Matching Items (7)
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- All Subjects: Astronomy
- All Subjects: Radio Astronomy
- All Subjects: Star Formation
- Creators: Windhorst, Rogier
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
ContributorsPowell, Devon (Author) / Gardner, Carl (Thesis director) / Scannapieco, Evan (Committee member) / Windhorst, Rogier (Committee member) / Barrett, The Honors College (Contributor)
Created2012-05
Description
I test the hypothesis that galactic magnetic fields originate from regions of dense
star formation (Dahlem et al. 2006) by comparing maps of 120-240 MHz synchrotron emission and hydrogen alpha (Hα) emission of the tidally-interacting, edge-on, barred spiral galaxy UGC 9665. Synchrotron emission traces magnetic field strength to a rough first order, while Hα emission traces recent massive star formation. UGC 9665 was selected because it was included in the LOw Frequency ARray (LOFAR) TwoMetre Sky Survey (LoTSS; Shimwell et al. (2017)) as well as the Calar Alto Legacy Integral Field Area Survey (CALIFA; Sanchez et al. (2012)). I generated vertical intensity profiles at several distances along the disk from the galactic center for synchrotron emission and Hα in order to measure how the intensity of each falls off with distance from the midplane. In addition to correlating the vertical profiles to see if there is a relationship between star formation and magnetic field strength, I fit the LOFAR vertical profiles to characteristic Gaussian and exponential functions given by Dumke et al. (1995). Fitting these equations have been shown to be good indicators of the main mode of cosmic ray transport, whether it is advection (exponential fit) or diffusion (Gaussian fit) (Heesen et al. 2016). Cosmic rays originate from supernova,
and core collapse supernovae occur in star forming regions, which also produce
advective winds, so I test the correlation between star-forming regions and advective regions as predicted by the Heesen et al. (2016) method. Similar studies should be conducted on different galaxies in the future in order to further test these hypotheses and how well LOFAR and CALIFA complement each other, which will be made possible by the full release of the LOFAR Two-Metre Sky Survey (LoTSS) (Shimwell et al. 2017).
star formation (Dahlem et al. 2006) by comparing maps of 120-240 MHz synchrotron emission and hydrogen alpha (Hα) emission of the tidally-interacting, edge-on, barred spiral galaxy UGC 9665. Synchrotron emission traces magnetic field strength to a rough first order, while Hα emission traces recent massive star formation. UGC 9665 was selected because it was included in the LOw Frequency ARray (LOFAR) TwoMetre Sky Survey (LoTSS; Shimwell et al. (2017)) as well as the Calar Alto Legacy Integral Field Area Survey (CALIFA; Sanchez et al. (2012)). I generated vertical intensity profiles at several distances along the disk from the galactic center for synchrotron emission and Hα in order to measure how the intensity of each falls off with distance from the midplane. In addition to correlating the vertical profiles to see if there is a relationship between star formation and magnetic field strength, I fit the LOFAR vertical profiles to characteristic Gaussian and exponential functions given by Dumke et al. (1995). Fitting these equations have been shown to be good indicators of the main mode of cosmic ray transport, whether it is advection (exponential fit) or diffusion (Gaussian fit) (Heesen et al. 2016). Cosmic rays originate from supernova,
and core collapse supernovae occur in star forming regions, which also produce
advective winds, so I test the correlation between star-forming regions and advective regions as predicted by the Heesen et al. (2016) method. Similar studies should be conducted on different galaxies in the future in order to further test these hypotheses and how well LOFAR and CALIFA complement each other, which will be made possible by the full release of the LOFAR Two-Metre Sky Survey (LoTSS) (Shimwell et al. 2017).
