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Description
This work examines star formation in the debris associated with collisions of dwarf and spiral galaxies. While the spectacular displays of major mergers are famous (e.g., NGC 4038/9, ``The Antennae''), equal mass galaxy mergers are relatively rare compared to minor mergers (mass ratio <0.3) Minor mergers are less energetic than

This work examines star formation in the debris associated with collisions of dwarf and spiral galaxies. While the spectacular displays of major mergers are famous (e.g., NGC 4038/9, ``The Antennae''), equal mass galaxy mergers are relatively rare compared to minor mergers (mass ratio <0.3) Minor mergers are less energetic than major mergers, but more common in the observable universe and, thus, likely played a pivotal role in the formation of most large galaxies. Centers of mergers host vigorous star formation from high gas density and turbulence and are surveyed over cosmological distances. However, the tidal debris resulting from these mergers have not been well studied. Such regions have large reservoirs of gaseous material that can be used as fuel for subsequent star formation but also have lower gas density. Tracers of star formation at the local and global scale have been examined for three tidal tails in two minor merger systems. These tracers include young star cluster populations, H-alpha, and [CII] emission. The rate of apparent star formation derived from these tracers is compared to the gas available to estimate the star formation efficiency (SFE). The Western tail of NGC 2782 formed isolated star clusters while massive star cluster complexes are found in the UGC 10214 (``The Tadpole'') and Eastern tail of NGC 2782. Due to the lack of both observable CO and [CII] emission, the observed star formation in the Western tail of NGC 2782 may have a low carbon abundance and represent only the first round of local star formation. While the Western tail has a normal SFE, the Eastern tail in the same galaxy has an low observed SFE. In contrast, the Tadpole tidal tail has a high observed star formation rate and a corresponding high SFE. The low SFE observed in the Eastern tail of NGC 2782 may be due to its origin as a splash region where localized gas heating is important. However, the other tails may be tidally formed regions where gravitational compression likely dominates and enhances the local star formation.
ContributorsKnierman, Karen A (Author) / Scowen, Paul (Thesis advisor) / Groppi, Christopher (Thesis advisor) / Mauskopf, Philip (Committee member) / Windhorst, Rogier (Committee member) / Jansen, Rolf (Committee member) / Arizona State University (Publisher)
Created2013
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Description
The IceCube Neutrino Observatory has provided the first map of the high energy (~0.01 – 1 PeV) sky in neutrinos. Since neutrinos propagate undeflected, their arrival direction is an important identifier for sources of high energy particle acceleration. Reconstructed arrival directions are consistent with an extragalactic origin, with possibly a

The IceCube Neutrino Observatory has provided the first map of the high energy (~0.01 – 1 PeV) sky in neutrinos. Since neutrinos propagate undeflected, their arrival direction is an important identifier for sources of high energy particle acceleration. Reconstructed arrival directions are consistent with an extragalactic origin, with possibly a galactic component, of the neutrino flux. We present a statistical analysis of positional coincidences of the IceCube neutrinos with known astrophysical objects from several catalogs. For the brightest gamma-ray emitting blazars and for Seyfert galaxies, the numbers of coincidences is consistent with the random, or “null”, distribution. Instead, when considering starburst galaxies with the highest flux in gamma-rays and infrared radiation, up to n = 8 coincidences are found, representing an excess over the ~4 predicted for the null distribution. The probability that this excess is realized in the null case, the p-value, is p = 0.042. This value falls to p = 0.003 for a set of gamma-ray detected starburst galaxies and superbubbles in the galactic neighborhood. Therefore, it is possible that these might account for a subset of IceCube neutrinos. The physical plausibility of such correlation is discussed briefly.
ContributorsEmig, Kimberly L (Author) / Windhorst, Roiger (Thesis advisor) / Lunardini, Cecilia (Thesis advisor) / Groppi, Christopher (Committee member) / Arizona State University (Publisher)
Created2015
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Description
This thesis contains an overview, as well as the history of optical interferometers. A new approach to interferometric measurements of stars is proposed and explored. Modern updates to the classic techniques are described along with some theoretical derivations showing why the method of single photon counting shows significant promise relative

This thesis contains an overview, as well as the history of optical interferometers. A new approach to interferometric measurements of stars is proposed and explored. Modern updates to the classic techniques are described along with some theoretical derivations showing why the method of single photon counting shows significant promise relative to the currently used amplitude interferometry.

Description of a modular intensity interferometer system using commercially available single-photon detectors is given. Calculations on the sensitivity and \emph{uv}-plane coverage using these modules mounted on existing telescopes on Kitt Peak, Arizona is presented.

