New perspectives on the supernova remnant Puppis A based on a radio polarization study

We present a polarization study towards the supernova remnant (SNR) Puppis A based on original observations performed with the Australia Telescope Compact Array. Based on the analysis of a feature detected outside the SNR shell (called 'the tail' throughout the paper), it was possible to disentangle the emission with origin in Puppis A itself from that coming from the foreground Vela SNR. We found a very low polarization fraction, of about 3 per cent on average. The upper limit of the magnetic field component parallel to the line of sight is estimated to be B ~ 20 μG. The statistical behaviour of the magnetic vectors shows two preferential directions, almost perpendicular to each other, which are approximately aligned with the flat edges of Puppis A. A third, narrow peak oriented perpendicular to the Galactic plane suggests the existence of an interstellar magnetic field locally aligned in this direction. There is evidence that the magnetic vectors along the shell are aligned with the shock front direction. The low polarization fraction and the statistical behaviour of the magnetic vectors are compatible with a scenario where the SNR evolves inside a stellar wind bubble with a box-like morphology, produced by the interaction of the different stellar winds, one of them magnetized, launched by the SN progenitor. This scenario can furthermore explain the morphology of Puppis A, rendering little support to the previously accepted picture which involved strong density gradients to explain the flat, eastern edge of the shell.Fil: Reynoso, Estela Marta. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Velázquez, P. F.. Universidad Nacional Autónoma de México. Instituto de Ciencias Nucleares; MéxicoFil: Cichowolski, Silvina. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

An Effelsberg HI study of the ISM around WR 126, WR 154 and WR 155

The neutral hydrogen distribution has been studied in the direction of three Galactic Wolf-Rayet (WR) stars using the 100 m Effelsberg radio telescope. Cavities in the HI distribution, regions of low HI emissivity, are observed over a 8-9 km s-1 velocity range for WR 126 (≡ST 2), WR 154 (≡HD 213049) and WR 155 (≡HD 214419). These minima are interpreted as the observable 21-cm HI line counterpart of interstellar bubbles created by the winds of the WR stars and their progenitors. The HI cavities are elongated structures depicting an axial ratio ranging from 1.3 (WR 155) to 3 (WR 126). The WR stars are always eccentric with respect to either the geometric centre of the HI cavity or the absolute minimum inside it. This offset ranges from 50% to 80% of the HI hole's minor axis. The major axis of these structures range from 13 (WR 155) to 27 pc (WR 126), while the missing HI mass amounts to 45-50 M⊙ (WR 126), 60 M⊙ (WR 155) and 85 M⊙ (WR 154).Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de Radioastronomí

The radio and infrared counterparts of the ring nebula around HD 211564

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 Geofísica

An HI interstellar bubble linked to the O-type stars BD +24°3866 and BD +25°3952

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 GeofísicasInstituto Argentino de Radioastronomí

An Effelsberg HI study of the ISM around WR 126, WR 154 and WR 155

The neutral hydrogen distribution has been studied in the direction of three Galactic Wolf-Rayet (WR) stars using the 100 m Effelsberg radio telescope. Cavities in the HI distribution, regions of low HI emissivity, are observed over a 8-9 km s-1 velocity range for WR 126 (≡ST 2), WR 154 (≡HD 213049) and WR 155 (≡HD 214419). These minima are interpreted as the observable 21-cm HI line counterpart of interstellar bubbles created by the winds of the WR stars and their progenitors. The HI cavities are elongated structures depicting an axial ratio ranging from 1.3 (WR 155) to 3 (WR 126). The WR stars are always eccentric with respect to either the geometric centre of the HI cavity or the absolute minimum inside it. This offset ranges from 50% to 80% of the HI hole's minor axis. The major axis of these structures range from 13 (WR 155) to 27 pc (WR 126), while the missing HI mass amounts to 45-50 M⊙ (WR 126), 60 M⊙ (WR 155) and 85 M⊙ (WR 154).Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de Radioastronomí

Triggered star formation in a molecular shell created by a SNR?

We present a study of a new molecular shell, G126.1-0.8-14, using available multiwavelegth Galactic plane surveys and optical Gemini observations. A well defined shell-like structure is observed in the CO(1--0) line emission at (l,b) = (126.1, -0.8), in the velocity range --10.5 to --15.5 km/s. The HI, emission shows a region of low emissivity inside G126.1-0.8-14, while radio continuum observations reveal faint non-thermal emission possibly related to this shell. Optical spectra obtained with Gemini South show the existence of B-type stars likely to be associated with G126.1-0.8-14. An estimate of the stellar wind energy injected by these stars show that they alone can not be able to create such a structure. On the other hand, one supernova explosion would provide enough energy to generate the shell. Using the MSX, IRAS, and WISE Point Source Catalogues we have found about 30 young stellar objects candidates, whose birth could have been triggered by the expansion of G126.1-0.8-14. In this context, Sh2-187 could be a consequence of the action on its surroundings of the most massive (and thus most evolve) of the stars formed by the expanding molecular shell.Comment: 13 pages, 10 figures, accepted in MNRA

An HI interstellar bubble linked to the O-type stars BD +24°3866 and BD +25°3952

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 GeofísicasInstituto Argentino de Radioastronomí

VLA and Effelsberg observations of the interstellar medium around the runaway star WR 124

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 GeofísicasInstituto Argentino de Radioastronomí

The radio and infrared counterparts of the ring nebula around HD 211564

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 Geofísica

GS 100-02-41: a new HI shell in the outer part of the Galaxy

GS100-02-41 es una supercáscara de hidrógeno neutro (HI) localizada en la parte externa de la Galaxia, a una distancia de 2.8 kpc del Sol. A partir del análisis de los datos de HI varios parámetros que caracterizan a la estructura (dimensiones, masa, densidad, energía cinética, edad dinámica, etc.) han sido determinados. En base a consideraciones energéticas, se estima que GS100-02-41 podría haberse originado por la acción conjunta de los vientos estelares y explosiones de supernova de las estrellas miembros de Cep OB1.    Si bien la supercáscara no es observable ni en el continuo de radio ni en el infrarrojo lejano, en ambos rangos de frecuencia se detectan, proyectadas sobre los bordes de GS100-01-41, cuatro fuentes discretas. La más intensa de ellas corresponde a la región Sh2-132. Determinaciones de las densidades de flujo a distintas frecuencias permiten establecer, para las tres fuentes restantes, que las mismas son de naturaleza térmica (regiones HII). El análisis de la base de datos del CGPS, permite identificar más minimos de HI en el gas neutro de GS100-02-41, que guardan una excelente correlación morfológica con la distribución del gas ionizado de las cuatro fuentes de continuo. Esto permitiría  vincular físicamente dichas regiones con GS100-02-41. Por  último, a partir de distintas estimaciones para las edades de las estucturas involucradas, se analiza la posibilidad de que la formación de las estrellas excitatrices de las regiones HII haya sido inducida por la expansión de GS100-02-41.Fil: Suad, Laura Andrea. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Cichowolski, Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Arnal, Edmundo Marcelo. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Testori, Juan Carlos. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; Argentina54ª Reunión Anual de la Asociación Argentina de AstronomíaSan JuanArgentinaInstituto de Ciencias Astronómicas, de la Tierra y del Espaci