2004/07/20 by Eric Keto, George B. Rybicki, Edwin A. Bergin +1 · 4 citations
Physics and Astronomy · #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Scientific Research and Discoveries #astro-ph
paper · pdf · doi:10.1086/422987
published as Astrophys.J. 613 (2004) 355-373 · 42 pages, 17 figures, to appear in ApJ
arxiv created 2004/07/20 · openalex publication_date 2004/09/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/04
We develop a method of analyzing radio-frequency spectral line observations to derive data on the temperature, density, velocity, and molecular abundance of the emitting gas. The method incorporates a radiative transfer code with a new technique for handling overlapping hyperfine emission lines within the accelerated Λ-iteration algorithm and a heuristic search algorithm based on simulated annealing. We apply this method to new observations of N 2 H + in three Lynds clouds thought to be starless cores in the first stages of star formation and determine their density structure. A comparison of the gas densities derived from the molecular line emission and the millimeter dust emission suggests that the required dust mass opacity is about κ 1.3 mm = 0.04 cm 2 g -1 , consistent with models of dust grains that have opacities enhanced by ice mantles and fluffy aggregrates.