Determining fundamental stellar properties is essential for testing models of stellar evolution as well as for deriving physical properties of transiting exoplanets. The proposed method shows great promise in measuring the angular size of stars. Simulations indicate that it is possible to measure stellar diameters of bright stars with AB magnitude <6 with a precision of >5% in a single night of observation.

Additionally, a description is given of a custom time-to-digital converter designed to time tag individual photons from multiple single-photon detectors with high count rate, continuous data logging, and low systematics. The instrument utilizes a tapped-delay line approach on an FPGA chip which allows for sub-clock resolution of <100 ps. The TDC is implemented on a Re-configurable Open Architecture Computing Hardware Revision 2 (ROACH2) board which allows for continuous data streaming and time tagging of up to 20 million events per second. The functioning prototype is currently set-up to work with up to ten independent channels. Laboratory characterization of the system, including RF, pick up and mitigation, as well as measurement of in-lab photon correlations from an incoherent light source (artificial star), are presented. Additional improvements to the TDC will also be discussed, such as improving the data transfer rate by a factor of 10 via an SDP+ Mezzanine card and PCIe 2SFP+ 10 Gb card, as well as scaling to 64 independent channels.

Furthermore, a modified nulling interferometer with image inversion is proposed, for direct imaging of exoplanets below the canonical Rayleigh resolution limit. Image inversion interferometry relies on splitting incoming radiation from a source, either spatially rotating or reflecting the electric field from one arm of the interferometer before recombining the signals and detecting the resulting images in the two output ports with an array of high-speed single-photon detectors. Sources of incoming radiation that have cylindrical symmetry and are centered on the rotation axis will cancel in one of the output ports and add in the other output port. The ability to suppress light from a host star, as well as the ability to resolve past the Rayleigh limit, enables sensitive detection of exoplanets from a stable environment without the need for a coronagraph. The expected number of photons and the corresponding variance in the measurement for different initial contrast ratios are shown, with some first-order theoretical instrumental errors.

Lastly, preliminary results from a sizeable photometric survey are presented. This survey is used to derive bolometric flux alongside from angular size measurements and the effective stellar temperatures.
ContributorsPilyavsky, Genady (Author) / Mauskopf, Philip (Thesis advisor) / Groppi, Christopher (Committee member) / Butler, Nathaniel (Committee member) / Bowman, Judd (Committee member) / Scowen, Paul (Committee member) / Arizona State University (Publisher)
Created2018
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Description
The composition of planets and their volatile contents are intimately connected to the structure and evolution of their parent protoplanetary disks. The transport of momentum and volatiles is often parameterized by a turbulent viscosity parameter $\alpha$, which is usually assumed to be spatially and temporally uniform across the disk. I

The composition of planets and their volatile contents are intimately connected to the structure and evolution of their parent protoplanetary disks. The transport of momentum and volatiles is often parameterized by a turbulent viscosity parameter $\alpha$, which is usually assumed to be spatially and temporally uniform across the disk. I show that variable $\alpha$(r,z) (where $r$ is radius, and $z$ is height from the midplane) attributable to angular momentum transport due to MRI can yield disks with significantly different structure, as mass piles up in the 1-10 AU region resulting in steep slopes of p $>$ 2 here (where p is the power law exponent in $\Sigma \propto r^{-p}$). I also show that the transition radius (where bulk mass flow switches from inward to outward) can move as close in as 3 AU; this effect (especially prominent in externally photoevaporated disks) may significantly influence the radial water content available during planet formation.

I then investigate the transport of water in disks with different variable α profiles. While radial temperature profile sets the location of the water snowline (i.e., inside of which water is present as vapor; outside of which, as ice on solids), it is the rates of diffusion and drift of small icy solids and diffusion of vapor across the snow line that determine the radial water distribution. All of these processes are highly sensitive to local $\alpha$. I calculate the effect of radially varying α on water transport, by tracking the abundance of vapor in the inner disk, and fraction of ice in particles and larger asteroids beyond the snow line. I find one α profile attributable to winds and hydrodynamical instabilities, and motivated by meteoritic constraints, to show considerable agreement with inferred water contents observed in solar system asteroids.

