The majority of the baryons in the present-day universe are missing in thatthey are not in galaxies or as cool intergalactic gas (<1E5K). These baryons aremost likely diffuse gas at 1E6 - 1E7 K in regions of modest overdensity, and thesuperposition of many such regions can produce detectable X-ray emission thataccounts for about 10-30% of the X-ray background in the 0.2-1 keV range. Todetect this emission, we used the shadowing properties of the gas in the edge-ongalaxy NGC 891, and we find a shadow at the 99% confidence level, consistentwith a fraction of the XRB in a diffuse cosmic component. We propose additionalobservations of a better edge-on system, NGC 5907, to determine whether shadowsare universal and to better measure the level of this cosmic diffuse XRB.
Instrument
EMOS1, EMOS2, EPN, OM, RGS1, RGS2
Temporal Coverage
2003-02-20T15:33:39Z/2003-03-01T04:17:31Z
Version
17.56_20190403_1200
Mission Description
The European Space Agencys (ESA) X-ray Multi-Mirror Mission (XMM-Newton) was launched by an Ariane 504 on December 10th 1999. XMM-Newton is ESAs second cornerstone of the Horizon 2000 Science Programme. It carries 3 high throughput X-ray telescopes with an unprecedented effective area, and an optical monitor, the first flown on a X-ray observatory. The large collecting area and ability to make long uninterrupted exposures provide highly sensitive observations. Since Earths atmosphere blocks out all X-rays, only a telescope in space can detect and study celestial X-ray sources. The XMM-Newton mission is helping scientists to solve a number of cosmic mysteries, ranging from the enigmatic black holes to the origins of the Universe itself. Observing time on XMM-Newton is being made available to the scientific community, applying for observational periods on a competitive basis.
European Space Agency, Prof Joel Bregman, 2004, 'Shadowing the Diffuse Extragalactic X-Ray Background', 17.56_20190403_1200, European Space Agency, https://doi.org/10.5270/esa-15fmbmf
