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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 (⁠∼200 pc×350 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 ∼1039 erg s−1⁠. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society., The authors also acknowledge the financial support from NASA and the Chandra X-ray Center through the grant GO9-20074X. TW acknowledges financial support from the coordination of the participation in SKA-SPAIN, financed by the Ministry of Science and Innovation (MCIN), and from the State Agency for Research of the Spanish Ministry of Science, Innovation and Universities through the ‘Centre of Excellence Severo Ochoa’ award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709).

20 pags., 20 figs., 2 tabs., Context. The role of feedback in the self-regulation of star formation is a fundamental question in astrophysics. The Orion Nebula is the nearest site of ongoing and recent massive star formation. It is a unique laboratory for the study of stellar feedback. Recent SOFIA [C ¯II] 158 μm observations have revealed an expanding bubble, the Veil shell, that is powered by stellar winds and ionization feedback. Aims. We have identified a protrusion-like substructure in the northwestern portion of the Orion Veil shell that may indicate additional, highly directional feedback mechanisms. Our goal is to investigate the origin of the protrusion by quantifying its possible driving mechanisms. Methods. We use the [C ¯II] 158 μm map of the Orion Nebula obtained with the upGREAT instrument on board SOFIA. The spectral and spatial resolution of the observations are 0.3 km s 1 and 16", respectively. The velocity-resolved [C ¯II] observations allow us to construct position-velocity (pv) diagrams to measure the morphology and the expansion velocity of the protrusion. For the morphology, we also use new observations of 12CO and 13CO J = 2-1 (to trace molecular gas), Spitzer 8 μm observations (to trace the far-ultraviolet-illuminated surfaces of photodissociation regions), and Hα observations (to trace ionized gas). For the kinematics, we perform a line-profile analysis of [C ¯II], 13CO, and 12CO at 12 positions, covering the entire protrusion. To quantify the stellar feedback, we estimate the mass of the protrusion by fitting the dust thermal emission. We compare the kinetic energy with the stellar wind of θ Ori C and the momentum of the outflows of massive protostars to investigate the driving mechanism of the protrusion. Results. The pv diagrams reveal two half-shells expanding at velocities of +6 km s 1 and +12 km s 1. We find that the protrusion has a diameter of ∼1.3 pc with a ∼45 M- shell expanding at +12 km s 1 at the northwestern rim of the Veil. The thickness of the expanding shell is ∼0.1 pc. Using the mass in the limb-brightened shell and the maximum expansion velocity, we calculate the kinetic energy and the momentum of the protrusion to be ∼7 Ã - 1046 erg and 540 M- km s 1, respectively. We consider three possible origins for this protrusion: fossil outflow cavities created by jets and outflows during the protostellar accretion phase, preexisting "clumpiness"in the OMC-1 core, and the stellar wind during the main-sequence phase. Based on the energetics and the morphology, we conclude that the northwestern part of the preexisting cloud was locally perturbed by outflows ejected from massive protostars in the Trapezium cluster. This suggests that the protrusion of the Veil is the result of mechanical rather than radiative feedback. Furthermore, we argue that the location of the protrusion is a suitable place to break Orion's Veil owing to the photo-ablation from the walls of the protrusion. Conclusions. We conclude that the outflows of massive protostars can influence the morphology of the future H II region and even cause breakages in the ionization front. Specifically, the interaction of stellar winds of main-sequence stars with the molecular core preprocessed by the protostellar jet is important., We also thank Marc William Pound and Mark Wolfire for their help on the PDR Toolbox. Studies of interstellar dust and gas at Leiden Observatory are supported by a Spinoza award from the Dutch Science agency, NWO. JRG thanks the Spanish MICINN for funding support under grant PID2019-106110GB-I00 partially based on IRAM 30 m telescope observations. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). This study was based on observations made with the NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA). SOFIA is jointly operated by the Universities Space Research Association Inc. (USRA), under NASA contract NAS2-97001, and the Deutsches SOFIA Institut (DSI), under DLR contract 50 OK 0901 to the University of Stuttgart. upGREAT is a development by the MPI für Radioastronomie and the KOSMA/Universität zu Köln, in cooperation with the DLR Institut für Optische Sensorsysteme. We acknowledge the work, during the C+upGREAT square degree survey of Orion, of the USRA and NASA staff of the Armstrong Flight Research Center in Palmdale, the Ames Research Center in Mountain View (California), and the Deutsches SOFIA Institut.

Astronomy and astrophysics 661, A128 (2022). doi:10.1051/0004-6361/202142747, Context. Galactic cosmic rays (CRs) are widely assumed to arise from diffusive shock acceleration, specifically at shocks in supernova remnants (SNRs). These shocks expand in a complex environment, particularly in the core-collapse scenario as these SNRs evolve inside the wind-blown bubbles created by their progenitor stars. The CRs at core-collapse SNRs may carry spectral signatures of that complexity.Aims. We study particle acceleration in the core-collapse SNR of a progenitor with an initial mass of 60 M⊙ and realistic stellar evolution. The SNR shock interacts with discontinuities inside the wind-blown bubble and generates several transmitted and reflected shocks. We analyse their impact on particle spectra and the resulting emission from the remnant.Methods. To model the particle acceleration at the forward shock of a SNR expanding inside a wind bubble, we initially simulated the evolution of the pre-supernova circumstellar medium (CSM) by solving the hydrodynamic equations for the entire lifetime of the progenitor star. As the large-scale magnetic field, we considered parameterised circumstellar magnetic field with passive field transport. We then solved the hydrodynamic equations for the evolution of a SNR inside the pre-supernova CSM simultaneously with the transport equation for CRs in test-particle approximation and with the induction equation for the magnetohydrodynamics in 1D spherical symmetry.Results. The evolution of a core-collapse SNR inside a complex wind-blown bubble modifies the spectra of both the particles and their emission on account of several factors including density fluctuations, temperature variations, and the magnetic field configuration. We find softer particle spectra with spectral indices close to 2.5 during shock propagation inside the shocked wind, and this softness persists at later evolutionary stages. Further, our calculated total production spectrum released into the interstellar medium demonstrates spectral consistency at high energy (HE) with the injection spectrum of Galactic CRs, which is required in propagation models. The magnetic field structure effectively influences the emission morphology of SNRs as it governs the transportation of particles and the synchrotron emissivity. There is rarely a full correspondence of the intensity morphology in the radio, X-ray, and gamma-ray bands.Key words: ISM: supernova remnants / ISM: bubbles / cosmic rays★ Movie associated to Fig. B.1 is only available at https://www.aanda.org, Published by EDP Sciences, Les Ulis

We present 3D hydrodynamical simulations of the circumstellar bubble from a Wolf-Rayet runaway star. In the models two properties were taken into account: (a) the proper motion of the central star through the interstellar medium (ISM) and (b) the evolution of the stellar wind from the red supergiant (RSG) stage to the Wolf-Rayet (WR) stage. From the hydrodynamic results synthetic X-ray maps in the [0.3 − 1.2] keV energy range were computed. These maps show that the bubble morphology is affected by the stellar motion, producing a bow shock in the RSG stage that can explain the limb-brightened morphology observed. Additionally, these synthetic maps show filamentary and clumpy appearance produced by instabilities triggered from the interaction between the WR wind and the RSG shell. It was found that these types of collisions can explain the origin of the X-ray emission observed in the nebulae of Wolf- Rayet stars. Fil: Reyes Iturbide, J.. Universidad Nacional Autónoma de México. Instituto de Ciencias Nucleares; México. Tecnológico de Estudios Superiores de Tianguistenco; México Fil: Velázquez, Pablo F.. Universidad Nacional Autónoma de México. Instituto de Ciencias Nucleares; México Fil: Rosado, M.. Universidad Nacional Autónoma de México. Instituto de Astronomía; México Fil: Schneiter, Ernesto Matías. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; Argentina Fil: Ramírez Ballinas, I.. Universidad Nacional Autónoma de México. Instituto de Astronomía; México

We present Multi-Unit Spectroscopic Explorer (MUSE) integral-field spectroscopy of ESO 253-G003, which hosts a known active galactic nucleus (AGN) and the periodic nuclear transient ASASSN-14ko, observed as part of the All-weather MUse Supernova Integral-field of Nearby Galaxies survey. The MUSE observations reveal that the inner region hosts two AGN separated by 1.4±0.1 kpc (≍1 ′′. 7). The brighter nucleus has asymmetric broad permitted emission-line profiles and is associated with the archival AGN designation. The fainter nucleus does not have a broad emission-line component but exhibits other AGN characteristics, including vFWHM≈700 km~s−1 forbidden line emission, log10([OIII]/Hβ)≈1.1 , and high-excitation potential emission lines, such as [Fe VII] λ6086 and He II λ4686. The host galaxy exhibits a disturbed morphology with large kpc-scale tidal features, potential outflows from both nuclei, and a likely superbubble. A circular relativistic disc model cannot reproduce the asymmetric broad emission-line profiles in the brighter nucleus, but two non-axisymmetric disc models provide good fits to the broad emission-line profiles: an elliptical disc model and a circular disc + spiral arm model. Implications for the periodic nuclear transient ASASSN-14ko are discussed., MAT acknowledges support from the DOE CSGF through grant no. DE-SC0019323. BJS and CSK are supported by NSF grant no. AST-1907570. BJS is also supported by NASA grant no. 80NSSC19K1717 and NSF grants AST-1920392 and AST-1911074. CSK is supported by NSF grant no. AST-181440. KAA is supported by the Danish National Research Foundation (DNRF132). Support for JLP is provided in part by FONDECYT through grant n.1191038 and by the Ministry for the Economy, Development, and Tourism’s Millennium Science Initiative through grant no. IC120009, awarded to The Millennium Institute of Astrophysics, MAS. LG acknowledges financial support from the Spanish Ministry of Science, Innovation and Universities (MICIU) under the 2019 Ramón y Cajal program RYC2019-027683 and from the Spanish MICIU project PID2020-115253GA-I00. Parts of this research were supported by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. LG was funded by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 839090, and partially supported by the Spanish grant no. PGC2018-095317-B-C21 within the European Funds for Regional Development (FEDER). Support for TW-SH was provided by NASA through the NASA Hubble Fellowship grant no. #HST-HF2-51458.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere under ESO programme 096.D-0296(A).

