EXCLAIM and Intensity mapping
Astrophysics: Cosmology
The light emitted by atomic transitions in the distant universe will be redshifted by the time it reaches us today. By measuring the spectrum over a region of the sky, a survey can infer the three-dimensional distribution of emission from galaxies in a large volume of the universe.
The EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM) is a cryogenic balloon-borne instrument to survey galaxy and star formation history over cosmological time scales. Rather than identifying individual objects, EXCLAIM will be a pathfinder to demonstrate an intensity mapping approach. EXCLAIM will operate at 420-540 GHz with a spectral resolution R=512 to measure the integrated CO and [CII] in redshift windows spanning 0 < z < 3.5. CO and [CII] line emissions are valuable tracers of the gas phases in the interstellar medium involved in star-formation processes. Thus, EXCLAIM will shed light on why the star formation rate declines at z < 2, despite continued clustering of the dark matter. The instrument will employ an array of six superconducting integrated grating-analog spectrometers (micro-spec) coupled to microwave kinetic inductance detectors (MKIDs).
Through a previous collaboration at CITA, Eric analyzed the statistical distribution of matter when the universe was half its present size, using the 21 cm transition of neutral hydrogen and data acquired with the Green Bank Telescope.
Measurements of the Cosmic Microwave Background
Astrophysics: Cosmology
High-resolution measurements of the CMB intensity have achieved great precision through the Planck Satellite, the Atacama Cosmology Telescope (ACT), and the South Pole Telescope (SPT). Eric was part of the team that developed ACT and its successor ACTPol. In addition to supporting a standard cosmological model of the universe dominated by dark energy and matter, these experiments have measured the gravitational lensing of the CMB by intervening matter and the perturbations to the CMB spectrum from the most massive clusters of galaxies in the universe. Galaxy clusters and high redshift galaxies detected in large high-resolution CMB surveys have guided fields for deeper observations by HST and JWST.
Cosmological inflation is our current leading theory of the early universe, and processes at that time are thought to produce a unique "B-mode" signature in the polarization of the CMB. The Primordial Inflation Polarization Explorer (PIPER) balloon mission is designed to measure this signature across a broad region of the sky and range of wavelengths. Switzer led the PIPER receiver development, implementing and testing a system to operate 2560 Transition Edge Sensors cooled to 100 mK using a Continuous Adiabatic Demagnetization refrigerator.
Atoms in the cosmos
Astrophysics: Cosmology
The early universe was a hot, ionized, and highly uniform gas. As it cooled through expansion, the gas could become neutral and transparent, liberating the thermal photons that are observed today as the cosmic microwave background (CMB). A detailed understanding of this cosmological recombination is required to interpret precise CMB anisotropy measurements of WMAP/Planck/ACT/SPT. Eric refined the calculation of helium recombination and was part of the community that brought the previous generation of analyses to a higher level of precision for modern CMB experiments. Following recombination, the first luminous objects are fueled by gas and reionize the universe -- atoms provide a diagnostic of this rich evolution up to the present.
