Magnetic field structure in the diffuse neutral ISM: a joint analysis of Zeeman splitting and filamentary HI emission

Marta Nowotka (Stanford)

The 21 cm line of neutral hydrogen offers two complementary probes of interstellar magnetic fields: Zeeman splitting, which measures the line-of-sight magnetic field strength, and the morphology of HI emission filaments, which traces the magnetic field orientation on the sky. I present a study combining these two tracers to investigate the three-dimensional structure of the magnetic field in the diffuse neutral interstellar medium. I also share new Zeeman measurements in HI absorption from FAST and discuss future opportunities to expand the Zeeman sample.

State of Cosmological Measurements from CHIME

Tristan Pinsonneault-Marotte (Stanford)

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has been observing the entire northern sky from the DRAO every day, for over 6 years. Designed to measure the redshifted 21 cm line of neutral Hydrogen and map the large-scale structure between 0.8 < z < 2.5, CHIME  uses interferometry and a large field-of-view over a broad, finely-sampled band to achieve a very rapid mapping speed. These unique characteristics also make it well-suited to other science cases such as pulsar monitoring, transient searches, and galactic science — areas where it has had a significant impact. In this talk I will focus on cosmological measurements from CHIME, which finds itself at the cutting edge of 21 cm cosmology. The main challenge facing the field is the difficulty of separating the faint signal from overwhelmingly bright radio foregrounds — a task complicated by the presence of RFI and instrumental calibration. Despite these issues, the CHIME team has already published detections of 21 cm emission in cross-correlation with galaxy redshfit surveys and the Lyman-alpha forest, the first of their kind. Analysis effort is now focused on producing a detection of the power spectrum on small scales from CHIME data alone. In parallel, a search for high-redshift neutral Hydrogen absorber systems is ongoing using an enhanced frequency resolution stream of the data. Finally, future avenues for cross-correlation are also under study, in particular with lensing of the CMB.

What has CHIME Accomplished?

Mark Halpern (UBC)

We could not have built CHIME without the help we received from people at the DRAO. I would like to share with you a description of what you have helped to create, a unique instrument exploring several quite different astronomical puzzles. I will try to explain to a non-specialist CHIME’s progress in mapping neutral hydrogen to track the expansion history of the Universe, finding and studying Fast Radio Bursts across cosmic distances, and measuring signals from all of the Galactic Pulsars visible from Canada at daily or weekly cadence. For each topic I will describe the puzzle we are trying to solve, explain how the properties of this very strange telescope we have built make it be so well suited to that particular puzzle, share some of what we have learned so far and describe what the future holds.