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Departmental Colloquium

The Arcus Soft X-ray Grating Explorer  
Guest Speaker
Dr. Randall Smith  
Guest Affiliation
Smithsonian Astrophysical Observatory, Harvard  
Prof. Phillip Stancil  
Thursday, November 2, 2017 3:30 pm - 4:30 pm  
Physics Auditorium (Rm 202)  

The Large Scale Structure (LSS) of the Universe grew via the gravitational collapse of dark matter, but the visible components that trace the LSS-galaxies, groups and clusters-have a more complex history. Their baryons experience shock heating, radiative cooling and feedback from black holes and star formation, which leave faint signatures of hot (T~10^5-10^8 K), metal-enriched gas in the interstellar and intergalactic media (ISM and IGM). While recent Planck and X-ray studies support this scenario, no current mission possesses the instrumentation necessary to provide direct observational evidence for these “missing baryons.” Arcus leverages recent advances in critical- angle transmission (CAT) gratings and silicon pore optics (SPOs), using CCDs with strong Suzaku heritage and electronics based on the Swift mission; both the spacecraft and mission operations reuse highly successful designs. Currently in a competitive Phase A and with a potential launch in 2023, Arcus will be the only observatory capable of studying, in detail, the hot galactic and intergalactic gas-the dominant baryonic component in the present-day Universe and ultimate reservoir of entropy, metals and the output from cosmic feedback. Its superior soft X-ray sensitivity will complement the forthcoming post-Hitomi and Athena calorimeters, which will have comparably high spectral resolution above 2 keV but poorer spectral resolution than XMM or Chandra in the Arcus bandpass.