L1506: a prestellar core in the making

Abstract

Exploring the structure and dynamics of cold starless clouds is necessary to understand the different steps leading to the formation of protostars. Because clouds evolve slowly, many of them must be studied in detail to pick up different moments of a cloud's lifetime. We study here L1506C in the Taurus region, a core with interesting dust properties which have been evidenced with the PRONAOS balloon-borne telescope. To trace the mass content of L1506C and its kinematics, we mapped the dust emission, and the line emission of two key species, C18O and N2H+ (plus 13CO and C17O). This cloud shows peculiar features: i) a large envelope traced solely by 13CO holding a much smaller core with a strong C18O depletion in its center despite a low maximum opacity (Av~20 mag), ii) extremely narrow C18O lines indicating a low, non-measurable turbulence, iii) contraction traced by C18O itself (plus rotation), iv) unexpectedly, the kinematical signature from the external envelope is opposite to the core one: the 13CO and C18O velocity gradients have opposite directions and opposite profiles (C18O blue peaked, 13CO red peaked). The core is large (r = 3E4 AU) and not very dense (n(H2) ? 5E4 cm-3 or less). This core is therefore not prestellar yet. All these facts suggest that the core is kinematically detached from its envelope and in the process of forming a prestellar core. This is the first time that the dynamical formation of a prestellar core is witnessed. The extremely low turbulence could be the reason for the strong depletion of this core despite its relatively low density and opacity in contrast with undepleted cores such as L1521E which shows a turbulence at least 4 times as high.

References in corpus (7)

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Cited by in corpus (14)

• Planck intermediate results. XXXIII. Signature of the magnetic field geometry of interstellar filaments in dust polarization maps
• Variation in dust properties in a dense filament of the Taurus molecular complex (L1506)
• ${}^{13}\mathrm{CO}$ Filaments in the Taurus Molecular Cloud
• Observation of rotation in star forming regions: clouds, cores, disks, and jets
• Grain size limits derived from 3.6 μm and 4.5 μm coreshine
• Abundance of HCN and its C and N isotopologues in L1498
• Coreshine in L1506C - Evidence for a primitive big-grain component or indication for a turbulent core history?
• Physical and chemical modeling of the starless core L1512
• Statistical study of dust properties in LMC molecular clouds
• Principal component analysis for estimating parameters of the L1287 dense core by fitting model spectral maps into observed ones
• First map of D${}_2$H${}^{+}$ emission revealing the true centre of a prestellar core: further insights into deuterium chemistry
• Very Large Array Ammonia Observations of the HH 111/HH 121 Protostellar System: a Detection of a New Source With a Peculiar Chemistry
• Modelling of dust emission of a filament in the Taurus molecular cloud
• Deuterium fractionation of the starless core L 1498