The six parameters of the standard ΛCDM model have best-fit values derived from the Planck temperature power spectrum that are shifted somewhat from the best-fit values derived from WMAP data. These shifts are driven by features in the Planck temperature power spectrum at angular scales that had never before been measured to cosmic-variance level precision. We have investigated these shifts to determine whether they are within the range of expectation and to understand their origin in the data. Taking our parameter set to be the optical depth of the reionized intergalactic medium, the baryon density ωb, the matter density ωm, the angular size of the sound horizon the spectral index of the primordial power spectrum, ns, and Ase-2τ (where As is the amplitude of the primordial power spectrum), we have examined the change in best-fit values between a WMAP-like large angular-scale data set (with multipole moment < 800 in the Planck temperature power spectrum) and an all angular-scale data set (< 2500Planck temperature power spectrum), each with a prior on τ of 0.07 ± 0.02. We find that the shifts, in units of the 1σ expected dispersion for each parameter, are {value of 8.0. We find that this χ2 value is exceeded in 15% of our simulated data sets, and that a parameter deviates by more than 2.2σ in 9% of simulated data sets, meaning that the shifts are not unusually large. Comparing < 800 instead to > 800, or splitting at a different multipole, yields similar results. We examined the < 800 model residuals in the > 800 power spectrum data and find that the features there that drive these shifts are a set of oscillations across a broad range of angular scales. Although they partly appear similar to the effects of enhanced gravitational lensing, the shifts in ΛCDM parameters that arise in response to these features correspond to model spectrum changes that are predominantly due to non-lensing effects; the only exception is, which, at fixed Ase-2τ, affects the > 800 temperature power spectrum solely through the associated change in As and the impact of that on the lensing potential power spectrum. We also ask, "what is it about the power spectrum at < 800 that leads to somewhat different best-fit parameters than come from the full range?" We find that if we discard the data at < 30, where there is a roughly 2σ downward fluctuation in power relative to the model that best fits the full range, the < 800 best-fit parameters shift significantly towards the < 2500 best-fit parameters. In contrast, including < 30, this previously noted "low-deficit" drives ns up and impacts parameters correlated with ns, such as ωm and H0. As expected, the < 30 data have a much greater impact on the < 800 best fit than on the < 2500 best fit. So although the shifts are not very significant, we find that they can be understood through the combined effects of an oscillatory-like set of high-residuals and the deficit in low-power, excursions consistent with sample variance that happen to map onto changes in cosmological parameters. Finally, we examine agreement between PlanckTT data and two other CMB data sets, namely the Planck lensing reconstruction and the TT power spectrum measured by the South Pole Telescope, again finding a lack of convincing evidence of any significant deviations in parameters, suggesting that current CMB data sets give an internally consistent picture of the ΛCDM model.

26 pags., 33 figs., 10 tabs., Context. The Orion Molecular Cloud is the nearest massive-star forming region. Massive stars have profound effects on their environment due to their strong radiation fields and stellar winds. Stellar feedback is one of the most crucial cosmological parameters that determine the properties and evolution of the interstellar medium in galaxies. Aims. We aim to understand the role that feedback by stellar winds and radiation play in the evolution of the interstellar medium. Velocity-resolved observations of the [C » II] 158 μm fine-structure line allow us to study the kinematics of UV-illuminated gas. Here, we present a square-degree-sized map of [C » II] emission from the Orion Nebula complex at a spatial resolution of 16′′ and high spectral resolution of 0.2 km s-1, covering the entire Orion Nebula (M 42) plus M 43 and the nebulae NGC 1973, 1975, and 1977 to the north. We compare the stellar characteristics of these three regions with the kinematics of the expanding bubbles surrounding them. Methods. We use [C » II] 158 μm line observations over an area of 1.2 deg2 in the Orion Nebula complex obtained by the upGREAT instrument onboard SOFIA. Results. The bubble blown by the O7V star θ1 Ori C in the Orion Nebula expands rapidly, at 13 km s-1. Simple analytical models reproduce the characteristics of the hot interior gas and the neutral shell of this wind-blown bubble and give us an estimate of the expansion time of 0.2 Myr. M 43 with the B0.5V star NU Ori also exhibits an expanding bubble structure, with an expansion velocity of 6 km s-1. Comparison with analytical models for the pressure-driven expansion of H » II regions gives an age estimate of 0.02 Myr. The bubble surrounding NGC 1973, 1975, and 1977 with the central B1V star 42 Orionis expands at 1.5 km s-1, likely due to the over-pressurized ionized gas as in the case of M 43. We derive an age of 0.4 Myr for this structure. Conclusions. We conclude that the bubble of the Orion Nebula is driven by the mechanical energy input by the strong stellar wind from θ1 Ori C, while the bubbles associated with M 43 and NGC 1977 are caused by the thermal expansion of the gas ionized by their central later-type massive stars., This work is based on observations made with the NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA). SOFIA is jointly operated by the Universities Space Research Association, Inc. (USRA), under NASA contract NNA17BF53C, and the Deutsches SOFIA Institut (DSI) under DLR contract 50 OK 0901 to the University of Stuttgart. J.R.G. thanks the ERC and the Spanish MCIU for funding support under grants ERC-2013- Syg-610256-NANOCOSMOS and AYA2017-85111-P, respectively. Research on the interstellar medium at Leiden Observatory is supported through a Spinoza award of the Dutch Science Organisation (NWO).

We present a multiwavelength study of the iconic Bubble Nebula (NGC 7635) and its ionizing star BD+60 degrees 2521 We obtained XMM Newton EPIC X-ray observations to search for. extended X-ray emission as in other similar wind-blown bubbles around massive stars. We also obtained San Pedro Madir spectroscopic observations with. the Manchester Echelle Spectrometer to study the dynamics of the Bubble Nebula. Although our EPIC observations are deep, we do not detect extended X-ray emission from this wind-blown bubble. On the other hand, BD+60 degrees 2522 is a bright X-ray source similar to other 0 stars. We used the stellar atmosphere code PolATR to characterize BD+60 degrees 2522 and found that this star is a young O-type star with stellar wind capable of producing a wirid-blown bubble that in principle could be filled with hot gas. We discussed our findings in line with recent ntirnerical simulations'proposing that the Bubble Nebula has been formed as the result of the fast motion of BD+60 degrees 2522 through the medium. Our kinematic study shows that the Bubble Nebula is composed by a series of nested shells, some showing blister-like structures, but with little signatures of hydrodynamical instabilities that would mix the material producing diffuse X-ray emission as seen in other wind-blown bubbles. Its morphology seems to be merely the result of projection effects of these different shells. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society, This work is based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. The NOT data presented were obtained with ALFOSC and FIES, which are provided by the Instituto de Astroffsica de Andalucfa (IAA-CSIC) under ajoint agreement with the University of Copenhagen and NOTSA. This paper makes use of observations carried out at the Observatorio Astronomico Nacional on the Sierra San Pedro Mdfrtir (OAN-SPM), Baja California, Mexico. We thank the daytime and night support staff at the OAN-SPM for facilitating and helping obtain our observations. JAT, MAG, and HT are funded by UNAM DGAPA PAPIIT projects IA100318 and IA100720. GRL acknowledges support from Fundacion Marcos Moshinsky, CONACyT, and PRODEP (Mexico). MAG acknowledges support of the grants AYA 201457280-P and PGC2018-102184-B-I00 of the Spanish Ministerio de Ciencia, Innovacion y Universidades, cofunded with FEDER funds. LS is supported by Direccion General de Asuntos del Personal Acadmico, Universidad Nacional Autonoma de Mexico project IN101819.

18 pags., 21 figs., 5 tabs, 1 app., Strong winds and ultraviolet (UV) radiation from O-type stars disrupt and ionize their molecular core birthplaces, sweeping up material into parsec-size shells. Owing to dissociation by starlight, the thinnest shells are expected to host low molecular abundances and therefore little star formation. Here, we expand previous maps made with observations using the IRAM 30 m telescope (at 11″ ≃ 4500 AU resolution) and present square-degree 12CO and 13CO (J = 2-1) maps of the wind-driven "Veil bubble"that surrounds the Trapezium cluster and its natal Orion molecular core (OMC). Although widespread and extended CO emission is largely absent from the Veil, we show that several CO "globules"exist that are blueshifted in velocity with respect to OMC and are embedded in the [C » II] 158 μm-bright shell that confines the bubble. This includes the first detection of quiescent CO at negative local standard of rest velocities in Orion. Given the harsh UV irradiation conditions in this translucent material, the detection of CO globules is surprising. These globules are small (Rg = 7100 AU), not massive (Mg = 0.3 M⊙ ), and are moderately dense: nH = 4 × 104 cm-3 (median values). They are confined by the external pressure of the shell, Pext∕ k ≳ 107 cm-3 K, and are likely magnetically supported. They are either transient objects formed by instabilities or have detached from pre-existing molecular structures, sculpted by the passing shock associated with the expanding shell and by UV radiation from the Trapezium. Some represent the first stages in the formation of small pillars, others of isolated small globules. Although their masses (Mg, We warmly thank the operators, AoDs, and chefs at the IRAM 30 m telescope for their support while the CO observations were conducted. This work is also based on observations made with the NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA). SOFIA is jointly operated by the Universities Space Research Association, Inc. (USRA), under NASA contract NNA17BF53C, and the Deutsches SOFIA Institut (DSI) under DLR contract 50 OK 0901 to the University of Stuttgart. We acknowledge the work, during the C+ upGREAT square degree survey of Orion, of the USRA and NASA staff of the Armstrong Flight Research Center in Palmdale, the Ames Research Center in Mountain View (California), and the Deutsches SOFIA Institut. We thank the Spanish MICIU for funding support under grant AYA2017-85111-P. Research on the ISM at Leiden Observatory is supported through a Spinoza award.

