We present new Multi Unit Spectroscopic Explorer (MUSE) Narrow Field Mode with adaptive optics observations of the optical torus surrounding a central compact object candidate within the oxygen-rich supernova remnant 1E 0102.2-7219 located in the Small Magellanic Cloud. These data provide nearly an order-of-magnitude improvement in spatial resolution over previous MUSE Wide Field Mode observations. The improved spatial resolution resolved the previously identified torus into a cavity-like structure with a sharply defined inner edge and diffuse, outer filamentary substructure. The emission shows continuous velocity connectivity, broad intrinsic line widths, and cospatial contributions from neutral and partially ionized species, including O i, Ne i, [O i], [O ii], and [O iii]. Spatially resolved line-ratio maps indicate that the emission arises from a multiphase, nonequilibrium medium rather than a single homogeneous component. Comparison with photoionization and shock models shows that no single-component model within the explored parameter space can simultaneously reproduce both the strong neutral and high-ionization diagnostics, indicating that multiple physical conditions must coexist. We favor an interpretation in which shocks propagating through density inhomogeneities in the ejecta shape the observed morphology and excitation, while also considering alternative mechanisms linked to the central source, binary evolution, or interaction with an embedded object within the remnant.

The internal dust attenuation of the H II region reduces the observed emission-line fluxes. Turbulent density fields within each H II region change the degree of the line-of-the-sight obscuration of the emission-line fluxes. In this paper, we implement the dust Monte Carlo radiative transfer in the latest M3D code, creating the emission-line maps attenuated by the internal turbulent dust obscuration with the varying Mach numbers. Due to the internal density and temperature fluctuations of H II regions the radiative transfer of hydrogen lines meet neither Case A nor Case B conditions, resulting in the global H α to H β ratio of approximately 3.02–3.03, differing from the widely used value of 2.86. This deviation from Case B is because the temperature of these H II regions is cooler than 10 000 K. We further derive the internal nebular attenuation curve from the attenuated hydrogen lines, finding that the clumpy structures within H II regions do not change the slope of the internal attenuation curve. This is because the beavy dust obscuration of dense clumps is canceled out by the high in situ production of emission-line intensities.

The distance to the Vela Junior supernova remnant (RX J0852.0–4622 or G266.2–1.2) has long remained uncertain, limiting our understanding of its physical properties. Using Very Large Telescope/Multi Unit Spectroscopic Explorer integral field spectroscopy, we uncover chemical and kinematic connections between the nebula surrounding its central compact object (CXOU J085201.4–461753) and the nearby Herbig–Haro outflow of Ve 7–27 (Wray 16–30), indicating a shared nitrogen-rich, Fe-peak-enhanced environment. This link ties stellar birth and death, with the young star Ve 7–27 embedded in material expelled by Vela Junior’s massive progenitor, and the remnant’s blast wave is expanding through the same medium. Adopting the Gaia-based distance to Ve 7–27, we revise Vela Junior’s distance to 1.41 ± 0.14 kpc. At this distance, the remnant’s physical radius is 23.3 ± 2.3 pc, and X-ray proper motions of the northwestern rim correspond to shock speeds of (2.8 ± 0.7) × 10 ^3 to (5.6 ± 1.5) × 10 ^3 km s ^−1 . These imply an age of ∼1.6–3.3 kyr and a very low ambient density, indicating that Vela Junior is expanding within a highly rarefied wind-blown cavity carved by a massive progenitor—consistent with the nondetection of strong thermal X-ray emission. This distance update also resolves long-standing inconsistencies, with major implications for its energy budget, particle acceleration efficiency, and compact object evolution.

We present new MUSE Narrow Field Mode with Adaptive Optics observations of the optical torus surrounding a Central Compact Object (CCO) candidate within the oxygen-rich supernova remnant 1E 0102.2-7219 (E0102) located in the Small Magellanic Cloud. These data provide nearly an order-of-magnitude improvement in spatial resolution over previous MUSE Wide Field Mode observations. The improved spatial resolution resolved the previously identified torus into a cavity-like structure with a sharply defined inner edge and diffuse, outer filamentary substructure. The emission shows continuous velocity connectivity, broad intrinsic line widths, and co-spatial contributions from neutral and partially ionized species, including O I, Ne I, [O I], [O II], and [O III]. Spatially resolved line-ratio maps indicate that the emission arises from a multiphase, non-equilibrium medium rather than a single homogeneous component. Comparison with photoionization and shock models shows that no single-component model within the explored parameter space can simultaneously reproduce both the strong neutral and high-ionization diagnostics, indicating that multiple physical conditions must coexist. We favor an interpretation in which shocks propagating through density inhomogeneities in the ejecta shape the observed morphology and excitation, while also considering alternative mechanisms linked to the central source, binary evolution, or interaction with an embedded object within the remnant.

