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

Author(s)

E. D. Aguti, C. J. Lada, E. A. Bergin, J. F. Alves, M. Birkinshaw

Abstract

High-resolution molecular line observations of CS (J=2-->1),

HCO⁺ (J=1-->0), C¹⁸O (J=1-->0),

C¹⁸O (J=2-->1), and N₂H⁺

(J=1-->0) were obtained toward the starless globule FeSt 1-457 in

order to investigate its kinematics and chemistry. The HCO⁺

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 C¹⁸O and

N₂H⁺ (J=1-->0) 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 l=2

mode with a period of ~3×10⁵ yr. Deformation of the

globule due to the large amplitude l=2 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

C¹⁸O and perhaps HCO⁺, while

N₂H⁺ (J=1-->0) may be undepleted to a cloud

depth of ~40 mag of visual extinction.

Organisation(s)

Department of Astrophysics

External organisation(s)

Harvard-Smithsonian Center for Astrophysics, University of Bristol, University of Michigan

Journal

The Astrophysical Journal: an international review of astronomy and astronomical physics

Volume

665

Pages

457-465

ISSN

0004-637X

DOI

https://doi.org/10.1086/519272

Publication date

08-2007

Peer reviewed

Yes

Austrian Fields of Science 2012

103004 Astrophysics

Keywords

Portal url

https://ucrisportal.univie.ac.at/en/publications/0812d482-a99a-4ca0-bd26-d357049ea3eb

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