78 research outputs found
The Physics of LIGO
In the spring term of 1994, I organized a course at Caltech on the The Physics of LIGO (i.e., the physics of the Laser Interferometer Gravitational Wave Observatory). The course consisted of eighteen 1.5-hour-long tutorial lectures, delivered by members of the LIGO team and others, and it was aimed at advanced undergraduates and graduate students in physics, applied physics and in engineering and applied sciences and also at interested postdoctoral fellows, research staff, and faculty
Mapping Cosmic Dawn and Reionization: Challenges and Synergies
Cosmic dawn and the Epoch of Reionization (EoR) are among the least explored
observational eras in cosmology: a time at which the first galaxies and
supermassive black holes formed and reionized the cold, neutral Universe of the
post-recombination era. With current instruments, only a handful of the
brightest galaxies and quasars from that time are detectable as individual
objects, due to their extreme distances. Fortunately, a multitude of
multi-wavelength intensity mapping measurements, ranging from the redshifted 21
cm background in the radio to the unresolved X-ray background, contain a
plethora of synergistic information about this elusive era. The coming decade
will likely see direct detections of inhomogenous reionization with CMB and 21
cm observations, and a slew of other probes covering overlapping areas and
complementary physical processes will provide crucial additional information
and cross-validation. To maximize scientific discovery and return on
investment, coordinated survey planning and joint data analysis should be a
high priority, closely coupled to computational models and theoretical
predictions.Comment: 5 pages, 1 figure, submitted to the Astro2020 Decadal Survey Science
White Paper cal
Cosmology with the Highly Redshifted 21cm Line
In addition to being a probe of Cosmic Dawn and Epoch of Reionization
astrophysics, the 21cm line at is also a powerful way to constrain
cosmology. Its power derives from several unique capabilities. First, the 21cm
line is sensitive to energy injections into the intergalactic medium at high
redshifts. It also increases the number of measurable modes compared to
existing cosmological probes by orders of magnitude. Many of these modes are on
smaller scales than are accessible via the CMB, and moreover have the advantage
of being firmly in the linear regime (making them easy to model theoretically).
Finally, the 21cm line provides access to redshifts prior to the formation of
luminous objects. Together, these features of 21cm cosmology at provide
multiple pathways toward precise cosmological constraints. These include the
"marginalizing out" of astrophysical effects, the utilization of redshift space
distortions, the breaking of CMB degeneracies, the identification of signatures
of relative velocities between baryons and dark matter, and the discovery of
unexpected signs of physics beyond the CDM paradigm at high redshifts.Comment: Science white paper submitted to Decadal 2020 surve
Design and implementation of a noise temperature measurement system for the Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX)
This paper describes the design, implementation, and verification of a
test-bed for determining the noise temperature of radio antennas operating
between 400-800MHz. The requirements for this test-bed were driven by the HIRAX
experiment, which uses antennas with embedded amplification, making system
noise characterization difficult in the laboratory. The test-bed consists of
two large cylindrical cavities, each containing radio-frequency (RF) absorber
held at different temperatures (300K and 77K), allowing a measurement of system
noise temperature through the well-known 'Y-factor' method. The apparatus has
been constructed at Yale, and over the course of the past year has undergone
detailed verification measurements. To date, three preliminary noise
temperature measurement sets have been conducted using the system, putting us
on track to make the first noise temperature measurements of the HIRAX feed and
perform the first analysis of feed repeatability.Comment: 19 pages, 12 figure
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