Title: Hydrogen chloride in diffuse interstellar clouds along the line of sight to W31C (G10.6-0.4) Authors: R. R. Monje, D. C. Lis, E. Roueff, M. Gerin, M. De Luca, D. A. Neufeld, B. Godard, T. G. Phillips
We report the detection of hydrogen chloride, HCl, in diffuse molecular clouds on the line of sight towards the star-forming region W31C (G10.6-0.4). The J = 1-0 lines of the two stable HCl isotopologues, H35Cl and H37Cl, are observed using the 1b receiver of the Heterodyne Instrument for the Far-Infrared (HIFI) aboard the Herschel Space Observatory. The HCl line is detected in absorption, over a wide range of velocities associated with diffuse clouds along the line of sight to W31C. The analysis of the absorption strength yields a total HCl column density of few 10^13 cm^-2, implying that HCl accounts for ~0.6 % of the total gasphase chlorine, which exceeds by a factor of ~6 the theoretical model predictions. This result is comparable to those obtained from the chemically-related species H2Cl+ and HCl+, for which large column densities have also been reported on the same line of sight. The source of discrepancy between models and observations is still unknown; however, the detection of these Cl-bearing molecules, provides key constraints for the chlorine chemistry in the diffuse gas.
Title: Competitive accretion in the protocluster G10.6-0.4? Authors: Tie Liu, Yuefang Wu, Jingwen Wu, Sheng-Li Qin, Huawei Zhang
We present the results of high spatial resolution observations at 1.1 mm waveband, with the Submillimeter Array (SMA), towards the protocluster G10.6-0.4. The 1.1 mm continuum emission reveals seven dense cores, in which infall motions are all detected with the red-shifted absorption dips in HCN (3--2) line. This is the first time that infall is seen towards multiple sources in a protocluster. The dense core located in the center has the largest mass and mass infall rate and dominates the gas accretion of the protocluster, while the off-center cores have much smaller masses and mass infall rates, which favours the "competitive accretion" model. We also identified four infrared point sources in this region, which are most likely Class 0/I protostars. Two jet-like structures are also identified from Spitzer/IRAC image.