Matching Items (145)
Description
Quasars, the visible phenomena associated with the active accretion phase of super- massive black holes found in the centers of galaxies, represent one of the most energetic processes in the Universe. As matter falls into the central black hole, it is accelerated and collisionally heated, and the radiation emitted can outshine the combined light of all the stars in the host galaxy. Studies of quasar host galaxies at ultraviolet to near-infrared wavelengths are fundamentally limited by the precision with which the light from the central quasar accretion can be disentangled from the light of stars in the surrounding host galaxy. In this Dissertation, I discuss direct imaging of quasar host galaxies at redshifts z ≃ 2 and z ≃ 6 using new data obtained with the Hubble Space Telescope. I describe a new method for removing the point source flux using Markov Chain Monte Carlo parameter estimation and simultaneous modeling of the point source and host galaxy. I then discuss applications of this method to understanding the physical properties of high-redshift quasar host galaxies including their structures, luminosities, sizes, and colors, and inferred stellar population properties such as age, mass, and dust content.
ContributorsMechtley, Matt R (Author) / Windhorst, Rogier A (Thesis advisor) / Butler, Nathaniel (Committee member) / Jansen, Rolf A (Committee member) / Rhoads, James (Committee member) / Scowen, Paul (Committee member) / Arizona State University (Publisher)
Created2014
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 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
Description
I combine, compare, and contrast the results from two different numerical techniques (grid vs. particle methods) studying multi-scale processes in galaxy and structure formation. I produce a method for recreating identical initial conditions for one method from those of the other, and explore methodologies necessary for making these two methods as consistent as possible. With this, I first study the impact of streaming velocities of baryons with respect to dark matter, present at the epoch of reionization, on the ability for small halos to accrete gas at high redshift. With the inclusion of this stream velocity, I find the central density profile of halos is reduced, overall gas condensation is delayed, and infer a delay in the inevitable creation of stars.
I then combine the two numerical methods to study starburst outflows as they interact with satellite halos. This process leads to shocks catalyzing the formation of molecular coolants that lead to bursts in star formation, a process that is better captured in grid methods. The resultant clumps of stars are removed from their initial dark matter halo, resemble precursors to modern-day globular clusters, and their formation may be observable with upcoming telescopes.
Finally, I perform two simulation suites, comparing each numerical method's ability to model the impact of energetic feedback from accreting black holes at the core of giant clusters. With these comparisons I show that black hole feedback can maintain a hot diffuse medium while limiting the amount of gas that can condense into the interstellar medium, reducing the central star formation by up to an order of magnitude.
I then combine the two numerical methods to study starburst outflows as they interact with satellite halos. This process leads to shocks catalyzing the formation of molecular coolants that lead to bursts in star formation, a process that is better captured in grid methods. The resultant clumps of stars are removed from their initial dark matter halo, resemble precursors to modern-day globular clusters, and their formation may be observable with upcoming telescopes.
Finally, I perform two simulation suites, comparing each numerical method's ability to model the impact of energetic feedback from accreting black holes at the core of giant clusters. With these comparisons I show that black hole feedback can maintain a hot diffuse medium while limiting the amount of gas that can condense into the interstellar medium, reducing the central star formation by up to an order of magnitude.
ContributorsRichardson, Mark Lawrence Albert (Author) / Scannapieco, Evan (Thesis advisor) / Rhoads, James (Committee member) / Scowen, Paul (Committee member) / Timmes, Frank (Committee member) / Young, Patrick (Committee member) / Arizona State University (Publisher)
Created2014
Description
Lyman-alpha (Lyα) galaxies (LAEs) and Lyα blobs (LABs) are objects identified and studied due to their bright Lyα emission lines. This bright emission allows LAEs and LABs to be studied in the distant universe, providing a glimpse into the physical processes occuring in the early universe. This dissertation presents three complementary studies of LAEs and LABs at z ~ 3.1. The two main foci of this work are (1) to understand the gas kinematics in both classes of objects and (2) to improve spectral energy distribution (SED) fitting processes to better determine the physical characteristics of LAEs. Gas kinematics in this dissertation means looking for signatures of large-scale winds. This is an exciting astrophysical endeavor, because the results can provide insight into how Lyα photons escape distant galaxies and traverse the IGM, and the results have implications for how the epoch of reionization can be studied with the Lyα line and because winds can be a signature of powerful star formation events. In the first two studies we find signatures of winds in three LAEs by measuring the velocity offset between the redshifts of [OIII] and Lyα in these galaxies. The first two LAEs presented here represent the first ever measurements of [OIII] in Lyα-selected field galaxies. The third study reports no velocity offset between [OIII] and Lyα when the methodology is transferred to a z ~ 3.1 LAB. This lack of velocity offset is an interesting result, however, as powerful outflows and star formation events, which should impart a velocity offset, have been hypothesized as power sources for LABs. In addition to understanding the kinematics of these objects, we introduce a new parameter into the SED fitting process typically used to characterize LAEs. This new parameter enables better determination of characteristics like the age, mass, metallicity, dust content and star formation history of the galaxies in our sample. These characteristics provide a snapshot of galaxies in the universe ~ 11 billion years ago and also provide insight into how these characteristics compare to galaxies at other epochs.
