La corriente magallánica

Nuevas observaciones en la línea de 21 cm realizadas con alta sensibilidad en la región comprendida entre declinaciones -44° y -20° ( alrededor del polo sur galáctico), revelan la extrema complejidad en la distribución del gas en la dirección de la Corriente Magallánica. En dicha región es posible observar, además del HI correspondiente a la corriente otras componentes adicionales de la misma, gas posiblemente vinculado al grupo de Sculptor y típicas nubes de alta velocidad.Asociación Argentina de Astronomí

Estudio de la distribución de HI a grandes distancias del plano galáctico

Desde el IAR se realizaron observaciones hacia el interior de la galaxia (270°500 pc crece, en forma sistemática, desde el interior de la galaxia (R< 3 kpc) hasta la región solar (R ≃ 10 kpc). Igual crecimiento fue observado; por otros autores, estudiando la región comprendida entre longitudes 0 y 90. No obstante, los datos del 4to. cuadratne de longitudes parecen mostrar una asimetría, en la distribución del gas HI, respecto del 1er. cuadrante.Asociación Argentina de Astronomí

Estructura fina en nubes de alta velocidad positiva

Se presentan los resultados observacionales de dos complejos de HI: HVC 287.5 + 225 + 240 y HVC 273 + 9.5 + 247. Los mismos fueron observados con una resolución angular de 35' y una resolución en velocidad de 2 km/seg.Asociación Argentina de Astronomí

Observaciones en la línea de 21 cm. del hidrógeno neutro en la región del polo sur celeste (δ ≤ -85°)

Data from the observation of the 21-cm neutral hydrogen line are presented for the region 297º <l< 309º, -22º<b<-32º, and -90 < v < 90 km/s. Shown are 143 profiles of the zone and isophotes at constant l, constant b, and constant velocity from -36 to +12 km/s, every 4 km/s.Asociación Argentina de Astronomí

Observaciones en la línea de 21 cm. del hidrógeno neutro en la región del polo sur celeste (δ ≤ -85°)

Data from the observation of the 21-cm neutral hydrogen line are presented for the region 297º <l< 309º, -22º<b<-32º, and -90 < v < 90 km/s. Shown are 143 profiles of the zone and isophotes at constant l, constant b, and constant velocity from -36 to +12 km/s, every 4 km/s.Asociación Argentina de Astronomí

High Velocity Cloud Complex H: A Satellite of the Milky Way in a Retrograde Orbit?

Observations with the Green Bank Telescope of 21cm HI emission from the high-velocity cloud Complex H suggest that it is interacting with the Milky Way. A model in which the cloud is a satellite of the Galaxy in an inclined, retrograde circular orbit reproduces both the cloud's average velocity and its velocity gradient with latitude. The model places Complex H at approximately 33 kpc from the Galactic Center on a retrograde orbit inclined about 45 degrees to the Galactic plane. At this location it has an HI mass > 6 10^6 Msun and dimensions of at least 10 by 5 kpc. Some of the diffuse HI associated with the cloud has apparently been decelerated by interaction with Galactic gas. Complex H has similarities to the dwarf irregular galaxy Leo A and to some compact high-velocity clouds, and has an internal structure nearly identical to parts of the Magellanic Stream, with a pressure P/k about 100 cm^{-3} K.Comment: 12 pages includes 4 figures. To be published in Astrophysical Journal Letters, 1 July 200

A high sensitivity HI survey of the sky at delta < -25 deg Final data release

We present the final data release of the high sensitivity lambda 21-cm neutral hydrogen survey of the sky south of delta < -25 degr. A total of 50980 positions lying on a galactic coordinate grid with points spaced by (Delta l, Delta b) = ((0.5 deg)/cos b, 0.5 deg) were observed with the 30-m dish of the Instituto Argentino de Radioastronomia (IAR). The angular resolution of the survey is HPBW = 0.5 deg and the velocity coverage spans the interval -450 km/s to +400 km/s (LSR). The velocity resolution is 1.27 km/s and the final rms noise of the entire database is 0.07 K. The data are corrected for stray radiation and converted to brightness temperatures.Comment: 10 pages, 10 figures, accepted for publication by Astronomy & Astrophysic

The Metallicity and Dust Content of HVC 287.5+22.5+240: Evidence for a Magellanic Clouds Origin

We estimate the abundances of S and Fe in the high velocity cloud HVC 287.5+22.5+240, which has a velocity of +240 km/s with respect to the local standard of rest and is in the Galactic direction l~287, b~23. The measurements are based on UV absorption lines of these elements in the Hubble Space Telescope spectrum of NGC 3783, a background Seyfert galaxy, as well as new H I 21-cm interferometric data taken with the Australia Telescope. We find S/H=0.25+/-0.07 and Fe/H=0.033+/-0.006 solar, with S/Fe=7.6+/-2.2 times the solar ratio. The S/H value provides an accurate measure of the chemical enrichment level in the HVC, while the super-solar S/Fe ratio clearly indicates the presence of dust, which depletes the gas-phase abundance of Fe. The metallicity and depletion information obtained here, coupled with the velocity and the position of the HVC in the sky, strongly suggest that the HVC originated from the Magellanic Clouds. It is likely (though not necessary) that the same process(es) that generated the Magellanic Stream is also responsible for HVC 287.5+22.5+240.Comment: AASTEX, 3 postscript figures, AJ, 1998, Jan issu

The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections

We present the final data release of observations of lambda 21-cm emission from Galactic neutral hydrogen over the entire sky, merging the Leiden/Dwingeloo Survey (LDS: Hartmann & Burton, 1997) of the sky north of delta = -30 deg with the Instituto Argentino de Radioastronomia Survey (IAR: Arnal et al., 2000, and Bajaja et al., 2005) of the sky south of delta = -25 deg. The angular resolution of the combined material is HPBW ~ 0.6 deg. The LSR velocity coverage spans the interval -450 km/s to +400 km/s, at a resolution of 1.3 km/s. The data were corrected for stray radiation at the Institute for Radioastronomy of the University of Bonn, refining the original correction applied to the LDS. The rms brightness-temperature noise of the merged database is 0.07 - 0.09 K. Residual errors in the profile wings due to defects in the correction for stray radiation are for most of the data below a level of 20 - 40 mK. It would be necessary to construct a telescope with a main beam efficiency of eta_{MB} > 99% to achieve the same accuracy. The merged and refined material entering the LAB Survey of Galactic HI is intended to be a general resource useful to a wide range of studies of the physical and structural characteristices of the Galactic interstellar environment. The LAB Survey is the most sensitive Milky Way HI survey to date, with the most extensive coverage both spatially and kinematically.Comment: 9 pages, 5 figures, accepted for publication by Astronomy & Astrophysic