ContributorsHuckabee, Gabriela R (Author) / Jansen, Rolf (Thesis director) / Windhorst, Rogier (Committee member) / Bowman, Judd (Committee member) / School of Earth and Space Exploration (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Abstract Located in southeastern Arizona, the Large Binocular Telescope is a great local resource for ASU astronomy/cosmology researchers. As a ground-based observatory, the Large Binocular Telescope can effectively provide deep, complementary observations of science fields in the wavelength range of 3,500 to 10,000 Angstroms. This gives scientists a lot of opportunity for various science projects, which can lead to massive amounts of observations being taken by research schools with ties to the LBT. Such is the case with ASU, which has obtained over 30 hours of data in just the SDT Uspec filter on board the Large Binocular Camera (Blue) and much more time in other filters observing longer wavelengths. Because of this, there is a huge need for establishing a system that will allow the reduction of raw astronomical images from the LBT to be quickly, but accurately. This manuscript serves as a presentation of the work done over the 2015-2016 school year to establish a pipeline for reducing LBT raw science images as well as a guide for future undergraduates and graduates to reduce data on their own.
ContributorsVehonsky, Jacob Ryan (Author) / Windhorst, Rogier (Thesis director) / Jansen, Rolf (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Standard cosmological models predict that the first astrophysical sources formed from a Universe filled with neutral hydrogen (HI) around one hundred million years after the Big Bang. The transition into Cosmic Dawn (CD) that seeded all the structures seen today can only be probed directly by the 21-cm line of neutral hydrogen. Redshifted by the Hubble expansion, HI signal during CD is expected to be visible in radio frequencies. Precisely characterized and carefully calibrated low-frequency instruments are necessary to measure the predicted ~10-200 mK brightness temperature of this cosmological signal against foregrounds. This dissertation focuses on improving the existing instrumental and analysis techniques for the Experiment to Detect the Global EoR Signature (EDGES) and building capabilities for future space-based 21-cm instruments, including the Farside Array for Radio Science Investigations of the Dark ages and Exoplanets (FARSIDE) concept.Frequency-dependent antenna beams of 21-cm instruments limit the removal of bright galactic foreground emission (~10^3 - 10^4K) from observations. Using three electromagnetic simulation packages, I modeled the EDGES low-band antenna, including the ground plane and soil, and quantified its variations as a function of frequency. I compared simulated observations to sky data and obtained absolute agreement within 4% and qualitatively similar spectral structures.
I used the new open-source edges-analysis pipeline to carry out rigorous fits of the absorption feature on the same low-band data and lab calibration measurements as (Bowman et. al. 2018). Using a Bayesian framework, I tested a few calibration choices and found posteriors of the best-fit 21-cm model parameters well within the 1σ values reported in B18. To test for the ``global'' nature of the reported cosmic absorption feature, I performed a time-dependent analysis. Initial results from this analysis successfully retrieved physical estimates for the foregrounds and estimates of the cosmic signal consistent with previous findings.
The array layout of FARSIDE, a NASA probe-class concept to place a radio interferometer on the lunar farside, is a four-arm spiral configuration consisting of 128 dual-polarized antennas with a spatial offset between the phase centers of its orthogonal polarizations. I modeled the impact of direction-dependent beams and phase offsets on simulated observations of all four Stokes parameter images of a model and quantified its effects on the two primary science cases: 21-cm cosmology and exoplanet studies.
ContributorsMahesh, Nivedita (Author) / Bowman, Judd D (Thesis advisor) / Jacobs, Daniel C (Committee member) / Groppi, Christopher (Committee member) / Shkolnik, Evgenya (Committee member) / Windhorst, Rogier (Committee member) / Arizona State University (Publisher)
Created2022
Description
Several key, open questions in astrophysics can be tackled by searching for and
mining large datasets for transient phenomena. The evolution of massive stars and
compact objects can be studied over cosmic time by identifying supernovae (SNe) and
gamma-ray bursts (GRBs) in other galaxies and determining their redshifts. Modeling
GRBs and their afterglows to probe the jets of GRBs can shed light on the emission
mechanism, rate, and energetics of these events.
