Letter to the Editor
Modeling the magnetic field in the protostellar source NGC 1333 IRAS 4A
Centro de Astronomia e Astrofísica da Universidade de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal e-mail: firstname.lastname@example.org
2 INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy e-mail: email@example.com
3 Institut de Ciències de l'Espai (CSIC–IEEC), Campus UAB–Facultat de Ciències, Torre C5–Parell 2, 08193 Bellaterra, Catalunya, Spain e-mail: firstname.lastname@example.org
Accepted: 25 September 2008
Context. Magnetic fields are believed to play a crucial role in the process of star formation.
Aims. We compare high-angular resolution observations of the submillimeter polarized emission of NGC 1333 IRAS 4A, tracing the magnetic field around a low-mass protostar, with models of the collapse of magnetized molecular cloud cores.
Methods. Assuming a uniform dust alignment efficiency, we computed the Stokes parameters and synthetic polarization maps from the model density and magnetic field distribution by integrations along the line-of-sight and convolution with the interferometric response.
Results. The synthetic maps are in good agreement with the data. The best-fitting models were obtained for a protostellar mass of 0.8 , of age 9 104 yr, formed in a cloud with an initial mass-to-flux ratio ~2 times the critical value.
Conclusions. The magnetic field morphology in NGC 1333 IRAS 4A is consistent with the standard theoretical scenario for the formation of solar-type stars, where well-ordered, large-scale, rather than turbulent, magnetic fields control the evolution and collapse of the molecular cloud cores from which stars form.
Key words: ISM: magnetic fields / stars: formation / magnetohydrodynamics (MHD) / polarization
© ESO, 2008