A Pre-Protostellar Core in L1551. II. State of Dynamical and Chemical Evolution

Abstract

Both analytic and numerical radiative transfer models applied to high spectral resolution CS and N2H+ data give insight into the evolutionary state of L1551 MC. This recently discovered pre-protostellar core in L1551 appears to be in the early stages of dynamical evolution. Line-of-sight infall velocities of >0.1km/s are needed in the outer regions of L1551 MC to adequately fit the data. This translates to an accretion rate of ~ 1e-6 Msun/yr, uncertain to within a factor of 5 owing to unknown geometry. The observed dynamics are not due to spherically symmetric gravitational collapse and are not consistent with the standard model of low-mass star formation. The widespread, fairly uniform CS line asymmetries are more consistent with planar infall. There is modest evidence for chemical depletion in the radial profiles of CS and C18O suggesting that L1551 MC is also chemically young. The models are not very sensitive to chemical evolution. L1551 MC lies within a quiescent region of L1551 and is evidence for continued star formation in this evolved cloud.

27 pages, 7 figures, ApJ accepted

References in corpus (7)

• Molecular Evolution in Collapsing Prestellar Cores III: Contraction of A Bonnor-Ebert Sphere
• Evolution of Chemistry and Molecular Line Profile during Protostellar Collapse
• Molecular Line Profile Fitting with Analytic Radiative Transfer Models
• Generalized Collapse Solutions with Nonzero Initial Velocities for Star Formation in Molecular Cloud Cores
• Centrally Condensed Collapse of Starless Cores
• A Pre-Protostellar Core in L1551
• W49A North - Global or Local or No Collapse?

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• A Case Study of Low-Mass Star Formation
• Molecular line profiles as diagnostics of protostellar collapse: modelling the `blue asymmetry' in inside-out infall
• Dense gas and the nature of the outflows
• The intrinsic abundance ratio and X-factor of CO isotopologues in L1551 shielded from FUV photodissociation
• Velocity distribution of collapsing starless cores, L694-2 and L1197
• A 2MASS Analysis of the Stability of Southern Bok Globules
• The molecular emission of the irradiated star forming core ahead of HH 80N