Radio recombination lines (RRL) are produced when atoms cascade into a series of successively lower ionisation states. In particular, the RRLs found at low frequencies are highly sensitive probes of the environment where the atoms are found, making them useful diagnostics of temperature, density and pressure.
RRLs at low frequencies were first discovered in 1980 and have since been discovered at frequencies from 14 to 1420MHz. However, the region between 100 — 200MHz is not well studied. Early studies suggest that somewhere between 100 and 200MHz the RRLs transition from emission lines to absorption lines. Recent constraints from studies by LOFAR have suggested that this transition may be around 130MHz.
This project will utilize data cubes generated and published by Tremblay et al (MNRAS submitted) as part of a spectral line survey with the Murchison Widefield Array (MWA) to search for RRLs, with a particular focus on carbon recombination lines from 103 to 133MHz.
In 2017 the MWA received upgrades to increase its resolution, so new data taken in this mode may also be used to search for lines, adopting existing spectral line pipelines. This project is suited to a student with a strong grounding in astrophysics and a good understanding or willingness to learn statistics so that these sensitive measurements may be made in a robust and quantitative way.
Dr. Chenoa Tremblay
PostDoctoral ResearcherRead More