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A superbubble is a hot, dilute, and X-ray-emitting gas cavity produced by stellar winds and supernova explosions. It is an intriguing feature for the study of stellar feedback processes. We report a study of possible superbubbles in the Andromeda Galaxy (M31). We identify one out of 83 extended sources as a strong superbubble candidate, SB1, from the M31 X-ray source catalogue. SB1 is located in the northern disc of M31 and exhibits soft, extended X-ray emission surrounded by an Hα shell. The XMM–Newton spectral analysis reveals that SB1 has a temperature of ∼0.14 keV and an X-ray luminosity of |$L_{\rm X}\sim 3.5\times 10^{37}\,{\rm erg\, s}^{-1}$| in the 0.3–10.0 keV band. Two stellar clusters are found at the west rim of SB1. The estimated age of SB1 is similar to that of an overlapping young stellar cluster, and the colour-magnitude diagram reveals the presence of young stellar objects with an age of less than 10 Myr. We propose that SB1 is a superbubble, likely having triggered star formation in this cluster by compressing the accumulated gas, thereby leading to the formation of gas-dense regions. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) bubble structure of the Sgr-B molecular-cloud complex is derived by a kinematical analysis of CO-line archival cube data of the Galactic Centre (GC) observed with the Nobeyama 45-m telescope. The line-of-sight depth is estimated by applying the face-on transformation method of radial velocity to the projected distance on the Galactic plane considering the Galactic rotation of the central molecular zone (CMZ). The 3D complex exhibits a conical-horn structure with the Sgr-B2 cloud located in the farthest end on the line of sight at radial velocity |$v_{\rm lsr} \sim 70$|  km s |$^{-1}$|⁠ , and the entire complex composes a lopsided bubble opening toward the Sun at |$v_{\rm lsr}\sim 50$| to 30 km s |$^{-1}$|⁠. The line-of-sight extent of the complex is |$\sim 100$|  pc according to the large velocity extent for several tens of km s |$^{-1}$| from Sgr-B2 to the outskirts. The entire complex exhibits a flattened conical bubble with full sizes |$\sim 40 \ {\rm pc} \times 20 \ {\rm pc} \times 100 \ {\rm pc}$| in the l, b and line-of-sight directions, respectively. Based on the 3D analysis, we propose a formation scenario of the giant molecular bubble structure due to a galactic bow shock, and suggest that the star formation in Sgr-B2 was enhanced by dual-side compression (DSC) of the B2 cloud by the Galactic shock wave from up-stream and expanding H  ii region from the down-stream side of the GC Arm I in Galactic rotation. [ABSTRACT FROM AUTHOR]

Three-dimensional dust density maps are crucial for understanding the structure of the interstellar medium of the Milky Way and the processes that shape it. However, constructing these maps requires large data sets and the methods used to analyse them are computationally expensive and difficult to scale up. As a result, it has only recently become possible to map kiloparsec-scale regions of our Galaxy at parsec-scale grid sampling. We present all-sky three-dimensional dust density and extinction maps of the Milky Way out to 2.8 kpc in distance from the Sun using the fast and scalable Gaussian Process algorithm Dustribution. The sampling of the three-dimensional map is l, b, d  = 1° × 1° × 1.7 pc. The input extinction and distance catalogue contains 120 million stars with photometry and astrometry from Gaia DR2, 2MASS and AllWISE. This combines the strengths of optical and infrared data to probe deeper into the dusty regions of the Milky Way. We compare our maps with other published 3D dust maps. All maps quantitatively agree at the 0.001 mag pc−1 scale with many qualitatively similar features, although each map also has its own features. We recover Galactic features previously identified in the literature. Moreover, we also see a large under-density that may correspond to an inter-arm or -spur gap towards the Galactic Centre. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive multiwavelength investigation of the intermediate-age open cluster NGC 1912. We identified 401 member stars for NGC 1912 using K-nearest neighbour and Gaussian Mixture Model machine learning techniques. The fundamental parameters determined for the cluster are metallicity (z) = 0.0141 |$\pm$| 0.0006, log(age) = 8.519 |$\pm$| 0.040, binary fraction (⁠|$b_{\text{frac}}$|⁠) = 0.445 |$\pm$| 0.035, visual extinction (⁠|$A_V$|⁠) = 0.864 |$\pm$| 0.033 mag, total-to-selective extinction ratio (⁠|$R_V$|⁠) = 3.007 |$\pm$| 0.096, distance = 1096 |$\pm$| 15 pc. The central density (⁠|$\rho _o$|⁠), core radius (⁠|$r_c$|⁠), tidal radius (⁠|$r_t$|⁠), and background density (⁠|$\rho _{\mathrm{bg}}$|⁠) for the cluster are obtained as 0.643 |$\pm$| 0.067 stars arcmin |$^{-2}$| , 7.743 |$\pm$| 0.784 arcmin, 84.633 |$\pm$| 7.188 arcmin, and 0.001 |$\pm$| 0.000 stars arcmin |$^{-2}$| , respectively. Dynamical mass segregation study revealed a concentration of some apparently massive stars towards the cluster centre. Polarimetric analysis of 90 stars in |$BVR_cI_c$| wavelength bands revealed that the observed polarization in NGC 1912 is not solely attributed to interstellar dust. The Galactic magnetic field is dominant in this region. Dust grain sizes within the intracluster region are found to be relatively smaller than that of the general ISM. The extinction map revealed the existence of a potential 'interstellar bubble' located close to the cluster region. Towards the periphery of the probable bubble region, which displays an ovoid-like geometry, 16 probable young stellar objects have been detected, suggesting the ongoing triggering of secondary star formation events in this region. [ABSTRACT FROM AUTHOR]

A major prediction of most super-Eddington accretion theories is the presence of anisotropic emission from supercritical discs, but the degree of anisotropy and its dependence on energy remain poorly constrained observationally. A key breakthrough allowing to test such predictions was the discovery of high-excitation photoionized nebulae around ultraluminous X-ray sources (ULXs). We present efforts to tackle the degree of anisotropy of the ultraviolet/extreme ultraviolet (UV/EUV) emission in super-Eddington accretion flows by studying the emission-line nebula around the archetypical ULX NGC 1313 X–1. We first take advantage of the extensive wealth of optical/near-UV and X-ray data from Hubble Space Telescope, XMM–Newton, Swift X-ray telescope, and NuSTAR observatories to perform multiband, state-resolved spectroscopy of the source to constrain the spectral energy distribution (SED) along the line of sight. We then compare spatially resolved cloudy predictions using the observed line-of-sight SED with the nebular line ratios to assess whether the nebula 'sees' the same SED as observed along the line of sight. We show that to reproduce the line ratios in the surrounding nebula, the photoionizing SED must be a factor of ≈4 dimmer in UV emission than along the line of sight. Such nearly iosotropic UV emission may be attributed to the quasi-spherical emission from the wind photosphere. We also discuss the apparent dichotomy in the observational properties of emission-line nebulae around soft and hard ULXs, and suggest that only differences in mass-transfer rates can account for the EUV/X-ray spectral differences, as opposed to inclination effects. Finally, our multiband spectroscopy suggests that the optical/near-UV emission is not dominated by the companion star. [ABSTRACT FROM AUTHOR]

