The magnetic field of IRAS 16293-2422 as traced by shock-induced H2O masers

Abstract

Shock-induced H2O masers are important magnetic field tracers at very high density gas. Water masers are found in both high- and low-mass star-forming regions, acting as a powerful tool to compare magnetic field morphologies in both mass regimes. In this paper, we show one of the first magnetic field determinations in the low-mass protostellar core IRAS 16293-2422 at volume densities as high as 10^(8-10) cm^-3. Our goal is to discern if the collapsing regime of this source is controlled by magnetic fields or other factors like turbulence. We used the Very Large Array (VLA) to carry out spectro-polarimetric observations in the 22 GHz Zeeman emission of H2O masers. From the Stokes V line profile, we can estimate the magnetic field strength in the dense regions around the protostar. A blend of at least three maser features can be inferred from our relatively high spatial resolution data set (~ 0.1"), which is reproduced in a clear non-Gaussian line profile. The emission is very stable in polarization fraction and position angle across the channels. The maser spots are aligned with some components of the complex outflow configuration of IRAS 16293-2422, and they are excited in zones of compressed gas produced by shocks. The post-shock particle density is in the range of 1-3 x 10^9 cm^-3, consistent with typical water masers pumping densities. Zeeman emission is produced by a very strong line-of-sight magnetic field (B ~ 113 mG). The magnetic field pressure derived from our data is comparable to the ram pressure of the outflow dynamics. This indicates that the magnetic field is energetically important in the dynamical evolution of IRAS 16293-2422.

7 pages, 6 figures, accepted for publication in A&A

References in corpus (7)

• An interferometric study of the low-mass protostar IRAS 16293-2422: small scale organic chemistry
• Arcsecond resolution images of the chemical structure of the low-mass protostar IRAS 16293-2422
• A new probe of magnetic fields during high-mass star formation: Zeeman splitting of 6.7 GHz methanol masers
• The structure of the magnetic field in the massive star-forming region W75N
• The CO Molecular Outflows of IRAS 16293-2422 Probed by the Submillimeter Array
• The properties and polarization of the H2O and CH3OH maser environment of NGC7538-IRS1
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