The CODEX of the Milky Way

Space Science Institute, Boulder CO

Investigators

Abstract

Stars are the basic building blocks of galaxies like our own Milky Way. Understanding galaxy evolution, and indeed the history of the universe, requires a thorough understanding of how different types of stars change with time. Stars have their own life cycle, from stellar birth in cold clouds, through their maturity as the stars we see at night, to their ends as red giants or sometimes spectacular supernovae. The process of forming stars, however, is still poorly understood, mainly due to the difficulty in observing the processes that take place inside cold, dark molecular clouds which visible light cannot penetrate. Instead, astronomers use longer-wavelength radiation, like infrared light or radio waves, to discover important details of star formation, including the temperature, density and abundances of elements that are needed to form molecules. The investigator will share their research with the public in a striking way, by launching a “science+art” outreach effort to schoolchildren, emphasizing the important connections between science and art for the general public's appreciation, and increasing the impact of this research. A primary goal of the investigator’s research is testing models for molecular emission in the galaxy, based on maps of mm-wave emission from carbon monoxide (CO) molecules in clouds. Astronomers make CO observations of the Milky Way because the molecule is widespread and relatively easy to observe. The investigator has recently published research suggesting simple interpretations of CO mapping may be subtly misleading our understanding of the physical conditions in clouds, which are mostly made up of molecular hydrogen (H2) that is very difficult to detect directly. In short, the CO maps can be biased in tracing H2. The investigator will complete and release to the community their molecular line survey of the Milky Way as the Combined Dense Gas and Excitation Atlas of the Milky Way (the CODEX). In addition, they will provide a more sophisticated calculation of the physical conditions in molecular clouds, something which has not been attempted before excepting on much smaller scales. This will allow astronomers to better understand how the H2 molecules assemble under the influence of gravity to make stars throughout the Milky Way, and by extension, in other spiral galaxies. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.