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Why IXO?

High-energy phenomena in the X-ray band characterize the evolution of cosmic structures on both large and small scales.

On the smallest scales, X-rays provide the only electromagnetic spectral signatures from the regions of strong gravity near black holes through absorption and emission features, such as the Fe Kalpha emission line at 6.4 keV and its profile [Brenneman et al.], and can penetrate the surrounding gas and dust allowing us to uncover the earliest massive black holes and measure their distances [Nandra et al.]. In neutron stars, X-ray spectra and light curves carry the observable imprints of exotic processes occurring in these objects [Paerels et al.].

WFI Simulation of the Chandra Deep Field South with Hubble Ultra Deep Field (HUDF) in inset. Simulated spectra of various sources are shown, illustrating IXO’s ability (clockwise from top left) to:

  1. determine redshift autonomously in the X- ray band,
  2. determine temperatures and abundances even for low luminosity groups to z<1,
  3. make spin measurements of AGN to a similar redshift,
  4. uncover the most heavily obscured, Compton-thick AGN.
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On the largest scales, X-rays are essential for detecting the “missing” 50% of baryons in the local Universe, as a probe of both dark energy and dark matter [Bregman et al.] and to measure the energy deposited in the surrounding medium by AGN’s jets and winds [Miller et al., Fabian et al.].

Building on a rich technological heritage, IXO will have improved instrumental capabilities beyond the current generation of X-ray missions (e.g. Chandra, XMM, RXTE, and Suzaku) in X-ray imaging, timing, and spectroscopy. Moreover, IXO will carry an X-ray polarimeter which will open a new window on the study of high-energy phenomena. See Requirements. These will enable observations that will address the above science issues among others with unprecedented detail and precision.

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See also

Before IXO: Con-X and XEUS out of section
Science performance requirements out of section
IXO technology drivers out of section

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Selected References

  1. Astro2010 Science White Paper (submitted to both CFP and GCT) Spin and Relativistic Phenomena Around Black Holes, Brenneman et al.
  2. The Growth of Supermassive Black Holes Across Cosmic Time, Nandra et al.
  3. The Behavior of Matter Under Extreme Conditions – A White Paper Submitted to the Astro2010 Decadal Survey of Astronomy and Astrophysics, F. Paerels et al.
  4. The Cosmic Web of Baryons, A White Paper submitted to Galaxies across Cosmic Time (GCT) and The Cosmology and Fundamental Physics (CFP) Science Frontiers Panels, Bregman et al.
  5. Astro2010 Science White Paper (GCT) – Fundamental Accretion and Ejection Astrophysics, Miller et al.
  6. Cosmic Feedback from Supermassive Black Holes, Fabian et al.