Lyman Alpha Intensity Mapping via Grism Spectrotomography
thesis
posted on 2019-11-13, 19:35 authored by Zhonghao LuoThe discovery of cosmic acceleration implies that universe is dominated by some form of \dark energy" that causes repulsive gravity. This accelerated expansion of the universe can be probed by Baryon Acoustic Oscillations (BAO). BAO is a well developed method to measure the expansion history and the structure growth of the universe. Intensity mapping is a new observation technique that can probe BAO
and large scale structures. A new type of telescope, the Grism Spectrotomographic Imager (GSTI), is described in the thesis. The GSTI is designed for Lyman Alpha
(Ly ) intensity mapping. A grism, the combination of grating and prism, is placed in front of a camera to disperse the light of each point on the sky into a spectrum and
shift the spectrum back closer to the original image point. Images are taken as the grism rotates about the optical axis, resulting in a set of grism-dispersed images with
diff erent spectra orientations. A hyperspectral data cube is then reconstructed from this set of grism-dispersed images through back projection and point spread function
(PSF) deconvolution. The Richardson-Lucy method is chosen as the deconvolution algorithm in the thesis due to its speed and performance. In contrast to other wide
eld spectroscopy techniques, Grism Spectrotomography collects all available photons simultaneously and efficiently yields the spectrum of each sky pixel within the field
of view. It has high throughput and a multiplex advantage. A prototype GSTI was built, and the data acquisition pipeline was developed for the telescope. GSTI was tested in the lab and on the sky. Reconstruction results show that GSTI is
capable of simultaneously providing spectra of multiple sources in the fi eld. The star foreground was also carefully studied for intensity mapping. Masking of Milky Way stars is required for cosmological Lya intensity mapping because bright stars can a ffect the detection and the power spectrum of Lya sources. A masking and filtering scheme is proposed to obtain a high signal-to-noise Lya power spectrum
using intensity mapping.
and large scale structures. A new type of telescope, the Grism Spectrotomographic Imager (GSTI), is described in the thesis. The GSTI is designed for Lyman Alpha
(Ly ) intensity mapping. A grism, the combination of grating and prism, is placed in front of a camera to disperse the light of each point on the sky into a spectrum and
shift the spectrum back closer to the original image point. Images are taken as the grism rotates about the optical axis, resulting in a set of grism-dispersed images with
diff erent spectra orientations. A hyperspectral data cube is then reconstructed from this set of grism-dispersed images through back projection and point spread function
(PSF) deconvolution. The Richardson-Lucy method is chosen as the deconvolution algorithm in the thesis due to its speed and performance. In contrast to other wide
eld spectroscopy techniques, Grism Spectrotomography collects all available photons simultaneously and efficiently yields the spectrum of each sky pixel within the field
of view. It has high throughput and a multiplex advantage. A prototype GSTI was built, and the data acquisition pipeline was developed for the telescope. GSTI was tested in the lab and on the sky. Reconstruction results show that GSTI is
capable of simultaneously providing spectra of multiple sources in the fi eld. The star foreground was also carefully studied for intensity mapping. Masking of Milky Way stars is required for cosmological Lya intensity mapping because bright stars can a ffect the detection and the power spectrum of Lya sources. A masking and filtering scheme is proposed to obtain a high signal-to-noise Lya power spectrum
using intensity mapping.
History
Date
2017-09-17Degree Type
- Dissertation
Department
- Physics
Degree Name
- Doctor of Philosophy (PhD)