La corriente magallánica

Se presentan resultados observacionales de una región de la Corriente Magallánica (CM). Las mismas fueron realizadas con gran sensibilidad y resoluciones en velocidad de 16 y 2 km s⁻¹. Dichas observaciones muestran componentes adicionales de la CM y ponen en evidencia a la extrema complejidad de la distribución de velocidades de la misma. Estos hechos deben ser tenidos en cuenta en los modelos que tratan de explicar su existencia.Asociación Argentina de Astronomí

Starlight polarization and CO observations towards the Lupus clouds

We performed an observational study of the dark filaments Lupus 1 and Lupus 4 using both polarimetric observations of 190 stars and a sample of 72 12CO profiles towards these clouds. We have estimated lower limits to the distances of Lupus 1 and Lupus 4 (* 140 and * 125 pc, respectively). The observational strategy of the survey allows us to compare the projected magnetic field in an extended area around each cloud with the magnetic field direction observed to prevail along the clouds. Lupus 4 could have collapsed along the magnetic field lines, while in Lupus 1 the magnetic field appears to be less ordered, having the major axis of the filaments parallel to the large-scale projected magnetic field. These differences would imply that both filaments have different pattern evolutions. From the CO observations we have probed the velocity fields of the filaments and the spatial extension of the molecular gas with respect to the dust.Instituto Argentino de RadioastronomíaFacultad de IngenieríaFacultad de Ciencias Astronómicas y Geofísica

Determinación de la distancia a unos complejos de HI en base a mediciones de polarización de la luz estelar

La orientación general del campo magnético, determinada a partir de observaciones de la luz estelar, es paralela a tres complejos elongados de HI detectados en el Instituto Argentino de Radioastronomía. A partir de esta correlación y sobre la base de analizar la hipótesis de que el gas HI está mezclado con el polvo que produce la polarización de la luz, se intenta determinar la distancia a los complejos de HI.Asociación Argentina de Astronomí

A new survey for high velocity HI detections in the southern hemisphere

A new high-sensitivity HI survey of the southern sky was made south of Declination , at the Instituto Argentino de Radioastronomía (IAR), on a half-degree grid in galactic coordinates. A total of 50980 positions were observed. One of the goals of this survey was to search for high velocity clouds (HVCs). The HI profiles have been smoothed to a velocity resolution of 8 km s-1. The resulting rms noise falls in the range 0.015 to 0.020 K. We have detected 6848 high velocity (HV) components.Fil: Morras, Ricardo. 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: Bajaja, Esteban. 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: Arnal, Edmundo Marcelo. 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: Poppel, W. G. L.. 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; Argentin

Estructura fina en nubes de alta velocidad

Observaciones de nubes de alta velocidad, en la linea de 21 cm del HI, con alta resolución espectral (2 km s⁻¹), están siendo realizados en el IAR. El objeto del trabajo es estudiar su estructura espacial y en velocidad a fin de reconocer diferencias sistemáticas entre nubes en distintas áreas del cielo, que ayuden a su clasificación.Asociación Argentina de Astronomí

A new survey for high velocity HI detections in the Southern Hemisphere

A new high-sensitivity HI survey of the southern sky was made south of Declination -25°, at the Instituto Argentino de Radioastronomía (IAR), on a half-degree grid in galactic coordinates. A total of 50980 positions were observed. One of the goals of this survey was to search for high velocity clouds (HVCs). The HI profiles have been smoothed to a velocity resolution of 8 km s-1. The resulting rms noise falls in the range 0.015 to 0.020 K. We have detected 6848 high velocity (HV) components.Facultad de Ciencias Astronómicas y Geofísica

The interstellar medium surrounding the Scorpius-Centaurus association revisited

Aims. We want to make a large-scale study of the morphology, kinematics, and origin of the HI, which surrounds the Sco-Cen association. Methods. We combine our high-sensitivity southern HI survey with the Leiden/Dwingeloo Survey, considering l = 240°-400°, b =-60° to +60°, and radial velocities of V =-41.8 to +40.8 kms-1.We point out the main HI branches surrounding the association and derive their kinematics. Kinematical HI-maps were compared with spatial maps of interstellar (IS) Na I from the literature. Upper limits for distances d were derived from optical IS absorption components from the literature. Models of expanding spherical HI shells were fitted around each stellar subgroup. Results. The expanding ring of HI associated with the Gould Belt (GB) is very prominent. At each l, its radial velocity shifts ∼-7 kms-1 within an interval Δb ∼ 10°-25°. On the sky, the shifts occur within a narrow stripe extending between l. b ∼ 250°.-18° and 400°. +50°. The ranges of distances and radial thicknesses of most HI branches are nearly 70-160 pc and 40-90 pc, respectively. The shell-models fit the main branches. Interactions between the shells built a large expanding bubble with a transverse diameter of nearly 250 pc around the association. The near face is approaching with a mean velocity V ∼-6.6 kms-1 at d = 76 pc from the Sun, covering about 102° × 65° (l. b), forming an "HI-wall". There are streamers at V ∼-15 to-35 km s-1, as well as gas presumably overshot into Galactic Quadrant II. The receding gas is more tenuous. Conclusions. The association is traversing the ring since a time comparable to its age producing a significant disturbance on the expanding GB-ring of gas. The latter was almost totally shocked by the association, northerly of the stripe of velocity shifts. Southerly there are large amounts of preshocked gas, as well as smaller more localized shocked regions. Hot gas within the bubble produces most of the 1/4 keV radiation detected toward it by ROSAT. The total mass of the GB gas embedding the Sco-Cen association is estimated at Mt ∼ 368 000 M⊙ ± 60%, including ∼34 000 M⊙ of associated H2 and 30% of He. About 39% of the embedding gas was shocked by the association. At |b|≥35°, a comparison of the observations with test points moving on ballistic orbits is consistent with the formation of the Sco-Cen association within the gas ring of the GB and the presumable explosive origin of the latter. The rotation of the ring is assumed.Facultad de Ciencias Astronómicas y Geofísica