The excitation sources in galaxies are frequently mixed owing to active galactic nucleus (AGN) and stellar feedback, including star formation, AGN, and shock excitation. Disentangling the star formation, AGN, and shocks in galaxy integral field unit (IFU) spectra at optical wavelengths is crucial to expanding the galaxy sample for AGN and stellar feedback studies, given the lack of multiwavelength observations for most of the galaxies that are observed in optical wavelengths. Previous methods to address this issue either have a limited application range or are highly uncertain in separating AGN from shock excitation. Here we propose a theoretical three-dimensional (3D) diagram. This theoretical 3D diagram overcomes the limitations of previous methods and can simultaneously separate star formation, AGN, and shocks in active galaxies. Along with the separation, the new theoretical 3D diagram also constrains the gas metallicity, ionization parameter, and gas pressure within the galaxy. By applying the Very Large Telescope/MUSE IFU data and the Wide Field Spectrograph IFU data for NGC 5728 on the theoretical 3D diagram, we find a star-forming ring surrounding the galaxy center with a projected radius of ∼1 kpc in the sky plane, an AGN ionized bicone extended up to ∼2 kpc from the nuclear center, and a fast-shock-dominated disk region at the base of the AGN outflow, which is likely associated with a nuclear accretion disk or the result of jet–interstellar medium interaction. The theoretical 3D diagram opens a new window in which to study the interplay among star formation, AGN, and shocks in active galaxies.

Type Ia supernovae play a fundamental role as cosmological probes of dark energy and produce more than half of the iron in our Galaxy. Despite their central importance, a comprehensive understanding of their progenitor systems and triggering mechanism is still a long-standing fundamental problem. Here we present high-resolution integral field spectroscopic observations of the young supernova remnant SNR 0509-67.5 in the Large Magellanic Cloud. We uncover a double-shell morphology of highly ionized calcium [Ca XV] and a single shell of sulphur [S XII], observed in the reverse shocked ejecta. Our analysis reveals that the outer calcium shell originates from the helium detonation at the base of the outer envelope, while the inner shell is associated with the carbon-oxygen core detonation. This morphological distribution of intermediate-mass elements agrees qualitatively with the predicted signature of the double detonation of a sub-Chandrasekhar-mass white dwarf from a hydrodynamical explosion simulation. Our observations reveal two distinct, spatially separated peaks in surface brightness of [Ca XV] from the supernova remnant phase, providing substantial evidence that sub-Chandrasekhar-mass explosions through the double-detonation mechanism could occur in nature. They also highlight the importance of remnant tomography in understanding explosion mechanisms from the remnant phase.

Gas metallicity, ionization parameter, and gas pressure can affect the observed ratios of specific strong emission lines within galaxies. While the theoretical strong lines diagnostics for gas metallicity, ionization parameters, and gas pressure in star-forming regions are well-established, theoretical diagnostics for active galactic nuclei (AGNs) narrow-line regions are still lacking. In P. Zhu et al., we presented a new AGN model that provides the best predictions for observations spanning the UV, optical, and infrared wavelengths. This paper presents a suite of theoretical diagnostics for the gas metallicity, ionization parameter, gas pressure, and the peak energy in AGN ionizing radiation field E peak for AGN narrow-line regions spanning the UV and optical wavelengths. We investigate the model dependency on the ionization parameter, gas pressure, E peak, and the nitrogen scaling relation and make recommendations on metallicity diagnostics that are most robust against these parameters. We test our new AGN metallicity diagnostics using optical galaxy spectra from Sloan Digital Sky Survey DR16. These tests show that the metallicities measured from different diagnostics in this paper are consistent within similar to 0.3 dex. We compare consistent H ii and AGN diagnostics and demonstrate that H ii and AGN diagnostics should not be used interchangeably. With a wide wavelength coverage, we anticipate that these AGN diagnostics will enable new metallicity studies of galaxies dominated by AGN.