Aims: We use new deep XMM-Newton observations of the northern disk of M 31 to trace the hot interstellar medium (ISM) in unprecedented detail and to characterise the physical properties of the X-ray emitting plasmas. Methods: We used all XMM-Newton data up to and including our new observations to produce the most detailed image yet of the hot ISM plasma in a grand design spiral galaxy such as our own. We compared the X-ray morphology to multi-wavelength studies in the literature to set it in the context of the multi-phase ISM. We performed spectral analyses on the extended emission using our new observations as they offer sufficient depth and count statistics to constrain the plasma properties. Data from the Panchromatic Hubble Andromeda Treasury were used to estimate the energy injected by massive stars and their supernovae. We compared these results to the hot gas properties. Results: The brightest emission regions were found to be correlated with populations of massive stars, notably in the 10 kpc star-forming ring. The plasma temperatures in the ring regions are ~0.2 keV up to ~0.6 keV. We suggest this emission is hot ISM heated in massive stellar clusters and superbubbles. We derived X-ray luminosities, densities, and pressures for the gas in each region. We also found large extended emission filling low density gaps in the dust morphology of the northern disk, notably between the 5 kpc and 10 kpc star-forming rings. We propose that the hot gas was heated and expelled into the gaps by the populations of massive stars in the rings. Conclusions. It is clear that the massive stellar populations are responsible for heating the ISM to X-ray emitting temperatures, filling their surroundings, and possibly driving the hot gas into the low density regions. Overall, the morphology and spectra of the hot gas in the northern disk of M 31 is similar to other galaxy disks., 23 pages, 14 figures, accepted for publication in Astronomy & Astrophysics

We present images of radio recombination lines (RRLs) at wavelengths around 17 cm from the star-forming region W49A to determine the kinematics of ionized gas in the THOR survey (The HI/OH/Recombination line survey of the inner Milky Way) at an angular resolution of 16.8"x13.8". The distribution of ionized gas appears to be affected by feedback processes from the star clusters in W49A. The velocity structure of the RRLs shows a complex behavior with respect to the molecular gas. We find a shell-like distribution of ionized gas as traced by RRL emission surrounding the central cluster of OB stars in W49A. We describe the evolution of the shell with the recent feedback model code WARPFIELD that includes the important physical processes and has previously been applied to the 30 Doradus region in the Large Magellanic Cloud. The cloud structure and dynamics of W49A are in agreement with a feedback-driven shell that is re-collapsing. The shell may have triggered star formation in other parts of W49A. We suggest that W49A is a potential candidate for star formation regulated by feedback-driven and re-collapsing shells., 17 pages, 9 figures. Published in A&A. Updated to match published version

We analyse new optical spectroscopic, direct-image and X-ray observations of the recently discovered a high-proper motion cataclysmic variable V1838 Aql. The data were obtained during its 2013 superoutburst and its subsequent quiescent state. An extended emission around the source was observed up to 30 d after the peak of the superoutburst, interpreted it as a bow shock formed by a quasi-continuous outflow from the source in quiescence. The head of the bow shock is coincident with the high-proper motion vector of the source (v⊥ = 123 ± 5 km s⁻¹) at a distance of d = 202 ± 7 pc. The object was detected as a weak X-ray source (0.015 ± 0.002 counts s⁻¹) in the plateau of the superoutburst and its flux lowered by two times in quiescence (0.007 ± 0.002 counts s⁻¹). Spectroscopic observations in quiescence we confirmed the orbital period value Porb = 0.0545 ± 0.0026 d, consistent with early-superhump estimates, and the following orbital parameters: γ = −21 ± 3 km s−1 and K₁ = 53 ± 3 km s⁻¹. The white dwarf is revealed as the system approaches quiescence, which enables us to infer the effective temperature of the primary Teff = 11 600 ± 400 K. The donor temperature is estimated ≲2200 K and suggestive of a system approaching the period minimum. Doppler maps in quiescence show the presence of the hotspot in He i line at the expected accretion disc-stream shock position and an unusual structure of the accretion disc in Hα.

Clusters or associations of early-type stars are often associated with a 'superbubble' of hot gas. The formation of such superbubbles is caused by the feedback from massive stars. The complex N206 in the Large Magellanic Cloud exhibits a superbubble and a rich massive star population. We observed these massive stars using the FLAMES multi-object spectrograph at ESO-VLT. Available UV spectra from HST, IUE, and FUSE are also used. The spectral analysis is performed with Potsdam Wolf-Rayet (PoWR) model atmospheres. We present the stellar and wind parameters of the OB stars and the two WR binaries in the N206 complex. Twelve percent of the sample show Oe/Be type emission lines, although most of them appear to rotate far below critical. We found eight runaway stars based on their radial velocity. The wind-momentum luminosity relation of our OB sample is consistent with the expectations. The HRD of the OB stars reveals a large age spread (1-30 Myr), suggesting different episodes of star formation in the complex. The youngest stars are concentrated in the inner part of the complex, while the older OB stars are scattered over outer regions. We derived the present day mass function for the entire N206 complex as well as for the cluster NGC2018. Three very massive Of stars are found to dominate the feedback among 164 OB stars in the sample. The two WR winds alone release about as much mechanical luminosity as the whole OB star sample. The cumulative mechanical feedback from all massive stellar winds is comparable to the combined mechanical energy of the supernova explosions that likely occurred in the complex. Accounting also for the WR wind and supernovae, the mechanical input over the last five Myr is ~$2.3\times10^{52}$ erg, which exceeds the current energy content of the complex by more than a factor of five. The morphology of the complex suggests a leakage of hot gas from the superbubble., Comment: Accepted for publication in A&A

Context. Efforts to compare polarization measurements with synthetic observations from magnetohydrodynamics (MHD) models have previously concentrated on the scale of molecular clouds. Aims. We extend the model comparisons to kiloparsec scales, taking into account hot shocked gas generated by supernovae and a non-uniform dynamo-generated magnetic field at both large and small scales down to 4 pc spatial resolution. Methods. We used radiative transfer calculations to model dust emission and polarization on top of MHD simulations. We computed synthetic maps of column density NH, polarization fraction p, and polarization angle dispersion S, and studied their dependencies on important properties of MHD simulations. These include the large-scale magnetic field and its orientation, the small-scale magnetic field, and supernova-driven shocks. Results. Similar filament-like structures of S as seen in the Planck all-sky maps are visible in our synthetic results, although the smallest scale structures are absent from our maps. Supernova-driven shock fronts and S do not show significant correlation. Instead, S can clearly be attributed to the distribution of the small-scale magnetic field. We also find that the large-scale magnetic field influences the polarization properties, such that, for a given strength of magnetic fluctuation, a strong plane of the sky mean field weakens the observed S, while strengthening p. The anticorrelation of p and S, and decreasing p as a function of NH are consistent across all synthetic observations. The magnetic fluctuations follow an exponential distribution, rather than Gaussian characteristic of flows with intermittent repetitive shocks. Conclusions. The observed polarization properties and column densities are sensitive to the line-of-sight distance over which the emission is integrated. Studying synthetic maps as the function of maximum integration length will further help with the interpretation of observations. The effects of the large-scale magnetic field orientation on the polarization properties are difficult to be quantified from observations solely, but MHD models might turn out to be useful for separating the effect of the large-scale mean field.

We analyse new optical spectroscopic, direct-image and X-ray observations of the recently discovered a high-proper motion cataclysmic variable V1838 Aql. The data were obtained during its 2013 superoutburst and its subsequent quiescent state. An extended emission around the source was observed up to 30 d after the peak of the superoutburst, interpreted it as a bow shock formed by a quasi-continuous outflow from the source in quiescence. The head of the bow shock is coincident with the high-proper motion vector of the source (v⊥ = 123 ± 5 km s−1) at a distance of d = 202 ± 7 pc. The object was detected as a weak X-ray source (0.015 ± 0.002 counts s−1) in the plateau of the superoutburst and its flux lowered by two times in quiescence (0.007 ± 0.002 counts s−1). Spectroscopic observations in quiescence we confirmed the orbital period value Porb = 0.0545 ± 0.0026 d, consistent with early-superhump estimates, and the following orbital parameters: γ = −21 ± 3 km s−1 and K1 = 53 ± 3 km s−1. The white dwarf is revealed as the system approaches quiescence, which enables us to infer the effective temperature of the primary Teff = 11 600 ± 400 K. The donor temperature is estimated 2200K and suggestive of a system approaching the period minimum. Doppler maps in quiescence show the presence of the hotspot in He I line at the expected accretion disc-stream shock position and an unusual structure of the accretion disc in Hα., The authors are indebted to Universidad Nacional Autonoma de Mexico (UNAM)/DGAPA for financial support via PAPIIT projects IN111713, IN122409, IN100617, IN102517, IN102617, IN108316, and IN114917. JVHS is supported by a Vidi grant awarded to N. Degenaar by the Netherlands Organization for Scientific Research (NWO) and acknowledges travel support from DGAPA/UNAM. JE acknowledges support from an LKBF travel grant to visit the Anton Panekoek Institute. VN acknowledges the financial support from the visitor and mobility program of the Finnish Centre for Astronomy with ESO (FINCA), funded by the Academy of Finland grant No. 306531. GT acknowledges Consejo Nacional de Ciencia y Tecnologia (CONACyT) grant 166376. E. de la F. wishes to thank CGCI-Universidad de Guadalajara staff for mobility support. VS thanks Deutsche Forschungsgemeinschaft (DFG) for financial support (grant WE 1312/51-1). His work was also funded by the subsidy allocated to Kazan Federal University for the state assignment in the sphere of scientific activities (3.9780.2017/8.9). We thank Tom Marsh for the use of MOLLY. We acknowledge with thanks the variable star observations from the AAVSO International Data base contributed by observers worldwide and used in this research. We acknowledge the use of public data from the Swift data archive. This research made use of ASTROPY, a community-developed core PYTHON package for Astronomy (Astropy Collaboration et al. 2013), MATPLOTLIB (Hunter 2007) and APLPY (Robitaille & Bressert 2012). Based (partly) on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias in the island of La Palma (GTC7-16AMEX). Partly based on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. The data presented here were obtained in part with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOTSA. The results presented in this paper are based on observations collected at the European Southern Observatory under programme ID 0100.D0932. We thank the day and night-time support staff at the OANSPM for facilitating and helping obtain our observations. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. We thank J. van den Eijnden for help on Swift's DDT proposal.