We performed a |$^{12}$| CO- and |$^{13}$| CO-line study of the "Brick" (G0.253+0.016) in the Galactic Center (GC) by analyzing archival data obtained with the Nobeyama 45 m telescope. We present kinematics and molecular gas distributions in the longitude–velocity diagram, and suggest that the Brick is located along the GC Arm I in the central molecular zone (CMZ), which yields a distance from the Sun of 8 kpc and a Galactocentric distance of 0.2 kpc. The major- and minor-axis diameters of the Brick are |$D_x\times D_y=8.4 \times 4.1\, {\rm pc}$| at position angles of 40 and |$130^\circ$|⁠ , respectively, and the scale radius is |$r_{\rm Bri}=\sqrt{D_x D_y}=2.96\, {\rm pc}$|⁠. The molecular mass inferred from the |$^{12}$| CO-line integrated intensity is |$M_{\mathrm{Bri};X_\mathrm{CO}}\sim 5.1\times 10^4\, M_\odot$| for a conversion factor |$X_{\rm CO;GC}=1.0\times 10^{20}$| H |$_2$| cm |$^{-2}$| [K km s |$^{-1}]^{-1}$|⁠. On the other hand, the dynamical (virial) mass for the measured velocity dispersion of |$\sigma _v=10.0\, {\rm km\ s^{-1}}$| is calculated to be |$M_{\rm Bri;vir}\sim 6.8 \times 10^4\,M_\odot$|⁠ , which yields a new conversion factor of |$X_{\rm CO;Bri}=1.3\times 10^{20}$| H |$_2$| cm |$^{-2}$| [K km s |$^{-1}]^{-1}$|⁠. The Brick's center has a cavity surrounded by a spherical molecular bubble of radius |$r_{\rm bub}=1.85$| pc and mass |$\sim 1.7\times 10^4\,M_\odot$| expanding at |$v_{\rm exp}\simeq 10 \ {\rm km\ s^{-1}}$| with a kinetic energy of |$E_0\sim 1.7\times 10^{49}$| erg. If the bubble is approximated by an adiabatic spherical shock wave, the age is estimated to be |$t\sim 2/5 r_{\rm bub}/v_{\rm exp}\sim 7.2\times 10^4$| yr. Neither non-thermal radio structures nor thermal radio emission indicative of the H  ii region are found in the archival data from MeerKAT. We suggest that the molecular bubble is a dark supernova remnant buried in the Brick, which has therefore experienced past (⁠|${\sim}0.1$| Myr ago) massive star formation with a supernova explosion. [ABSTRACT FROM AUTHOR]

Context. Over the past few years, chemical studies have revealed multiple structures in the vicinity of young stellar objects (YSOs). It has become evident that specific physical conditions are associated with the emission of particular molecular lines, allowing us to use molecular probes of the YSO physics. Consequently, chemical surveys are now necessary to fully constrain the origin of the observed structures. Several surveys have been conducted to explore the chemistry of YSOs, focusing on Class 0 and Class II objects. However, our knowledge of intermediate objects, that are Class I objects, remains limited. Aims. To bridge the gap and establish the relationship between observed structures and molecular line emission at the Class I evolutionary stage, we investigate the spatial distribution of key molecular gas species in the low-mass Class I protostar L1489 IRS (IRAS 04016+2610), a source part of the ChemYSO survey. Methods. We performed a 3 mm line survey at high spatial and high spectral resolution using the NOEMA interferometer and the IRAM-30 m telescope. For the data analysis, we applied and compared two methods: a streamline model and the new python package TIPSY. Results. We present here the ten brightest lines of our survey, in which we identified a new ~3000 au long streamer in HC3N, C2H, and c–C3H2 emission, likely associated with more localized accretion shocks probed in SO. In addition, two ~10 000 au bubbles are seen with the dense molecular tracers HCO+, CS, and HCN around the YSO. We retrieve previously identified structures, like an outflow in HCO+ and another streamer in C2H. Additionally, potential indicators of a second outflow appear in CS and HCN emission, but its nature remains to be confirmed. Conclusions. The late infall identified at large scales may originate from the nearby prestellar core L1489 and is likely responsible for the formation of an external warped disk in this system. The detection of a potential second outflow could be the direct evidence of a binary system. Finally, we hypothesize that the bubbles may result from the magnetic pressure as observed in numerical simulations. [ABSTRACT FROM AUTHOR]

While much has been learned in recent decades about the X-ray emission of the extragalactic ultraluminous X-ray sources (ULXs), their radiative output in the ultraviolet (UV) band remains poorly constrained. Understanding of the full ULX spectral energy distribution (SED) is imperative to constrain the accretion flow geometry powering them, as well as their radiative power. Here we present constraints on the UV emission of the pulsating ULX (PULX) NGC 1313 X-2 based on the absence of nebular He  ii  λ4686 emission in its immediate environment. To this end, we first perform multiband spectroscopy of the ULX to derive three realistic extrapolations of the SED into the inaccessible UV, each predicting varying levels of UV luminosity. We then perform photoionization modelling of the bubble nebula and predict the He  ii  λ4686 fluxes that should have been observed based on each of the derived SEDs. We then compare these predictions with the derived upper limit on He  ii  λ4686 from the Multi-Unit Spectroscopic Explorer data, which allows us to infer a UV luminosity L UV ≲ 1 × 1039 erg s−1 in the PULX NGC 1313 X-2. Comparing the UV luminosity inferred with other ULXs, our work suggests there may be an intrinsic difference between hard and soft ULXs, either related to different mass-transfer rates and/or the nature of the accretor. However, a statistical sample of ULXs with inferred UV luminosities is needed to fully determine the distinguishing features between hard and soft ULXs. Finally, we discuss ULXs ionizing role in the context of the nebular He  ii  λ4686 line observed in star-forming metal-poor galaxies. [ABSTRACT FROM AUTHOR]

While 30 Dor C is a unique superbubble in the Large Magellanic Cloud for its luminous non-thermal X-ray emission, the thermal X-ray emission it emanates has not yet been thoroughly investigated and well constrained. Based on the separate ∼1 Ms deep XMM–Newton and Chandra observations, we report the discovery of the thermally emitting plasma in some portions of the western half of 30 Dor C. The thermal emission can be reproduced by a collisional-ionization-equilibrium plasma model with an average electron temperature of ∼0.4 keV. We find a significant overabundance of the intermediate-mass elements such as O, Ne, Mg, and Si, which may be indicative of a recent supernova explosion in 30 Dor C. Dynamical properties in combination with the information of the OB association LH 90 suggest that the internal post-main-sequence stars dominate the power of the superbubble and blow it out in the past ∼1 Myr. [ABSTRACT FROM AUTHOR]

We have conducted an analysis of nebulae around Wolf–Rayet (WR) stars in M33 using data collected by the imaging Fourier transform spectrometer SITELLE at the Canada–France–Hawaii telescope as part of the SIGNALS Large Program. Of the 211 known WR stars in M33, 178 are located in the fields observed in this study. We present the results of this analysis in the form of a comprehensive summary of all nebulae found around the observed WR stars. Based on three criteria we find to be the most effective for their detection, we detect a clear association with a circumstellar bubble around 33 of them (19 per cent). Our results show that the presence of bubbles does not correlate with the spectral type of the central star. The mean diameter of the WR nebulae we have found is 21 parsec. [ABSTRACT FROM AUTHOR]