Finally, I calculate the timing of gap formation due to the formation of a planet in disks around different stars. Here, I assume that pebble accretion is the dominant mechanism for planetary growth and that the core of the first protoplanet forms at the water snow line. I discuss the dependence of gap timing to various stellar and disk properties.
ContributorsKalyaan, Anusha (Author) / Desch, Steven J (Thesis advisor) / Groppi, Christopher (Committee member) / Young, Patrick (Committee member) / Shkolnik, Evgenya (Committee member) / Bell, James (Committee member) / Arizona State University (Publisher)
Created2018
Description
The lowest-mass stars, known as M-dwarfs, form target samples for upcoming exoplanet searches, and together with lower-mass substellar objects known as brown dwarfs, are among prime targets for detailed study with high-contrast adaptive optics (AO) imaging and sub-millimeter interferometry. In this thesis, I describe results from three studies investigating the

The lowest-mass stars, known as M-dwarfs, form target samples for upcoming exoplanet searches, and together with lower-mass substellar objects known as brown dwarfs, are among prime targets for detailed study with high-contrast adaptive optics (AO) imaging and sub-millimeter interferometry. In this thesis, I describe results from three studies investigating the companion properties and environments of low-mass systems: (1) The 245-star M-dwarfs in Multiples (MinMs) Survey, a volume-limited survey of field M-dwarf companions within 15 pc, (2) the Taurus Boundary of Stellar/Substellar (TBOSS) Survey, an ongoing study of disk properties for low-mass members within the Taurus star-forming region, and (3) spectroscopy of a brown dwarf companion using the Gemini Planet Imager (GPI).

Direct imaging of M-dwarfs is a sensitive technique to identify low-mass companions over a wide range of orbital separation, and the high proper motion of nearby M-dwarfs eases confirmation of new multiple stars. Combining AO and wide-field imaging, the MinMs Survey provides new measurements of the companion star fraction (CSF), separation distribution, and mass ratio distribution for the nearest K7-M6 dwarfs. These results demonstrate the closer orbital separations (~6 AU) and lower frequency (~23% CSF) of M-dwarf binaries relative to higher-mass stars.

From the TBOSS project, I report 885µm Atacama Large Millimeter/sub-millimeter Array continuum measurements for 24 Taurus members spanning the stellar/substellar boundary (M4-M7.75). Observations of submillimeter emission from dust grains around the lowest-mass hosts show decreasing disk dust mass for decreasing host star mass, consistent with low frequencies of giant planets around M-dwarfs. Compared to the older stellar association of Upper Scorpius, Taurus disks have a factor of four higher mass in submillimeter-sized grains.

From the GPI Exoplanet Survey, I describe near-infrared spectroscopy of an unusually red companion orbiting inside the debris disk of an F5V star. As the second brown dwarf discovered within the innermost region of a debris disk, the properties of this system offer important dynamical constraints for companion-disk interaction and a useful benchmark for brown dwarf and giant planet atmospheric study.
ContributorsWard-Duong, Kimberly Dolan (Author) / Patience, Jennifer (Thesis advisor) / Young, Patrick (Committee member) / Butler, Nathaniel (Committee member) / Bowman, Judd (Committee member) / Groppi, Christopher (Committee member) / Arizona State University (Publisher)
Created2017
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Description
The Balloon-borne Large Aperture Submillimeter Telescope - The Next Generation (BLAST-TNG) was designed to map the polarized emission from dust in star forming regions of our galaxy. The dust is thought to trace magnetic fields and thus inform us of the role that it plays in star formation. BLAST-TNG improves

The Balloon-borne Large Aperture Submillimeter Telescope - The Next Generation (BLAST-TNG) was designed to map the polarized emission from dust in star forming regions of our galaxy. The dust is thought to trace magnetic fields and thus inform us of the role that it plays in star formation. BLAST-TNG improves upon the previous generation of balloon-borne sub-mm polarimeters by increasing the number of detectors by over an order of magnitude. A novel detector technology which is naturally multiplexed, Kinetic Inductance Detectors have been developed as an elegant solution to the challenge of packing cryogenic focal plane arrays with detectors. To readout the multiplexed arrays, custom firmware and control software was developed for the ROACH2 FPGA based system. On January 6th 2020 the telescope was launched on a high-altitude balloon from Antarctica and flew for approximately 15 hours in the mid-stratosphere. During this time various calibration tasks occurred such as atmospheric skydips, the mapping of a sub-mm source, and the flashing of an internal calibration lamp. A mechanical failure shortened the flight so that only calibration scans were performed. In this dissertation I will present my analysis of the in-flight calibration data leading to measures of the overall telescope sensitivity and detector performance. The results of which prove kinetic inductance detectors as a viable candidate for future space based sub-mm telescopes. In parallel the fields of digital communications and radar signal processing have spawned the development of the Radio Frequency System On a Chip (RFSoC). This product by Xilinx incorporates a fabric of reconfigurable logic, ARM microprocessors, and high speed digitizers all into one chip. The system specs provide an improvement in every category of size, weight, power, and bandwidth.This is naturally the desired platform for the next generation of far-infrared telescopes which are pushing the limits of detector counts. I present the development of one of the first frequency multiplexed detector readouts on the RFSoC platform. Alternative firmware designs implemented on the RFSoC are also discussed. The firmware work presented will be used in part or in full for multiple current and upcoming far-infrared telescopes.
ContributorsSinclair, Adrian Kai (Author) / Mauskopf, Philip D (Thesis advisor) / Borthakur, Sanchayeeta (Committee member) / Groppi, Christopher (Committee member) / Jacobs, Daniel (Committee member) / Hubmayr, Johannes (Committee member) / Arizona State University (Publisher)
Created2021
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Description
Brown dwarfs are a unique class of object which span the range between the lowest mass stars, and highest mass planets. New insights into the physics and chemistry of brown dwarfs comes from the comparison between spectroscopic observations, and theoretical atmospheric models. In this thesis, I present a uniform atmospheric

