PI: Rik J. Williams, Carnegie Institution for Science, email@example.com
Address: The Observatories, 813 Santa Barbara St., Pasadena, CA 91101, USA
CoI: John Mulchaey, Carnegie Observatories
Title: Finding the galactic counterparts to low-redshift X-ray absorption systems
Abstract: Several recent studies have claimed detection of the warm-hot intergalactic medium (WHIM) at z\lesssim 0.1 through UV and X-ray absorption lines from highly-ionized metals, possibly tracing the ``missing'' cosmic baryons in the local universe. But the mere presence of 10^6 K gas is not sufficient proof of the WHIM's existence since such gas can also arise in galaxies and galactic winds, groups, cluster outskirts, and other environments. To better understand the origin of these absorbers, we are undertaking a project combining archival Chandra observations of nearby AGN sightlines with multi-object Magellan spectroscopy of galaxies around these sightlines. Interestingly, our initial results suggest that X-ray ``WHIM'' absorbers in fact lie mostly in or near bound halos (like individual galaxies and groups). However, the most compelling WHIM detections are in the ultradeep Chandra spectrum of Mrk 421, too far north to reach with Magellan. We thus request two nights with WIYN/Hydra to survey galaxies around this one-of- a-kind sightline, determining the true nature of the absorbers therein.
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