2025-09-05
Title: Measuring interstellar magnetic fields via spectral-line polarization observations
Speaker: Dr. Tao-Chung Ching (NRAO)
Date: Sep 5 at 14:30
Location: R521, Institute of Astronomy
Abstract:
Spectral-line polarization observations of Zeeman effect and Goldreich-Kylafis effect can probe interstellar magnetic fields with velocity information that is not available for continuum polarization observations such as dust thermal emission or synchrotron emission. Zeeman effect is the most direct method to measure line-of-sight magnetic field strength in interstellar medium, and Goldreich-Kylafis effect reveals the plane-of-sky magnetic field structure. Here I present the multi-beam polarization calibration and HI 21-cm Zeeman observations of the FAST telescope and the ALMA CO (2-1) observations of Goldreich-Kylafis effect. The curl of the plane-of-sky magnetic field strength inferred from CO polarization and the line-of-sight electronic current inferred from CO total emission satisfy the Ampère's law in Maxwell's equations to determine the plane-of-sky magnetic field direction. The combination of spectral-line polarization surveys of Zeeman effect and Goldreich-Kylafis effect thus provides a potential method to map the 3-dimensional magnetic field structure in 3-dimensional interstellar space.