This collaboration, led by Dr. A.Wolfe, will examine the relationship between neutral gas and young stars at high redshift, by applying diagnostic tools developed for the local interstellar medium (ISM). Most of what we know about star formation in high-redshift galaxies stems from observing them in emission, but damped Lyman-alpha systems (DLAs) are detected in absorption against quasars. In general, these galaxies are more representative than any other high-redshift objects detected in emission. This study will (1) discover and analyze over 1000 new DLAs, identifying a large sample of galaxies for ISM research, (2) triple the number of DLAs with detected carbon-II absorption in the ultraviolet, to measure the gas cooling and heating rates, (3) pursue preliminary observations of carbon-II emission in the sub-millimeter wavelength range, coming from the cold neutral gas in DLAs, to determine the sizes and masses of high-redshift galaxies, (4) search for Hydrogen-alpha emission from DLAs, mapping the velocity field of the ionized gas for evidence of galaxy rotation, (5) measure the temperature, density, molecular content and multi-phase structure of the ISM in young galaxies, and finally, (6) measure magnetic fields in intermediate-redshift DLAs by detecting Zeeman splitting in the 21-cm absorption lines using the Green Bank Telescope.
The impact of DLA science has steadily grown beyond the field of quasar absorption lines, to include chemical evolution and nucleosynthesis in the early Universe, variations in the fine-structure constant; and global constraints on critical aspects of galaxy formation. The present research will therefore be widely disseminated to the astronomical population, and beyond to the general education community through an advanced Web site. In addition, support for graduate students and exposing undergraduates to cutting-edge research are staple activities of these researchers.
The purpose of this document is to provide a brief summary of the nature and results of our NSF funded project AST 0709235 entitled "Collaborative Research: Exploring Star Formation in the Early Universe through Investigations of High-Redshift ISM". This project supported the efforts of Professors A. M. Wolfe at the University of California, San Diego and J. X. Prochaska at the University of California, Santa Cruz. The goal of this projct was to study the gas responsible for star formation in high-redshift galaxies. Specifically we focused on a class of objects named "the damped Lyα absorption systems" (DLAs). These objects are distinct from the bulk of the galaxies detected in the early universe in that their detection is based on the amount of cold, neutral gas they contain rather than on the brightness of the starlight that they emit. The DLAs are detected by the spectroscopic imprint that the neutral gas leaves on the light emitted by quasars that lie behind them; i.e., an absorption line arising from neutral hydrogen and several lines arising from abundant elements such as carbon, iron, silicon, etc. In fact DLAs have dominated the neutral-gas content of the Universe for that past 12 billion years, i.e., for most of the time elapsed since the Big Bang. The importance of cold, neutral gas is that it provides the conditions necessary for new stars to form. Because the gas in DLAs is detected in absorption against the bright light emitted by background quasars, DLAs need not be embedded in luminous galaxies. Indeed, DLAs are expected to trace star formation and as well as other processes in objects that are representative of the full mass distribution of galaxies in the early Universe rather than the rare, ultra-luminous galaxies typically found in surveys based on the direct detection of starlight. The original proposal identified several key lines of research that would help us to better understand the evolution of early galaxies. In particular our goals were to probe physical conditions in their interstellar media (ISM), i.e., in the diffuse gas occupying the space between the stars, and the interactions between stars and gas in such objects.
