Polarisation of submillimetre lines from interstellar medium

Magnetic fields play important roles in many astrophysical processes. However, there is no universal diagnostic for the magnetic fields in the interstellar medium (ISM) and each magnetic tracer has its limitation. Any new detection method is thus valuable. Theoretical studies have shown that submillimetre fine-structure lines are polarised due to atomic alignment by Ultraviolet (UV) photon-excitation, which opens up a new avenue to probe interstellar magnetic fields. We will, for the first time, perform synthetic observations on the simulated three-dimensional ISM to demonstrate the measurability of the polarisation of submillimetre atomic lines. The maximum polarisation for different absorption and emission lines expected from various sources, including Star-Forming Regions (SFRs) are provided. Our results demonstrate that the polarisation of submillimetre atomic lines is a powerful magnetic tracer and add great value to the observational studies of the submilimetre astronomy.