Investigating Low Surface Brightness Objects Identified in the Subaru Survey

The goal of this project is to use the Green Bank Telescope (GBT) to measure the HI spectra of 25 low surface-brightness galaxies (LSBs) detected by the Subaru telescope through the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP or HSC), specifically potential ultra-diffuse galaxies (UDGs). The HSC was an optical survey, so while it detected 781 LSBs, it did not collect spectral information, meaning the distances are mostly unknown. Being a radio telescope, the GBT will be able to take spectra on these objects, allowing us to measure the redshift of the 21 cm HI emission line. From the redshift, we can determine the distance, and therefore absolute brightness and mass, as well as how much neutral hydrogen gas (HI) the galaxy contains. Since HI is the material used in star formation, so knowing that gas content is critical to understanding its formation and evolution. Leisman et al. 2017 found that UDGs in non-cluster environments had an unusually high HI content, but the fact that the objects were radio-selected (which biases results towards HI-rich galaxies) makes it difficult to tell how typical that is. The main goal of this project is to the galaxies observed in Leisman et al. 2017 are the norm for UDGs, by looking at the gas content of optically-selected galaxies, which is another (potentially substantial) piece in the puzzle of figuring how and why these unusual galaxies form