A correlation between chemistry, polarization and dust properties in the Pipe Nebula starless core FeSt 1-457

Abstract

Pre-stellar cores within molecular clouds provide the very initial conditions in which stars are formed. We use the IRAM 30m telescope and the PdBI to study the chemical and physical properties of the starless core FeSt 1-457 (Core 109), in the Pipe nebula. We fit the hyperfine structure of the N2H+(1-0) IRAM 30m data. This allow us to measure with high precision the velocity field, line widths and opacity and derive the excitation temperature and column density in the core. We use a modified Bonnor-Ebert sphere model adding a temperature gradient towards the center to fit the 1.2 mm continuum emission and visual extinction maps. Using this model, we estimate the abundances of the N2H+ and the rest of molecular lines detected in the 30 GHz wide line survey performed at 3 mm with IRAM 30m using ARTIST software. The core presents a rich chemistry with emission from early (C3H2, HCN, CS) and late-time molecules (e.g., N2H+), with a clear chemical spatial differentiation for nitrogen, oxygen and sulphurated molecules. For most of the molecules detected (HCN, HCO+, CH3OH, CS, SO, 13CO and C18O), abundances are best fitted with three values, presenting a clear decrease of abundance of at least 1 or 2 orders of magnitude towards the center of the core. The Bonnor-Ebert analysis indicates the core is gravitationally unstable and the magnetic field is not strong enough to avoid the collapse. Depletion of molecules onto the dust grains occurs at the interior of the core, where dust grain growth and dust depolarization also occurs. This suggests that these properties may be related. On the other hand, some molecules exhibit asymmetries in their integrated emission maps, which appear to be correlated with a previously reported submillimetre polarization asymmetry. These asymmetries could be due to a stronger interstellar radiation field in the western side of the core.

16 pages, 11 figures, accepted for publication in A&A

References in corpus (23)

• Cold Dark Clouds: The Initial Conditions for Star Formation
• Radiative torques: Analytical Model and Basic Properties
• Magnetic Fields in the Formation of Sun-Like Stars
• The stickiness of micrometer-sized water-ice particles
• Observing the gas temperature drop in the high-density nucleus of L 1544
• Identifying the Low Luminosity Population of Embedded Protostars in the c2d Observations of Clouds and Cores
• 2MASS wide field extinction maps - I. The Pipe nebula
• Magnetic Fields in High-Mass Infrared Dark Clouds
• On the internal structure of starless cores. II. A molecular survey of L1498 and L1517B
• Depletion and low gas temperature in the L183 prestellar core : the N2H+ - N2D+ tool
• The interstellar gas-phase chemistry of HCN and HNC
• Optical polarimetry toward the Pipe nebula: Revealing the importance of the magnetic field
• On the radiation driven alignment of dust grains: Detection of the polarization hole in a starless core
• Investigating grain growth in disks around southern T Tauri stars at millimetre wavelengths
• The Excitation of N${}_2$H${}^{+}$ in Interstellar Molecular Clouds. I - Models
• Deuteration and evolution in the massive star formation process: the role of surface chemistry
• The nature of the dense core population in the Pipe Nebula: A survey of NH3, CCS, and HC5N molecular line emission
• Deep Near-Infrared Survey of the Pipe Nebula II: Data, Methods, and Dust Extinction Maps
• The Dynamical State of the Starless Dense Core FeSt 1-457: A Pulsating Globule?
• The Dynamical State fo the Starless Dense Core FeSt 1-457: A Pulsating Globule?
• Deuterium enrichment of ammonia produced by surface N+H/D addition reactions at low temperature
• Formation of dense structures induced by filament collisions. Correlation of density, kinematics and magnetic field in the Pipe nebula
• Chemical and Physical Conditions in Molecular Cloud Core DC 000.4-19.5 (SL42) in Corona Australis

Cited by in corpus (3)

• The Central 1000 au of a Pre-stellar Core Revealed with ALMA. II. Almost Complete Freeze-out
• Distortion of Magnetic Fields in a Starless Core: Near-Infrared Polarimetry of FeSt 1-457
• Distortion of Magnetic Fields in a Starless Core VI: Application of Flux Freezing Model and Core Formation of FeSt 1-457