Molecular Line Profiles from Contracting Dense Cores

Abstract

We recently proposed that molecular cloud dense cores undergo a prolonged period of quasi-static contraction prior to true collapse. This theory could explain the observation that many starless cores exhibit, through their spectral line profiles, signs of inward motion. We now use our model, together with a publicly available radiative transfer code, to determine the emission from three commonly used species - N2H+, CS, and HCN. A representative dense core of 3 Msun that has been contracting for 1 Myr has line profiles that qualitatively match the observed ones. In particular, optically thick lines have about the right degree of blue-red asymmetry, the empirical hallmark of contraction. The J=2-1 rotational transition of CS only attains the correct type of profile if the species is centrally depleted, as has been suggested by previous studies. These results support the idea that a slow, but accelerating, contraction leads to protostellar collapse. In the future, the kind of analysis presented here can be used to assign ages to individual starless cores.

accepted by MNRAS

References in corpus (12)

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Cited by in corpus (13)

• Line Profiles of Cores within Clusters: I. The Anatomy of a Filament
• Observation of HCN hyperfine line anomalies towards low- and high-mass star-forming cores
• Internal Motions in Starless Dense Cores
• The dynamical state of the First Hydrostatic Core Candidate Cha-MMS1
• Assessing molecular line diagnostics of triggered star formation using synthetic observations
• Starless Cloud Core L1517B in Envelope Expansion with Core Collapse
• Externally Fed Star Formation: A Numerical Study
• Massive star formation around I05345+3157 -- I. The dense gas
• Sulphur-Bearing and Complex Organic Molecules in an Infrared Cold Core
• Studying Infall in Infrared Dark Clouds with Multiple HCO+ Transitions
• Externally Fed Accretion onto Protostars
• Planck Galactic Cold Clumps in Two Regions: the First Quadrant and the Anti-Center Direction Region
• Kinematic study of the molecular gas associated with two cometary globules in Sh2-236