ContributorsMcLinden, Emily (Author) / Rhoads, James (Thesis advisor) / Malhotra, Sangeeta (Committee member) / Timmes, Frank (Committee member) / Scowen, Paul (Committee member) / Young, Patrick (Committee member) / Arizona State University (Publisher)
Created2012
Description
Geology and its tangential studies, collectively known and referred to in this thesis as geosciences, have been paramount to the transformation and advancement of society, fundamentally changing the way we view, interact and live with the surrounding natural and built environment. It is important to recognize the value and importance of this interdisciplinary scientific field while reconciling its ties to imperial and colonizing extractive systems which have led to harmful and invasive endeavors. This intersection among geosciences, (environmental) justice studies, and decolonization is intended to promote inclusive pedagogical models through just and equitable methodologies and frameworks as to prevent further injustices and promote recognition and healing of old wounds. By utilizing decolonial frameworks and highlighting the voices of peoples from colonized and exploited landscapes, this annotated syllabus tackles the issues previously described while proposing solutions involving place-based education and the recentering of land within geoscience pedagogical models. (abstract)
ContributorsReed, Cameron E (Author) / Richter, Jennifer (Thesis director) / Semken, Steven (Committee member) / School of Earth and Space Exploration (Contributor, Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
The development of new Ultra-Violet/Visible/IR range (UV/Vis/IR) astronomical instrumentation that use novel approaches for imaging and increase the accessibility of observing time for more research groups is essential for rapid innovation within the community. Unique focal planes that are rapid-prototyped, low cost, and provide high resolution are key.
In this dissertation the emergent designs of three unique focal planes are discussed. These focal planes were each designed for a different astronomical platform: suborbital balloon, suborbital rocket, and ground-based observatory. The balloon-based payload is a hexapod-actuated focal plane that uses tip-tilt motion to increase angular resolution through the removal of jitter – known as the HExapod Resolution-Enhancement SYstem (HERESY), the suborbital rocket imaging payload is a Jet Propulsion Laboratory (JPL) delta-doped charge-coupled device (CCD) packaged to survive the rigors of launch and image far-ultra-violet (FUV) spectra, and the ground-based observatory payload is a star centroid tracking modification to the balloon version of HERESY for the tip-tilt correction of atmospheric turbulence.
The design, construction, verification, and validation of each focal plane payload is discussed in detail. For HERESY’s balloon implementation, pointing error data from the Stratospheric Terahertz Observatory (STO) Antarctic balloon mission was used to form an experimental lab test setup to demonstrate the hexapod can eliminate jitter in flight-like conditions. For the suborbital rocket focal plane, a harsh set of unit-level tests to ensure the payload could survive launch and space conditions, as well as the characterization and optimization of the JPL detector, are detailed. Finally, a modification of co-mounting a fast-read detector to the HERESY focal plane, for use on ground-based observatories, intended to reduce atmospherically induced tip-tilt error through the centroid tracking of bright natural guidestars, is described.
In this dissertation the emergent designs of three unique focal planes are discussed. These focal planes were each designed for a different astronomical platform: suborbital balloon, suborbital rocket, and ground-based observatory. The balloon-based payload is a hexapod-actuated focal plane that uses tip-tilt motion to increase angular resolution through the removal of jitter – known as the HExapod Resolution-Enhancement SYstem (HERESY), the suborbital rocket imaging payload is a Jet Propulsion Laboratory (JPL) delta-doped charge-coupled device (CCD) packaged to survive the rigors of launch and image far-ultra-violet (FUV) spectra, and the ground-based observatory payload is a star centroid tracking modification to the balloon version of HERESY for the tip-tilt correction of atmospheric turbulence.