The interstellar medium surrounding the Scorpius-Centaurus association revisited

Aims. We want to make a large-scale study of the morphology, kinematics, and origin of the HI, which surrounds the Sco-Cen association. Methods. We combine our high-sensitivity southern HI survey with the Leiden/Dwingeloo Survey, considering l = 240°-400°, b =-60° to +60°, and radial velocities of V =-41.8 to +40.8 kms-1.We point out the main HI branches surrounding the association and derive their kinematics. Kinematical HI-maps were compared with spatial maps of interstellar (IS) Na I from the literature. Upper limits for distances d were derived from optical IS absorption components from the literature. Models of expanding spherical HI shells were fitted around each stellar subgroup. Results. The expanding ring of HI associated with the Gould Belt (GB) is very prominent. At each l, its radial velocity shifts ∼-7 kms-1 within an interval Δb ∼ 10°-25°. On the sky, the shifts occur within a narrow stripe extending between l. b ∼ 250°.-18° and 400°. +50°. The ranges of distances and radial thicknesses of most HI branches are nearly 70-160 pc and 40-90 pc, respectively. The shell-models fit the main branches. Interactions between the shells built a large expanding bubble with a transverse diameter of nearly 250 pc around the association. The near face is approaching with a mean velocity V ∼-6.6 kms-1 at d = 76 pc from the Sun, covering about 102° × 65° (l. b), forming an "HI-wall". There are streamers at V ∼-15 to-35 km s-1, as well as gas presumably overshot into Galactic Quadrant II. The receding gas is more tenuous. Conclusions. The association is traversing the ring since a time comparable to its age producing a significant disturbance on the expanding GB-ring of gas. The latter was almost totally shocked by the association, northerly of the stripe of velocity shifts. Southerly there are large amounts of preshocked gas, as well as smaller more localized shocked regions. Hot gas within the bubble produces most of the 1/4 keV radiation detected toward it by ROSAT. The total mass of the GB gas embedding the Sco-Cen association is estimated at Mt ∼ 368 000 M⊙ ± 60%, including ∼34 000 M⊙ of associated H2 and 30% of He. About 39% of the embedding gas was shocked by the association. At |b|≥35°, a comparison of the observations with test points moving on ballistic orbits is consistent with the formation of the Sco-Cen association within the gas ring of the GB and the presumable explosive origin of the latter. The rotation of the ring is assumed.Facultad de Ciencias Astronómicas y Geofísica

Observaciones radioastronómicas y polarimetrías en la dirección de un filamento molecular

En el presente trabajo se detallan resultados de observaciones en 2.6 mm (CO: J = 1 —» 0) y de observaciones polarimétricas sobre una pequeña nube molecular, de apariencia elongada, y dispuesta casi perpendicularmente al plano galáctico, cercana a la región de Chamaleon. A partir de las observaciones en CO, fue posible estimar varias propiedades de esta nube, tales como su campo de velocidades, temperatura cinética y distribución angular del gas. Por otro lado, las observaciones polarimétricas permitieron inferir una cota inferior de la distancia y la dirección del campo magnético presente, que se dispone en forma transversal al filamento. Asimismo, análisis conjuntos de ambas técnicas proveyeron magnitudes tales como la masa total y densidad volumétrica del H2 presente en la nube y una estimación cinemática del valor máximo de su edad. Finalmente, se estimaron la importancia relativa de procesos tales como rotación, colapso gravitatorio, expansión y también la evolución de este objeto; sobre esto último, la orientación de la nube respecto al campo magnético indicaría que éste juega un rol dominante en las primeras etapas de su evolución, ya que retardaría el colapso en el sentido perpendicular a las líneas de campo.Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de Radioastronomí

Observaciones polarimétricas y de CO en la dirección de glóbulos filamentarios

CO observations at 115 GHz (J = 1 —0) and polarization measurements towards two globular filaments in Lupus (GF 17 and GF 19), are reported. From the CO observations, the velocity field and the distribution of the molecular gas into each cloud may be studied. On the other hand, from the polarization, it is possible to infer the direction of the plane-of-the-sky projected magnetic field, in relation to the geometry of each cloud, and the role played by itself on the evolution of both filaments.Asociación Argentina de Astronomí