Matching Items (3)
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- All Subjects: Radio
- Creators: Bowman, Judd
Description
Using data from the Arizona Radio Observatory Submillimeter Telescope, we have studied the active, star-forming region of the R Coronae Australis molecular cloud in 12CO (2-1), 13CO (2-1), and HCO+ (3-2). We baselined and mapped the data using CLASS. It was then used to create integrated intensity, outflow, and centroid velocity maps in IDL. These clearly showed the main large outflow, and then we identified a few other possible outflows.
ContributorsBlumm, Margaret Elizabeth (Author) / Groppi, Christopher (Thesis director) / Bowman, Judd (Committee member) / Mauskopf, Philip (Committee member) / Barrett, The Honors College (Contributor) / School of Earth and Space Exploration (Contributor)
Created2014-05
Description
In the upcoming decade, powerful new astronomical facilities such as the James Webb Space Telescope (JWST), the Square Kilometer Array (SKA), and ground-based 30-meter telescopes will open up the epoch of reionization to direct astronomical observation. One of the primary tools used to understand the bulk astrophysical properties of the high-redshift universe are empirically-derived star-forming laws, which relate observed luminosity to fundamental astrophysical quantities such as star formation rate. The radio/infrared relation is one of the more mysterious of these relations: despite its somewhat uncertain astrophysical origins, this relation is extremely tight and linear, with 0.3 dex of scatter over five orders of magnitude in galaxy luminosity. The effects of primordial metallicities on canonical star-forming laws is an open question: a growing body of evidence suggests that the current empirical star forming laws may not be valid in the unenriched, metal-poor environment of the very early universe.
In the modern universe, nearby dwarf galaxies with less than 1/10th the Solar metal abundance provide an opportunity to recalibrate our star formation laws and study the astrophysics of extremely metal-deficient (XMD) environments in detail. I assemble a sample of nearby dwarf galaxies, all within 100 megaparsecs, with nebular oxygen abundances between 1/5th and 1/50th Solar. I identify the subsample of these galaxies with space-based mid- and far-infrared data, and investigate the effects of extreme metallicities on the infrared-radio relationship. For ten of these galaxies, I have acquired 40 hours of observations with the Jansky Very Large Array (JVLA). C-band (4-8 GHz) radio continuum emission is detected from all 10 of these galaxies. These represent the first radio continuum detections from seven galaxies in this sample: Leo A, UGC 4704, HS 0822+3542, SBS 0940+544, and SBS 1129+476. The radio continuum in these galaxies is strongly associated with the presence of optical H-alpha emission, with spectral slopes suggesting a mix of thermal and non-thermal sources. I use the ratio of the radio and far-infrared emission to investigate behavior of the C-band (4-8 GHz) radio/infrared relation at metallicities below 1/10th Solar.
I compare the low metallicity sample with the 4.8 GHz radio/infrared relationship from the KINGFISHER nearby galaxy sample Tabatabaei et al. 2017 and to the 1.4 GHz radio/infrared relationship from the blue compact dwarf galaxy sample of Wu et al. 2008. The infrared/radio ratio q of the low metallicity galaxies is below the average q of star forming galaxies in the modern universe. I compare these galaxies' infrared and radio luminosities to their corresponding Halpha luminosities, and find that both the infrared/Halpha and the radio/H-alpha ratios are reduced by nearly 1 dex in the low metallicity sample vs. higher metallicity galaxies; however the deficit is not straightforwardly interpreted as a metallicity effect.
In the modern universe, nearby dwarf galaxies with less than 1/10th the Solar metal abundance provide an opportunity to recalibrate our star formation laws and study the astrophysics of extremely metal-deficient (XMD) environments in detail. I assemble a sample of nearby dwarf galaxies, all within 100 megaparsecs, with nebular oxygen abundances between 1/5th and 1/50th Solar. I identify the subsample of these galaxies with space-based mid- and far-infrared data, and investigate the effects of extreme metallicities on the infrared-radio relationship. For ten of these galaxies, I have acquired 40 hours of observations with the Jansky Very Large Array (JVLA). C-band (4-8 GHz) radio continuum emission is detected from all 10 of these galaxies. These represent the first radio continuum detections from seven galaxies in this sample: Leo A, UGC 4704, HS 0822+3542, SBS 0940+544, and SBS 1129+476. The radio continuum in these galaxies is strongly associated with the presence of optical H-alpha emission, with spectral slopes suggesting a mix of thermal and non-thermal sources. I use the ratio of the radio and far-infrared emission to investigate behavior of the C-band (4-8 GHz) radio/infrared relation at metallicities below 1/10th Solar.
I compare the low metallicity sample with the 4.8 GHz radio/infrared relationship from the KINGFISHER nearby galaxy sample Tabatabaei et al. 2017 and to the 1.4 GHz radio/infrared relationship from the blue compact dwarf galaxy sample of Wu et al. 2008. The infrared/radio ratio q of the low metallicity galaxies is below the average q of star forming galaxies in the modern universe. I compare these galaxies' infrared and radio luminosities to their corresponding Halpha luminosities, and find that both the infrared/Halpha and the radio/H-alpha ratios are reduced by nearly 1 dex in the low metallicity sample vs. higher metallicity galaxies; however the deficit is not straightforwardly interpreted as a metallicity effect.
ContributorsMonkiewicz, Jacqueline Ann (Author) / Bowman, Judd (Thesis advisor) / Scowen, Paul (Thesis advisor) / Mauskopf, Philip (Committee member) / Scannapieco, Evan (Committee member) / Jansen, Rolf (Committee member) / Arizona State University (Publisher)
Created2018
Description
The Hydrogen Epoch of Reionization Array, HERA, is a radio telescope currently being built in South Africa that plans to observe the early universe, specifically the earliest period of star and galaxy formation. It plans to use a tool called a delay spectrum to separate signal emitted from this time from the much brighter radio foregrounds. It is the purpose of this paper to outline the method used to characterize the contamination of these delay spectra by bright emissions of radio here on Earth called radio frequency interference, RFI. The portion of the bandwidth containing the signal from the period of initial star formation was specifically examined. In order to receive usable data, the HERA commissioning team was assisted in the evaluation of the most recent data releases. On the first batch of usable data, flagging algorithms were run in order to mask all of the RFI present. A method of filling these masked values was determined, which allowed for the delay spectrum to be observed. Various methods of injecting RFI into the data were tested which portrayed the large dependence of the delay spectrum on its presence. Finally, the noise power was estimated in order to predict whether or not the limitations observed in the dynamic range were comparable to the noise floor. By examining the evolution of the delay spectrum's power as a range of noise power was introduced, there is a good amount of evidence that this limitation is in fact the noise floor. From this, we see that excision algorithms and interpolation used are capable of removing the effects of most all of the RFI contamination.
ContributorsBechtel, Shane Kirkpatrick (Author) / Bowman, Judd (Thesis director) / Jacobs, Daniel (Committee member) / Beardsley, Adam (Committee member) / School of Earth and Space Exploration (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05