"Counting all the SHEEP": A summary of the past and present work associated with ASCA’s The Search for the High-Energy Extragalactic Population (SHEEP) survey.
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SubjectX-ray astronomy; Astrophysics; CHANDRA (Computer file); ROSAT (Artifical satellite); SHEEP survey; ASCA (Artificial satellite); Active Galactic Nuclei (AGN)
SHEEP is the Search for the High-Energy Extragalactic Population, a survey of X-rays sources found in 5-10 keV band images from the ASCA satellite. Because hard X-rays are difficult to obscure, SHEEP provides a largely unbiased accounting of the AGN population. We have been identifying SHEEP using new high-resolution Chandra images, and following up with deep optical imaging from Greece and near-infrared imaging from Wyoming. Spectral classifications are obtained at NOAO 4-meter telescopes. Our initial work shows a wide variety of optical classes, ranging from QSOs to optically normal galaxies (despite their high X-ray luminosities). We have also identified several high-redshift quasar pairs, which is intriguing given the size of the sample. Completion of identifications and classifications will permit us to finally "count the SHEEP" and provide a better picture of the AGN population and the sources contributing to the X-ray background.
Tim Weinzirl is a junior at Drake University, majoring in Physics and Astronomy. He presented this poster session at DUCURS (Drake University Conference on Undergraduate Research in the Sciences) held on the Drake campus on April 15, 2005.