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We report the detection of long, thin H I tails emanating from molecular clouds in the Perseus Arm of the Galaxy. The hypothesis that they are driven by stellar winds from one or both of the massive stars HD 17603 and WR 5 places strong constraints on the stellar wind environment: we find that a heavily mass-loaded wind bubble is required.

We report radio continuum observations at 1465 MHz obtained with the Very Large Array (VLA) in the DnC configuration toward the ring nebulae associated with the stars WR 101 and WR 113, with resolutions of ∼38″ and 30″, respectively. IRAS images of the nebulae with resolutions of about 2′ (90 M⊙, 40 cm-3) are also analyzed. A remarkable resemblance among the optical, infrared, and radio images of these ring nebulae is observed. The VLA data indicate that Anon. WR 101 is thermal in nature. An ionized mass of ≈230 ± 40 M⊙ and electron densities in the range ≈40-55 cm-3 were estimated for Anon. WR 101. The derived ionized masses and electron densities in the inner and outer shells of the nebula related to WR 113 are ≈20 ± 10 M⊙, 180-500 cm-3 and ≈90 M⊙ 40 cm-3, respectively. Based on infrared data at 60 and 100 μm, the derived masses and temperatures for the dust component in the ring nebula around WR 101 are 0.3-1 M⊙ and ≈40 K. The associated masses suggest that the ring nebula related to WR 101 and the outer arc associated with WR 113 consist of swept-up interstellar matter, while the relatively low ionized mass associated with the inner shell of the nebula around WR 113 may contain a nonnegligible contribution of expelled ejecta material. The derived electron densities for the nebula around WR 101 and the inner shell around WR 113 are comparable to electron densities for other W-R ring nebulae. Low filling factors are inferred for both nebulae. The nebulae probably originated during the current W-R phase of the stars., Facultad de Ciencias Astronómicas y Geofísicas, Instituto Argentino de Radioastronomía

We investigate the ISM in the vicinity of the O-type stars BD +24°3866 (O8.5II(f)), BD +24°3881 (O6.5III(f)) and BD +24°3952 (O8) based on radio continuum and HI line data obtained with the Synthesis Telescope of the Dominion Radio Astrophysical Observatory (DRAO) with synthesized beams of 1′.5 and 7′ at 1420 and 408 MHz, respectively. High angular resolution IRAS data (HIRES) are also analyzed. BD +24°3866 is found to be located close to the inner border of a slowly expanding shell. The evolved HII region Sh2-88, which is excited by BD +25°3952, appears to be interacting with neutral material in the approaching part of this shell. The whole structure is ata distance of 2.4 kpc and is about 23×15 pc in radius. The total swept up mass is 1300 M⊙. The stellar winds of BD +24°3866 and BD +25°3952, are mainly responsible for shaping the HI structure. An HI expanding shell was also found to be related to the HII region G61.7+0.9. At a kinematic distance of 2.4 kpc, this feature is 10 pc in radius and has neutral and ionized masses of 200 and 135 M⊙, respectively. The present observational data do not allow us to identify a definite interstellar HI feature associated with BD +24°3881. We consider different explanations for this fact., Facultad de Ciencias Astronómicas y Geofísicas, Instituto Argentino de Radioastronomía

