Missing cosmic metals revealed by X-ray absorption towards distant sources
Journal
Date Issued
2015
Author(s)
Description
We acknowledge useful discussions with E. Feigelson, F. Gastaldello, A. Moretti, L. Sage.
Abstract
The census of heavy elements (metals) produced by all stars through cosmic times up to present-day is limited to ≲ 50%; of these only half are still found within their parent galaxy. The majority of metals is expelled from galaxies into the circumgalactic (or even more distant, intergalactic) space by powerful galactic winds, leaving unpleasant uncertainty on the amount, thermal properties and distribution of these key chemical species. These dispersed metals unavoidably absorb soft X-ray photons from distant sources. We show that their integrated contribution can be detected in the form of increasing X-ray absorption with distance, for all kinds of high-energy cosmic sources. Based on extensive cosmological simulations, we assess that ~10% of all cosmic metals reside in the intergalactic medium. Most of the X-ray absorption arises instead from a few discrete structures along the line of sight. These extended structures, possibly pin-pointing galaxy groups, contain million degree, metal-enriched gas, 100-1000 times denser than the cosmic mean. An additional ~10% of cosmic metals could reside in this phase.
Appendix A is available in electronic form at http://www.aanda.org
Volume
575
Start page
A43
Issn Identifier
0004-6361
Ads BibCode
2015A&A...575A..43C
Rights
open.access
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