Characterizing maser polarization: effects of saturation, anisotropic pumping and hyperfine structure
In one sentence
I introduce CHAMP, the first code that solves polarized maser radiative transfer with arbitrary saturation, full hyperfine structure of the maser transition, and non-Zeeman polarization mechanisms — answering long-standing questions about how much of an observed maser polarization signal really comes from the magnetic field.
What’s the question?
Cosmic masers — natural radio amplifiers in molecules like SiO, H₂O, and methanol — are often strongly polarized. The polarization is nominally a probe of the magnetic field via the Zeeman effect, but the actual signal that reaches a telescope is shaped by an entanglement of effects: how saturated the maser is, the hyperfine structure of the transition, and various non-Zeeman polarization mechanisms (anisotropic pumping, polarized seed radiation). Earlier maser-polarization codes handled some of these but not all, and certainly not all together.
What did we do?
I built CHAMP — CHAracterizing Maser Polarization — a 1-D radiative-transfer solver that handles all of the above in one self-consistent calculation. Applied to SiO and water masers, it reveals which features of an observed polarization spectrum are diagnostic of the magnetic field and which are diagnostic of pumping geometry, transition saturation, or hyperfine structure.
Why does it matter?
CHAMP is the working tool with which my later maser papers actually do their physics, and it is open-source so that other groups can use it on their own data. It also clarifies, paper-by-paper, how cleanly a given maser observation can be turned into a magnetic-field measurement.
My role
First author. Designed the algorithm, wrote the code, ran the simulations, and wrote the paper. CHAMP is open-source — see Code.