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Physics & Astronomy Colloquium
October 18 @ 3:30 pm - 5:00 pm
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.