In this paper, we present a glimpse of our observations of two Wolf-Rayet (WR) nebulae, NGC2359 and NGC6888 obtained with the SITELLE imaging Fourier transform spectrograph. The data are of unprecedented spatial coverage and cover a broad wavelength range. [ABSTRACT FROM AUTHOR]

Stellar feedback plays a crucial role in regulating baryon cycles of a galactic ecosystem, and may manifest itself in the formation of superbubbles in the interstellar medium. In this work, we used a set of high-resolution simulations to systematically study the properties and evolution of superbubbles in galactic environments. The simulations were based on the SMUGGLE galaxy formation framework using the hydrodynamical moving-mesh code arepo , reaching a spatial resolution of |$\sim 4 \, \rm pc$| and mass resolution of |$\sim 10^3 \, \rm M_{\odot }$|⁠. We identified superbubbles and tracked their time evolution using the parent stellar associations within the bubbles. The X-ray luminosity-size distribution of superbubbles in the fiducial run is largely consistent with the observations of nearby galaxies. The size of superbubbles shows a double-peaked distribution, with the peaks attributed to early feedback (radiative and stellar wind feedback) and supernova feedback. The early feedback tends to suppress the subsequent supernova feedback, and it is strongly influenced by star formation efficiency, which regulates the environmental density. Our results show that the volume filling factor of hot gas (T > 105.5 K) is about |$12~{{\ \rm per\ cent}}$| averaged over a region of 4 kpc in height and 20 kpc in radius centred on the disc of the galaxy. Overall, the properties of superbubbles are sensitive to the choice of subgrid galaxy formation models and can, therefore, be used to constrain these models. [ABSTRACT FROM AUTHOR]

We present the first implementation of hyperbolic thermal conduction in smoothed particle hydrodynamics. Hyperbolic conduction is a physically motivated alternative to traditional, parabolic conduction. It incorporates a relaxation time, which ensures that heat propagates no faster than a physical signal speed. This allows for larger, Courant-like, time-steps for explicit schemes. Numerical solutions of the hyperbolic conduction equations require added dissipation to remain stable at discontinuities and we present a novel scheme for this. Test cases include a simple step, the Sod Shock Tube, the Sedov–Taylor blast, and a super bubble. We demonstrate how longer relaxation times limit conduction, recovering the purely hydrodynamical results, while short relaxation times converge on the parabolic conduction result. We demonstrate that our scheme is stable with explicit Courant-like time-steps and can be orders of magnitude faster than explicit parabolic conduction, depending on the application. [ABSTRACT FROM AUTHOR]

We investigated the ionized and atomic gas kinematics and excitation state in the central region of ongoing star formation of the nearby low-metallicity dwarf galaxy Sextans B. The analysis is based on the new observations performed in the H α emission line with high resolution (R ∼ 16 000) scanning Fabry–Perot interferometer at the 6-m BTA Special Astrophysical Observatory of the Russian Academy of Sciences telescope, and on the long-slit spectral observations at the 9.2-m SALT and 2.5-m Caucasian Mountain Observatory of Sternberg Astronomical Institute of Moscow State University telescopes. Strong non-circular gas motions detected in the studied regions probably resulted from the off-plane gas motions and impact of stellar feedback. We identified six regions of elevated H α velocity dispersion, five of which exhibit asymmetric or two-component H α line profiles. Three of these regions are young (<1.1 Myr) expanding (⁠|$V_\mathrm{exp} \sim 25-50 \, \mbox{km}\, \mbox{s}^{-1}$|⁠) superbubbles. We argue that at least three regions in the galaxy could be supernova remnants. We conclude that supernovae feedback is the dominant source of energy for superbubbles in Sextans B, which is expected for such a low metallicity, although we cannot rule out a strong impact of pre-supernova feedback for one superbubble. [ABSTRACT FROM AUTHOR]

Observations of pulsar scintillation are among the few astrophysical probes of very small-scale (≲ au) phenomena in the interstellar medium (ISM). In particular, characterization of scintillation arcs, including their curvature and intensity distributions, can be related to interstellar turbulence and potentially overpressurized plasma in local ISM inhomogeneities, such as supernova remnants, H  ii regions, and bow shocks. Here we present a survey of eight pulsars conducted at the Five-hundred-metre Aperture Spherical Telescope (FAST), revealing a diverse range of scintillation arc characteristics at high sensitivity. These observations reveal more arcs than measured previously for our sample. At least nine arcs are observed toward B1929+10 at screen distances spanning |$\sim 90~{{\ \rm per\ cent}}$| of the pulsar's 361 pc path length to the observer. Four arcs are observed toward B0355+54, with one arc yielding a screen distance as close as ∼105 au (<1 pc) from either the pulsar or the observer. Several pulsars show highly truncated, low-curvature arcs that may be attributable to scattering near the pulsar. The scattering screen constraints are synthesized with continuum maps of the local ISM and other well-characterized pulsar scintillation arcs, yielding a three-dimensional view of the scattering media in context. [ABSTRACT FROM AUTHOR]

Asymptotic giant branch (AGB) stars experience heavy episodes of mass-loss through a slow stellar wind during the thermal pulse phase that form large, pc-scale structures around them. As the AGB stellar wind interacts with the interstellar medium (ISM), the otherwise isotropic ejecta gets distorted, resulting in asymmetric shapes, bow-shock structures and, in the case of fast motion relative to the surrounding ISM, extended wakes and tails as unexpectedly detected in GALEX ultraviolet (UV) images of o  Cet, also known as Mira. Since that discovery, another fourteen AGB stars have been reported to exhibit extended UV emission around them. Here, we present the discovery of extended UV emission around another three AGB stars, namely R For, R Hor, and DM Tuc. The analysis of the overall properties of the regions of extended UV emission indicates that these are preferentially detected in closer AGB stars far away from the Galactic plane, i.e. sources less extincted. Faster AGB stars tend to have more elongated shapes, with bow-shocks and wakes or tails of material, while AGB stars farther away from the Galactic plane tend to be surrounded by larger regions of UV emission. [ABSTRACT FROM AUTHOR]

Context. During the first four all-sky surveys eRASS:4, which was carried out from December 2019 to 2021, the extended Roentgen Survey with an Imaging Telescope Array (eROSITA) on board the Spektrum-Roentgen-Gamma (Spektr-RG, SRG) observed the Galactic H II region, the Carina nebula. Aims. We analysed the eRASS:4 data to study the distribution and spectral properties of the hot interstellar plasma and the bright stellar sources in the Carina nebula. Methods. The spectral extraction regions of the diffuse emission were defined based on the X-ray spectral morphology and multi-wavelength data. The spectra were fit with a combination of thermal and non-thermal emission models. The X-ray bright point sources in the Carina nebula are the colliding wind binary η Car, several O stars, and Wolf–Rayet (WR) stars. We extracted the spectra of the brightest stellar sources, which can be well fit with a multi-component thermal plasma model. Results. The spectra of the diffuse emission in the brighter parts of the Carina nebula are well reproduced by two thermal models, a lower-temperature component (~0.2 keV) and a higher-temperature component (0.6–0.8 keV). An additional non-thermal component dominates the emission above ~1 keV in the Central region around η Car and the other massive stars. Significant orbital variation in the X-ray flux was measured for η Car, WR 22, and WR 25. η Car requires an additional time-variable thermal component in the spectral model, which is associated with the wind-wind collision zone. Conclusions. Properties such as temperature, pressure, and luminosity of the X-ray emitting plasma in the Carina nebula derived from the eROSITA data are consistent with theoretical calculations of emission from superbubbles. This confirms that the X-ray emission is caused by the hot plasma inside the Carina nebula that has been shocked-heated by the stellar winds of the massive stars, in particular, of η Car. [ABSTRACT FROM AUTHOR]

