Kinematics at Cosmic Noon
Hello! I’m Cassidy Novack, a senior Physics-Astronomy major here at Whitman. The Whitman Internship Grant allowed me to spend my summer at the University of Texas at Austin to do high-redshift extragalactic research.
My project focuses on 5 star-forming galaxies that are located at a redshift of ~1-2, during a period in the Universe’s formation history known as cosmic noon. About ten billion years ago, galaxies began forming stars at a rate higher than ever observed, but we don’t exactly know why. Since star formation is fueled by the gas within the interstellar medium (ISM) in a galaxy, one way we can investigate this uniquely high star formation rate is to examine the gas, specifically the singly ionized carbon ([CII]) emission line at 157.7 microns. This line traces the cooling of gas within the ISM and has been observed to correlate well with the star-formation rate in galaxies. While [CII] normally emits light at a far-infrared wavelength, the distance from us to these galaxies causes the emitted light to be red-shifted into the radio regime, which means we can observe it through the Atacama Large Millimeter Array (ALMA). This is great for us because there is currently not an active far-infrared observatory!
Most of my project has been spent taking already-processed data from ALMA and running it through various astro computer programs or python code to create maps of the velocity of gas within the galaxies and the dispersion of that velocity. The ratio of velocity to velocity dispersion can help us classify the galaxy: a high ratio ( >1.5) would indicate that the galaxy is rotationally supported, and could be a spiral galaxy just like our Milky Way, while a low ratio would indicate that much of the movement within the galaxy is random, and the galaxy is likely an elliptical. Since galaxies at this distance from us are not easily identifiable by eye, we can use this clever method to get around that.
Since all of my work is done through my laptop, a typical work day consisted of me taking the bus to campus in the morning, going all the way up to the 16th floor of the Physics, Math, and Astronomy building, and sitting in a room with as pleasant as a vibe I could find to do my work. Depending on the day, I might then have my individual meeting with my advisor or a group meeting with the other researchers in my group to share what we each have been working on.
Additionally, I spent one week out of the summer in West Texas at the McDonald Observatory to learn how to conduct an observing run at the Harlan J. Smith Telescope (HJST). It was amazing to see how big these telescopes are in comparison to the observatories we have at Whitman; the HJST is 2.7 meters across, and the Hobby-Eberly Telescope’s (HET) mirror is 11 meters across! See photo of a freshly cleaned mirror segment of the HET, one of 91 segments that make up the entire mirror.