ABSTRACT Galaxies’ stellar masses, gas-phase oxygen abundances (metallicity), and star formation rates (SFRs) obey a series of empirical correlations, most notably the mass–metallicity relation (MZR) and fundamental metallicity relation (FZR), which relates oxygen abundance to a combination of stellar mass and SFR. However, due to the difficulty of measuring oxygen abundances and SFRs in galaxies that host powerful active galactic nuclei (AGN), to date it is unknown to what extent AGN-host galaxies also follow these correlations. In this work, we apply Bayesian methods to the MaNGA integral field spectrographic (IFS) survey that allow us to measure oxygen abundances and SFRs in AGN hosts, and use these measurements to explore how the MZR and FZR differ between galaxies that do and do not host AGN. We find similar MZRs at stellar masses above $10^{10.5} \, \mathrm{M}_\odot$, but that at lower stellar masses AGN hosts show up to $\sim 0.2$ dex higher oxygen abundances. The offset in the FZR is significantly smaller, suggesting that the larger deviation in the MZR is a result of AGN-host galaxies having systematically lower SFRs at fixed stellar mass. However, within the AGN-host sample there is little correlation between SFR and oxygen abundance. These findings support a scenario in which an AGN can halt efficient gas accretion, which drives non-AGN host galaxies to both higher SFR and lower oxygen abundance, resulting in the galaxy evolving off the star-forming main sequence (SFMS). As a consequence, as the SFR declines for an individual system its metallicity remains mostly unchanged.

Investigating the impact of galaxy properties on emergent Ly alpha emission is crucial for reionization studies, given the sensitivity of Ly alpha to neutral hydrogen. This study presents an analysis of the physical characteristics of 155 star-forming galaxies, 29 with Ly alpha detected, and 126 with Ly alpha not detected with Ly alpha EW < 20 & Aring;, at z = 1.9-3.5, drawn from the MOSFIRE Deep Evolution Field survey, that have overlapping observations from the Hobby-Eberly Telescope Dark Energy Experiment survey. To unravel the interstellar medium (ISM) conditions in our sample, we developed a custom nebular line modeling algorithm based on the MAPPINGS V photoionization model grid and the emcee framework. Combining nebular-based ISM properties with photometry-based global properties, constrained via Bagpipes, we explore distinctions in the stellar and gas properties between Ly alpha-detected and Ly alpha-nondetected galaxies. Our analysis reveals statistically significant differences between the two samples in terms of stellar mass and dust attenuation (A(V)) at >2 sigma significance, as determined via a Kolmogorov-Smirnov test. Moreover, there are weaker (less than or similar to 1 sigma significance) indications that the ionization parameter and metallicity differ between the two samples. Our results demonstrate that the escape fraction of Ly alpha (f(esc)(Ly alpha)) is inversely correlated with stellar mass, star formation rate, and dust attenuation, while it is positively correlated with the ionization parameter, with significance levels exceeding 2 sigma. Our findings suggest that the interstellar environments of Ly alpha-detected galaxies, characterized by low mass, low dust, low gas-phase metallicity, and high ionization parameters, play a pivotal role in promoting the escape of Ly alpha radiation.

ABSTRACT Central compact objects (CCOs), neutron stars found near the centre of some supernova remnants (SNRs), have been almost exclusively studied in X-rays and are thought to lack the wind nebulae typically seen around young, rotation-powered pulsars. We present the first, spatially resolved, morphological and spectroscopic study of the optical nebula observed at the location of CXOU J085201.4−461753, the CCO in the heart of the Vela Junior SNR. It is currently the only Galactic CCO with a spatially coincident nebula detected at optical wavelengths, whose exact nature remains uncertain. New Multi Unit Spectroscopic Explorer integral field spectroscopy data confirm that the nebula, shaped like a smooth blob extending 8 arcsec in diameter, is dominated by [N ii]${\lambda } {\lambda }$6548, 6583 emission. The data reveal a distinct and previously unobserved morphology of the H ${\alpha }$ emission, exhibiting an arc-like shape reminiscent of a bow shock nebula. We observe a significantly strong [N ii] emission relative to H ${\alpha }$, with the [N ii]${\lambda } {\lambda }$6548, 6583 up to 34 times the intensity of the H ${\alpha }$ emission within the optical nebula environment. Notably, the [N ii] and H ${\alpha }$ structures are not spatially coincident, with the [N ii] nebula concentrated to the south of the CCO and delimited by the H ${\alpha }$ arc-like structure. We detect additional emission in [N i], He i, [S ii], [Ar iii], [Fe ii], and [S iii]. We discuss our findings in the light of a photoionization or Wolf–Rayet nebula, pointing to a very massive progenitor and further suggesting that very massive stars do not necessarily make black holes.

