Millimeter-Wave Galaxy Spectroscopy: SuperSpec On-Chip Spectrometer Technology Development and ALMA Observations of Molecular Gas In The Arp 220 Nucleus

Wheeler, Jordan

Graduate Thesis Or Dissertation

Millimeter-Wave Galaxy Spectroscopy: SuperSpec On-Chip Spectrometer Technology Development and ALMA Observations of Molecular Gas In The Arp 220 Nucleus Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/ht24wk31x

Abstract

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.

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