PORTAL--three-dimensional polarized (sub)millimeter line radiative transfer

Abstract

Context. Magnetic fields are important to the dynamics of many astrophysical processes and can typically be studied through polarization observations. Polarimetric interferometry capabilities of modern (sub)millimeter telescope facilities have made it possible to obtain detailed velocity resolved maps of molecular line polarization. To properly analyze these for the information they carry regarding the magnetic field, the development of adaptive three-dimensional polarized line radiative transfer models is necessary. Aims. We aim to develop an easy-to-use program to simulate the polarization maps of molecular and atomic (sub)millimeter lines in magnetized astrophysical regions, such as protostellar disks, circumstellar envelopes, or molecular clouds. Methods. By considering the local anisotropy of the radiation field as the only alignment mechanism, we can model the alignment of molecular or atomic species inside a regular line radiative transfer simulation by only making use of the converged output of this simulation. Calculations of the aligned molecular or atomic states can subsequently be used to ray trace the polarized maps of the three-dimensional simulation. Results. We present a three-dimensional radiative transfer code, POlarized Radiative Transfer Adapted to Lines (PORTAL), that can simulate the emergence of polarization in line emission through a magnetic field of arbitrary morphology. Our model can be used in stand-alone mode, assuming LTE excitation, but it is best used when processing the output of regular three-dimensional (nonpolarized) line radiative transfer modeling codes. We present the spectral polarization map of test cases of a collapsing sphere and protoplanetary disk for multiple three-dimensional magnetic field morphologies.

13 pages, 8 figures, Accepted for publication in A&A

References in corpus (9)

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• ALMA Reveals Transition of Polarization Pattern with Wavelength in HL Tau's Disk
• ALMA observations of dust polarization and molecular line emission from the Class 0 protostellar source Serpens SMM1
• Review of Zeeman Effect Observations of Regions of Star Formation
• Stringent limits on the magnetic field strength in the disc of TW Hya: ALMA observations of CN polarisation
• Polarization of absorption lines as a diagnostics of circumstellar, interstellar and intergalactic magnetic fields: Fine structure atoms
• Transport on Adaptive Random Lattices
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Cited by in corpus (13)

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• Low Level Carbon Monoxide Line Polarization in two Protoplanetary Disks: HD 142527 and IM Lup
• Discovery of Molecular Line Polarization in the Disk of TW Hya
• Collisional polarization of molecular ions: a signpost of ambipolar diffusion
• Three-dimensional magnetic field imaging of protoplanetary disks using Zeeman broadening and linear polarization observations
• Mapping circumstellar magnetic fields of late-type evolved stars with the Goldreich-Kylafis effect: CARMA observations at $\lambda 1.3$ mm of R Crt and R Leo
• Tracing the large-scale magnetic field morphology in protoplanetary disks using molecular line polarization
• Polarisation of molecular lines in the circumstellar envelope of the post-Asymptotic Giant Branch star OH 17.7-2.0
• Polarization properties of methanol masers
• The magnetic fields of the dusty nuclei and molecular outflows of Arp 220
• Molecular line polarisation from the circumstellar envelopes of Asymptotic Giant Branch stars
• History of the Solar Nebula from Meteorite Paleomagnetism