Brown dwarfs are a unique class of object which span the range between the lowest mass stars, and highest mass planets. New insights into the physics and chemistry of brown dwarfs comes from the comparison between spectroscopic observations, and theoretical atmospheric models. In this thesis, I present a uniform atmospheric retrieval analysis of the coolest Y, and late-T spectral type brown dwarfs using the CaltecH Inverse ModEling and Retrieval Algorithms (CHIMERA). In doing so, I develop a foundational dataset of retrieved atmospheric parameters including: molecular abundances, thermal structures, evolutionary parameters, and cloud properties for 61 different brown dwarfs. Comparisons to other modeling techniques and theoretical expectations from the James Webb Space Telescope (JWST) are made. Finally, I describe the techniques used to improve CHIMERA to run on Graphical Processing Units (GPUs), which directly enabled the creation of this large dataset.
ContributorsZalesky, Joseph (Author) / Line, Michael R (Thesis advisor) / Patience, Jennifer (Committee member) / Groppi, Christopher (Committee member) / Young, Patrick (Committee member) / Bose, Maitrayee (Committee member) / Arizona State University (Publisher)
Created2022
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Description
This dissertation details the development of an open source, frequency domain multiplexed (FDM) readout for large-format arrays of superconducting lumped-element kinetic inductance detectors (LEKIDs). The system architecture is designed to meet the requirements of current and next generation balloon-borne and ground-based submillimeter (sub-mm), far-infrared (FIR) and millimeter-wave (mm-wave) astronomical cameras,

This dissertation details the development of an open source, frequency domain multiplexed (FDM) readout for large-format arrays of superconducting lumped-element kinetic inductance detectors (LEKIDs). The system architecture is designed to meet the requirements of current and next generation balloon-borne and ground-based submillimeter (sub-mm), far-infrared (FIR) and millimeter-wave (mm-wave) astronomical cameras, whose science goals will soon drive the pixel counts of sub-mm detector arrays from the kilopixel to the megapixel regime. The in-flight performance of the readout system was verified during the summer, 2018 flight of ASI's OLIMPO balloon-borne telescope, from Svalbard, Norway. This was the first flight for both LEKID detectors and their associated readout electronics. In winter 2019/2020, the system will fly on NASA's long-duration Balloon Borne Large Aperture Submillimeter Telescope (BLAST-TNG), a sub-mm polarimeter which will map the polarized thermal emission from cosmic dust at 250, 350 and 500 microns (spatial resolution of 30", 41" and 59"). It is also a core system in several upcoming ground based mm-wave instruments which will soon observe at the 50 m Large Millimeter Telescope (e.g., TolTEC, SuperSpec, MUSCAT), at Sierra Negra, Mexico.

The design and verification of the FPGA firmware, software and electronics which make up the system are described in detail. Primary system requirements are derived from the science objectives of BLAST-TNG, and discussed in the context of relevant size, weight, power and cost (SWaP-C) considerations for balloon platforms. The system was used to characterize the instrumental performance of the BLAST-TNG receiver and detector arrays in the lead-up to the 2019/2020 flight attempt from McMurdo Station, Antarctica. The results of this characterization are interpreted by applying a parametric software model of a LEKID detector to the measured data in order to estimate important system parameters, including the optical efficiency, optical passbands and sensitivity.

