Author ORCID Identifier

https://orcid.org/0000-0002-3354-3859

Semester

Fall

Date of Graduation

2023

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Physics and Astronomy

Committee Chair

Duncan Lorimer

Committee Co-Chair

Kevin Bandura

Committee Member

Loren Anderson

Committee Member

Emmanuel Fonseca

Committee Member

Tapasi Ghosh

Abstract

The radio sky spans tens of orders of magnitude in length, density, and time.
In this thesis, using novel filtering techniques and two different telescopes,
we investigate two tracers of cosmic structure: Baryon Acoustic Oscillations
(BAOs) and Fast Radio Bursts (FRBs). BAOs formed as the universe cooled
after the Big Bang. BAOs provide a fiducial length scale of the universe
throughout cosmic time and thus can be used to understand how the universe
is evolving. FRBs are very bright, short timescale, bursts of as-yet unknown
origin which occur uniformly on the sky at a rate of a few thousand per day.
Now robustly identified with host galaxies in the redshift range 0 < z < 1,
FRBs are promising probes of cosmology and fundamental physics and provide
a new means to probe large-scale structure.
Both of these projects suffer from radio frequency interference, anthropomorphic radio energy received by radio telescopes. These signals can be
significantly brighter than the radio sky, obscuring or degrading observations
of signals that are astrophysical in origin. We discuss how this interference
negatively impacts these experiments and present filtering strategies to eliminate these signals and enhance our sensitivity.
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) probes
the large-scale structure of the universe by mapping the 21 cm line from
neutral hydrogen (HI) in the redshift range 0.8 < z < 2.5. We used HI
intensity maps produced by the CHIME telescope cross correlated with an
optical survey of galaxies known as WiggleZ. We discuss why, as expected, this
cross correlation fails while other correlations succeed. The cross correlation
methodology is a step towards detecting the large-scale structure with only
the CHIME intensity map. Particularly, CHIME cosmology aims to detect
BAOs. These maps can be used to understand the density power spectrum
as well as constraints on fundamental physics, such as neutrino mass.
Finding FRBs is of interest to understand their progenitors, which are
likely to be highly relativistic objects (for example, strongly magnetized neutron stars) at cosmological distances. Although individual events last only a
few milliseconds, FRB searches require thousands of hours to detect a statistically meaningful sample. In this context, we describe GREENBURST a
real-time giant pulse search running on the Green Bank Telescope and present
the latest constraints it is making to the all-sky FRB rate, which we measure
to be 1120+320
−270 bursts per day with flux densities above one Jansky. As part
of this work, we present GREENBURST discoveries of PSR J0038+54, a 2.2 s
pulsar in the Galactic field, and FRB 220718, a new transient radio source
which exhibits an 851 ms periodicity within the burst.

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