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Proceedings Paper

NEW: a mission to explore the warm-hot intergalactic medium
Author(s): Jan-Willem den Herder; Jelle S. Kaastra; Frits B. S. Paerels; Piet A. J. de Korte; Lucien Kuiper; Henk F. C. Hoevers; Wim Hermsen; Mariano Mèndez; Steven M. Kahn; Andrew P. Rasmussen
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Paper Abstract

The most recent observations of the cosmic microwave background (e.g., WMAP) show that baryons contribute about 4% to the total density of the Universe. However at redshift less than or equal to 1, about half of these baryons have not yet been observed. Cosmological simulations predict that these "missing" baryons should be distributed in filaments, have temperatures of 105 to 107 K and overdensities of a few to hundred times the average baryon density, forming the so-called Warm-Hot Intergalactic Medium (WHIM). There is increasing evidence from Chandra and XMM-Newton that the WHIM may indeed exist. However it is clear that to map the morphology of the WHIM and to measure its physical conditions, a completely different class of instruments is required. Measuring the WHIM in emission in the soft X-ray band is a promising option. To detect the relatively weak, extended emission of the WHIM, the instrument should have a large grasp (collecting area times field of view), and an energy resolving power of about 500 at 1 keV is required to separate the emission of these large scale filaments from foreground emission. We discuss a design that includes X-ray mirrors in combination with a large 2D cryogenic detector, which will allow us to map a significant fraction of this gas. Such detector and its read-out based on Frequency Domain Multiplexing, are currently under development at SRON. It seems feasible to build an array of 24 x 24 pixels of TES microcalorimeters with good energy resolution (few eV). This detector will be combined with a mirror design which is based on 2 and 4 reflections and gives a large area (> 500 cm2) over a relatively large field of view. A preliminary study of the mission concept indicates that this can be implemented in a relatively small satellite (total weight 650 kg). While the main goal of this satellite will be to map and study the physical properties of the missing baryons, the instrument's large area and large field of view will also result in major progress in related fields.

Paper Details

Date Published: 13 June 2006
PDF: 12 pages
Proc. SPIE 6266, Space Telescopes and Instrumentation II: Ultraviolet to Gamma Ray, 62660H (13 June 2006);
Show Author Affiliations
Jan-Willem den Herder, Netherlands Institute for Space Research (Netherlands)
Jelle S. Kaastra, Netherlands Institute for Space Research (Netherlands)
Frits B. S. Paerels, Columbia Astrophysics Lab. (United States)
Piet A. J. de Korte, Netherlands Institute for Space Research (Netherlands)
Lucien Kuiper, Netherlands Institute for Space Research (Netherlands)
Henk F. C. Hoevers, Netherlands Institute for Space Research (Netherlands)
Wim Hermsen, Netherlands Institute for Space Research (Netherlands)
Mariano Mèndez, Netherlands Institute for Space Research (Netherlands)
Steven M. Kahn, Stanford Linear Accelerator Ctr. (United States)
Andrew P. Rasmussen, Stanford Linear Accelerator Ctr. (United States)

Published in SPIE Proceedings Vol. 6266:
Space Telescopes and Instrumentation II: Ultraviolet to Gamma Ray
Martin J. L. Turner; Günther Hasinger, Editor(s)

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