The role that magnetic fields (B-fields) play in shaping structures on various scales in the interstellar medium is one of the central areas of research which is carried out by sub-mm/FIR observatories. The Davis-Chandrasekhar-Fermi Method (DCFM) is applied to a BLASTPol 2012 map (smoothed to 5') of the inner ~1.25 deg2 of the Carina Nebula Complex (CNC, NGC 3372) in order to estimate the strength of the B-field in the plane-of-the-sky (B-pos). The resulting map contains estimates of B-pos along several thousand sightlines through the CNC. This data analysis pipeline will be used to process maps of the CNC and other science targets which will be produced during the upcoming BLAST-TNG flight. A target selection survey of five nearby external galaxies which will be mapped during the flight is also presented.
ContributorsGordon, Samuel, Ph.D (Author) / Mauskopf, Philip (Thesis advisor) / Groppi, Christopher (Committee member) / Scowen, Paul (Committee member) / Bowman, Judd (Committee member) / Jacobs, Daniel (Committee member) / Arizona State University (Publisher)
Created2019
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Description
The interaction between galaxies and the surrounding gas plays a key role in galaxy formation and evolution. Feedback processes driven by star formation and active galactic nuclei facilitate the exchange of mass and energy between the galaxy and the circumgalactic medium through inflowing and outflowing gas. These outflows have a

The interaction between galaxies and the surrounding gas plays a key role in galaxy formation and evolution. Feedback processes driven by star formation and active galactic nuclei facilitate the exchange of mass and energy between the galaxy and the circumgalactic medium through inflowing and outflowing gas. These outflows have a significant impact on the star formation rate and metallicity of the galaxy. Observations of outflows have provided evidence that these outflows are multi-phase in nature, identifying both low energy ions such as Mg II and C III and high energy ions such as O VI. The underlying physics maintaining the two phases as well as the ionization mechanism for these phases remains unclear. In order to better understand galactic outflows, hydrodynamic simulations are used to study the evolution of wind-cloud interactions. In this work, I carried out a suite of magnetohydrodynamic simulations to characterize the influence of magnetic fields on the evolution and lifetime of cold clouds. I found magnetic fields either provided little improvement to cloud stability over other influences such as radiative cooling or accelerated cloud disruption by pushing cloud material in the direction orthogonal to the wind and magnetic fields. To investigate the ionization mechanism of the material within outflows I first considered estimating the column densities of various ions within wind-cloud simulations with the post-processing tool Trident. Under the assumption of ionization equilibrium, the simulations did not reproduce the observed absorption profiles demonstrating the need for a more detailed treatment of the ionization processes. I then performed a new set of simulations with the non-equilibrium chemistry solver, MAIHEM. The column densities produced in the non-equilibrium model alter the evolution of the cloud and highlight the increased ionization along the boundary of the cloud.
ContributorsBlough-Swingen, J'Neil (Author) / Scannapieco, Evan (Thesis advisor) / Groppi, Christopher (Committee member) / Young, Patrick (Committee member) / Borthakur, Sanchayeeta (Committee member) / Mauskopf, Phillip (Committee member) / Arizona State University (Publisher)
Created2021
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Description
The distribution of galaxies traces the structure of underlying dark matter, and carries signatures of both the cosmology that evolved the universe as well as details of how galaxies interact with their environment and each other. There are many ways to measure the clustering of galaxies, each with unique strengths,

The distribution of galaxies traces the structure of underlying dark matter, and carries signatures of both the cosmology that evolved the universe as well as details of how galaxies interact with their environment and each other. There are many ways to measure the clustering of galaxies, each with unique strengths, uses, theoretical background, and connection to other physical concepts. One uncommon clustering statistic is the Void Probability Function (VPF): it simply asks, how likely is a circle/sphere of a given size to be empty in your galaxy sample? Simple and efficient to calculate, the VPF is tied to all higher order volume-averaged correlation functions as the 0$^{\text{th}}$ moment of count-in-cells, and encodes information from higher order clustering that the robust two-point correlation function cannot always capture. Using simulations of Lyman-alpha emitting galaxies across either redshift history or the epoch of reionization, this work asks: how powerful is the VPF itself? When can and should it be used for galaxy clustering? What unique constraints or guidelines can it give for the pacing of reionization, in the Lyman-$\alpha$ Galaxies in the Epoch of Reionization (LAGER) narrowband survey or across the Roman Space Telescope grism? This work provides practical guidelines for creating and carrying out clustering studies using the the VPF, and motivates the use of the VPF for reionization. The VPF of LAEs can complement LAGER constraints for the end of reionization, and thoroughly inform the timing and pace of reionization with Roman.
ContributorsPerez, Lucia Alexandra (Author) / Malhotra, Sangeeta (Thesis advisor) / Butler, Nathaniel (Thesis advisor) / Groppi, Christopher (Committee member) / Scannapieco, Evan (Committee member) / Rhoads, James E (Committee member) / Arizona State University (Publisher)
Created2022