Two papers published by an assistant professor at the University of California, Riverside and several collaborators explain why the universe has enough energy to become
transparent1. The study led by Naveen Reddy, an assistant professor in the Department of Physics and Astronomy at UC Riverside, marks the first
quantitative2 study of how the gas content within
galaxies3 scales with the amount of interstellar dust.
This analysis shows that the gas in galaxies is like a "
picket4 fence," where some parts of the
galaxy5 have little gas and are directly visible, whereas other parts have lots of gas and are effectively
opaque6 to ionizing radiation. The findings were just published in The Astrophysical Journal.
The ionization of hydrogen is important because of its effects on how galaxies grow and evolve. A particular area of interest is assessing the contribution of different astrophysical sources, such as stars or black holes, to the budget of ionizing radiation.
Most studies suggest that faint galaxies are responsible for providing enough radiation to ionize the gas in the early history of the universe. Moreover, there is anecdotal evidence that the amount of ionizing radiation that is able to escape from galaxies depends on the amount of hydrogen within the galaxies themselves.
The research team led by Reddy developed a model that can be used to predict the amount of escaping ionizing radiation from galaxies based on
straightforward7 measurements on how "red," or dusty, their
spectra8 appear to be.