Photoionization models frequently assume constant temperature or density within H II regions. We investigate this assumption by measuring the detailed temperature and density structures of four H II regions in the Large Magellanic Cloud and the Small Magellanic Cloud, using integral-field spectroscopic data from the Wide-Field Spectrograph on the ANU 2.3 m telescope. We analyze the distribution of emission lines of low-ionization, intermediate-ionization, and high-ionization species. We present the complex electron temperature and density structures within H II regions. All four nebulae present a negative gradient in the electron density profile. Both positive and negative temperature gradients are observed in the nebulae. We create a series of nebula models with constant interstellar medium (ISM) pressure and varying temperature and density distributions. A comparison of the line ratios between our H II regions and models suggests that none of the simple nebula models can reproduce the observed temperature and density structures. Comparison between the models and the data suggests that the ISM pressure of nebulae in the LMC and SMC is between log(P/k) = 6 and 7.5. Complex internal structures of the nebulae highlight the importance of future Monte Carlo photoionization codes for accurate nebula modeling, which include a comprehensive consideration of arbitrary geometries of H II regions.

The photoionization model of narrow-line regions in active galactic nuclei (AGNs) has been investigated for decades. Many published models are restricted to simple linear scaling abundance relations, dust-free assumption, uniform AGN radiation field, and using one specific photoionization code, which restricts them from providing a satisfactory prediction on a broad range of AGN observations. Through a comprehensive investigation, here we present how the choice of abundance scaling relations, dust inclusion, AGN radiation fields, and different photoionization codes CLOUDY and MAPPINGS affect the predictions on the strength of strong UV, optical, and infrared emission lines. We find the dust-depleted radiation-pressure-dominated AGN model built with the latest nonlinear abundance sets and photoionization code MAPPINGS V are consistent with AGN observations across a broad range of wavelengths. We also assess new potential H ii -AGN separation diagrams in the optical and UV wavelengths.

The Messenger Interface Monte Carlo Mappings V (M 3 ) is a photoionization code adopting the fully self-consistent Monte Carlo radiative transfer (MCRT) technique, which presents a major advance over previous photoionization models with simple geometries. M 3 is designed for modeling nebulae in arbitrary three-dimensional geometries. In this paper, we describe the MCRT technique and the microphysics implemented in M 3 , including photoionization, collisional ionization, free–free and free–bound recombination, and two-photon radiation. We put M 3 through the Lexington/Meudon benchmarks to test the reliability of the new code. We apply M 3 to three H ii region models with fiducial geometries, demonstrating that M 3 is capable of dealing with nebulae with complex geometries. M 3 is a promising tool for understanding emission-line behavior in the era of SDSS-V/LVM and James Webb Space Telescope, which will provide high-quality data of spatially resolved nearby H ii regions and highly turbulent local and high-redshift H ii regions.

We create a photoionization model embedded in the turbulent interstellar medium (ISM) by using the state-of-the-art Messenger Monte Carlo MAPPINGS V code (M 3 ) in conjunction with the CMFGEN stellar atmosphere model. We show that the turbulent ISM causes the inhomogeneity of electron temperature and density within the nebula. The fluctuation in the turbulent ISM creates complex ionization structures seen in nearby nebulae. The inhomogeneous density distribution within the nebula creates a significant scatter on the spatially resolved standard optical diagnostic diagrams, which cannot be represented by the spherical constant-density photoionization model. We analyze the dependence of different optical emission lines on the complexity of nebular geometry, finding that the emission lines residing on the nebular boundary are highly sensitive to the complexity of nebular geometry, while the emission lines produced throughout the nebula are sensitive to the density distribution of the ISM within the nebula. Our fractal photoionization model demonstrates that a complex nebular geometry is required for the accurate modeling of H ii regions and emission-line galaxies, especially for the high-redshift galaxies, where the ISM is highly turbulent based on increasing observational evidence.

Relativistic jets are believed to have a substantial impact on the gas dynamics and evolution of the interstellar medium (ISM) of their host galaxies. In this paper, we aim to draw a link between the simulations and the observable signatures of jet-ISM interactions by analyzing the emission morphology and gas kinematics resulting from jet-induced shocks in simulated disc and spherical systems. We find that the jet-induced laterally expanding forward shock of the energy bubble sweeping through the ISM causes large-scale outflows, creating shocked emission and high-velocity dispersion in the entire nuclear regions (∼2 kpcs) of their hosts. The jetted systems exhibit larger velocity widths (> 800 kms−1), broader Position-Velocity maps and distorted symmetry in the disc’s projected velocities than systems without a jet. We also investigate the above quantities at different inclination angles of the observer with respect to the galaxy. Jets inclined to the gas disc of its host are found to be confined for longer times, and consequently couple more strongly with the disc gas. This results in prominent shocked emission and high-velocity widths, not only along the jet’s path, but also in the regions perpendicular to them. Strong interaction of the jet with a gas disc can also distort its morphology. However, after the jets escape their initial confinement, the jet-disc coupling is weakened, thereby lowering the shocked emission and velocity widths.

