Dr. Jason Prochaska at the University of California, Santa Cruz (UCSC) will undertake a program that involves investigations of damped Ly-a (DLA) systems. Additionally the PI will undertake a survey of chemical abundances in the Galactic thick disk, an analysis of the differential chemical depletion in the Milky Way, spectroscopy of gamma-ray burst afterglows, and abundance analyses of a modest sample of high redshift DLA systems. These projects will allow Dr. Prochaska to establish a comprehensive program for studying nucleosynthesis and galaxy formation during the first few Gyr of the universe.
Dr. Prochaska will also undertake a science education program designed to promote inquiry-based learning in high schools. The context for the program will be astronomical spectra, which provides for an integration of the research tool he and his colleagues use with his educational efforts. The program will have two main activities: 1) inquiry-based learning in several Santa Cruz high school classrooms; and 2) teacher symposia in inquiry learning held on UCSC campus
The formation of heavy elements (e.g. carbon, oxygen, iron; also referred to as "metals" by astronomers), including the ingredients of life, is known to occur in stars which themselves have formed in galaxies over the past 10 billions years. The actual timing of this enrichment and an understanding of the contributions of various processees of nucleosynthesis is not well understood. As such, it is a highly active area of research in modern astrophysics. The focus of this program was to assess the chemical enrichment of gas in the early universe, primarily in young galaxies. Our experiment is unconventional: we obtain spectroscopy of the most distant, intrinsically luminous sources whose light coincidentally travels through gas in a galaxy (between us and the light source). The hydrogen and heavy elements in this gas absorb a fraction of the light, imprinting signatures in the spectrum that reveal the gas' enrichment, chemical patterns, and other valuable physical diagnostics. This project primarily funded new observations with the Keck 10m telescopes on Mauna Kea, Hawaii of distant quasars -- supermassive black holes that shine with terrific luminosity. Analysis on the high resolution spectroscopy of these quasars yielded a terrific set of results on the enrichment of gas in the young universe. The primary results of this research included: (1) at early times, heavy elements are produced by stars at a rapid rate such that the enrichment of galaxies doubles approximately every billion years; (2) the youngest galaxies studied are usually highly deficient in heavy elements (e.g. 1/100 that of our Sun) but surprisingly are never entirely devoid of metals. This implies a very early episode of stellar nucleosynthesis; (3) although very rare, pockets of primordial (metal-free) gas do exist and have properties consistent with modern theories of the nucleosynthesis that occurs just a few minutes after the Big Bang; (4) There is a rare but valuable set of galaxies just a few billion years old that are as chemically mature as our own galaxy. The other main research of this program was to study the light from the explosions of massive stars in young, star-forming galaxies. The bursts of emission (termed Gamma-Ray Bursts or GRBs) are amongst the most energetic events known and enable studies of gas to the edge of the universe. Spectroscopic analysis of these events revealed: (i) stars in the early universe occur in environments that are very similar to those in lower mass galaxies of the modern universe; (ii) such observations occasionally reveal molecules of hydrogen and carbon monoxide as well as signatures of dust. This material will fuel future star-formation and possibly the growth of planets. This grant also enabled the mentoring of 2 postdoctoral fellows, 4 PhD graduate students, and one undergraduate at UC Santa Cruz. Each was engaged in all aspects of scientific research: experimental design, data acquisition, data analysis, the preparation of publications, and oral presentation. Several of these persons were also very active in K-12 education, bringing their passion for science to the classroom.
