Dissertation/Thesis Abstract

Millimeter-Wave Galaxy Spectroscopy: SuperSpec On-Chip Spectrometer Technology Development and ALMA Observations of Molecular Gas in the Arp 220 Nucleus
by Wheeler, Jordan, Ph.D., University of Colorado at Boulder, 2019, 205; 13904594
Abstract (Summary)

This dissertation is comprised of two components: millimeter-wave spectrometer technology development and millimeter-wave observations and interstellar medium modeling of the nucleus of an ultra luminous galaxy. SuperSpec is an on-chip spectrometer developed for multi-object, moderate resolution (R = 300), large-bandwidth survey spectroscopy of high-redshift galaxies for the 1.0 to 1.5 mm atmospheric transmission window. SuperSpec targets the CO ladder in the redshift range of z = 0 to 4, the [C II] 158 um line from z = 5 to 9, and the [N II] 205 um line from z = 4 to 7. SuperSpec employs a novel architecture in which detectors are coupled to a series of resonant filters along a microwave feedline instead of using dispersive optics. This construction allows for the creation of a spectrometer occupying only a few cm2 of silicon, a reduction in volume of several orders of magnitude when compared to grating spectrometers. This small profile will enable the production of future multi-object spectrometers.

Results from the characterization of SuperSpec test devices are presented. In particular, spectral response profiles, filterbank efficiency, and detector noise equivalent powers are presented. The design motivation and implementation for science-grade SuperSpec spectrometers based on these test results are also presented.

In the second part of the thesis, ALMA observations of Arp 220 using 12CO J = 3 → 2, and 13CO J = 4 → 3, where J is the angular momentum quantum number, are analyzed. Arp 220 is an ultra-luminous infrared galaxy in the late stages of a merger between two gas-rich galaxies, with a high nuclear star formation rate and an extremely large dust optical depth, exhibiting strong evidence for a molecular outflow. Observations are compared to gas excitation and non-LTE radiative transfer models created using the Line Modeling Engine for simple gas dynamics, yielding insight into how parameters such as rotational velocity, velocity dispersion, temperature, outflow velocity, and gas mass can reproduce the observed kinematic features. Together, these observational and technological aspects of the thesis demonstrate the power of millimeter-wave spectroscopy for understanding galaxy evolution.

Indexing (document details)
Advisor: Glenn, Jason
Commitee: Comerford, Julie, Green, James, Halverson, Nils, Popovic, Zoya
School: University of Colorado at Boulder
Department: Astrophysical and Planetary Sciences
School Location: United States -- Colorado
Source: DAI-B 81/3(E), Dissertation Abstracts International
Subjects: Astrophysics, Astronomy
Keywords: Arp 220, Galaxy evolution, Instrumentation, Kinetic inductance detectors, Spectrometer, Star formation
Publication Number: 13904594
ISBN: 9781088322895
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