Collaborative Research: Finding the Gas that Lights up Galaxies

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Damped Lyman-alpha (DLA) systems, layers of low-ionization gas with neutral hydrogen column densities characteristic of modern, gas-rich galaxies, are frequently detected in spectra of background quasars. DLA systems are important probes of the history of galaxy formation and heavy-element enrichment in the universe. The proposing team plans to continue their ongoing work on DLA systems in this project, which has three major components: (1) A survey for DLAs at redshifts near 5. The team will measure ionic column densities, in order to track the build-up of metals in these first galaxies and the evolution of the neutral gas, and will search for a decrease in ionization level close to the re-ionization epoch. (2) A search for 158-micron emission from singly-ionized carbon in galaxies at redshifts near 2, using the ALMA observatory. The targeted galaxies are already known to have [CII] absorption; ALMA observations will connect properties of the gas detected in emission and in absorption to constrain their sizes, dynamics, and star formation rates. Numerical simulations will also be used to predict the [CII] emission properties of galaxies at higher redshift. (3) Imaging far ultraviolet (FUV) light from DLAs. The team will use stacked images of Lyman-break galaxies at redshifts between 1 and 5 identified in the Hubble ultra-deep field to search for low surface-brightness emission. They plan also to exploit the chance alignment of a DLA with a higher redshift, optically-thick absorber to obtain imaging and spectroscopy of the star-forming regions in the FUV and estimate the star formation rate, size and morphology of the galaxy. The project will support the work and training of two graduate students, and the collaborating Principal Investigators will participate in outreach talks in various venues, including a charter minority-serving high school and a science festival for middle school girls. They maintain a public website dedicated to DLA science targeted to both the general public and the research community. The team intends to release all of the high-resolution spectra obtained in this program through the website within 2 years of the first observations.