In Chapter 1, I discuss the current state of astronomical transient study, including
sources of interest, instrumentation, and data reduction techniques, with a focus
on work in the infrared. In Chapter 2, I present original work published in the
Proceedings of the Astronomical Society of the Pacific, testing InGaAs infrared
detectors for astronomical use (Strausbaugh, Jackson, and Butler 2018); highlights of
this work include observing the exoplanet transit of HD189773B, and detecting the
nearby supernova SN2016adj with an InGaAs detector mounted on a small telescope
at ASU. In Chapter 3, I discuss my work on GRB jets published in the Astrophysical
Journal Letters, highlighting the interesting case of GRB 160625B (Strausbaugh et al.
2019), where I interpret a late-time bump in the GRB afterglow lightcurve as evidence
for a bright-edged jet. In Chapter 4, I present a look back at previous years of
RATIR (Re-ionization And Transient Infra-Red Camera) data, with an emphasis on
the efficiency of following up GRBs detected by the Fermi Space Telescope, before
some final remarks and brief discussion of future work in Chapter 5.
mining large datasets for transient phenomena. The evolution of massive stars and
compact objects can be studied over cosmic time by identifying supernovae (SNe) and
gamma-ray bursts (GRBs) in other galaxies and determining their redshifts. Modeling
GRBs and their afterglows to probe the jets of GRBs can shed light on the emission
mechanism, rate, and energetics of these events.
In Chapter 1, I discuss the current state of astronomical transient study, including
sources of interest, instrumentation, and data reduction techniques, with a focus
on work in the infrared. In Chapter 2, I present original work published in the
Proceedings of the Astronomical Society of the Pacific, testing InGaAs infrared
detectors for astronomical use (Strausbaugh, Jackson, and Butler 2018); highlights of
this work include observing the exoplanet transit of HD189773B, and detecting the
nearby supernova SN2016adj with an InGaAs detector mounted on a small telescope
at ASU. In Chapter 3, I discuss my work on GRB jets published in the Astrophysical
Journal Letters, highlighting the interesting case of GRB 160625B (Strausbaugh et al.
2019), where I interpret a late-time bump in the GRB afterglow lightcurve as evidence
for a bright-edged jet. In Chapter 4, I present a look back at previous years of
RATIR (Re-ionization And Transient Infra-Red Camera) data, with an emphasis on
the efficiency of following up GRBs detected by the Fermi Space Telescope, before
some final remarks and brief discussion of future work in Chapter 5.
ContributorsStrausbaugh, Robert (Author) / Butler, Nathaniel (Thesis advisor) / Jansen, Rolf (Committee member) / Mauskopf, Phil (Committee member) / Windhorst, Rogier (Committee member) / Arizona State University (Publisher)
Created2019
Description
I present a multi-spectral analysis of the faint, uJy, radio source population in the James Webb Space Telescope North Ecliptic Pole Time Domain Field. Very Long Baseline Array pointings at the 127 brightest of ~2500 radio galaxies identified with the Very Large Array indicate active galactic nucleus contamination of approximately 9.45%. My estimates of 4.8 GHz brightness of this radio source population indicate an upper bound on this contamination of 10.6%. This is well within acceptable limits, in population studies, for the use of the radio-FIR relation in the JWST NEP TDF. This improves the utility of the field to the community by reducing the need for expensive FIR observations. I have also developed an extensive catalog of magnitudes and other data in visible bands of this population. My analysis in these bands does not give any conclusive criteria for distinguishing between AGN and SFGs. The strongest trends I do identify appear to be due to reddening by interstellar dust. Future follow-up will focus on characterizing individual sources in further depth.
ContributorsNolan, Liam (Author) / Jansen, Rolf (Thesis director) / Windhorst, Rogier (Committee member) / Barrett, The Honors College (Contributor) / School of International Letters and Cultures (Contributor) / School of Earth and Space Exploration (Contributor) / Department of Physics (Contributor)
Created2022-05