ABSTRACT Understanding the evolution of the N/O ratio in the interstellar medium (ISM) of galaxies is essential if we are to complete our picture of the chemical evolution of galaxies at high redshift, since most observational calibrations of O/H implicitly depend upon the intrinsic N/O ratio. The observed N/O ratio, however, shows large scatter at low O/H, and is strongly dependent on galactic environment. We show that several heretofore unexplained features of the N/O distribution at low O/H can be explained by the N seen in metal-poor galaxies being mostly primary nitrogen that is returned to the ISM via pre-supernova winds from rapidly rotating massive stars (M ≳ 10 M⊙, v/vcrit ≳ 0.4). This mechanism naturally produces the observed N/O plateau at low O/H. We show that the large scatter in N/O at low O/H also arises naturally from variations in star-formation efficiency. By contrast, models in which the N and O come primarily from supernovae provide a very poor fit to the observed abundance distribution. We propose that the peculiar abundance patterns we observe at low O/H are a signature that dwarf galaxies retain little of their SN ejecta, leaving them with abundance patterns typical of winds.

We present the Stromlo Stellar Tracks, a set of stellar evolutionary tracks, computed by modifying the Modules for Experiments in Stellar Astrophysics (MESA) 1D stellar evolution package, to fit the Galactic Concordance abundances for hot (T > 8000 K) massive (≥10 M ⊙) main-sequence (MS) stars. Until now, all stellar evolution tracks have been computed at solar, scaled-solar, or α-element-enhanced abundances, and none of these models correctly represent the Galactic Concordance abundances at different metallicities. This paper is the first implementation of Galactic Concordance abundances to the stellar evolution models. The Stromlo tracks cover massive stars (10 ≤ M/M ⊙ ≤ 300) with varying rotations (v/v crit = 0.0, 0.2, 0.4) and a finely sampled grid of metallicities (−2.0 ≤ [Z/H] ≤ +0.5; Δ[Z/H] = 0.1) evolved from the pre-main sequence to the end of 12C burning. We find that the implementation of Galactic Concordance abundances is critical for the evolution of MS, massive hot stars in order to estimate accurate stellar outputs (L, T eff, g), which, in turn, have a significant impact on determining the ionizing photon luminosity budgets. We additionally support prior findings of the importance that rotation plays on the evolution of massive stars and their ionizing budget. The evolutionary tracks for our Galactic Concordance abundance scaling provide a more empirically motivated approach than simple uniform abundance scaling with metallicity for the analysis of H ii regions and have considerable implications for determining nebular emission lines and metallicity. Therefore, it is important to refine existing stellar evolutionary models for comprehensive high-redshift extragalactic studies. The Stromlo tracks are available to the astronomical community.

In this paper we examine the Direct Method for measuring electron temperatures in H ii regions, and the extent to which such measurements can provide meaningful information on the physical conditions in these regions. We discuss the limits to what can be inferred about electron temperatures from nebular emission line fluxes. We provide a new simplified method for estimating electron temperatures, including parameters that can be used to determine this from UV [O iii] and [O ii] oxygen lines observable in high-redshift objects using ground-based telescopes. We test this method on published UV high redshift observations and compare the results with reported electron temperatures.

Abstract Understanding the nucleosynthetic origin of nitrogen and the evolution of the N/O ratio in the interstellar medium is crucial for a comprehensive picture of galaxy chemical evolution at high-redshift because most observational metallicity (O/H) estimates are implicitly dependent on the N/O ratio. The observed N/O at high-redshift shows an overall constancy with O/H, albeit with a large scatter. We show that these heretofore unexplained features can be explained by the pre-supernova wind yields from rotating massive stars (M≳10M⊙,ν/νcrit≳0.4). Our models naturally produce the observed N/O plateau, as well as the scatter at low O/H. We find the scatter to arise from varying star formation efficiency. However, the models that have supernovae dominated yields produce a poor fit to the observed N/O at low O/H. This peculiar abundance pattern at low O/H suggests that dwarf galaxies are most likely to be devoid of SNe yields and are primarily enriched by pre-supernova wind abundances.