Context. S 308 is an X-ray emitting bubble that surrounds the Wolf–Rayet star WR6. The structure shines in the optical as well and is thus known as the Dolphin Nebula. Due to its large angular extent, it has been covered at only 90% with past XMM-Newton observations. Aims. Thanks to the unique dataset provided by the all-sky survey performed in X-rays by SRG/eROSITA, we can show for the first time the image of the bubble in its entire extent in this band, together with its spectral characterization. Moreover, we have tried to apply the same procedure for other wind-blown bubbles detected in the optical/IR and we searched for X-ray extended emission around them. Methods. We first analyzed the diffuse emission of S308, providing a detailed spectral analysis. We then considered a sample of 22 optical/IR selected wind-blown bubbles from a previous study based on WISE data, providing an estimate of the X-ray flux for the first time. Results. We obtained the best fit for S308 with a two-temperature non-equilibrium plasma model (kT1 = 0.8-0.3+0.8 keV and kT2 = 2-1+3 keV) showing super-solar N abundance and low absorption. We did not detect any of the 22 optical/IR emitting bubbles in X-rays, but using our best fit model, we estimated the 3σ flux upper limits for each bubble. Conclusions. We demonstrate the new possibility offered by SRG/eROSITA to study known wind-blown bubbles and look for other ones. A two-temperature plasma description seems to fit the data quite well for S308. Since all of the 22 bubbles studied still remain undetected by SRG/eROSITA, it is very likely that absorption effects and spatial compactness are responsible for the challenges standing in the way of detecting these bubbles in soft X-rays. [ABSTRACT FROM AUTHOR]

Expanding nebulae are produced by mass loss from stars, especially during late stages of evolution. We describe the algorithms and methods implemented in the radiation-magnetohydrodynamics (MHD) code PION for highly scalable simulations using static mesh-refinement. We present results from 3D MHD simulations of bow shocks around runaway massive stars, and of the expansion of a fast wind from a Wolf-Rayet star into the slow wind from a previous red supergiant phase of evolution. PION is free software that can be downloaded from https://www.pion.ie/ [ABSTRACT FROM AUTHOR]

The superbubbles (SBs) carved in the interstellar medium by stellar winds and supernovae (SNe) are filled with hot (T > 106 K) gas that produces soft X-ray emission (0.3–2.0 keV). Models that assume a constant density medium and central SNe events fail to reproduce the soft X-ray luminosity that is observed in some SBs. We address this problem by generating models that trace the history of SNe in the SB, and produce off-centre SNe, and account for the missing soft X-ray emission. We test the models against archival, radio, optical, and X-ray observations of the SB DEM L50 located in the Large Magellanic Cloud. The soft X-ray properties of DEM L50, including its high luminosity, make it a perfect candidate to test our models. Furthermore, the multiple wave-band observations of this object will help us assess how well our models can reproduce other SB properties beside its soft X-ray properties. We find that a configuration where DEM L50 forms at the edge of a filament reproduces the observed soft X-ray luminosity, optical morphology, shell velocity, and swept-up mass of neutral gas. This configuration is supported by IR observations of the LMC. In addition, we find that off-centre SNe, which enhance soft X-ray emission, naturally occur for all of the initial ambient conditions we tested in our models. Finally, we show that an off-centre SN can explains the observed soft X-ray luminosity of DEM L50, and that the resulting luminosity is consistent with a plasma in non-equilibrium ionization. [ABSTRACT FROM AUTHOR]

As one of the brightest Galactic γ-ray sources, the Cygnus Cocoon superbubble has been observed by many detectors, such as Fermi -LAT, ARGO, HAWC, and LHAASO. However, the origin of γ-ray emission for the Cygnus Cocoon and the possible contribution to PeV cosmic rays are still under debate. The recent ultrahigh-energy γ-ray observations by LHAASO up to 1.4 PeV towards the direction of the Cygnus Cocoon, as well as the neutrino event report of IceCube-201120A coming from the same direction, suggest that the Cygnus Cocoon may be one of the sources of high-energy cosmic rays in the Galaxy. In this work, we propose a dual-zone diffusion model for the Cygnus Cocoon: the cocoon region and surrounding interstellar medium (ISM). This scenario can account for the γ-ray data from GeV to ∼50 TeV and agree with the one sub-PeV neutrino event result from IceCube so far. Moreover, it predicts a non-negligible contribution γ-ray emission at hundreds TeV from the ISM surrounding the Cygnus Cocoon. This possible diffuse TeV–PeV gamma-ray features can be resolved by the future LHAASO observations. [ABSTRACT FROM AUTHOR]

Analysing the high-resolution CO line survey of the Galactic plane with the Nobeyama 45-m telescope (FUGIN), we show that the star-forming complex G18.15-0.30+51 (G18) at radial velocity of 51 km s−1 is a tight triple association of a giant molecular cloud (GMC), H  ii regions, and a supernova remnant (SNR). The radial velocity of G18 allows three possible kinematic distances of d  = 3.9 ± 0.2 kpc for near solution or 12 ± 0.2 kpc for far solution, if we assume circular Galactic rotation, or d  = 6.1 ± 0.1 kpc, if it is moving with the 3-kpc expanding ring at an expanding velocity of 50 km s−1. The H  i line absorption of radio continuum from the H  ii region constrains the distance to 5.6 ≲ d SNR ≤ 7.6 kpc. The Σ− D (radio brightness–diameter) relation yields the distance to the SNR of |$d_{\rm SNR}=10.1^{+11.5}_{-4.7}$| kpc, allowing for a minimum distance of 5.4 kpc. From these, we uniquely determined the distance of G18 to be 6.07 ± 0.13 kpc in the 3-kpc expanding ring with the SNR being physically associated. The molecular mass of the GMC is estimated to be M mol ∼ 3 × 105 M⊙. The ratio of virial to luminous molecular masses is greater than unity in the central region and decreases outward to ≲0.2 at the cloud edge, indicating that the central region is dynamic, while the entire cloud is stable. We discuss the origin of the G18 triple system and propose a sustainable GMC model with continuous star formation. [ABSTRACT FROM AUTHOR]

We present the results of current observations of the young compact cluster of massive stars Westerlund 2 (Wd2) with the Mikhail Pavlinsky ART-XC telescope aboard the Spectrum-Roentgen-Gamma (SRG) observatory which we analysed together with the archival Chandra data. In general, Wd2 was detected over the whole electromagnetic spectrum including high-energy gamma rays, which revealed a cosmic ray acceleration in this object to the energies up to tens of TeV. The detection of Wd2 with ART-XC allowed us to perform a joint spectral analysis together with the high resolution Chandra observations of the diffuse emission from a few selected regions in the vicinity of the Wd2 core in the 0.4–20 keV range. To fit the Wd2 X-ray spectrum above a few keV one needs either a non-thermal power-law emission component, or a hot plasma with temperatures ∼ 5 keV. Our magnetohydrodynamic modelling of the plasma flows in Wd2 shows substantially lower electron temperatures in the system and thus the presence of the non-thermal component is certainly preferable. A kinetic model of the particle acceleration demonstrated that the non-thermal component may originate from the synchrotron radiation of multi-TeV electrons and positrons produced in Wd2 in accordance with the TeV photons detection from the source. [ABSTRACT FROM AUTHOR]

