High-density gas in the core of the Sagittarius B2 molecular cloud

Abstract

view Abstract Citations (70) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS High-Density Gas in the Core of the Sagittarius B2 Molecular Cloud Lis, Dariusz C. ; Goldsmith, Paul F. Abstract We have observed several transitions of HC3N in the ground and vibrationally excited states in order to determine the density and kinetic temperature in the core of the Sagittarius B2 molecular cloud. Statistical equilibrium analysis of the J = 12 → 11 and 4 → 3 data suggests that warm and dense gas with a kinetic temperature of ∼20-40 K and a mean H2 density of ∼105 cm-3 present in the inner region of the cloud ∼10 pc in size. The HC3N column density does not correlate well with the C18O column density, suggesting strong variations of the HC3N fractional abundance in the region by a factor of ∼3 on a 1' scale. The HC3N fractional abundance derived at the center of the cloud is ∼3 × 10-10, comparable to that derived for the ridge component of the Orion KL nebula. Detection of the J = 39 → 38 transition of HC3N suggests H2 densities greater than ∼107 cm-3 and mean kinetic temperatures greater than ∼60 K and 80 K in 21" FWHM beams centered at the positions of the Sgr B2(M) and (N) sources. Because this transition is most likely collisionally excited, the higher intensity and excitation temperature derived at the position of the Sgr B2(N) continuum source indicate higher density in the northern core compared to the middle core. Vibrationally excited HC3N gives a ∼260 K estimate for the mean radiation field temperature for both cores in a 45" FWHM beam. Publication: The Astrophysical Journal Pub Date: March 1991 DOI: 10.1086/169746 Bibcode: 1991ApJ...369..157L Keywords: Gas Density; Interstellar Gas; Molecular Clouds; Orion Nebula; Sagittarius Constellation; Carbon Monoxide; Radiation Distribution; Statistical Analysis; interstellar: abundances interstellar: molecules nebulae: individual (Sagittarius B2); Astrophysics; INTERSTELLAR: ABUNDANCES; INTERSTELLAR: MOLECULES; NEBULAE: INDIVIDUAL NAME: SAGITTARIUS B2 full text sources ADS | data products SIMBAD (2)