLT/MUSE spectroscopic data. To classify the young, low-mass stars, we employ a deep learning approach in the form of a conditional invertible neural network (cINN). We describe the results of testing the network on our new set of data as well as the need to extend the current method to include hotter stars.

Hydrogen recombination lines provide key diagnostics of ionized gas in galaxies, yet most hydrodynamical simulations estimate hydrogen level populations using interpolated emissivity tables rather than computing them directly from local physical conditions. We present HyLight, a Python-based atomic model that calculates hydrogen level populations and line emissivities from the gas density, temperature, and ionization state, enabling accurate predictions in both equilibrium and non-equilibrium environments. Benchmark comparisons show that HyLight reproduces Cloudy predictions for Balmer, Paschen, and Brackett emissivities to within 1 per cent under typical photoionized nebular conditions, while discrepancies of several tens of per cent arise relative to other published calculations. As an illustrative application, we use HyLight to compute photoionization-to-line intensity ratios in an H ii nebula and generate synthetic hydrogen emission maps from a radiation-hydrodynamical simulation that includes non-equilibrium thermochemistry. Combining physical consistency with flexibility, HyLight provides a robust framework for connecting hydrodynamical simulations with observational diagnostics of photoionized regions, and enhances our ability to interpret hydrogen emission in complex, non-equilibrium astrophysical environments.

An element's astrophysical origin should be reflected in the spatial distribution of its abundance, yielding measurably different spatial distributions for elements with different nucleosynthetic sites. However, most extragalactic multi-element analyses of gas-phase abundances to date have been limited to small numbers of sightlines, making statistical characterization of differences in spatial distributions of elements impossible. Here we use integrated field spectroscopic data covering the full face of the nearby dwarf galaxy NGC 5253 sampled at 3.5-pc resolution to produce maps of the abundances of oxygen, nitrogen, and sulfur using independent direct methods. We find strong evidence for differences in the elements' spatial statistics that mirror their predicted nucleosynthetic origins: the spatial distributions of oxygen and sulfur, both predominantly produced in core-collapse supernovae, indicate that initial injection occurs on larger scales than for nitrogen, which is predominantly produced by asymptotic giant branch stars. All elements are well-correlated but oxygen and sulfur are much better correlated with each other than with nitrogen, consistent with recent results for stellar abundances in the Milky Way. These findings both open a new avenue to test nucleosynthetic models, and make predictions for the structure of stellar chemical abundance distributions.

We present optical integral field unit (IFU) observations of the Mystic Mountains, a dust pillar complex in the center of the Carina Nebula that is heavily irradiated by the nearby young massive cluster Trumpler 14. With the continuous spatial and spectral coverage of data from the Multi-Unit Spectroscopic Explorer (MUSE), we measure the physical properties in the ionized gas including the electron density and temperature, excitation, and ionization. MUSE also provides an excellent view of the famous jets HH 901, 902, and 1066, revealing them to be high-density, low-ionization outflows despite the harsh environment. HH 901 shows spatially extended [C I] emission tracing the rapid dissociation of the photoevaporating molecular outflow in this highly irradiated source. We compute the photoevaporation rate of the Mystic Mountains and combine it with recent ALMA observations of the cold molecular gas to estimate the remaining lifetime of the Mystic Mountains and the corresponding shielding time for the embedded protostars. The longest remaining lifetimes are for the smallest structures, suggesting that they have been compressed by ionizing feedback. Our data do not suggest that star formation in the Mystic Mountains has been triggered but it does point to the role that ionization-driven compression may play in enhancing the shielding of embedded stars and disks. Planet formation models suggest that the shielding time is a strong determinant of the mass and orbital architecture of planets, making it important to quantify in high-mass regions like Carina that represent the type of environment where most stars form.