Total infrared fluxes are estimated for 99 HII regions around massive stars. The following wavebands have been used for the analysis: 8 and 24 $\mu$m, based on data from Spitzer space telescope (IRAC and MIPS, respectively); 70, 160, 250, 350, and 500 $\mu$m, based on data from Herschel Space Observatory (PACS and SPIRE). The estimated fluxes are used to evaluate the mass fraction of polycyclic aromatic hydrocarbons ($q_{\rm PAH}$) and the intensity of the ultraviolet emission in the studied objects. It is shown that the PAH mass fraction, $q_{\rm PAH}$, is much lower in these objects than the average Galactic value, implying effective destruction of aromatic particles in HII regions. Estimated radiation field intensities ($U$) are close to those derived for extragalactic HII complexes. Color indices [$F_{24}$/$F_{8}$], [$F_{70}$/$F_{24}$], [$F_{160}$/$F_{24}$], [$F_{160}$/$F_{70}$] are compared to criteria proposed to distinguish between regions of ionized hydrogen and planetary nebulae. Also, we relate our results to analogous color indices for extragalactic complexes of ionized hydrogen., Comment: 12pages, 3 figures, accepted for publication in Research in Astronomy and Astrophysics

We present a multiwavelength investigation of the HII region G25.8700+0.1350, located in the inner part of the Galaxy. In radio continuum emission, the region is seen as a bright arc-shaped structure. An analysis of the HI line suggests that G25.8700+0.1350 lies at a distance of 6.5 kpc. The ionized gas is bordered by a photodissociation region which is encircled by a molecular structure where four molecular clumps are detected. At infrared wavelengths, the region is also very conspicuous. Given the high level of visual absorption in the region, the exciting stars should be searched for in the infrared band. In this context, we found in the literature one Wolf-Rayet and one red supergiant which, together with 37 2MASS sources candidates to be O-type stars, could be related to the origin of G25.8700+0.1350. Finally, as expanding HII regions are hypothesized to trigger star formation, we used different infrared point source catalogues to search for young stellar object candidates (cYSOs). A total of 45 cYSOs were identified projected onto the molecular clouds., 15 pages, 12 figures, 6 tables. Accepted for publication in MNRAS

We model the combined effects of photoionization and momentum--driven winds from O--stars on molecular clouds spanning a parameter space of initial conditions. The dynamical effects of the winds are very modest. However, in the lower--mass clouds, they influence the morphologies of the HII regions by creating 10pc--scale central cavities.\\ The inhomogeneous structures of the model GMCs make them highly permeable to photons, ionized gas and supernova ejecta, and the leaking of ionized gas in particular strongly affects their evolution, reducing the effectiveness of feedback. Nevertheless, feedback is able to expel large fractions of the mass of the lower escape--velocity clouds. Its impact on star formation is more modest, decreasing final star formation efficiencies by 10--20$\%$, and the rate of change of the star formation efficiency per freefall time by about one third. However, the clouds still form stars substantially faster than observed GMCs., 21 pages, 19 figures, accepted for publication in MNRAS

The Orion star-forming region is the nearest active high-mass star-forming region and has created a large superbubble, the Orion-Eridanus superbubble. Recent work by Ochsendorf et al. has extended the accepted boundary of the superbubble. We fit Kompaneets models of superbubbles expanding in exponential atmospheres to the new, larger shape of the Orion-Eridanus superbubble. We find that this larger morphology of the superbubble is consistent with the evolution of the superbubble being primarily controlled by expansion into the exponential Galactic disk ISM if the superbubble is oriented with the Eridanus side farther from the Sun than the Orion side. Unlike previous Kompaneets model fits that required abnormally small scale heights for the Galactic disk (, 8 pages, 3 figures, accepted by ApJ, minor grammatical changes

Massive stars with strong stellar winds are expected to have a huge impact on their interstellar surroundings, an effect which, in a surprisingly large number of cases, is not observed. This work is part of a concerted effort to obtain a better and more homogeneous observational data base with which to test the predictions of theoretical models. Analysis of the interstellar medium around the Of star HD 229196 shows that it coincides (in projection) with a region of lower radio continuum emission. This suggests that the star has shaped the surrounding interstellar medium via its ionizing flux and stellar wind. However, we find no clear evidence of the star's action in atomic hydrogen images. The radio continuum morphology and absence of a clear expanding H i shell are consistent with the possibility that the star, which is travelling supersonically at ∼30 km s-1 with respect to its local interstellar medium, is creating a weak bow shock. We cannot however rule out the possibility that the observed asymmetry is due to an inhomogeneous interstellar density distribution. We use data from the Canadian Galactic Plane Survey to carry out this study., Facultad de Ciencias Astronómicas y Geofísicas, Instituto Argentino de Radioastronomía

The physical mechanisms that induce the transformation of a certain mass of gas in new stars are far from being well understood. Infrared bubbles associated with HII regions have been considered to be good samples of investigating triggered star formation. In this paper we report on the investigation of the dust properties of the infrared bubble N4 around the HII region G11.898+0.747, analyzing its interaction with its surroundings and star formation histories therein, with the aim of determining the possibility of star formation triggered by the expansion of the bubble. Using Herschel PACS and SPIRE images with a wide wavelength coverage, we reveal the dust properties over the entire bubble. Meanwhile, we are able to identify six dust clumps surrounding the bubble, with a mean size of 0.50 pc, temperature of about 22 K, mean column density of 1.7 $\times10^{22}$ cm$^{-2}$, mean volume density of about 4.4 $\times10^{4}$ cm$^{-3}$, and a mean mass of 320 $M_{\odot}$. In addition, from PAH emission seen at 8 $\mu$m, free-free emission detected at 20 cm and a probability density function in special regions, we could identify clear signatures of the influence of the HII region on the surroundings. There are hints of star formation, though further investigation is required to demonstrate that N4 is the triggering source., Comment: Accepted by ApJ (16 pages, 11 figures, 9 tables)

Context. The infrared emission (IR) of the interstellar dust has been claimed to be a tracer of the star formation rate. However, the conversion of the IR emission into star formation rate can be strongly dependent on the physical properties of the dust, which are a ected by the environmental conditions where the dust is embedded. Aims. We study here the dust properties of a set of Hii regions in the Local Group galaxy M33 presenting different spatial configurations between the stars, gas, and dust to understand the dust evolution indierent environments. Methods. We modelled the spectral energy distribution (SED) of each region using the DustEM tool and obtained the mass relative to hydrogen for very small grains (VSG, YVSG), polycyclic aromatic hydrocarbons (YPAH), and big grains (BG, YBG). We furthermore performed a pixel-by-pixel SED modelling and derived maps of the relative mass of each grain type for the whole surface of the two most luminous Hii regions in M33, NGC 604 and NGC 595. Results. The relative mass of the VSGs (YVSG/YTOTAL) changes with the morphology of the region: YVSG/YTOTAL is a factor of ∼1.7 higher for Hii regions classified as filled and mixed than for regions presenting a shell structure. The enhancement in VSGs within NGC 604 and NGC 595 is correlated to expansive gas structures with velocities ≥50 km s. The gas-to-dust ratio derived for the Hii regions in our sample exhibits two regimes related to the Hi.H2 transition of the interstellar medium (ISM). Regions corresponding to the Hi diffuse regime present a gas-to-dust ratio compatible with the expected value if we assume that the gas-to-dust ratio scales linearly with metallicity, while regions corresponding to a H2 molecular phase present a flatter dust-gas surface density distribution. Conclusions. The fraction of VSGs can be affected by the conditions of the interstellar environment: strong shocks of ∼5090km s existing in the interior of the most luminous Hii regions can lead to fragmentation of BGs into smaller ones, while the more evolved shell and clear shell objects provide a more quiescent environment where reformation of dust BGs might occur. The gas-to-dust variations found in this analysis might imply that grain coagulation and/or gas-phase metal incorporation into the dust mass is occurring in the interior of the Hii regions in M33. © 2016 ESO., Part of this research has been supported by the PERG08-GA-2010-276813 from the EC. This work was partially supported by the Junta de Andalucia Grant FQM108 and Spanish MEC Grants, AYA-2011-24728 and AYA-2014-53506-P. EPM thanks Spanish MINECO grant AYA-2013-47742-C4-1-P of the Spanish Plan for Astronomy and Astrophysics. This work was in part supported through NSF ATI grant 1106284.