The ratio of Hα intensity to 1.4-GHz radio continuum intensity in the North Polar Spur (NPS) is measured to be ≲ 50, two orders of magnitude smaller than the values of ∼104 observed in the typical shell-type old supernova remnants of the Cygnus Loop and S147. The extremely low Hα-to-radio intensity ratio favours the Galactic Centre explosion model for the NPS, which postulates a giant shock wave at a distance of several kiloparsecs in the hot and low-density Galactic halo with a low hydrogen recombination rate, over the local supernova(e) remnant model. [ABSTRACT FROM AUTHOR]

Many asymptotic giant branch (AGB) and supergiant stars exhibit extended detached shells in the far-infrared, resembling rings or arcs. These structures have long been interpreted as the bow shock formed in the interface between the stellar wind and the interstellar medium (ISM), the astrosphere. To date, only a few AGB stars have been observed showing an extended shell in the ultraviolet (UV): the cometary tail drifting away from o Ceti, and a bubble around IRC+10216, CIT6, and U Hya. This paper describes a search of UV extended shells around AGB stars using archival Galaxy Evolution Explorer (GALEX) far-UV images. After inspecting visually 282 GALEX images, we identified the fourth discovery of a UV bubble around the AGB star R Dor. The bubble is seen as a 26 arcmin × 29 arcmin ring, corresponding to an actual diameter of 0.41 × 0.46 parsec2. The mass of the thin UV bubble is estimated to be ≃0.003 M⊙. The morphological asymmetry (less than ∼20 per cent) and brightness variations of this shell are uncorrelated with the stellar proper motion and thus they can rather be ascribed to inhomogeneities in the ISM. Archival Infrared Astronomical Satellite 60 and 100 μm images reveal that the bubble is filled with cold (i.e. |${\lesssim} 32$|  K) dust. All UV bubbles known to date are limited to be within a distance |${\lesssim} 350$| pc and at high Galactic latitudes (⁠|$|b| \gtrsim 35^{\circ }$|⁠), which suggests that their detection is hampered in most cases by the strong UV interstellar extinction. [ABSTRACT FROM AUTHOR]

We here study the multiband properties of a kiloparsec-size superbubble in the late-type spiral galaxy NGC 628. The superbubble is the largest of many holes seen in the early release images using James Webb Space Telescope (JWST)/MIRI filters that trace the polycyclic aromatic hydrocarbon (PAH) emissions. The superbubble is located in the interarm region ∼3 kpc from the Galactic Centre in the south-east direction. The shell surrounding the superbubble is detected in H  i , CO, and H α with an expansion velocity of 12 km s−1 and contains as much as 2 × 107 M⊙ of mass in gas that is mostly in molecular form. We find a clear excess of blue, bright stars inside the bubble as compared to the surrounding disc on the Hubble Space Telescope /Advanced Camera for Surveys images. These excess blue, bright stars are part of a stellar population of 105 M⊙ mass that is formed over the last 50 Myr in different star formation episodes, as determined from an analysis of colour–magnitude diagrams using a Bayesian technique. The mechanical power injected by the massive stars of these populations is sufficient to provide the energy necessary for the expansion of the shell gas. Slow and steady, rather than violent, injection of energy is probably the reason for the maintenance of the shell structure over the kiloparsec scale. The expanding shell is currently the site for triggered star formation as inferred from the JWST 21 µm (F2100W filter) and the H α images. [ABSTRACT FROM AUTHOR]

We have carried out the NH3(J, K) = (1, 1), (2, 2), and (3, 3) mapping observations toward the Galactic infrared bubble N49 (G28.83−0.25) using the Nobeyama 45 m telescope. Three NH3 clumps (A, B, and C) were discovered along the molecular filament with the radial velocities of ∼96, 87, and 89 km s−1, respectively. The kinetic temperature derived from the NH3(2, 2)/NH3(1, 1) shows T kin = 27.0 ± 0.6 K enhanced at Clump B in the eastern edge of the bubble, where position coincides with massive young stellar objects (MYSOs) associated with the 6.7 GHz class II methanol maser source. This result shows the dense clump is locally heated by stellar feedback from the embedded MYSOs. The NH3 Clump B also exists at the 88 km s−1 and 95 km s−1 molecular filament intersection. We therefore suggest that the NH3 dense gas formation in Clump B can be explained by a filament–filament interaction scenario. On the other hand, NH3 Clumps A and C at the northern and southern sides of the molecular filament might be the sites of spontaneous star formation because these clumps are located ∼ 5–10 pc away from the edge of the bubble. [ABSTRACT FROM AUTHOR]

Diffuse 1-ray line emission traces freshly produced radioisotopes in the interstellar gas, providing a unique perspective on the entire Galactic cycle of matter from nucleosynthesis in massive stars to their ejection and mixing in the interstellar medium (ISM). We aim to construct a model of nucleosynthesis ejecta on a galactic scale that is specifically tailored to complement the physically most important and empirically accessible features of 1ray measurements in the MeV range, in particular for decay 1 rays such as 26Al, 60Fe, or 44Ti. Based on properties of massive star groups, we developed a Population SYnthesis COde (PSYCO), which can instantiate galaxy models quickly and based on many different parameter configurations, such as the star formation rate (SFR), density profiles, or stellar evolution models. As a result, we obtain model maps of nucleosynthesis ejecta in the Galaxy which incorporate the population synthesis calculations of individual massive star groups. Based on a variety of stellar evolution models, supernova (SN) explodabilities, and density distributions, we find that the measured 26Al distribution from INTEGRAL/SPI can be explained by a Galaxy-wide population synthesis model with a SFR of 4-8 M yr-1 and a spiral-arm-dominated density profile with a scale height of at least 700 pc. Our model requires that most massive stars indeed undergo a SN explosion. This corresponds to a SN rate in the Milky Way of 1.8-2.8 per century, with quasi-persistent 26Al and 60Fe masses of 1.2-2.4 Mand 1-6 M, respectively. Comparing the simulated morphologies to SPI data suggests that a frequent merging of superbubbles may take place in the Galaxy, and that an unknown yet strong foreground emission at 1.8MeV could be present. [ABSTRACT FROM AUTHOR]

The Haze is an excess of microwave intensity emission surrounding the Galactic Centre. It is spatially correlated with the γ-ray Fermi bubbles, and with the S-PASS radio polarization plumes, suggesting a possible common provenance. The models proposed to explain the origin of the Haze, including energetic events at the Galactic Centre and dark matter decay in the Galactic halo, do not yet provide a clear physical interpretation. In this paper, we present a reanalysis of the Haze including new observations from the Multi-Frequency Instrument (MFI) of the Q-U-I Joint TEnerife (QUIJOTE) experiment, at 11 and 13 GHz. We analyse the Haze in intensity and polarization, characterizing its spectrum. We detect an excess of diffuse intensity signal ascribed to the Haze. The spectrum at frequencies 11 GHz |$\, \le \nu \le \,$| 70 GHz is a power law with spectral index βH = −2.79 ± 0.08, which is flatter than the Galactic synchrotron in the same region (βS = −2.98 ± 0.04), but steeper than that obtained from previous works (βH ∼ −2.5 at 23 GHz |$\, \le \, \nu \le \,$| 70 GHz). We also observe an excess of polarized signal in the QUIJOTE-MFI maps in the Haze area. This is a first hint detection of polarized Haze, or a consequence of curvature of the synchrotron spectrum in that area. Finally, we show that the spectrum of polarized structures associated with Galactic Centre activity is steep at low frequencies (β ∼ −3.2 at 2.3 GHz ≤ ν ≤ 23 GHz), and becomes flatter above 11 GHz. [ABSTRACT FROM AUTHOR]