This work is the continuation of a series attempting to characterize the local warm ionized medium through both static and time dependent simulations. We build upon our three dimensional, observationally-derived simulation of the local photoionized interstellar medium - based on static photoionization simulations constrained by 3D dust maps - to include metals required to predict collisionally excited optical and infrared emission lines, providing the first all-sky prediction of a series of lines including [SII] 6716$\mathring{A}$, [NII] 6584$\mathring{A}$ and [OIII] 5007$\mathring{A}$. While these predictions only include O-star photoionization under ionization equilibrium, we also carry out a suite of radiation-hydrodynamics simulations including time-dependent metal ionization and the effects of supernova feedback to highlight missing features in our predicted skies. We use the simulations to estimate the very local (1 $\rm kpc^{2}$) Galactic star formation rate, finding a rate of 370 $\rm M_{\odot}~Myr^{-1}~kpc^{-2}$ provides the best match between the observationally-derived and ab-initio simulations. This is approximately a factor of four lower than previous estimates for the star formation rate required to support an observed layer of high-altitude diffuse ionized gas, possibly suggesting a `bursty' star formation history in the region surrounding the Sun. We also investigate the effects of O-star environments on their ability to ionize large volumes of diffuse ionized gas, and find it is likely ionized by a small number of luminous O-stars located in regions where the leakage of their Lyman continuum photons can produce the vast volumes of ionized gas observed in the midplane and at high galactic altitudes.

Massive stars drive the ionization and mechanical feedback within young star-forming regions. The Large Magellanic Cloud (LMC) is an ideal galaxy for studying individual massive stars and quantifying their feedback contribution to the environment. We analyze eight exemplary targets in LMC N11,B from the Hubble UV Legacy Library of Young Stars as Essential Standards (ULLYSES) program using novel spectra from and in the UV, and from VLT ( in the optical. We model the spectra of early to late O-type stars using state-of-the-art PoWR atmosphere models. We determine the stellar and wind parameters (e.g. L_⋆ and varv ∞ $) of the analyzed objects, chemical abundances (C, N, and O), ionizing and mechanical feedback ( and and X-rays. We report ages of $2-4.5$ Myr and masses of $30-60$ for the analyzed stars in N11,B, which are consistent with a scenario of sequential star formation. We note that the observed wind-momentum--luminosity relation is consistent with theoretical predictions. We detect nitrogen enrichment by up to a factor of seven in most of the stars. However, we do not find a correlation between nitrogen enrichment and projected rotational velocity. Finally, based on their spectral type, we estimate the total ionizing photons injected from the O-type stars in N11,B into its environment. We report log (∑ ph,s^-1, log (∑ ph,s^-1, and log (∑ ph,s^-1, consistent with the total ionizing budget in N11.

Gas-phase oxygen abundance (metallicity) properties can be constrained through emission line analyses, and are of great importance to investigate galaxy evolution histories. We present an analysis of the integrated and spatially resolved rest-frame optical emission line properties of the ionized gas in 43 star-forming galaxies at z similar to 1.5 in the K-band Multi Object Spectrograph Ultra-deep Rotational Velocity Survey. Using the [NII]A6584/H alpha (N-2 ), ([OII]AA3727, 9 +[OIII]AA4959, 5007)/H beta (R23), and for the first time [NII]A6584/[OII]AA3727, 9 (N2O2 ) indicators at this redshift, we measure the gas-phase metallicities and their radial gradients. On similar to 4-kpc scales metallicity gradients measured from N2O2 and those measured from N-2 are in good agreement when considering the spatial distributions of dust in each galaxy, as parametrized by dust attenuation radial gradients. We report a nearly flat metallicity gradient distribution typically at z similar to 1.5, with the 50th, 16th, and 84th percentiles at 0.01, -0.03, and 0.05 dex kpc(-1), respectively. The findings agree well with previous observational studies and simulations at this epoch. We ascribe the observed negative metallicity gradients to a natural result from self-regulating systems, and the positive ones to potential galactic fountains and higher merger rates.

Power spectra (PS) of high-resolution images of M51 (NGC 5194) taken with the Hubble Space Telescope and the James Webb Space Telescope (JWST) have been examined for evidence of disk thickness in the form of a change in slope between large scales, which map two-dimensional correlated structures, and small scales, which map three-dimensional correlated structures. Such a slope change is observed here in H α , and possibly Pa α , using average PS of azimuthal intensity scans that avoid bright peaks. The physical scale of the slope change occurs at ∼120 pc and ∼170 pc for these two transitions, respectively. A radial dependence in the shape of the H α PS also suggests that the length scale drops from ∼180 pc at 5 kpc, to ∼90 pc at 2 kpc, to ∼25 pc in the central ∼kpc. We interpret these lengths as comparable to the thicknesses of the star-forming disk traced by H ii regions. The corresponding emission measure is ∼100 times larger than what is expected from the diffuse ionized gas. The PS of JWST Mid-IR Instrument images in eight passbands have more gradual changes in slope, making it difficult to determine a specific value of the thickness for this emission.

