Graduate Thesis Or Dissertation
Increasing the Detail and Sensitivity of Far-Infrared/Submillimeter Observations In Astrophysics: Kinetic Inductance Detector Development and Molecular Gas Dynamics In Galaxy Merger NGC 6240 Public Deposited
To push the boundaries of astrophysics we need to be able to look at the universe in increasing detail. This thesis work advances this goal in two ways: with a technology development project and by using existing technology to investigate an archetypal merging galaxy in extreme detail.
Technology development: Far-infrared observations are ultimately limited by the background radiation emitted by our galaxy and solar system. Large far-infrared observatories that are limited by this background will be critical for understanding galactic and star formation histories over time. To enable this goal, arrays of far-infrared detectors with high enough sensitivities to be astrophysical background limited need to be developed. Working with a team from the Jet Propulsion Laboratory and the National Institute for Standards and Technology, I have investigated two methods for increasing the sensitivities of kinetic inductance detectors (KIDs) in the far-infrared. First, we have fabricated low-volume aluminum and aluminum/titanium nitride bilayer devices to decrease active detector metal volume thereby increasing responsivity. To optimize future iterations on these designs, I have also measured signal lifetimes as a function of aluminum thickness. Second, we investigated phonon recycling devices (simulations and fabrications) that trap phonons generated by recombining Cooper pairs in the active area to elongate quasi-particle recombination time, thereby boosting responsivity.
Observational component: Galactic mergers are immensely complex, often resulting in tidal tails, extremely turbulent gas, active galactic nuclei (AGN), superwinds, and bursts in star formation to only name a few impacts. Using the Atacama Large Millimeter Array (ALMA), I observe the molecular gas in the well-studied galaxy merger NGC 6240 in more detail than ever before.We analyze high-resolution observations of CO J = 3 − 2 and 6 − 5 of the central few kpc of NGC 6240 taken with ALMA. Using these CO line observations, we model the kinematics of the molecular gas located between the nuclei of the progenitor galaxies. Our models suggest this gas is a tidal bridge linking the two nuclei that could fall onto the nuclei prior to second pass and feed future starbursts. We also observe high velocity gas (> 300 km/s) that could be accelerated by either gravitational forces from the merger or an AGN outflow. These findings shed light onto small-scale processes that can affect galaxy evolution and the corresponding star formation, with the tidal bridge depositing molecular gas onto the nuclei while other energetic forces accelerate molecular gas further out of the nuclear region.
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