Physics & Astronomy Colloquium

Speaker: Max Bonamente  (University of Alabama, Huntsville)

Title: X-ray absorption lines from the Warm-Hot intergalactic medium (WHIM) and the missing baryons in the low-redshift universe

Abstract: Approximately 50% of the ordinary matter is unaccounted for in the local universe. At high redshift, most of the baryons are in diffuse Lyman-alpha clouds, while at low redshift only a portion of that mass is successfully detected. There is theoretical and observational evidence that the missing baryons are in a diffuse plasma that stretches across galaxies, the so-called warm-hot intergalactic medium (WHIM). The cooler portion of the WHIM has been successfully detected via Far Ultra-Violet detectors. The hotter portion is just now being investigated with X-ray grating spectrometers on board the two major X-ray satellites, Chandra and XMM.
A new detection of extragalactic OVIII K-alpha, tentatively associated with the WHIM, is presented, along with challenges and prospects for the future.