Aims: We present very large array (VLA) and Effelsberg radio continuum and 21 cm Hi line observations of the interstellar medium (ISM) surrounding the runaway star WR 124 and the nebula M 1-67. The HI data have been used to investigate the effects that a star with a strong stellar wind and a high peculiar velocity has on the ISM. Methods: The VLA 21 cm HI observations were combined with single-dish Effelsberg observations to produce a series of HI images sensitive to all angular scales from the VLA resolution limit (∼46") up to the primary field of individual VLA antennae (FWHM = 36'). MSX and IRIS images were used to analyze the infrared emission around the star. Because the star is highly supersonic with respect to its local ISM, the observed HI distribution around the star is interpreted in terms of a simple bow shock model. Results: The analysis of the HI data reveals the presence of a cavity centered on the star at an LSR velocity of ∼60 km s-1, consistent with a distance estimate of 5 kpc for WR124. A second HI cavity is observed located 10' to the north of the stellar position, consistent with the direction of motion of WR 124. The VLA continuum image at 8.5 GHz shows a remarkable resemblance to the optical images. All available radio continuum data suggest a purely thermal spectrum for the nebula. The MSX and IRIS infrared data show a changing morphology with wavelength. The dust temperature deduced from the infrared luminosities is in agreement with previous observations of bow shocks., Facultad de Ciencias Astronómicas y Geofísicas, Instituto Argentino de Radioastronomía

Aims. We analyze the distribution of the interstellar matter in the environs of the Hn region Gum 31, excited by the open cluster NGC 3324, located in the complex Carina region, with the aim of investigating the action of the massive stars on the surrounding neutral material. Methods. We use neutral hydrogen 21-cm line data, radio continuum images at 0.843, 2.4 and 4.9 GHz, 12CO(1-0) observations, and IRAS and MSX infrared data. Results. Adopting a distance of 3 kpc for the Hn region and the ionizing cluster, we derived an electron density of 33± 3 cm-3 and an ionized mass of (3.3 ±1.1) × 103 M⊙ based on the radio continuum data at 4.9 GHz. The Hl 21-cm line images revealed an Hl shell surrounding the Hn region. The Hl structure is 10.0 ±1.7 pc in radius, has a neutral mass of 1500 ±500 M⊙, and is expanding at 11 km s-1. The associated molecular gas amounts to (1.1 ±0.5) × 105 M⊙, being its volume density of about 350 cm-3. This molecular shell could represent the remains of the cloud where the young open cluster NGC 3324 was born or could have originated by the shock front associated with the Hn region. The difference between the ambient density and the electron density of the Hn region suggests that the Hn region is expanding. The distributions of the ionized and molecular material, along with that of the emission in the MSX band A, suggest that a photodissociation region has developed at the interface between the ionized and molecular gas. The copious UV photon flux from the early type stars in NGC 3324 keeps the Hn region ionized. The characteristics of a relatively large number of the IRAS, MSX, and 2MASS point sources projected onto the molecular envelope are compatible with protostellar candidates, showing the presence of active star forming regions. Very probably, the expansion of the Hn region has triggered stellar formation in the molecular shell., Instituto Argentino de Radioastronomía, Instituto de Astrofísica de La Plata, Facultad de Ciencias Astronómicas y Geofísicas

We present a study of the molecular CO gas and mid/far-infrared radiation arising from the environment surrounding the Wolf-Rayet (WR) star 130. We use the multiwavelength data to analyse the properties of the dense gas and dust, and its possible spatial correlation with that of young stellar objects (YSOs). We use 12CO J=1-0 data from the Five College Radio Astronomy Observatory survey as tracer of the molecular gas, and mid/far-infrared data from the recent Wide-Field Infrared Survey Explorer (WISE) and Herschel space surveys to study the dust continuum radiation and to identify a population of associated candidate YSOs. The spatial distribution of the molecular gas shows a ring-like structure very similar to that observed in the H I gas, and over the same velocity interval. The relative spatial distribution of the H I and CO components is consistent with a photodissociation region. We have identified and characterized four main and distinct molecular clouds that create this structure. Cold dust is coincident with the dense gas shown in the CO measurements. We have found several young stellar object candidates that lie along the regions with the highest gas column density, and suggest that they are spatially correlated with the shell. These are indicative of regions of star formation induced by the strong wind and ionization of the WR star., Facultad de Ciencias Astronómicas y Geofísicas, Instituto Argentino de Radioastronomía

We examine the combined effects of winds and photoionizing radiation from O--type stars on embedded stellar clusters formed in model turbulent molecular clouds covering a range of masses and radii. We find that feedback is able to increase the quantities of dense gas present, but decreases the rate and efficiency of the conversion of gas to stars relative to control simulations in which feedback is absent. Star formation in these calculations often proceeds at a rate substantially slower than the freefall rate in the dense gas. This decoupling is due to the weakening of, and expulsion of gas from, the deepest parts of the clouds' potential wells where most of the star formation occurs in the control simulations. This results in large fractions of the stellar populations in the feedback simulation becoming dissociated from dense gas. However, where star formation \emph{does} occur in both control and feedback simulations, it does so in dense gas, so the correlation between star formation activity and dense gas is preserved. The overall dynamical effects of feedback on the \emph{clusters} are minimal, with only small fraction of stars becoming unbound, despite large quantities of gas being expelled from some clouds. This owes to the settling of the stars into virialised and stellar--dominated configurations before the onset of feedback. By contrast, the effects of feedback on the observable properties of the clusters -- their U--, B-- and V--band magnitudes -- are strong and sudden. The timescales on which the clusters become visible and unobscured are short compared with the timescales which the clouds are actually destroyed., 19 pages, 17 figures (many degraded to get below submission size limit), accepted by MNRAS

The progenitor stars of long Gamma-Ray Bursts (GRBs) are thought to be Wolf-Rayet stars, which generate a massive and energetic wind. Nevertheless, about 25 percent of all GRB afterglows light curves indicate a constant density medium close to the exploding star. We explore various ways to produce this, by creating situations where the wind termination shock arrives very close to the star, as the shocked wind material has a nearly constant density. Typically, the distance between a Wolf-Rayet star and the wind termination shock is too large to allow afterglow formation in the shocked wind material. Here, we investigate possible causes allowing for a smaller distance: A high density or a high pressure in the surrounding interstellar medium (ISM), a weak Wolf-Rayet star wind, the presence of a binary companion, and fast motion of the Wolf-Rayet star relative to the ISM. We find that all four scenarios are possible in a limited parameter space, but that none of them is by itself likely to explain the large fraction of constant density afterglows. A low GRB progenitor metallicity, and a high GRB energy make the occurrence of a GRB afterglow in a constant density medium more likely. This may be consistent with constant densities beingpreferentially found for energetic, high redshift GRBs., Comment: 13 pages, 13 figures, new version: as accepted by Astronomy & Astrophysics

In star forming disk galaxies, matter circulation between stars and the interstellar gas, and, in particular the energy input by random and clustered supernova explosions, determine the dynamical and chemical evolution of the ISM, and hence of the galaxy as a whole. Using a 3D MHD code with adaptive mesh refinement developed for this purpose, we have investigated the r\^ole of magnetized matter circulation between the gaseous disk and the surrounding galactic halo. Special emphasis has been put on the effect of the magnetic field with respect to the volume and mass fractions of the different ISM ``phases'', the relative importance of ram, thermal and magnetic pressures, and whether the field can prevent matter transport from the disk into the halo. The simulations were performed on a grid with an area of 1 kpc$^{2}$, centered on the solar circle, extending $\pm 10$ kpc perpendicular to the galactic disk with a resolution as high as 1.25 pc. The simulations were run for a time scale of 400 Myr, sufficiently long to avoid memory effects of the initial setup, and to allow for a global dynamical equilibrium to be reached in case of a constant energy input rate. (...) We find that in general gas transport into the halo in 3D is not prevented by an initial disk parallel magnetic field, but only delayed initially, for as long as it is needed to punch holes into the thick magnetized gas disk. The mean volume filling factor of the hot phase in the disk is similar in HD and MHD (the latter with a total field strength of 4.4 $\mu$G) runs, amounting to $\sim 17-21%$ for the Galactic supernova rate., Comment: Paper accepted for publication in A&A (31 Jan); 17 pages with 10 Figures including 6 images and 16 plots (all in low quality jpeg files). For better resolution images contact the authors

The abundance evolution of galaxies depends critically on the balance between the mixing of metals in their interstellar medium, the inflow of new gas and the outflow of enriched gas. We study these processes in gas columns perpendicular to a galactic disk using sub-parsec resolution simulations that track stellar ejecta with the Flash code. We model a simplified interstellar medium stirred and enriched by supernovae and their progenitors. We vary the density distribution of the gas column and integrate our results over an exponential disk to predict wind and ISM enrichment properties for disk galaxies. We find that winds from more massive galaxies are hotter and more highly enriched, in stark contrast to that which is often assumed in galaxy formation models. We use these findings in a simple model of galactic enrichment evolution, in which the metallicity of forming galaxies is the result of accretion of nearly pristine gas and outflow of enriched gas along an equilibrium sequence. We compare these predictions to the observed mass-metallicity relation, and demonstrate how the galaxy's gas fraction is a key controlling parameter. This explains the observed flattening of the mass-metallicity relation at higher stellar masses., 19 pages, 15 figures, accepted to MNRAS

Aims. We present here a study of the cold dust in the close environs of the ring nebula Gum 31. We aim at deriving the physical properties of the molecular gas and dust associated with the nebula, and investigating its correlation with the star formation in the region, which was probably triggered by the expansion of the ionization front against its environment. Methods. We make use of 870 μm emission data obtained with the Large APEX Bolometer Camera (LABOCA) to map the dust emission. The 870 μm emission provides an excellent probe of mass and density of dense molecular clouds. The obtained LABOCA image was compared to archival infrared, radio continuum, and optical images. Results. The 870 μm emission follows the 8 μm (Spitzer), 250 μm, and 500 μm (Herschel) emission distributions showing the classical morphology of a two-dimensional projection of a spherical shell. We use the 870 μm and 250 μm images to identify 60 dust clumps in the collected layers of molecular gas using the Gaussclumps algorithm. The clumps have effective deconvolved radii between 0.16 pc and 1.35 pc, masses between 70 M⊙ and 2800 M⊙, and volume densities between 1.1 × 103 cm-3 and ~2.04 × 105 cm-3. The total mass of the clumps is ~37 600 M⊙. The dust temperature of the clumps is in the range from 21 K to 32 K, while inside the Hii region it reaches ~40 K. The clump mass distribution for the sample is fitted by a power law dN/dlog (M/M⊙) ∝ M-α, with α = 0.93 ± 0.28. The slope differs from those obtained for the stellar IMF in the solar neighborhood, suggesting that the clumps are not direct progenitors of single stars/protostars. The mass-radius relationship for the 41 clumps detected in the 870 μm emission shows that only 37% of them lie in or above the high-mass star formation threshold. Most of this 37% have candidate YSOs projected inside their limits. A comparison of the dynamical age of the Hii region with the fragmentation time, allowed us to conclude that the collect-and-collapse mechanism may be important for the star formation at the edge of Gum 31, although other processes may be acting simultaneously. The position of the identified young stellar objects in the region is also a strong indicator that the collect-and-collapse process is acting., Facultad de Ciencias Astronómicas y Geofísicas, Instituto Argentino de Radioastronomía