The design, construction, verification, and validation of each focal plane payload is discussed in detail. For HERESY’s balloon implementation, pointing error data from the Stratospheric Terahertz Observatory (STO) Antarctic balloon mission was used to form an experimental lab test setup to demonstrate the hexapod can eliminate jitter in flight-like conditions. For the suborbital rocket focal plane, a harsh set of unit-level tests to ensure the payload could survive launch and space conditions, as well as the characterization and optimization of the JPL detector, are detailed. Finally, a modification of co-mounting a fast-read detector to the HERESY focal plane, for use on ground-based observatories, intended to reduce atmospherically induced tip-tilt error through the centroid tracking of bright natural guidestars, is described.
ContributorsMiller, Alexander Duke (Author) / Scowen, Paul (Thesis advisor) / Groppi, Christopher (Committee member) / Mauskopf, Philip (Committee member) / Jacobs, Daniel (Committee member) / Butler, Nathaniel (Committee member) / Arizona State University (Publisher)
Created2019
Description
In the past three decades with the deployment of space-based from x-rays to infrared telescopes and operation of 8-10 m class ground based telescopes, a hand-full of regions of the sky have emerged that probe the distant universe over relatively wide fields with the aim of understanding the assembly of apparently faint galaxies. To explore this new frontier, observations were made with the Large Binocular Cameras (LBCs) on the Large Binocular Telescope (LBT) of a well-studied deep field, GOODS-North, which has been observed by a wide range of telescopes from the radio to x-ray. I present a study of the trade-off between depth and resolution using a large number of LBT/LBC U-band and R-band imaging observations in the GOODS-N field. Having acquired over 30 hours of data (315 images with 5-6 minute exposures) for U-band and 27 hours for R-band (828 images with 2 minute exposures), multiple mosaics were generated, starting with images taken under the best atmospheric conditions (FWHM <0.8"). For subsequent mosaics, data with coarser seeing values were added in until the final, deepest mosaic included all images with FWHM <1.8". For each mosaic, object catalogs were made to compare the optimal-resolution, yet shallower image to the low-resolution but deeper image. For the brightest galaxies within the GOODS-N field, structure and clumpy features within the galaxies are more prominent in the optimal-resolution image compared to the deeper mosaics. I conclude that for studies of brighter galaxies and features within them, the optimal-resolution image should be used. However, to fully explore and understand the faintest objects, the deeper imaging with lower resolution are also required. For the 220 and 360 brightest galaxies in the U-band and R-band images respectively, there is only a marginal difference between the optimal-resolution and lower-resolution light-profiles and their integrated total fluxes. This helps constrain how much flux can be missed in galaxy outskirts, which is important for studies of Extragalactic Background Light. Finally, I also comment on a collection of galaxies in the field with tidal tails and streams, diffuse plumes, and bridges.
ContributorsAshcraft, Teresa Ann (Author) / Windhorst, Rogier A (Thesis advisor) / Borthakur, Sanchayeeta (Committee member) / Jansen, Rolf A (Committee member) / Scowen, Paul (Committee member) / Groppi, Chris (Committee member) / Arizona State University (Publisher)
Created2018
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 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.
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
Description
Accurately predicting local ranges of isotopic signatures in human populations is essential for answering questions about past migrations and mobility. While local ranges of δ18O can be estimated using modern baseline samples and precipitation models, there are many environmental and anthropogenic drivers that can cause these ranges to deviate from the ranges seen in human populations. This study performs a geostatistical meta-analysis on a large dataset (n = 1,370) of spatially contextualized archaeological δ18O samples from 30 publications in order to generate a predictive model of local human δ18O ranges in the Central Andes. Two models were generated, one using archaeological samples of both humans and fauna, and the other using only humans. The model using only human samples makes more accurate predictions, cautioning against the incorporation of faunal δ18O samples in studies of human provenance. The models are also compared against a model of δ18O values found in precipitation across the study area, and significant differences lead to the conclusion that precipitation models are insufficient for predicting local human δ18O ranges.
ContributorsHatley, Camden Miller (Author) / Knudson, Kelly (Thesis director) / Scaffidi, Beth (Committee member) / School of Earth and Space Exploration (Contributor) / School of Human Evolution & Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
In this study, the packaging and labeling of milk and coffee was compared between Walmart and Sprouts. The pricing, the sourcing, the certifications and the overall shelf presence of the items was taken under consideration. After studying the packaging of both, a new design incorporating the applicable labels, customer appeal and appropriate green marketing was created for both the commodities.
ContributorsBhatt, Rashi Hitesh (Author) / Collins, Shari (Thesis director) / Keahey, Jennifer (Committee member) / School of International Letters and Cultures (Contributor) / School of Earth and Space Exploration (Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05