The Physics and Chemistry of Small Translucent Molecular Clouds. VI. Organo-Sulfur Species

Abstract

view Abstract Citations (29) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Physics and Chemistry of Small Translucent Molecular Clouds. VI. Organo-Sulfur Species Turner, B. E. Abstract A survey of HCS+ and CS has been conducted in most of our standard samples of 11 cirrus cores and 27 Clemens-Barvainis translucent objects whose structures and chemistry have been studied earlier in this series. CS (J = 2-1) is seen quite strongly in all cirrus cores and CB objects, and CS (J = 3-2) in seven cirrus clouds and 25 CB objects. HCS+ (J = 2-1) is detected in four of seven cirrus cores searched, and 15 of 20 CB objects. These observations are modeled in terms of our previous hydrostatic equilibrium and n ∼ r-α structures together with other chemical and physical properties derived earlier. We find high CS abundances, over the wide range 10-9 to 10-7.2, increasing monotonically with increasing extinction in the 1.2-2.6 mag range. The HCS+ abundances are much lower, in the range 10-10 to 10-9.3, again increasing monotonically with increasing extinction. Thus these species display the same characteristic transition between diffuse and dense cloud chemistry as do SO, SO2, HCO+, and other species studied in this series. The same simple ion-molecule network as used by Turner (1995b; Paper V) is extended to include the organo-sulfur species, and when solved analytically, predicts the observed parameters of SO, SO2, and HCS+ successfully. The median abundance of CS is also predicted but the slope with respect to extinction is flatter than observed. The overall success of the model strongly endorses ion-molecule chemistry for all sulfur species so far studied. Other sulfur chemistries (grain catalysis, shock processes) are entirely inconsistent with the observed abundances of any of the four sulfur species studied to date in these translucent objects. Publication: The Astrophysical Journal Pub Date: April 1996 DOI: 10.1086/177052 Bibcode: 1996ApJ...461..246T Keywords: ISM: ABUNDANCES; ISM: CLOUDS; ISM: MOLECULES full text sources ADS | data products SIMBAD (41) Related Materials (12) Part 1: 1994ApJ...420..661T Part 2: 1994ApJ...437..658T Part 3: 1995ApJ...444..708T Part 4: 1995ApJ...449..635T Part 5: 1995ApJ...455..556T Part 7: 1996ApJ...468..694T Part 8: 1997ApJ...483..235T Part 9: 1998ApJS..115...91T Part 10: 1998ApJ...495..804T Part 11: 1998ApJ...501..731T Part 12: 1999ApJ...518..699T Part 13: 2000ApJS..126..427T