Aims. We carry out a multiwavelength study to characterize the H I supershell designated GS118+01-44, and to analyse its possible origin. Methods. A multiwavelength study has been carried out to study the supershell and its environs. We performed an analysis of the H I, CO, radio continuum, and infrared emission distributions. Results. The Canadian Galactic Plane Survey (CGPS) H I data reveals that GS118+01-44 is centred at (l,b) = (117°.7, 1°.4) with a systemic velocity of -44.3 km s-1. According to Galactic rotation models this structure is located at 3.0 ± 0.6 kpc from the Sun. There are several H II regions and three supernova remnants (SNRs) catalogued in the region. On the other hand, the analysis of the temperature spectral index distribution shows that in the region there is a predominance of non-thermal emission. Infrared emission shows that cool temperatures dominate the area of the supershell. Concerning the origin of the structure, we found that even though several OB stars belonging to CasOB5 are located in the interior of GS118+01-44, an analysis of the energy injected by these stars through their stellar winds indicates that they do not have sufficient energy to create GS118+01-44. Therefore, an additional energy source is needed to explain the genesis of GS118+01-44. On the other hand, the presence of several H II regions and young stellar object candidates in the edges of GS118+01-44 shows that the region is still active in forming new stars., Facultad de Ciencias Astronómicas y Geofísicas, Instituto Argentino de Radioastronomía

The extended circumstellar envelopes (CSE) of evolved low-mass stars display a large variety of morphologies. Understanding the various mechanisms that give rise to these extended structures is important to trace their mass-loss history. Here we aim to examine the role of the interstellar magnetic field in shaping the extended morphologies of slow dusty winds of Asymptotic Giant-branch (AGB) stars in an effort to pin-point the origin of so-called eye shaped CSE of three carbon-rich AGB stars. In addition, we seek to understand if this pre-planetary nebula (PN) shaping can be responsible for asymmetries observed in PNe. Hydrodynamical simulations are used to study the effect of typical interstellar magnetic fields on the free-expanding spherical stellar winds as they sweep up the local interstellar medium (ISM). The simulations show that typical Galactic interstellar magnetic fields of 5 to 10 muG, are sufficient to alter the spherical expanding shells of AGB stars to appear as the characteristic eye shape revealed by far-infrared observations. The typical sizes of the simulated eyes are in accordance with the observed physical sizes. However, the eye shapes are of transient nature. Depending on the stellar and interstellar conditions they develop after 20,000 to 200,000~yrs and last for about 50,000 to 500,000 yrs, assuming that the star is at rest relative to the local interstellar medium. Once formed the eye shape will develop lateral outflows parallel to the magnetic field. The ``explosion'' of a PN in the center of the eye-shaped dust shell gives rise to an asymmetrical nebula with prominent inward pointing Rayleigh-Taylor instabilities. Interstellar magnetic fields can clearly affect the shaping of wind-ISM interaction shells. The occurrence of the eyes is most strongly influenced by stellar space motion and ISM density. Observability of this transient phase is favoured for lines-of-sight perpendicular to the interstellar magnetic field direction. The simulations indicate that shaping of the pre-PN envelope can strongly affect the shape and size of PNe. ispartof: Astronomy & Astrophysics vol:570 status: published

We have examined the interstellar medium in the vicinity of massive stars belonging to the Per OB1 association based on neutral hydrogen 21 cm observations obtained with the 100 m radio telescope at Effelsberg (HPBW = 8′.4) and complementary data from the Leiden-Dwingeloo H I Survey (HPBW = 36′). The higher angular resolution H I observations allowed us to discover probable wind-blown bubbles related to four massive stars in the association, namely, HD 14442 [O5n(f)p], HD 14947 [O5If+], HD 13022 [O9.5II-III((n))], and HD 13338 [O9.5V], while the detection of a wind-blown bubble associated with HD 16691 [O5If+] is less conclusive. A clear H I shell coincident in position with two B1III stars (HD 15233 and Hilt 311) was also detected. Some of these features also have infrared and/or molecular counterparts. The energetics of the structures related to each massive star is analyzed. The new H I interstellar bubbles appear to be similar to the ones found surrounding Wolf-Rayet stars and other Of stars. The large-scale maps obtained using the lower angular resolution H I data show that most of the early-type stars belonging to Per OB1 are placed in a region of low H I emission. The association could have blown a H I shell of about 350 × 550 pc in size. This large H I shell has an infrared counterpart., Facultad de Ciencias Astronómicas y Geofísicas, Instituto Argentino de Radioastronomía

Many evolved stars travel through space at supersonic velocities, which leads to the formation of bow shocks ahead of the star where the stellar wind collides with the interstellar medium (ISM). Herschel observations of the bow shock of $\alpha$-Orionis show that the shock is almost free of instabilities, despite being, at least in theory, subject to both Kelvin-Helmholtz and Rayleigh-Taylor instabilities. A possible explanation for the lack of instabilities lies in the presence of an interstellar magnetic field. We wish to investigate whether the magnetic field of the interstellar medium (ISM) in the Orion arm can inhibit the growth of instabilities in the bow shock of $\alpha$-Orionis. We used the code MPI-AMRVAC to make magneto-hydrodynamic simulations of a circumstellar bow shock, using the wind parameters derived for $\alpha$-Orionis and interstellar magnetic field strengths of $B\,=\,1.4,\, 3.0$, and $5.0\, \mu$G, which fall within the boundaries of the observed magnetic field strength in the Orion arm of the Milky Way. Our results show that even a relatively weak magnetic field in the interstellar medium can suppress the growth of Rayleigh-Taylor and Kelvin-Helmholtz instabilities, which occur along the contact discontinuity between the shocked wind and the shocked ISM. The presence of even a weak magnetic field in the ISM effectively inhibits the growth of instabilities in the bow shock. This may explain the absence of such instabilities in the Herschel observations of $\alpha$-Orionis., Comment: 5 pages, including 7 figures. The published version will include 4 animations. Accepted for publication in A&A

Aims. With the aim of investigating the presence of molecular and dust clumps linked to two star forming regions identified in the expanding molecular envelope of the stellar wind bubble RCW 78, we analyzed the distribution of the molecular gas and cold dust. Methods. To accomplish this study we performed dust continuum observations at 870 μm and 13CO(2-1) line observations with the Atacama Pathfinder EXperiment (APEX) telescope, using the Large Apex BOlometer CAmera (LABOCA) and SHeFI-1 instruments, respectively, and analyzed Herschel images at 70, 160, 250, 350, and 500 μm. Results. These observations allowed us to identify cold dust clumps linked to region B (that we have named the southern clump) and region C (clumps 1 and 2), and an elongated filament. Molecular gas was clearly detected linked to the southern clump and the filament. The velocity of the molecular gas is compatible with the location of the dense gas in the expanding envelope of RCW 78. We estimate dust temperatures and total masses for the dust condensations from the emissions at different wavelengths in the far-IR and from the molecular line using local thermodynamic equilibrium and the virial theorem. Masses obtained through different methods agree within a factor of 2-6. Color-color diagrams and spectral energy distribution analysis of young stellar objects (YSOs) confirmed the presence of intermediate and low-mass YSOs in the dust regions, indicating that moderate star formation is present. In particular, a cluster of IR sources was identified inside the southern clump. The IRAC image at 8 μm revealed the existence of an infrared dust bubble of 16′′ in radius probably linked to the O-type star HD 117797 located at 4 kpc. The distribution of the near-and mid-IR emission indicate that warm dust is associated with the bubble., Facultad de Ciencias Astronómicas y Geofísicas, Instituto Argentino de Radioastronomía, Instituto de Astrofísica de La Plata

We present high-quality VLT-FLAMES optical spectroscopy of the nebular gas in the giant star-forming region 30 Doradus. In this paper, the first of a series, we introduce our observations and discuss the main kinematic features of 30 Dor, as revealed by the spectroscopy of the ionized gas in the region. The primary data set consists of regular grid of nebular observations, which we used to produce a spectroscopic datacube of 30 Dor, centered on the massive star cluster R136 and covering a field-of-view of 10'x10'. The main emission lines present in the datacube are from Halpha and [NII]6548,6584. The Halpha emission-line profile varies across the region from simple single-peaked emission to complex, multiple-component profiles, suggesting that different physical mechanisms are acting on the excited gas. To analyse the gas kinematics we fit Gaussian profiles to the observed Halpha features. Unexpectedly, the narrowest Halpha profile in our sample lies close to the supernova remnant 30 Dor B. We present maps of the velocity field and velocity dispersion across 30 Dor, finding five previously unclassified expanding structures. These maps highlight the kinematic richness of 30 Dor (e.g. supersonic motions), which will be analysed in future papers., 24 pages, 12 figures. Accepted for publication in Astronomy and Astrophysics

We present a dynamical model of supernova feedback which follows the evolution of pressurised bubbles driven by supernovae in a multi-phase interstellar medium (ISM). The bubbles are followed until the point of break-out into the halo, starting from an initial adiabatic phase to a radiative phase. We show that a key property which sets the fate of bubbles in the ISM is the gas surface density, through the work done by the expansion of bubbles and its role in setting the gas scaleheight. The multi-phase description of the ISM is essential, and neglecting it leads to order of magnitude differences in the predicted outflow rates. We compare our predicted mass loading and outflow velocities to observations of local and high-redshift galaxies and find good agreement over a wide range of stellar masses and velocities. With the aim of analysing the dependence of the mass loading of the outflow, beta (i.e. the ratio between the outflow and star formation rates), on galaxy properties, we embed our model in the galaxy formation simulation, GALFORM, set in the LCDM framework. We find that a dependence of beta solely on the circular velocity, as is widely assumed in the literature, is actually a poor description of the outflow rate, as large variations with redshift and galaxy properties are obtained. Moreover, we find that below a circular velocity of 80km/s the mass loading saturates. A more fundamental relation is that between beta and the gas scaleheight of the disk, hg, and the gas fraction, fgas, as beta hg^(1.1) fgas^(0.4), or the gas surface density, \Sigma_g, and the gas fraction, as beta \Sigma_g^(-0.6) fgas^(0.8). We find that using the new mass loading model leads to a shallower faint-end slope in the predicted optical and near-IR galaxy luminosity functions., Comment: 33 pages. Accepted for publication in MNRAS. Difference with previous version is a discussion of the effect of extreme interstellar medium conditions on beta and outflow velocity