We study the physical drivers of slow molecular cloud mergers within a simulation of a Milky Way-like galaxy in the moving-mesh code arepo , and determine the influence of these mergers on the mass distribution and star formation efficiency of the galactic cloud population. We find that 83 per cent of these mergers occur at a relative velocity below 5 km s−1, and are associated with large-scale atomic gas flows, driven primarily by expanding bubbles of hot, ionized gas caused by supernova explosions and galactic rotation. The major effect of these mergers is to aggregate molecular mass into higher-mass clouds: mergers account for over 50 per cent of the molecular mass contained in clouds of mass M > 2 × 106 M⊙. These high-mass clouds have higher densities, internal velocity dispersions and instantaneous star formation efficiencies than their unmerged, lower mass precursors. As such, the mean instantaneous star formation efficiency in our simulated galaxy, with its merger rate of just 1 per cent of clouds per Myr, is 25 per cent higher than in a similar population of clouds containing no mergers. [ABSTRACT FROM AUTHOR]

Supernovae explosions (SNe) in a stratified interstellar disc can create large scale structures and outflows perpendicular to the disc. Their morphology and emission characteristics depend on interrelations between the number of exploded SNe, the ISM vertical scale height, the height above the ISM disc at which SNe are located, and the mid-plane density of ambient gas. When observed such out-of-plane gas structures do characterize properties of the driving SNe and reveal the presence of underlying stellar clusters. Even though the morphology and emission properties of such structures are sensitive to characteristics of ambient gas they might be used for rough estimates of the clusters’ mass.

Feedback from massive stars shapes the interstellar medium (ISM) and affects the evolution of galaxies, but its mechanisms acting at the small scales (∼10 pc) are still not well constrained observationally, especially in the low-metallicity environments. We present the analysis of the ionized gas (focusing on its kinematics, which were never studied before) and its connection to the massive stars in the nearby (D ∼ 1.4 Mpc) star-forming very metal poor (⁠|$Z\sim 0.07 \, \mathrm{Z}_\odot$|⁠) galaxy Sextans A. The analysis is based on the observations with a scanning Fabry–Perot interferometer, long-slit spectroscopy, and imaging in emission lines with narrow-band tunable filters. We found 10 expanding superbubbles of ionized gas with ages of 1–3 Myr. We argue that three of them are probable supernova remnants, while the pre-supernova feedback is an important source of energy for blowing out the remaining superbubbles. The two brightest sites of star formation exhibit signs of outflowing ionized gas, which is traced by its ionized and atomic gas kinematics and (in one case) by its emission line flux ratios. Overall, the ionized gas kinematics in Sextans A is highly affected by the feedback from several generations of massive stars and inconsistent with the mere solid-body rotation observed in atomic hydrogen. [ABSTRACT FROM AUTHOR]

We develop a simple analytical model for what happens when an O star (or compact cluster of OB stars) forms in a shock-compressed layer and carves out an approximately circular hole in the layer, at the waist of a bipolar H  ii region (H  ii R). The model is characterized by three parameters: the half-thickness of the undisturbed layer, |$Z_{_{\rm LAYER}}$|⁠ , the mean number density of hydrogen molecules in the undisturbed layer, |$n_{_{\rm LAYER}}$|⁠ , and the (collective) ionizing output of the star(s), |$\dot{\cal N}_{_{\rm LyC}}$|⁠. The radius of the circular hole is given by |$W_{_{\rm IF}}(t)\sim 3.8\, {\rm pc}\, [Z_{_{\rm LAYER}}/0.1\,{\rm pc}]^{-1/6}[n_{_{\rm LAYER}}/10^4\,{\rm cm^{-3}}]^{-1/3}[\dot{\cal N}_{_{\rm LyC}}/10^{49}\,{\rm s^{-1}}]^{1/6}[t/{\rm Myr}]^{2/3}$|⁠. Similar power-law expressions are obtained for the rate at which ionized gas is fed into the bipolar lobes, the rate at which molecular gas is swept up into a dense ring by the shock front that precedes the ionization front, and the density in this dense ring. We suggest that our model might be a useful zeroth-order representation of many observed H  ii Rs. From viewing directions close to the mid-plane of the layer, the H  ii R will appear bipolar. From viewing directions approximately normal to the layer, it will appear to be a limb-brightened shell but too faint through the centre to be a spherically symmetric bubble. From intermediate viewing angles, more complicated morphologies can be expected. [ABSTRACT FROM AUTHOR]

In the Galactic center, there are many massive stars blowing strong stellar winds, which will strongly influence the surrounding environment and even the Galactic feedback. The Galactic center is quiescent at present, so the unique continuous energy input source is the massive star, consequently giving rise to many special features, such as the radio bubbles, the X-ray chimneys, the non-thermal filaments and high-metallicity abundance. However, it is difficult to quantify their contributions due to the complex environment in this region, and the past supernovae and Sgr A* activity are also important factors shaping these features. In this work, we discuss some structures possibly related to the stellar winds and perform preliminary simulations to study their evolution. We conclude the stellar winds can obviously influence a large scale ∼ 100 pc, and can possibly influence a larger scale environment indirectly. [ABSTRACT FROM AUTHOR]

Ultracompact Hii regions (UC-HII) are the young, very dense cores of massive star-forming regions in dwarf galaxies, where newly formed massive OB stars are surrounded by natal molecular clouds. Thermal energy deposited by mechanical feedback from a cluster of massive OB stars can form a superwind, which may lead to a wind-blown bubble as well as radiative cooling. We investigate the formation of radiatively cooling superwinds in UC-HII using a radiative cooling module in the hydrodynamics program. We built a grid of hydrodynamic simulations to determine the dependence of radiative cooling on the cluster radius, mass-deposition rate, wind velocity, and ambient medium in UC-HII. Our findings could help to better understand star formation in massive star-forming regions, where cool superwinds could trigger the formation of molecular clumpy regions. [ABSTRACT FROM AUTHOR]

Active galactic nucleus (AGN) bubbles could play an important role in accelerating high-energy cosmic rays (CRs) and galactic feedback. Only in nearby galaxies could we have high enough angular resolution in multiwavelengths to study the sub-kpc environment of the AGN, where the bubbles are produced and strongly interact with the surrounding interstellar medium. In this paper, we present the latest Chandra observations of the Virgo cluster galaxy NGC 4438, which hosts multiscale bubbles detected in various bands. The galaxy also has low current star formation activity, so these bubbles are evidently produced by the AGN rather than a starburst. We present spatially resolved spectral analysis of the Chandra data of the ∼3 arcsec × 5 arcsec (⁠|${\sim} 200{\rm ~pc}\times 350\rm ~pc$|⁠) nuclear bubble of NGC 4438. The power-law tail in the X-ray spectra can be most naturally explained as synchrotron emission from high-energy CR leptons. The hot gas temperature increases, while the overall contribution of the non-thermal X-ray emission decreases with the vertical distance from the galactic plane. We calculate the synchrotron cooling time-scale of the CR leptons responsible for the non-thermal hard X-ray emission to be only a few tens to a few hundreds of years. The thermal pressure of the hot gas is about three times the magnetic pressure, but the current data cannot rule out the possibility that they are still in pressure balance. The spatially resolved spectroscopy presented in this paper may have important constraints on how the AGN accelerates CRs and drives outflows. We also discover a transient X-ray source only ∼5 arcsec from the nucleus of NGC 4438. The source was not detected in 2002 and 2008, but became quite X-ray bright in 2020 March, with an average 0.5–7 keV luminosity of |${\sim} 10^{39}\rm ~erg~s^{-1}$|⁠. [ABSTRACT FROM AUTHOR]

