Experimental results on the formation of molecular hydrogen on amorphous silicate surfaces are presented for the first time and analyzed using a rate equation model. The energy barriers for the relevant diffusion and desorption processes are obtained. They turn out to be significantly higher than those obtained earlier for polycrystalline silicates, demonstrating the importance of grain morphol...

has been detected using infrared absorption spectroscopy along the lines of sight to six infrared 3 sources in dense molecular clouds : AFGL 2136, W33A, Mon R2 IRS 3, AFGL 961E, AFGL 2591, and AFGL 490. Upper limits to the column densities of are reported for an additional nine sources. The 3 column densities of CO toward Mon R2 IRS 3 and AFGL 961E have been determined from observations of the ...

We present images of the HH 211 molecular jet in the SiO v=0, J=1–0 line at 43 GHz made with the Very Large Array at approximately 0.5 arcsec resolution. The SiO emission appears to trace primarily internal bowshocks in the outflow, suggesting that the dust and molecular gas are accelerated via prompt entrainment at internal working surfaces in the jet. There is also some evidence for limb-brig...

We report the first high angular resolution imaging (3.4× 3.0) of deuterated formaldehyde (HDCO) toward Orion–KL, carried out with the Submillimeter Array (SMA). We find that the spatial distribution of the formaldehyde emission systematically differs from that of methanol: while methanol is found towards the inner part of the region, HDCO is found in colder gas that wraps around the methanol e...

Interstellar dark clouds are the sites of star formation. Their main component, dihydrogen exists under two states, ortho and para. H2 is supposed to form in the ortho:para ratio (OPR) of 3:1 and to subsequently decay to almost pure para–H2 (OPR ≤ 0.001). Only if the H2 OPR is low enough, will deuteration enrichment, as observed in the cores of these clouds, be efficient. The second condition f...

We present observations of CO, CO, HCO, HCO, DCO and N2H + line emission towards the Barnard 68 starless core. The line profiles are interpreted using a chemical network coupled with a radiative transfer code in order to reconstruct the radial velocity profile of the core. Our observations and modeling indicate the presence of complex radial motions, with the inward motions in the outer layers ...

We investigate the alignment between outflow axes in nine of the youngest binary/multiple systems in the Perseus Molecular Cloud. These systems have typical member spacing larger than 1000 AU. For outflow identification, we use CO(2-1) and CO(3-2) data from a large survey with the Submillimeter Array: Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES). The distribution o...

We report on the first results of experiments to measure the recombination rate of hydrogen on surfaces of astrophysical interest. Our measurements give lower values for the recombination efficiency (sticking probability S x probability of recombination upon H-H encounter γ) than model-based estimates. We propose that our results can be reconciled with average estimates of the recombination rat...

We present observations of the 22 GHz water vapor megamasers in the Circinus galaxy made with the Tidbinbilla 70 m telescope. These observations confirm the rapid variability seen earlier by Greenhill et al. (1997). We show that this rapid variability can be explained by interstellar scintillation, based on what is now known of the interstellar scintillation seen in a significant number of flat...

Recently, Lattelais et al. (2009) have interpreted aggregated observations of molecular isomers to suggest that there exists a “minimum energy principle”, such that molecular formation will favor more stable molecular isomers for thermodynamic reasons. To test the predictive power of this principle, we have fully characterized the spectra of the three isomers of C3H2O toward the well known mole...