Ultraviolet observations of galaxy clusters unlock structures invisible to x-rays
This project is the product of a recent collaboration with Joe Burchett, Daisuke Nagai, Michael Tremmel, Tom Quinn, and Jessica Werk. Check out the full text on the arXiv!
Galaxy clusters govern galaxy evolution
Galaxy clusters are the largest gravitationally-bound structures in the Universe, composed of hundreds, or even thousands of galaxies. The space between galaxies in a cluster is composed of a hot, dense gas known as the intracluster medium (ICM). Compared to isolated galaxies, cluster galaxies have less gas in their disk and halo and are more likely to have stopped forming stars. Although astronomers know that the cluster environment is responsible for this difference, the exact mechanisms are not well-understood. One way to constrain the mechanisms responsible for stripping cluster galaxies of their gas is to study the structure of the ICM for clues about its history.
Traditionally, cluster galaxies have been studied by observing the hot phase of the ICM in X-ray emission. However, the ICM is highly multiphased - it contains gas spanning several orders of magnitude in temperature and density. Studying the different phases of the ICM can place stringent constraints to theories of the role of environment on galaxy evolution. Although the diffuse, cool/warm ICM gas is virtually invisible to X-rays, it can be observed indirectly through UV absorption. In this work, we demonstrate the properties of the multiphase ICM, make testable predictions for UV observations,and discuss future observational prospects.
Figure 1: The RomulusC cluster simulation at a redshift of 0.31. The top row shows quantities of the cluster that are readily available simulations: the gas density, temperature, and metallicity. However these properties cannot be directly observed and must be inferred from careful modeling. The bottom row shows quantities that can be directly observed: the X-ray emission and the O VI and H I absorption column density. X-ray emission traces the hot, dense intracluster medium, which has a dramatically different structure from the diffuse, cool-warm gas traced by absorption in the UV.