HUBS: a dedicated hot circumgalactic medium explorer
Space Telescopes and Instrumentation: Ultraviolet to Gamma Ray
Abstract
The Hot Universe Baryon Surveyor (HUBS) mission is proposed to study “missing” baryons in the universe. Unlike dark matter, baryonic matter is made of elements in the periodic table, and can be directly observed through the electromagnetic signals that it produces. Stars contain only a tiny fraction of the baryonic matter known to be present in the universe. Additional baryons are found to be in diffuse (gaseous) form, in or between galaxies, but a significant fraction has not yet been seen. The latter (“missing” baryons) are thought to be hiding in low-density warm-hot ionized medium (WHIM), based on results from theoretical studies and recent observations, and be distributed in the vicinity of galaxies (i.e., circumgalactic medium) and between galaxies (i.e., intergalactic medium). Such gas would radiate mainly in the soft X-ray band and the emission would be very weak, due to its very low density. HUBS is optimized to detect the X-ray emission from the hot baryons in the circumgalactic medium, and thus fill a void in observational astronomy. The goal is not only to detect the “missing” baryons, but to characterize their physical and chemical properties, as well as to measure their spatial distribution. The results would establish the boundary conditions for understanding galaxy evolution. Though highly challenging, detecting “missing” baryons in the intergalactic medium could be attempted, perhaps in the outskirts of galaxy clusters, and could shed significant light on the large-scale structures of the universe. The current design of HUBS will be presented, along with the status of technology development.
Authors 3
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Tsinghua University · Technical Institute of Physics and Chemistry
Affiliation as printed
Technical Institute of Physics and Chemistry (China)
Tsinghua Univ. (China)
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Space Research Organisation Netherlands
Affiliation as printed
SRON Netherlands Institute for Space Research (Netherlands)
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Space Research Organisation Netherlands
Affiliation as printed
SRON Netherlands Institute for Space Research (Netherlands)
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