Using precise full-sky observations from Planck, and applying several methods of component separation, we identify and characterise the emission fromthe Galactic “haze” at microwave wavelengths. The haze is a distinct component of diffuse Galactic emission, roughly centered on the Galactic centre, and extends to |b| ∼ 35−50◦ in Galactic latitude and |l| ∼ 15−20◦ in longitude. By combining the Planck data with observations from the Wilkinson Microwave Anisotropy Probe, we were able to determine the spectrum of this emission to high accuracy, unhindered by the strong systematic biases present in previous analyses. The derived spectrum is consistent with power-law emission with a spectral index of −2.56 ± 0.05, thus excluding free-free emission as the source and instead favouring hard-spectrum synchrotron radiation from an electron population with a spectrum (number density per energy) dN/dE ∝ E−2.1. At Galactic latitudes |b| < 30◦, the microwave haze morphology is consistent with that of the Fermi gamma-ray “haze” or “bubbles”, while at b ∼ −50◦ we have identified an edge in the microwave haze that is spatially coincident with the edge in the gamma-ray bubbles. Taken together, this indicates that we have a multi-wavelength view of a distinct component of our Galaxy. Given both the very hard spectrum and the extended nature of the emission, it is highly unlikely that the haze electrons result from supernova shocks in the Galactic disk. Instead, a new astrophysical mechanism for cosmic-ray acceleration in the inner Galaxy is implied., European Space Agency, Centre National D'etudes Spatiales, CNRS/INSU-IN2P3-INP (France), Agenzia Spaziale Italiana (ASI), Italian National Research Council, Istituto Nazionale Astrofisica (INAF), National Aeronautics & Space Administration (NASA), United States Department of Energy (DOE), Science & Technology Facilities Council (STFC), UKSA (UK), Consejo Superior de Investigaciones Cientificas (CSIC), Spanish Government, JA (Spain), Finnish Funding Agency for Technology & Innovation (TEKES), AoF (Finland), CSC (Finland), Helmholtz Association German Aerospace Centre (DLR), Max Planck Society, CSA (Canada), DTU Space (Denmark), SER/SSO (Switzerland), RCN (Norway), Science Foundation Ireland, Portuguese Foundation for Science and Technology, European Union (EU), Harvey L. Karp Discovery Award, Science & Technology Facilities Council (STFC) ST/G003874/1 ST/J00152X/1 ST/J001562/1 ST/J004812/1 ST/I005765/1 ST/J001538/1 ST/K000985/1 ST/K003674/1 ST/L001314/1

Numerical models of the wind-blown bubble of massive stars usually only account for the wind of a single star. However, since massive stars are usually formed in clusters, it would be more realistic to follow the evolution of a bubble created by several stars. We develope a two-dimensional (2D) model of the circumstellar bubble created by two massive stars, a 40 solar mass star and a 25 solar mass star, and follow its evolution. The stars are separated by approximately 16 pc and surrounded by a cold medium with a density of 20 particles per cubic cm. We use the MPI-AMRVAC hydrodynamics code to solve the conservation equations of hydrodynamics on a 2D cylindrical grid using time-dependent models for the wind parameters of the two stars. At the end of the stellar evolution (4.5 and 7.0 million years for the 40 and 25 solar mass stars, respectively), we simulate the supernova explosion of each star. Each star initially creates its own bubble. However, as the bubbles expand they merge, creating a combined, aspherical bubble. The combined bubble evolves over time, influenced by the stellar winds and supernova explosions. The evolution of a wind-blown bubble created by two stars deviates from that of the bubbles around single stars. In particular, once one of the stars has exploded, the bubble is too large for the wind of the remaining star to maintain and the outer shell starts to disintegrate. The lack of thermal pressure inside the bubble also changes the behavior of circumstellar features close to the remaining star. The supernovae are contained inside the bubble, which reflects part of the energy back into the circumstellar medium., Accepted for publication in A&A. Six .avi files to be published online (uploaded to ArXiv DC and available as ancillary files) (updated after language corrections)

Aims. This work aims at investigating the characteristics of the molecular gas associated with the nebula G18.8+1.8, which is linked to the Wolf-Rayet star HD 168206 (WR 113), and its relation to other components of its local interstellar medium. Methods. We carried out molecular observations of the 12CO(J = 1-0) and (J = 2-1) lines with an angular resolution of 44′′ and 22′′ using the SEST telescope. Complementary NANTEN data of the 12CO(1-0) line were also used. The dust emission was analyzed using Spitzer-IRAC images at 8.0 μm, and WISE data at 3.4 μm, 4.6 μm, and 12.0 μm. Results. The SEST data allowed us to identify a molecular component (Cloud 3) that has velocities in the interval from ~+30 to +36 km s -1 and is most probably linked to the nebula. Morphological and kinematical properties suggest that Cloud 3 consists of a wind-blown molecular half-shell, which expands around WR 113. The ratio R2-1/1-0 and excitation temperatures indicate that the molecular gas is being irradiated by strong UV radiation. The location of the inner optical ring in the outer edge of Cloud 3 suggests that the stars SerOB2-1,-2,-3,-63, and-64 are responsables for the ionization of Cloud 3 and the inner ring nebula. A comparison between the spatial distribution of the molecular gas and the PAH emission at 8 μm indicates the existence of a photodissociation region between the ionized and the molecular gas. A search for candidate young stellar objects (YSOs) in the region around G18.8+1.8 based on available 2MASS, MSX, IRAS, and Spitzer-IRAC catalogs resulted in the detection of about sixty sources, some of them projected onto Cloud 3. Two small spots of clustered candidate YSOs are projected near the outer border of Cloud 3, although a triggered stellar formation scenario is doubtful., Facultad de Ciencias Astronómicas y Geofísicas, Instituto Argentino de Radioastronomía

Aims. We present the first high-resolution non-equilibrium ionization simulation of the joint evolution of the Local Bubble (LB) and Loop I superbubbles in the turbulent supernova-driven interstellar medium (ISM). The time variation and spatial distribution of the Li-like ions Civ ,N v ,a nd Ovi inside the LB are studied in detail. Methods. This work uses the parallel adaptive mesh refinement code EAF-PAMR coupled to the newly developed atomic and molecular plasma emission module E(A+M)PEC, featuring the time-dependent calculation of the ionization structure of H through Fe, using the latest revision of solar abundances. The finest AMR resolution is 1 pc within a grid that covers a representative patch of the Galactic disk (with an area of 1 kpc 2 in the midplane) and halo (extending up to 10 kpc above and below the midplane). Results. The evolution age of the LB is derived by the match between the simulated and observed absorption features of the Li-like ions Civ ,N v ,a nd Ovi. The modeled LB current evolution time is bracketed between 0.5 and 0.8 Myr since the last supernova reheated the cavity in order to have N(Ovi) < 8 × 10 12 cm −2 ,l og[N(Civ)/N(Ovi)] < −0.9 and log[N(Nv)/N(Ovi)] < −1 inside the simulated LB cavity, as found in Copernicus, IUE, GHRS-IST and FUSE observations.

The Sun is located inside an extremely low density region called the Local Bubble (LB). Although they have been studied through a large variety of techniques, the contours of its neutral boundary, defined by a dense wall of interstellar gas and dust, are still an open issue. Our aim is to determine the interstellar reddening in the LB region by means of Stromgren photometry, validating the conclusions through a comparison with high-resolution three-dimensional (3D) hydrodynamical models of the Local and Loop I bubbles' formation and evolution. We have obtained color excesses and distances using the uvbyHβ data of the General Catalogue of Photometric Data, complemented by 820 stars from more recent catalogs, for b ≤ 60°. A set of restrictive exclusion criteria has been applied to eliminate E(b – y) values inappropriate for the study of the interstellar medium (ISM). The final sample has 8492 stars located up to 500 pc from the Sun. Our main results are as follows: (1) the large-scale distribution of the interstellar dust in the LB is highly inhomogeneous; (2) on the Galactic plane, E(b – y) ≥ 0040 is observed at a distance of d ≈ 80-100 pc from l ≥ 270° until l ≤ 45°; (3) the color excess suggests that there are many tunnels and holes in the LB wall; and (4) there is a clear correlation between E(b – y) and the spatial density distribution of the interstellar gas inferred from the simulations.