In this work, we test the validity of T-e-T-e relations in resolved (10-200 pc) measurements of four nearby, low-metallicity (7.25 <= 12 + log(O/H) <= 8.33), low-mass (10(6 . 78) < M-*/M-(R) < 10(8 . 7) ), starburst (10(-4 . 5) <= sSFR < 10(-0.3)) galaxies. We obtain Very Large Telescope/X-Shooter spectra of NGC 5253, NGC 0625, SBS 0335-052E, and IC 2828, targeting regions within these galaxies with bright point-like sources and diffuse gas. Our observations are designed to extend from the galaxy mid-plane into extraplanar gas likely belonging to galactic winds. We measure electron temperatures from five different auroral lines: [N II ] lambda 5755, [OII] lambda lambda 7319, 7330, [S II ] lambda lambda 4069, 4076, [S III ] lambda 6312, and [O III ] lambda 4363. We compare the resulting T-e-T-e relations with previous studies of HII regions in nearby spiral galaxies. Our results show that T-e-T-e relations in low-metallicity starburst galaxies do not significantly deviate from T-e-T-e relations in HII regions of local spiral galaxies. We do not find significant differences in the diffuse, extraplanar gas. These results suggest that auroral lines provide a reliable metallicity diagnostic not only for high-redshift galaxies but also for the extended diffuse gas in extreme environments like outflows.

Hydrogen recombination lines are key diagnostics of ionized gas in the interstellar medium (ISM), particularly within photoionized nebulae. Hydrodynamical simulations, even those that include radiative transfer, do not usually determine the level population of hydrogen required to compute line intensities, but rather interpolate them from pre-computed tables. Here we present the HyLight atomic model, which captures the dominant processes governing the level populations, enabling the calculation of all dipole-allowed hydrogen transitions as well as two-photon transitions from the 2s to 1s state without the need to pre-computed tables. We compare HyLight predictions to those of other codes and published tables, finding differences between the various rates of up to factors of several per cent for common transitions, including those of the Balmer and Brackett series. However, we find sub-per cent agreement between HyLight and the Cloudy spectral synthesis code when enforcing photo-ionisation equilibrium in gas under typical nebular conditions of density and temperature. Importantly, HyLight can also predict emissivities if the gas is not in photo-ionisation equilibrium. As examples, we compute the ratios between the total photoionization rate and line intensities in a nebula, and post-process a snapshot from Sparcs, a hydrodynamical code that combines radiative transfer with non-equilibrium physics, and compute mock hydrogen emission line maps which can be compared directly to observations. Implemented in Python, HyLight is an accurate tool for determining the level population in neutral hydrogen, a crucial step in bridging the gap between simulations and observations in studies of photoionized regions in galaxies.

BlueMUSE is a blue-optimised, medium spectral resolution, panoramic integral field spectrograph under development for the Very Large Telescope (VLT). With an optimised transmission down to 350 nm, spectral resolution of R similar to 3500 on average across the wavelength range, and a large FoV (1 arcmin(2)), BlueMUSE will open up a new range of galactic and extragalactic science cases facilitated by its specific capabilities. The BlueMUSE consortium includes 9 institutes located in 7 countries and is led by the Centre de Recherche Astrophysique de Lyon (CRAL). The BlueMUSE project development is currently in Phase A, with an expected first light at the VLT in 2031. We introduce here the Top Level Requirements (TLRs) derived from the main science cases, and then present an overview of the BlueMUSE system and its subsystems fulfilling these TLRs. We specifically emphasize the tradeoffs that are made and the key distinctions compared to the MUSE instrument, upon which the system architecture is built.

The Large Magellanic Cloud (LMC) is home to many H ii regions, which may lead to significant outflows. We examine the LMC's multiphase gas (T similar to 104-5 K) in H i, S ii, Si iv, and C iv using 110 stellar sight lines from the Hubble Space Telescope's Ultraviolet Legacy Library of Young Stars as Essential Standards program. We develop a continuum fitting algorithm based on the concept of Gaussian process regression and identify reliable LMC interstellar absorption over v helio = 175-375 km s-1. Our analyses show disk-wide ionized outflows in Si iv and C iv across the LMC with bulk velocities of divided by v out, bulk divided by similar to 20-60 km s-1, which indicates that most of the outflowing mass is gravitationally bound. The outflows' column densities correlate with the LMC's star formation rate surface densities (Sigma SFR), and the outflows with higher Sigma SFR tend to be more ionized. Considering outflows from both sides of the LMC as traced by C iv, we conservatively estimate a total outflow rate of Mout greater than or similar to 0.03M circle dot yr-1 and a mass-loading factor of eta greater than or similar to 0.15. We compare the LMC's outflows with those detected in starburst galaxies and simulation predictions, and find a universal scaling relation of divided by vout,bulk divided by proportional to Sigma SFR0.23 over a wide range of star-forming conditions (Sigma SFR similar to 10-4.5-102 M circle dot yr-1 kpc-2). Lastly, we find that the outflows are corotating with the LMC's young stellar disk and the velocity field does not seem to be significantly impacted by external forces; we thus speculate on the existence of a bow shock leading the LMC, which may have shielded the outflows from ram pressure as the LMC orbits the Milky Way.

