This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
Dr. Madau and his team will combine observations of the gas from which the galaxies were formed with theoretical and numerical studies of the state of that gas. The intergalactic gas is ionized by the ultraviolet light from short-lived massive stars and from the active nuclei of galaxies, so the amount of neutral gas tells us about past star formation, and about the black holes that lie at the centers of galaxies and power their active nuclei. To set limits on this ionizing light at times when the cosmos had expanded only to a quarter of its present size, the team will examine the spectra of quasars dating from this period, and make a census of the deep absorption lines of neutral hydrogen in their light. They will take infrared spectra of even more distant quasars to measure the absorption lines of heavier elements that are produced in stellar interiors, to examine how rapidly these were produced from stars and flung into the intergalactic gas. By looking at spectra of pairs of quasars that are nearby on the sky, the team will study gas around the nearer quasar by its absorption of the light of the more distant object.
The team will improve CUBA, a one-dimensional radiative transfer code, and release it to the public. This code will be used to trace ionizing photons as they propagate through models of the cosmos that follow both the invisible dark matter and the gas, as gas condenses into star-forming galaxies. These calculations will also consider the effect of galactic winds in blowing the metals formed in the stars out into the intergalactic gas.
A graduate student and a postdoc will be trained by participating in the research. Team members expect to mentor undergraduate researchers, and to take part in a summer program for talented undergraduates from low-income families. The upgraded CUBA code will be released to the astronomical community, and visualizations from the simulation runs will be available for public outreach.
