Why I Stopped Waiting for Someone Else to Map the Warm-hot Circumgalactic Medium

Prof. Carlos Vargas (University of Arizona)
Tuesday, December 7, 2021 - 11:00am

For over half a century, observational astrophysics has been eager to successfully detect and map the most massive baryonic component of galaxies: warm-hot phase coronal gas extending into the circumgalactic medium (CGM). Despite its importance to galaxy evolution, this phase of gas is entirely unmapped in the nearby universe. Morphological characteristics, such as the presence, size, and extent of filamentary or cloud-like structures, are impossible to determine through pencil-beam absorption line studies. The evolution of galaxies relies heavily on the properties of gaseous halos, indicating an urgent need to map and measure these understudied regions. In the last decade, high-efficiency reflective coatings for UV optics have experienced improvements in reflectivity per bounce and overall coating stability in the far UV (FUV). Detector technology sensitive to FUV wavelengths has seen steady development of Microchannel Plate (MCP) detector technology. In parallel with these advances in UV technology, SmallSat missions with serious science objectives—which did not exist a decade ago—have emerged as a promising platform for high-impact science, an opportunity for more adventurous experiments and investigations. In this talk, I present Aspera (PI C. Vargas): a FUV SmallSat mission to detect and map warm-hot phase gas emission in nearby galaxies for the first time. The Aspera mission is designed to target the O VI emission line doublet from highly ionized oxygen, located at ll=1032, 1038 Å rest frame. Aspera combines a simple spectroscopic optical design using advances in highly-reflective FUV-coated optics with advanced UV MCP detectors to optimize throughput and sensitivity. Aspera will build multiple days of exposure time on each individual target to ensure spectroscopic detection of O VI emission and produce 2D morphological maps and direct measurements of physical conditions such as kinematics. The Aspera concept was recently selected for funding in the inaugural 2020 NASA Astrophysics Pioneers Program ($20M) in January of 2021.

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