Jose M. Girart

IRAS 21391+5802: The Molecular Outflow and Its Exciting Source

We present centimeter and millimeter observations of gas and dust around IRAS 21391+5802, an intermediate-mass source embedded in the core of IC 1396N. Continuum observations from 3.6 cm to 1.2 mm are used to study the embedded objects and overall distribution of the dust, while molecular line observations of CO, CS, and CH3OH are used to probe the structure and chemistry of the outflows in the region. The continuum emission at centimeter and millimeter wavelengths has been resolved into three sources separated ~15 from each other, and with one of them, BIMA 2, associated with IRAS 21391+5802. The dust emission around this source shows a very extended envelope, which accounts for most of the circumstellar mass of 5.1 M☉. This source is powering a strong molecular outflow, elongated in the east-west direction, which presents a complex structure and kinematics. While at high outflow velocities the outflow is clearly bipolar, at low outflow velocities the blueshifted and redshifted emission are highly overlapping and the strongest emission shows a V-shaped morphology. The outflow as traced by CS and CH3OH exhibits two well-differentiated and clumpy lobes, with two prominent northern blueshifted and redshifted clumps. The curved shape of the clumps and the spectral shape at these positions are consistent with shocked material. In addition, CS and CH3OH are strongly enhanced toward these positions with respect to typical quiescent material abundances in other star-forming regions. This kinematical and chemical evidence suggests that the clumps are tracing gas entrained within the surface of interaction between the molecular outflow and the dense ambient quiescent core and that the morphology of the molecular outflow is a result of this interaction. The circumstellar mass together with the power-law index of the dust emissivity measured, β = 1.1 ± 0.3, and the fact that the source is driving a molecular outflow are consistent with the source BIMA 2 being an embedded intermediate-mass protostar. In addition, the source fits very well correlations between source and outflow properties found for low-mass Class 0 objects. The other two sources in the region, BIMA 1 and BIMA 3, have a mass of 0.07 M☉ each, and their dust emissivity index, β < 0.3 and β = 0.1 ± 0.3, respectively, is consistent with more evolved objects. BIMA 1 is also driving a very collimated and small bipolar outflow elongated in the north-south direction.

Ammonia downstream from HH 80 North

HH 80-81 are two optically visible Herbig-Haro (HH) objects located about 5 minutes south of their exciting source IRAS 18162-2048. Displaced symmetrically to the north of this luminous IRAS source, a possible HH counterpart was recently detected as a radio continuum source with the very large array (VLA). This radio source, HH 80 North, has been proposed to be a member of the Herbig-Haro class since its centimeter flux density, angular size, spectral index, and morphology are all similar to those of HH 80. However, no object has been detected at optical wavelengths at the position of HH 80 North, possibly because of high extinction, and the confirmation of the radio continuum source as an HH object has not been possible. In the prototypical Herbig-Haro objects HH 1 and 2, ammonia emission has been detected downstream of the flow in both objects. This detection has been intepreted as a result of an enhancement in the ammonia emission produced by the radiation field of the shock associated with the HH object. In this Letter we report the detection of the (1,1) and (2,2) inversion transitions of ammonia downstream HH 80 North. This detection gives strong suppport to the interpretation of HH 80 North as a heavily obscured HH object. In addition, we suggest that ammonia emission may be a tracer of embedded Herbig-Haro objects in other regions of star formation. A 60 micrometer IRAS source could be associated with HH 80 North and with the ammonia condensation. A tentative explanation for the far-infrared emission as arising in dust heated by their optical and UV radiation of the HH object is presented.

The Ammonia Core in L723: Hot Spots at the Center of the Quadrupolar Molecular Outflow

We present the results of VLA NH3 and H2O observations, as well as Haystack 13CO, C18O, and H2O observations toward the center of the peculiar quadrupolar molecular outflow in L723. In NH3 we detected a high-density structure, ~17 (~0.15 pc) long, elongated in roughly the east-west direction, with the radio continuum source VLA 2 located near its center. We find evidence in the ammonia maps for heating and line broadening toward VLA 2, confirming that this source is driving the large lobe pair of the quadrupolar molecular outflow. Additionally, H2O maser emission is detected toward this radio continuum source. A second, very compact ammonia hot spot is observed 10 west of VLA 2. This hot spot may be heated by a deeply embedded (still undetected) young stellar object that could be the driving source of the more compact pair of molecular outflow lobes. No ammonia emission is detected at the position of the source VLA 1, which is probably a line-of-sight source.

The HCO+ Molecular Outflow in NGC 2071

We present high angular resolution and multitransition HCO+ observations toward the NGC 2071 molecular outflow. Comparison of the high-velocity (HV) HCO+ and the near-IR H2 in the molecular outflow shows a clear correlation. At high HCO+ flow velocities the spatial coincidence is especially remarkable. In addition, the HV HCO+ presents clear morphological and kinematical differences with the CO outflow. These differences appear not only in the HV HCO+ emission associated with the H2 but in the overall outflow. There is a clear HCO+ emission enhancement, relative to CO, at increasing flow velocities. This enhancement is probably due to an abundance enhancement produced by a velocity-dependent chemistry in the shocks. An overabundance of CH in low Mach shocks may cause the HCO+ abundance enhancement. Because of the short cooling time for H2, the correlation between the HCO+ and the H2 implies that HCO+ emission can provide a useful tool to study in detail the current interactions of protostellar winds with the dense ambient medium. At the position of the extremely high velocity (EHV) CO component in the red lobe we detect HCO+ (J = 3 → 2) emission within the velocity range of the EHV CO gas. This emission is roughly compatible with the expected HCO+ emission associated with EHV gas arising from behind dissociative shocks.

On the Nature of the Molecular Condensation Downstream from HH 80 North

We present HCO+ (J=3→2), H13CO+ (J=3→2), CS (J=5→4), and 13CO (J=2→1) Caltech Submillimeter Observatory observations toward the dense quiescent clump downstream from HH 80 North. This condensation is one in a class of sources that show anomalous molecular abundances, probably produced by UV radiation from a nearby shock. The HCO+ emission properties—location, size, center velocity, line widths, and excitation temperature—are similar to those of the ammonia emission, suggesting that it arises from the same region. The H13CO+ (J=3→2) and CS (J=5→4) lines are marginally detected. Comparison between NH3, HCO+, and CS implies an ammonia enhancement relative to CS of at least 1 order of magnitude, whereas HCO+ shows only a weak enhancement relative to CS. These results are compatible with the radiative shock-induced chemistry models (Taylor & Williams; Wolfire & Konigl) when we take into account the extinction. Our results suggest that the dense clump detected in NH3 and HCO+ is illuminated by HH 80 North, making this region a good laboratory for studying the chemical processes in a quiescent clump radiatively excited by shocks.

1.3 mm Polarized emission in the circumstellar disk of a massive protostar

Fil: Fernandez Lopez, Manuel. Provincia de Buenos Aires. Gobernacion. Comision de Investigaciones Cientificas. Instituto Argentino de Radioastronomia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - La Plata. Instituto Argentino de Radioastronomia; Argentina

SMA observations towards the compact, short-lived bipolar water maser outflow in the LkHα234 region

We present Submillimeter Array (SMA) 1.35 mm subarcsecond angular resolution observations toward the LkH{alpha} 234 intermediate-mass star-forming region. The dust emission arises from a filamentary structure of

Resolving the Polarized Dust Emission of the Disk around the Massive Star Powering the HH 80–81 Radio Jet

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The molecular core and the powering source of the bipolar molecular outflow in NGC 2264G

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A radio candidate for the exciting source of the L1287 bipolar outflow

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