Speaker
Description
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a cylinder radio telescope that is designed to map the redshifted 21 cm neutral hydrogen signal to constrain the expansion history of the Universe. The measurement is challenging due to bright astrophysical foregrounds, radio frequency interference (RFI) and a complex instrument response function. In this presentation, we focus on analysing subtle instrumental effects of focal-line expansion in CHIME.
CHIME consists of four large cylindrical reflectors. Each reflector collects radio waves and focuses them onto antennas along the steel focal line. The instrument temperature varies by up to 20 degrees daily and 60 degrees seasonally. As a result, the distances between antennas vary slightly with the time-dependent ambient temperature. This slight displacement subtly affects the phase of a source at a given sky position as a function of time (i.e., hour angle), which, in principle, can be observed in high-resolution sky images. Assuming that the focal-line expansion is small compared to other effects (e.g. astrophysical foregrounds or crosstalk), we use a 96-day visibility stack as a regression template to estimate the daily effect of focal line expansion. We present our first results on estimating the focal-line expansion in visibility and image domains. We aim to understand the properties of focal-line expansion, model it and eventually mitigate it.
| What is your career stage? | Non-tenured scientist (post PhD) |
|---|---|
| Which telescopes do you use / are you affiliated with? | LOFAR, CHIME |