Context. Bubble N107 was discovered in the infrared emission of dust in the Galactic Plane observed by the Spitzer Space Telescope (GLIMPSE survey: l ~ 51.0 deg, b ~ 0.1 deg). The bubble represents an example of shell-like structures found all over the Milky Way Galaxy. Aims. We aim to analyse the atomic and molecular components of N107, as well as its radio continuum emission. With the help of numerical simulations, we aim to estimate the bubble age and other parameters which cannot be derived directly from observations. Methods. From the observations of the HI (I-GALFA) and 13CO (GRS) lines we derive the bubble's kinematical distance and masses of the atomic and molecular components. With the algorithm DENDROFIND, we decompose molecular material into individual clumps. From the continuum observations at 1420 MHz (VGPS) and 327 MHz (WSRT), we derive the radio flux density and the spectral index. With the numerical code ring, we simulate the evolution of stellar-blown bubbles similar to N107. Results. The total HI mass associated with N107 is 5.4E3 Msun. The total mass of the molecular component (a mixture of cold gasses of H2, CO, He and heavier elements) is 1.3E5 Msun, from which 4.0E4 Msun is found along the bubble border. We identified 49 molecular clumps distributed along the bubble border, with the slope of the clump mass function of -1.1. The spectral index of -0.30 of a strong radio source located apparently within the bubble indicates nonthermal emission, hence part of the flux likely originates in a supernova remnant, not yet catalogued. The numerical simulations suggest N107 is likely less than 2.25 Myr old. Since first supernovae explode only after 3 Myr or later, no supernova remnant should be present within the bubble. It may be explained if there is a supernova remnant in the direction towards the bubble, however not associated with it., 15 pages, 11 figures

Based on CO (2-1) observations obtained with the Swedish-ESO Submillimeter Telescope, the distribution of molecular material associated with the Wolf-Rayet ring nebula NGC 2359 has been determined. The angular resolution is 22", and the velocity resolution is 0.33 km s-1. Three molecular components are detected in the direction of the nebula. The bulk of the molecular gas is observed at 54 km s-1 and follows the southeastern border of the nebula., Facultad de Ciencias Astronómicas y Geofísicas

Observations of the interstellar and circumstellar absorption components obtained with the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) along the line of sight toward the Wolf- Rayet-luminous blue variable (LBV) system HD 5980 in the Small Magellanic Cloud are analyzed., Facultad de Ciencias Astronómicas y Geofísicas

A 2° field centered at the optical position of the Wolf-Rayet (WR) star HD 193793 (≡ WR 140) was surveyed in the H I 21 cm line and in the 1420 MHz radio continuum, using the Dominion Radio Astrophysical Observatory interferometer. The aim of this observations was to look for evidence of an interaction between the WR star and its local interstellar medium (ISM). Our H I data displays a large oval minimum at a velocity of Vsys ≃ -12 km s-1, close to the optical position of HD 193793. We believe this H I void was created by WR 140 and its massive companion (HD 193793 is a member of a well-known binary system). The major axis of the H I void is ∼11.5 pc and its axial ratio, the ratio of major to minor axis, is ∼1.4. This structure is observable over a velocity range of around 11 km s-1. The H I minimum appears surrounded by a clumpy shell of H I in emission that has a total mass of neutral hydrogen of MH I ∼ 1300 solar masses. The kinematical distance corresponding to a local standard of rest velocity of -12 km s-1 is approximately 5.4 kpc, which disagrees with the distance of HD 193793, namely, around 1 kpc. Therefore, it is concluded that the H I bubble was blown in an ISM having nonnegligible peculiar motions. Hipparcos proper-motion measurements indicate that HD 193793 has a tangential velocity of 28 ± 3 km s-1 along the major axis of one of the H I minima detected in the interior of the main H I cavity. To reconcile this motion with the physical size of the H I structure blown by the winds of the binary system, it is concluded that such tangential velocity was acquired by the system a short while ago, namely, ∼1.3 × 105 yr. Maps from the IRAS database show a large-scale IR feature, with good spatial correlation with the H I shell surrounding the main H I void. We believe the emission from the IR shell arises from dust grains heated by the energetic stellar continuum photons emitted by the stellar objects., Facultad de Ciencias Astronómicas y Geofísicas, Instituto Argentino de Radioastronomía