In the Orion Nebula Cluster (ONC), protoplanetary disks exhibit ionized gas clouds in the form of a striking teardrop shape as massive stars irradiate the disk material. We present the first spatially and spectrally resolved observations of 12 proplyds, using Integral Field Spectroscopy observations performed with the MUSE instrument in Narrow Field Mode (NFM) on the VLT. We present the morphology of the proplyds in seven emission lines and measure the radius of the ionization front (I-front) of the targets in four tracers, covering transitions of different ionization states for the same element. We also derive stellar masses for the targets. The measurements follow a consistent trend of increasing I-front radius for a decreasing strength of the far-UV radiation as expected from photoevaporation models. By analyzing the ratios of the I-front radii as measured in the emission lines of Ha, [OI] 6300, [OII] 7330, and [OIII] 5007, we observe the ionization stratification, that is, the most ionized part of the flow being the furthest from the disk (and closest to the UV source). The ratios of I-front radii scale in the same way for all proplyds in our sample regardless of the incident radiation. We show that the stratification can help constrain the densities near the I-front by using a 1D photoionization model. We derive the upper limits of photoevaporative mass-loss rates by assuming ionization equilibrium, and estimate values decreasing towards lower impinging radiation. We do not find a correlation between Mloss and stellar mass. The highest mass-loss rate is for the proplyd 244-440. These values of Mloss, combined with estimates of the disk mass with ALMA, confirm previous estimates of the short lifetime of these proplyds. This work demonstrates the potential of this dataset and offers a new set of observables to be used to test current and future models of external photoevaporation.

We present new JWST observations of the nearby, prototypical edge-on, spiral galaxy NGC 891. The northern half of the disk was observed with NIRCam in its F150W and F277W filters. Absorption is clearly visible in the mid-plane of the F150W image, along with vertical dusty plumes that closely resemble the ones seen in the optical. A ∼ 10 × 3 kpc^2 area of the lower circumgalactic medium (CGM) was mapped with MIRI F770W at 12 pc scales. Thanks to the sensitivity and resolution of JWST, we detect dust emission out to ∼ 4 kpc from the disk, in the form of filaments, arcs, and super-bubbles. Some of these filaments can be traced back to regions with recent star formation activity, suggesting that feedback-driven galactic winds play an important role in regulating baryonic cycling. The presence of dust at these altitudes raises questions about the transport mechanisms at play and suggests that small dust grains are able to survive for several tens of million years after having been ejected by galactic winds in the disk-halo interface. We lay out several scenarios that could explain this emission: dust grains may be shielded in the outer layers of cool dense clouds expelled from the galaxy disk, and/or the emission comes from the mixing layers around these cool clumps where material from the hot gas is able to cool down and mix with these cool cloudlets. This first set of data and upcoming spectroscopy will be very helpful to understand the survival of dust grains in energetic environments, and their contribution to recycling baryonic material in the mid-plane of galaxies.

Massive star-forming regions are thought to be the most common birth environments in the Galaxy and the only birth places of very massive stars. Their presence in the stellar cluster alters the conditions within the cluster, impacting at the same time the evolution of other cluster members. In principle, copious amounts of ultraviolet radiation produced by massive stars can remove material from outer parts of the protoplanetary discs around low- and intermediate-mass stars in the process of external photoevaporation, effectively reducing the planet formation capabilities of those discs. Here, we present deep VLT/MUSE observations of low-mass stars in Trumpler 14, one of the most massive, young, and compact clusters in the Carina Nebula Complex. We provide spectral and stellar properties of 717 sources and based on the distribution of stellar ages, derive the cluster age of ∼1 Myr. The majority of the stars in our sample have masses ≤1M⊙, which makes our spectroscopic catalogue the deepest to date in term of mass and proves that detailed investigations of low-mass stars are possible in the massive but distant regions. Spectroscopic studies of low-mass members of the whole Carina Nebula Complex are missing. Our work marks an important step forward towards filling this gap and sets the stage for follow-up investigations of accretion properties in Trumpler 14.

