The following papers concluded two PhD theses in Physics (Astronomy
subtrack) at the University of Iowa. Congratulations, Dr. Joshua Steffen and Dr. Arran Gross!
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I am part of an international team who discovered the highly variable magnetised environment of an extremely active fast radio burst in a distant galaxy. I contributed to the analysis of the optical spectra of the host galaxy 1.4 billion lightyears away and the background (possibly lensed) galaxy. I also...
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In Fall 2021 and Spring 2022, two undergraduate students helped me commission a longslit spectrograph on the 17-in telescope (PlaneWave CDK17) at the Van Allen Observatory (VAO). The LISA Spectrograph is made by Shelyak Instruments. The spectrograph bundle includes the spectrograph optics, a small CCD camera for target acquisition, a...
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The important role played by collisions and mergers in galaxy evolution has been appreciated since the 1970’s. Previous spectroscopic studies of colliding/merging galaxies, while confirming several basic predictions (e.g., elevated nuclear star formation and/or black hole accretion), generally explored only their brighter inner-most regions in a largely non-uniform manner. This...
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Using absorption lines in the spectra of two background quasars and deep ALMA observations in CO, our group discovered a cold gas stream in a massive dark matter halo. The stream is made of gas that is extremely poor in heavy elements. The detection signifies that massive starburst galaxies existed...
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For the first time, we used the CO Tully-Fisher relation and a Bayesian statistical method to show the dramatic evolution in gas content of star-forming galaxies, confirming previous result that galaxies were much more gaseous billions of years ago. This new method avoids correcting the inclination angles of the galaxies...
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This study utilizes extremely deep high-resolution data from the Atacama Large Millimeter / submillimeter Array (ALMA). Various molecules (e.g., water, carbon monoxide) are detected in a pair of dusty starburst galaxies called ‘HXMM01’, a mega-merger that occurred 10 billion years ago (see news story on Los Angeles Times). In both...
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The NSF-funded augmented-reality sandbox, dubbed “Gravbox,” is the first interactive system of its kind to be used for astrophysics. Read the news story. For more information, see the Gravbox Website.
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