Aims. This work aims at investigating the interaction of HD 192281 (O5 Vn((f))p) with its local ISM. The purpose is to analyse the effects that a massive star has on the structure and kinematics of its surrounding gas. Methods. To carry out this study, we used high-resolution radio continuum and 21-cm H i line data from the Canadian Galactic Plane Survey (CGPS). This data base was complemented with radio continuum, infrared, and molecular data retrieved from available surveys. Given that HD 192281 is very likely a runaway star, we attempt to establish whether the observed H i distribution can be interpreted in terms of a simple bow shock model. Results. Analysis of the H i data shows the presence of an H i feature likely to be associated with HD 192281. This feature remains detectable from ~5 to-10 km s-1. At the most negative radial velocities, the shape of the H i feature is highly reminiscent of a bow shock structure seen projected onto the plane of the sky. This feature has counterparts at radio-continuum, infrared, and CO emissions. The analysis of the radio continuum data suggests a thermal spectrum for the gas related to this structure., Instituto Argentino de Radioastronomía, Facultad de Ciencias Astronómicas y Geofísicas

Aims. W49A is a giant molecular cloud which harbors some of the most luminous embedded clusters in the Galaxy. However, the explanation for this starburst-like phenomenon is still under debate.Methods. We investigated large-scale Spitzer mid-infrared images together with a Galatic Ring Survey (13)CO J = 1-0 image, complemented with higher resolution (similar to 11 '') (13)CO J = 2-1 and C(18)O J = 2-1 images over a similar to 15 x 13 pc(2) field obtained with the IRAM 30 m telescope.Results. Two expanding shells have been identified in the mid-infrared images, and confirmed in the position-velocity diagrams made from the (13)CO J = 2-1 and C(18)O J = 2-1 data. The mass of the averaged expanding shell, which has an inner radius of approximate to 3.3 pc and a thickness of approximate to 0.41 pc, is about 1.9 x 10(4) M(circle dot). The total kinetic energy of the expanding shells is estimated to be similar to 10(49) erg, which is probably provided by a few massive stars, whose radiation pressure and/or strong stellar winds drive the shells. The expanding shells are likely to have a common origin close to the two ultracompact HII regions (source O and source N), and their expansion speed is estimated to be similar to 5 k ms(-1), resulting in an age of similar to 3-7 x 10(5) years. In addition, on larger (similar to 35 x 50 pc(2)) scales, remnants of two gas ejections have been identified in the (13)CO J = 1-0 data. Both ejections seem to have the same center as the expanding shells with a total energy of a few times 10(50) erg. The main driving mechanism for the gas ejections is unclear, but likely related to the mechanism which triggers the starburst in W49A.

The Orion-Eridanus superbubble has been blown by supernovae and supersonic winds of the massive stars in the Orion OB associations. The formation history and current structure of the superbubble are still poorly understood. It possibly consists of a combination of nested shells along the line of sight. We have investigated the composite structure of the Eridanus side of the superbubble in the light of a new decomposition of the atomic and molecular gas. We used HI and CO emission lines to separate coherent gas shells in space and velocity, and we studied their relation to the warm ionised gas probed in H$\alpha$ emission, to the hot plasma emitting X-rays, and to the magnetic fields traced by dust polarised emission. We also constrained the relative distances to the clouds using dust reddening maps and X-ray absorption. We used the dust polarisation data to estimate the plane-of-sky components of the magnetic field in several clouds and along the outer rim of the superbubble. Our gas decomposition has revealed several shells inside the superbubble that span distances from about 150 pc to 250 pc. One of these shells forms a nearly complete ring filled with hot plasma. Other shells likely correspond to the layers of swept-up gas that is compressed behind the expanding outer shock wave. We used the gas and magnetic-field data downstream of the shock to derive a shock expansion velocity close to 20 km/s. Taking the X-ray absorption by the gas into account, we find that the pressure of the hot plasma inside the superbubble exceeds that in the Local Bubble. It comprises a mix of hotter (3-9 MK) and cooler (0.3-1.2 MK) gas along the lines of sight. The magnetic field along the western and southern rims and in the approaching wall of the superbubble appears to be shaped and compressed by the ongoing expansion. We find plane-of-sky magnetic strengths ranging from 3 to 15 $\mu$G along the rim., Comment: accepted for publication in A&A