The environment of S187, a nearby H  ii region (1.4 ± 0.3 kpc), is analyzed. A surrounding shell has been studied in the H  i line, molecular lines, and also in infrared and radio continua. We report the first evidence of a clumpy H  i environment in its photodissociation region. A background radio galaxy enables the estimation of the properties of cold atomic gas. The estimated atomic mass fraction of the shell is ∼260 M⊙, the median spin temperature is ∼50 K, the shell size is ∼4 pc with typical wall width around 0.2 pc. The atomic shell consists of ∼100 fragments. The fragment sizes correlate with mass with a power-law index of 2.39–2.50. The S187 shell has a complex kinematical structure, including the expanding quasi-spherical layer, molecular envelope, an atomic sub-bubble inside the shell and two dense cores (S187 SE and S187 NE) at different stages of evolution. The atomic sub-bubble inside the shell is young, contains a Class II young stellar object and OH maser in the centre and the associated YSOs in the walls of the bubble. S187 SE and S187 NE have similar masses (∼1200 and ∼900 M⊙, respectively). S187 SE is embedded into the atomic shell and has a number of associated objects, including high-mass protostars, outflows, maser sources, and other indicators of ongoing star formation. No YSOs inside S187 NE were detected, but indications of compression and heating by the H  ii region exist. [ABSTRACT FROM AUTHOR]

We investigate the effect of mass-loading from embedded clouds on the evolution of wind-blown bubbles. We use 1D hydrodynamical calculations and assume that the clouds are numerous enough that they can be treated in the continuous limit, and that rapid mixing occurs so that the injected mass quickly merges with the global flow. The destruction of embedded clouds adds mass into the bubble, increasing its density. Mass-loading increases the temperature of the unshocked stellar wind due to the frictional drag, and reduces the temperature of the hot shocked gas as the available thermal energy is shared between more particles. Mass-loading may increase or decrease the volume-averaged bubble pressure. Mass-loaded bubbles are smaller, having less retained energy and lower radial momentum, but in all cases examined, they are still able to do significant PdV work on the swept-up gas. In this latter respect, the bubbles more closely resemble energy-conserving bubbles than the momentum-conserving-like behaviour of 'quenched' bubbles. [ABSTRACT FROM AUTHOR]

We present a novel method for including the effects of early (pre-supernova) feedback in simulations of galaxy evolution. Rather than building a model which attempts to match idealized, small-scale simulations or analytic approximations, we rely on direct observational measurements of the time-scales over which star-forming molecular clouds are disrupted by early feedback. We combine observations of the spatial de-correlation between molecular gas and star formation tracers on ∼100 pc scales with an analytic framework for the expansion of feedback fronts driven by arbitrary sources or mechanisms, and use these to constrain the time-scale and momentum injection rate by early feedback. This allows us to directly inform our model for feedback from these observations, sidestepping the complexity of multiple feedback mechanisms and their interaction below the resolution scale. We demonstrate that this new model has significant effects on the spatial clustering of star formation, the structure of the ISM, and the driving of outflows from the galactic plane, while preserving the overall regulation of the galaxy-integrated star formation rate. We find that this new feedback model results in galaxies that regulate star formation through the rapid disruption of star-forming clouds, rather than by highly efficient, global galactic outflows. We also demonstrate that these results are robust to stochasticity, degraded numerical resolution, changes in the star formation model parameters, and variations in the single free model parameter that is unconstrained by observations. [ABSTRACT FROM AUTHOR]

We probe the environmental properties of X-ray supernova remnants (SNRs) at various points along their evolutionary journey, especially the S-T phase, and their conformance with theoretically derived models of SNR evolution. The remnant size is used as a proxy for the age of the remnant. Our data set includes 34 Milky Way, 59 Large Magellanic Cloud (LMC), and 5 Small Magellanic Cloud (SMC) SNRs. We select remnants that have been definitively typed as either core-collapse (CC) or Type Ia supernovae, with well-defined size estimates, and a thermal X-ray flux measured over the entire remnant. A catalog of SNR size and X-ray luminosity is presented and plotted, with ambient density and age estimates from the literature. Model remnants with a given density, in the Sedov-Taylor (S-T) phase, are overplotted on the diameter-versus-luminosity plot, allowing the evolutionary state and physical properties of SNRs to be compared to each other, and to theoretical models. We find that small, young remnants are predominantly Type Ia remnants or high luminosity CCs, suggesting that many CC SNRs are not detected until after they have emerged from the progenitor's wind-blown bubble. An examination of the distribution of SNR diameters in the Milky Way and LMC reveals that LMC SNRs must be evolving in an ambient medium which is 30 per cent as dense as that in the Milky Way. This is consistent with ambient density estimates for the Galaxy and LMC. [ABSTRACT FROM AUTHOR]

There is evidence that the star formation process is linked to the intricate net of filaments in molecular clouds, which may be also due to gas compression from external triggers. We studied the southern region of the Perseus NGC 1333 molecular cloud, known to be heavily shaped by similar external triggers, to shed light on the process that perturbed the filament where the Class 0 IRAS4 protostars lie. We use new IRAM-NOEMA observations of SiO and CH3OH, both known to trace violent events as shocks, towards IRAS 4A as part of the Large Program Seeds Of Life In Space (SOLIS). We detected three parallel elongated (>6000 au) structures, called fingers, with narrow-line profiles (∼1.5 km s−1) peaked at the cloud systemic velocity, tracing gas with high density ((5–20) × 105 cm−3) and high temperature (80–160 K). They are chemically different, with the northern finger traced by both SiO and CH3OH ([CH3OH]/[SiO] ∼ 160–300), while the other two only by SiO ([CH3OH]/[SiO] ≤ 40). Among various possibilities, a train of three shocks, distanced by ≥5000 yr, would be consistent with the observations if a substantial fraction of silicon, frozen on to the grain mantles, is released by the shocks. We suggest that the shock train is due to an expanding gas bubble, coming behind NGC 1333 from the south-west and clashing against the filament where IRAS 4A lies. Finally, we propose a solution to the two-decades-long debate on the nature and origin of the widespread narrow SiO emission observed in the south part of NGC 1333, namely that it is due to unresolved trains of shocks. [ABSTRACT FROM AUTHOR]