ABSTRACT We present the results of direct-method metallicity measurements in the disc and outflow of the low-metallicity starburst galaxy NGC 1569. We use Keck Cosmic Web Imager observations to map the galaxy across 54″ (800 pc) along the major axis and 48″ (700 pc) along the minor axis with a spatial resolution of 1″ (∼15 pc). We detect common strong emission lines ([O iii] λ5007, H β, [O ii] λ3727) and the fainter [O iii] λ4363 auroral line, which allows us to measure electron temperature (Te) and metallicity. Theory suggests that outflows drive metals out of the disc driving observed trends between stellar mass and gas-phase metallicity. Our main result is that the metallicity in the outflow is similar to that of the disc, Zout/ZISM ≈ 1. This is consistent with previous absorption line studies in higher mass galaxies. Assumption of a mass-loading factor of $\dot{M}_{\rm out}/{\rm SFR}\sim 3$ makes the metal-loading of NGC 1569 consistent with expectations derived from the mass–metallicity relationship. Our high spatial resolution metallicity maps reveal a region around a supermassive star cluster (SSC-B) with distinctly higher metallicity and higher electron density, compared to the disc. Given the known properties of SSC-B the higher metallicity and density of this region are likely the result of star formation-driven feedback acting on the local scale. Overall, our results are consistent with the picture in which metal-enriched winds pollute the circumgalactic medium surrounding galaxies, and thus connect the small-scale feedback processes to large-scale properties of galaxy haloes.

The Wide-field Spectroscopic Telescope (WST) is proposed as a new facility dedicated to the efficient delivery of spectroscopic surveys. This white paper summarises the initial concept as well as the corresponding science cases. WST will feature simultaneous operation of a large field-of-view (3 sq. degree), a high multiplex (20,000) multi-object spectrograph (MOS) and a giant 3x3 sq. arcmin integral field spectrograph (IFS). In scientific capability these requirements place WST far ahead of existing and planned facilities. Given the current investment in deep imaging surveys and noting the diagnostic power of spectroscopy, WST will fill a crucial gap in astronomical capability and work synergistically with future ground and space-based facilities. This white paper shows that WST can address outstanding scientific questions in the areas of cosmology; galaxy assembly, evolution, and enrichment, including our own Milky Way; origin of stars and planets; time domain and multi-messenger astrophysics. WST's uniquely rich dataset will deliver unforeseen discoveries in many of these areas. The WST Science Team (already including more than 500 scientists worldwide) is open to the all astronomical community. To register in the WST Science Team please visit https://www.wstelescope.com/for-scientists/participate

We measure resolved (kiloparsec-scale) outflow properties in a sample of 10 starburst galaxies from the Deep near-UV observations of Entrained gas in Turbulent (DUVET) galaxies sample, using Keck/KCWI observations of H beta and [O III] lambda 5007. We measure similar to 460 lines of sight that contain outflows, and use these to study scaling relationships of outflow velocity (v(out)), mass-loading factor (eta; mass outflow rate per star formation rate) and mass flux (Sigma(center dot)(out); mass outflow rate per area) with co-located star formation rate surface density (Sigma(SFR)) and stellar mass surface density (Sigma(& lowast;)). We find strong, positive correlations of Sigma(center dot)(out)proportional to Sigma(1.2)(SFR) and Sigma(center dot)(out)proportional to Sigma(1.5)(& lowast;). We also find shallow correlations between vout and both Sigma(SFR) and Sigma(& lowast;). Our resolved observations do not suggest a threshold in outflows with Sigma(SFR), but rather we find that the local specific star formation rate (Sigma(SFR)/Sigma(& lowast;)) is a better predictor of where outflows are detected. We find that outflows are very common above Sigma(SFR)/Sigma(& lowast;)greater than or similar to 0.1 Gyr(-1) and rare below this value. We argue that our results are consistent with a picture in which outflows are driven by supernovae, and require more significant injected energy in higher mass surface density environments to overcome local gravity. The correlations we present here provide a statistically robust, direct comparison for simulations and higher redshift results from JWST.