We investigate the distribution of gas (ionized, neutral atomic and molecular) and interstellar dust in the complex star-forming region NGC6357 with the goal of studying the interplay between the massive stars in the open cluster Pis24 and the surrounding interstellar matter. Our study of the distribution of the ionized gas is based on narrow-band Hα, [S II]and [O III] images obtained with the Curtis-Schmidt Camera at CTIO, Chile, and on radio continuum observations at 1465 MHz taken with the VLA with a synthesized beam of 40arcsec. The distribution of the molecular gas is analysed using 12CO(1-0) data obtained with the NANTEN radiotelescope, Chile (angular resolution = 2.7arcmin). The interstellar dust distribution was studied using mid-infrared data from the GLIMPSE survey and far-infrared observations from IRAS. NGC6357 consists of a large ionized shell and a number of smaller optical nebulosities. The optical, radio continuum, and near- and mid-IR images delineate the distributions of the ionized gas and interstellar dust in the H II regions and in previously unknown wind-blown bubbles linked to the massive stars in Pis24 revealing surrounding photodissociation regions. The CO line observations allowed us to identify the molecular counterparts of the ionized structures in the complex and to confirm the presence of photodissociation regions. The action of the WR star HD157504 on the surrounding gas was also investigated. The molecular mass in the complex is estimated to be (4 ± 2) × 105 M⊙. The mean electron densities derived from the radio data suggest electron densities >200 cm-3, indicating that NGC6357 is a complex formed in a region of high ambient density. The known massive stars in Pis24 and a number of newly inferred massive stars are mainly responsible for the excitation and photodissociation of the parental molecular cloud., Facultad de Ciencias Astronómicas y Geofísicas, Instituto de Astrofísica de La Plata, Instituto Argentino de Radioastronomía

We analyse the various interstellar components of the H II region Sh2-132. The main stellar source is the double binary system that includes the Wolf–Rayet star WR 153ab. We use radio continuum images at 408 and 1420 MHz, and H I 21-cm line data taken from the Canadian Galactic Plane Survey, molecular observations of the 12CO(1–0) line at 115 GHz from the Five College Radio Astronomy Observatory, and available mid- and far-infrared observations obtained with the MSX and IRAS satellites, respectively. Sh2-132 is composed of two shells showing radio continuum counterparts at both frequencies. The emission is thermal in nature. The estimated rms electron density and ionized mass of the nebula are ne≃ 20 cm−3 and MH II ≃ 1500 M⊙. The distribution of the CO emission shows molecular gas bordering the ionized nebula and interacting with it. The velocities of the molecular gas is in the range −38 to −53 km s−1, similar to the velocity of the ionized gas. The emission at 8.3 μm reveals a ring-like feature of about 15 arcmin that encircles the bright optical regions. This emission is due to the polycyclic aromatic hydrocarbons and marks the location of photodissociation regions. The gas distribution in the environs of Sh2-132 can be explained in a scenario where the massive stars in the region photodissociated, ionized and swept up the dense molecular material from the parental cloud through their strong stellar winds and intense ultraviolet (UV) photon flux., Facultad de Ciencias Astronómicas y Geofísicas

GSH91.5+2-114 is a large HI shell located in the outer Galaxy at a kinematic distance of about 15 kpc. It was first identified in the Canadian Galactic Plane Survey (CGPS) by Pineault et al. (2002) as being possibly associated with objects possessing infrared colors which indicates strong stellar winds. The HI shell has no obvious continuum counterpart in the CGPS radio images at 408 and 1420 MHz or in the IRAS images. We found no evidence for early-type massive stars, most likely as a result of the large extinction that is expected for this large distance. An analysis of the energetics and of the main physical parameters of the HI shell shows that this shell is likely the result of the combined action of the stellar winds and supernova explosions of many stars. We investigate whether a number of slightly extended regions characterized by a thermal radio continuum and located near the periphery of the HI shell could be the result of star formation triggered by the expanding shell., Comment: Accepted for publication in A&A, October 2010. Some figures were degraded to reduce file size

We report the detection of the radio and infrared (IR) counterparts of the ring nebula around the WN3(h) star HD 211564 (WR 152), located to the south-west of the H II region Sh2 132. Using radio continuum data from the Canadian Galactic Plane Survey, we identified the radio counterparts of the two concentric rings, of about 9 and 16 arcmin in radius, related to the star. After applying a filling factor f = 0.05-0.12, electron densities and ionized masses are in the range 10-16 cm-3 and 450-700 M⊙ respectively. The analysis of the H I gas emission distribution allowed the identification of 5900 M⊙ of neutral atomic gas with velocities between -52 and -43 km s-1 probably linked to the nebula. The region of the nebula is almost free of molecular gas. Only four small clumps were detected, with a total molecular mass of 790 M⊙. About 310 M⊙ are related to a small IR shell-like source linked to the inner ring, which is also detected in the MSX band A.AnIRAS young stellar object candidate is detected in coincidence with the shell-like IR source. We suggest that the optical nebula and its neutral counterparts originated from the stellar winds from the Wolf-Rayet star and its massive progenitor, and are evolving in the envelope of a slowly expanding shell centred at (l,b) = (102.30, -0°.50) of about 31 pc in radius. The bubble's energy conversion efficiency is in agreement with recent numerical analysis and with observational results., Facultad de Ciencias Astronómicas y Geofísicas

We study, by means of three-dimensional adaptive mesh refinement simulations, the spatial distribution of the Li-like ions C IV, N V, and O VI inside the Local Bubble (LB), powered by 19 missing stars of subgroup B1 of the Pleiades suggested as responsible for its origin. The ions C IV, N V, and O VI, and the distribution of their column density ratios (N(C IV)/N(O VI) and N(N V)/N(O VI)) in the simulations are monitored through lines of sight (with lengths as large as 150 pc) emanating from the Solar position. The main results are: (i) there is a weak distribution of C IV and N V in the regions where O VI is strong, (ii) there is a small amount of C IV and N V ions inside the bubble translating into upper limits of –1.0 of the ratios log[N(C IV)/N(O VI)] and log[N(N V)/N(O VI)], consistent with observations, and (iii) with the lack of heat conduction, turbulent mixing, due to the strong shear between the hotter and cooler regions inside the LB, is responsible for the generation and distribution of these ions.

Context. Using certain simplifications, Kompaneets derived a partial differential equation that states the local geometrical and kinematical conditions that each surface element of a shock wave, created by a point blast in a stratified gaseous medium, must satisfy. Kompaneets could solve his equation analytically for the case of a wave propagating in an exponentially stratified medium, obtaining the form of the shock front at progressive evolutionary stages. Complete analytical solutions of the Kompaneets equation for shock wave motion in further plane-parallel stratified media were not found, except for radially stratified media. Aims. We aim to analytically solve the Kompaneets equation for the motion of a shock wave in different plane-parallel stratified media that can reflect a wide variety of astrophysical contexts. We were particularly interested in solving the Kompaneets equation for a strong explosion in the interstellar medium of the Galactic disk, in which, due to intense winds and explosions of stars, gigantic gaseous structures known as superbubbles and supershells are formed. Methods. Using the Kompaneets approximation, we derived a pair of equations that we call adapted Kompaneets equations, that govern the propagation of a shock wave in a stratified medium and that permit us to obtain solutions in parametric form. The solutions provided by the system of adapted Kompaneets equations are equivalent to those of the Kompaneets equation. We solved the adapted Kompaneets equations for shock wave propagation in a generic stratified medium by means of a power-series method. Results. Using the series solution for a shock wave in a generic medium, we obtained the series solutions for four specific media whose respective density distributions in the direction perpendicular to the stratification plane are of an exponential, power-law type (one with exponent and the other with ) and a quadratic hyperbolic-secant. From these series solutions, we deduced exact solutions for the four media in terms of elemental functions. The exact solution for shock wave propagation in a medium of quadratic hyperbolic-secant density distribution is very appropriate to describe the growth of superbubbles in the Galactic disk., Facultad de Ciencias Astronómicas y Geofísicas

We investigate the morphology and kinematics of the interstellar medium in the environs of the open cluster Mrk 50, which includes the Wolf-Rayet star WR 157 and a number of early B-type stars. The analysis was performed using radio continuum images at 408 and 1420 MHz, and H i 21-cm line data taken from the Canadian Galactic Plane Survey, molecular observations of the 12CO (J = 1 → 0) line at 115 GHz from the Five College Radio Astronomy Observatory and available mid- and far-infrared (FIR) observations obtained with the Midcourse Space Experiment and IRAS satellites, respectively. This study allowed the identification of the radio continuum and molecular counterpart of the ring nebula SG 13, while no neutral atomic structure was found to be associated. The nebula is also detected in the images in the mid- and FIR, showing the existence of dust well mixed with the ionized gas. We estimate the main physical parameters of the material linked to the nebula. The interstellar gas distribution in the environs of Mrk 50 is compatible with a stellar wind bubble created by the mass loss from WR 157. The distribution of young stellar object candidates in the region shows that the stellar formation activity may be present in the molecular shell that encircles the ring nebula., Facultad de Ciencias Astronómicas y Geofísicas

Aims. We present a study of the ionized, neutral atomic, and molecular gas associated with the ring nebula RCW78 around the WR star HD117688 (=WR55) with the aim of analyzing the distribution of the associated gas and investigating its energetics. Methods. We base our study on 12CO(1-0) and 12CO(2-1) observations of the brightest section of the nebula carried out with the SEST telescope with angular resolutions of 45'' and 22'', respectively; and on complementary 12CO(1-0) data of a larger area obtained with the NANTEN telescope with an angular resolution of 2. ′ 7, Hi 21-cm line data taken from the ATCA survey, IRAS HIRES data, and radio continuum data at 4.85 GHz from the Parkes survey. Results. We report the detection of molecular gas having velocities in the range -56 to -33 kms -1 associated with the western region of RCW78. A few patches of molecular gas possibly linked to the eastern faint section are detected. The CO emission appears concentrated in a region of 23′ ×18′ in size, with a total molecular mass of (1.3 ±0.5) ×105 M ⊙, mainly connected to the western section. The analysis of the neutral atomic gas distribution reveals the Hi envelope of the molecular cloud, while the radio continuum emission shows a ring-like structure, which is the radio counterpart of the optical nebula. The gas distribution is compatible with the western section of RCW78 having originated in the photodissociation and ionization of the molecular gas by the UV photons of the WN7 star HD117688, and with the action of the stellar winds of the WR star on the surrounding gas. In this scenario, the interstellar bubble expanded more easily towards the east than towards the west due to the lack of dense molecular gas in the eastern section. The proposed scenario also explains the off center location of WR55. A number of infrared point sources classified as YSO candidates showed that star formation activity is present in the molecular gas linked to the nebula. The possibility that the expansion of the bubble triggered star formation in this region cannot be discarded., Facultad de Ciencias Astronómicas y Geofísicas, Instituto Argentino de Radioastronomía