We investigated the detailed plasma condition of the North Polar Spur (NPS)/Loop I using archival Suzaku data. In previous research, collisional ionization equilibrium (CIE) have been assumed for X-ray plasma state, but we also assume non-equilibrium ionization (NEI) to check the plasma condition in more detail. We found that most of the plasma in the NPS/Loop I favors the state of NEI, and has the density-weighted ionization timescale of ne t ∼ 1011–12 s cm−3 and the electron number density ne ∼ a few × 10−3 cm−3. The plasma shock age, t , or the time elapsed after the shock front passed through the plasma, is estimated to be on the order of a few |$\rm {Myr}$| for the NPS/Loop I, which puts a strict lower limit to the age of the whole NPS/Loop I structure. We found that NEI results in significantly higher temperature and lower emission measure than those currently derived under CIE assumption. The electron temperature under NEI is estimated to be as high as 0.5 keV toward the brightest X-ray NPS ridge at Δθ = −20○, which decreases to 0.3 keV at −10○, and again increases to ∼0.6 keV towards the outer edge of Loop I at Δθ ∼ 0○, about twice the currently estimated temperatures. Here, Δθ is the angular distance from the outer edge of Loop I. We discuss the implication of introducing NEI for the research in plasma states in astrophysical phenomena. [ABSTRACT FROM AUTHOR]

In this paper, we present a glimpse of our observations of two Wolf-Rayet (WR) nebulae, NGC2359 and NGC6888 obtained with the SITELLE imaging Fourier transform spectrograph. The data are of unprecedented spatial coverage and cover a broad wavelength range. [ABSTRACT FROM AUTHOR]

Recent studies have shown that live (not decayed) radioactive 60Fe is present in deep-ocean samples, Antarctic snow, lunar regolith, and cosmic rays. 60Fe represents supernova (SN) ejecta deposited in the Solar system around |$3 \, \rm Myr$| ago, and recently an earlier pulse |${\approx}7 \ \rm Myr$| ago has been found. These data point to one or multiple near-Earth SN explosions that presumably participated in the formation of the Local Bubble. We explore this theory using 3D high-resolution smooth-particle hydrodynamical simulations of isolated SNe with ejecta tracers in a uniform interstellar medium (ISM). The simulation allows us to trace the SN ejecta in gas form and those eject in dust grains that are entrained with the gas. We consider two cases of diffused ejecta: when the ejecta are well-mixed in the shock and when they are not. In the latter case, we find that these ejecta remain far behind the forward shock, limiting the distance to which entrained ejecta can be delivered to ≈100 pc in an ISM with |$n_\mathrm{H}=0.1\,\, \rm cm^{-3}$| mean hydrogen density. We show that the intensity and the duration of 60Fe accretion depend on the ISM density and the trajectory of the Solar system. Furthermore, we show the possibility of reproducing the two observed peaks in 60Fe concentration with this model by assuming two linear trajectories for the Solar system with 30-km s−1 velocity. The fact that we can reproduce the two observed peaks further supports the theory that the 60Fe signal was originated from near-Earth SNe. [ABSTRACT FROM AUTHOR]

N70 is a giant superbubble (SB) produced by the stellar cluster LH 114. The dynamic of the stellar SB can be explained with hydrodynamic simulations. However, the explanation of the observed X-ray luminosity is still a matter of debate. Observations show that this kind of superbubbles exhibits X-ray luminosities of the order of 1035 erg s−1, which cannot be explained by only considering the mechanical luminosity of the stellar components. Instead, theoretical models predict luminosities one order of magnitude lower. In this work, we attempt to answer this discrepancy by including a core-collapse supernova explosion (SN) and the photons emitted by each of the stars involved. We find that a core-collapse SN, with an initial mass of 10 M⊙, can explain the missing X-ray emission, lasting approximately 1000 yr. Also, the radiation produces an enhancement of the filamentary superbubble morphology and it increases the SB radius by |$\sim 23{{\ \rm per\ cent}}$| with respect to the pure hydrodynamic case. [ABSTRACT FROM AUTHOR]

This document is a correction to a previous publication titled "Hyperbolic conduction: A fast, physical conduction model implemented in Smoothed Particle Hydrodynamics." The original publication contained errors in equations (8) and (10), which have now been corrected. Additionally, a typographical error in the fourth paragraph of section 3.1 has been fixed. These corrections do not affect the conclusions of the paper. The authors are N. A. Owens and J. Wadsley. [Extracted from the article]

We study the effect of cosmic ray (CR) acceleration in the massive compact star cluster Westerlund 1 in light of its recent detection in γ-rays. Recent observations reveal a 1/ r radial distribution of the CR energy density. Here, we theoretically investigate whether or not this profile can help to distinguish between (1) continuous CR acceleration in the star cluster stellar wind-driven shocks and (2) discrete CR acceleration in multiple supernovae (SNe) shocks – which are often debated in the literature. Using idealized two-fluid simulations and exploring different acceleration sites and diffusion coefficients, we obtain the CR energy density profile and luminosity to find the best match for the γ-ray observations. We find that the inferred CR energy density profiles from observations of γ-ray luminosity and mass can be much different from the true radial profile. CR acceleration at either the cluster core region or the wind termination shock can explain the observations, if the diffusion coefficient is κ cr ∼ 1027 cm2 s−1 and a fraction of |${\approx}10-20{{\ \rm per\ cent}}$| of the shock power/post-shock pressure is deposited into the CR component. We also study the possibility of discrete SNe explosions being responsible for CR acceleration and find that with an injection rate of 1 SN in every ∼0.03 Myr, one can explain the observed γ-ray profile. This multiple SN scenario is consistent with X-ray observations only if the thermal conductivity is close to the Spitzer value. [ABSTRACT FROM AUTHOR]

The role of different stellar feedback mechanisms in giant molecular clouds is not well understood. This is especially true for regions with many interacting clouds as would be found in a galactic spiral arm. In this paper, building on previous work by Bending et al. we extract a |$500{\, \mathrm{pc}}\times 500{\, \mathrm{pc}}\times {100}{\, \mathrm{pc}}$| section of a spiral arm from a galaxy simulation. We use smoothed particle hydrodynamics to re-simulate the region at higher resolution (1 M⊙ per particle). We present a method for momentum-driven stellar winds from main-sequence massive stars, and include this with photoionization, self-gravity, a galactic potential, and interstellar medium heating/cooling. We also include cluster-sink particles with accretion radii of 0.78 pc to track star/cluster formation. The feedback methods are as robust as previous models on individual cloud scales (e.g. Dale et al.). We find that photoionization dominates the disruption of the spiral arm section, with stellar winds only producing small cavities (at most ∼30 pc). Stellar winds do not affect the resulting cloud statistics or the integrated star formation rate/efficiency, unlike ionization, which produces more stars, and more clouds of higher density and higher velocity dispersion compared to the control run without feedback. Winds do affect the sink properties, distributing star formation over more low-mass sinks (∼102 M⊙) and producing fewer high-mass sinks (∼103 M⊙). Overall, stellar winds play at best a secondary role compared to photoionization, and on many measures, they have a negligible impact. [ABSTRACT FROM AUTHOR]

We investigate the resolution dependence of H  ii  regions expanding past their Strömgren spheres. We find that their structure and size, and the radial momentum that they attain at a given time, is in good agreement with analytical expectations if the Strömgren radius is resolved with |$dr \le 0.3\, R_{\rm st}$|⁠. If this is not satisfied, the radial momentum may be over- or underestimated by factors up to 10 or more. Our work has significance for the amount of radial momentum that a H  ii  region can impart to the ambient medium in numerical simulations, and thus, on the relative importance of ionizing feedback from massive stars. [ABSTRACT FROM AUTHOR]