Maser polarization with ALMA

Abstract

Abstract. Once ALMA full polarization capabilities are offered, (sub-)mm polarization studies will enter a new era. It will become possible to perform detailed studies of polarized maser emission towards for example massive star forming regions and late-type stars such as (post-) Asymptotic Giant Branch stars and young Planetary Nebulae. In these environments, SiO, H 2 O and HCN are molecules that can naturally generate polarized maser emission observable by ALMA. The maser polarization can then be used to derive the strength and morphology of the magnetic field in the masing regions. However, in order to derive, in particular, the magnetic field orientation from maser linear polarization, a number of conditions involving the rate of stimulated emission, molecular state decay and Zeeman splitting need to be satisfied. In this work, we discuss these conditions for the maser transitions in the ALMA frequency range and highlight the optimum transitions to further our understanding of star formation and evolved star magnetic fields.

The ALMA Phasing System: A Beamforming Capability for Ultra-high-resolution Science at (Sub)Millimeter Wavelengths

“…Targets for maser observations include evolved stars, young stellar objects, and the circumnuclear disks of galaxies, where maser studies with the highest achievable spatial resolution provide unique information on physical conditions, kinematics, and magnetic fields (e.g., Pérez-Sánchez & Vlemmings 2012;Richards 2012;Humphreys et al 2016). Meanwhile, observations of absorption lines of HCN, HCO + , and other molecules with phased ALMA will be possible against background quasars in active galaxies, providing spatial information on the distribution of molecular gas (e.g., Carilli et al 2000;Muller & Guélin 2008), enabling detailed studies of molecular and isotopic abundance ratios as a function of redshift (e.g., Muller et al 2011), and providing constraints on possible variations of fundamental constants over cosmological times (e.g., Uzan 2011).…”