Starless Cloud Core L1517B in Envelope Expansion with Core Collapse

Abstract

Various spectral emission lines from star-forming molecular cloud core L1517B manifest red asymmetric double-peaked profiles with stronger red peaks and weaker blue peaks, in contrast to the oft-observed blue-skewed molecular spectral line profiles with blue peaks stronger than red peaks. Invoking a spherically symmetric general polytropic hydrodynamic shock model for the envelope expansion with core collapse (EECC) phase, we show the radial flow velocity, mass density and temperature structures of self-similar evolution for L1517B in a dynamically consistent manner. By prescribing simple radial profiles of abundance distribution for pertinent molecules, we perform molecular excitation and radiative transfer calculations using the publicly available RATRAN code set for the spherically symmetric case. Our computational results show that the EECC model reproduces molecular spectral line profiles in sensible agreement with observational data of IRAM, FCRAO and Effelsberg 100 m telescopes for L1517B. We also report spatially resolved observations of optically thick line HCO+(1-0) using the Purple Mountain Observatory (PMO) 13.7 m telescope at Delingha in China and the relevant fitting results. Hyperfine line structures of NH3 and N2H+ transitions are also fitted to consistently reveal the dynamics of central core collapse. As a consistent model check, radial profiles of 1.2 mm and 0.85 mm dust continua observed by IRAM 30 m telescope and SCUBA, respectively, are also fitted numerically using the same EECC model that produces the molecular line profiles. L1517B is likely undergoing an EECC shock phase. For future observational tests, we also predict several molecular line profiles with spatial distributions, radial profile of sub-millimeter continuum at wavelength 0.45mm, as well as the radial profiles of the column density and visual extinction for L1517B.

18 pages, 11 figures, accepted for publication in ApJ

References in corpus (16)

• Theory of Star Formation
• A SCUBA survey of Orion, the low-mass end of the core mass function
• On the internal structure of starless cores. II. A molecular survey of L1498 and L1517B
• The SCUBA HAlf Degree Extragalactic Survey (SHADES) - VII. Optical/IR photometry and stellar masses of sub-millimeter galaxies
• SCUBA polarisation observations of the magnetic fields in the prestellar cores L1498 and L1517B
• Oscillations of starless cores
• The Dynamical State fo the Starless Dense Core FeSt 1-457: A Pulsating Globule?
• The Dynamical State of the Starless Dense Core FeSt 1-457: A Pulsating Globule?
• Internal Motions in Starless Dense Cores
• Molecular Emission Line Formation in Prestellar Cores
• Molecular line profiles as diagnostics of protostellar collapse: modelling the `blue asymmetry' in inside-out infall
• Self-Similar Dynamics of a Magnetized Polytropic Gas
• Dynamic Evolution of a Quasi-Spherical General Polytropic Magnetofluid with Self-Gravity
• Dichotomy in the Dynamical Status of Massive Cores in Orion
• Oscillating Starless Cores: The Nonlinear Regime
• The Approach to Collapse of Molecular Clouds

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• Collapsing Index: A New Method to Identify Star-forming Cores Based on ALMA Images