The Dynamical State of the Starless Dense Core FeSt 1-457: A Pulsating Globule?

High-resolution molecular line observations of CS (), HCO super(+) (), C super(18)O (), C super(18)O (), and N sub(2)H super(+) () were obtained toward the starless globule FeSt 1-457 in order to Investigate its kinematics and chemistry. The HCO super(+) and CS spectra show clear self-reversed and a...

Full description

Saved in:
Bibliographic Details
Published in:The Astrophysical journal 2007-08, Vol.665 (1), p.457-465
Main Authors: Aguti, E. D, Lada, C. J, Bergin, E. A, Alves, J. F, Birkinshaw, M
Format: Article
Language:English
Subjects:
Astronomy
Earth, ocean, space
Exact sciences and technology
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:High-resolution molecular line observations of CS (), HCO super(+) (), C super(18)O (), C super(18)O (), and N sub(2)H super(+) () were obtained toward the starless globule FeSt 1-457 in order to Investigate its kinematics and chemistry. The HCO super(+) and CS spectra show clear self-reversed and asymmetric profiles across the face of the globule. The sense of the observed asymmetry is indicative of the global presence of expansion motions in the outer layers of the globule. These motions appear to be subsonic and significantly below the escape velocity of the globule. Comparison of our observations with near-infrared extinction data indicate that the globule is gravitationally bound. Taken together, these considerations lead us to suggest that the observed expansion has its origin in an oscillatory motion of the outer layers of the globule, which itself is likely in a quasi-stable state near hydrostatic equilibrium. Analysis of the observed line widths of C super(18)O and N sub(2)H super(+) confirm that thermal pressure is the dominant component of the cloud's internal support. A simple calculation suggests that the dominant mode of pulsation would be an mode with a period of similar to yr. Deformation of the globule due to the large amplitude oscillation may be responsible for the double-peaked structure of the core detected in high-resolution extinction maps. Detailed comparison of the molecular-line observations and extinction data provides evidence for significant depletion of C super(18)O and perhaps HCO super(+), while N sub(2)H super(+) () may be undepleted to a cloud depth of similar to 40 mag of visual extinction.
ISSN:0004-637X
1538-4357
DOI:10.1086/519272