Abstract: It's well proved from measurements that the universe expansion is accelerating although the long-distance gravitational force is attractive. To help understand this late-time cosmic acceleration, the Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a 21cm intensity mapping experiment designed to measure the Baryon Acoustic Oscillations (BAO) scale, therefore the universe expansion history in the redshift range [0.8, 2.5]. CHIME is a transit interferometer consisting of linear antenna arrays at the focal line of each of the four north-south aligned cylindrical reflectors. As the earth rotates, CHIME maps half of the sky every day.
The dual-polarized cloverleaf antenna array has been designed to feed the CHIME cylindrical reflectors. The array matches the next stage LNA so that its effective noise is about 25 Kelvin across both the frequency domain and the scanning angle domain for both polarizations.
To separate the cosmic 21cm signal from the 100,000 times brighter galaxy foreground, the CHIME beam needs to be calibrated to ~ 0.1%. Both measurement programs and simulation techniques are developed for this goal. With limitations found on both, the crosstalk approach to combine measurements and simulations together has been successful to calibrate the CHIME beam's north-south profile to ~ 5%. We are still working on improving this approach for higher accuracy and larger coverage.
As a pathfinder to mapping the whole northern hemisphere for better understanding and removal of the CHIME foreground and for galactic science, the north celestial cap has been mapped across the [400, 800] MHz in the declination range [75, 87.25] degree using the John A. Galt telescope and the CHIME receiver with gated noise source. The intensity map at 408 MHz is found to be consistent with the Haslam map except with fluctuations up to 3 Kelvins. The spectrum of the north celestial cap is measured across the [400, 800] MHz.
Add to Calendar
2020-02-06T10:00:002020-02-06T00:00:00"Antenna Array Design, Beam Calibration of the CHIME to Measure the Late-time Cosmic Acceleration and Mapping of the North Celestial Cap"Event Information:
Departmental Doctoral Oral Examination
Abstract:
It's well proved from measurements that the universe expansion is accelerating although the long-distance gravitational force is attractive. To help understand this late-time cosmic acceleration, the Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a 21cm intensity mapping experiment designed to measure the Baryon Acoustic Oscillations (BAO) scale, therefore the universe expansion history in the redshift range [0.8, 2.5]. CHIME is a transit interferometer consisting of linear antenna arrays at the focal line of each of the four north-south aligned cylindrical reflectors. As the earth rotates, CHIME maps half of the sky every day.
The dual-polarized cloverleaf antenna array has been designed to feed the CHIME cylindrical reflectors. The array matches the next stage LNA so that its effective noise is about 25 Kelvin across both the frequency domain and the scanning angle domain for both polarizations.
To separate the cosmic 21cm signal from the 100,000 times brighter galaxy foreground, the CHIME beam needs to be calibrated to ~ 0.1%. Both measurement programs and simulation techniques are developed for this goal. With limitations found on both, the crosstalk approach to combine measurements and simulations together has been successful to calibrate the CHIME beam's north-south profile to ~ 5%. We are still working on improving this approach for higher accuracy and larger coverage.
As a pathfinder to mapping the whole northern hemisphere for better understanding and removal of the CHIME foreground and for galactic science, the north celestial cap has been mapped across the [400, 800] MHz in the declination range [75, 87.25] degree using the John A. Galt telescope and the CHIME receiver with gated noise source. The intensity map at 408 MHz is found to be consistent with the Haslam map except with fluctuations up to 3 Kelvins. The spectrum of the north celestial cap is measured across the [400, 800] MHz.Event Location:
Room 191, IBLC (Irving K. Barber Learning Center)