How does cosmic feedback work and influence galaxy formation?

« For outflows that are radiatively accelerated in AGN, X-ray observations will determine the total column density and flow velocity, and hence the kinetic energy flux. IXO will be sensitive to ionization states from Fe I to Fe XXVI over a wide redshift range, allowing the first determination of how feedback affects all phases of interstellar and intergalactic gas, from million-degree collision-ionized plasmas to ten-thousand degree photo-ionized clouds. These measurements will probe over 10 decades in radial scale, from the inner accretion flow where the outflows are generated, to the halos of galaxies and clusters where the outflows deposit their energy.

In the centers of many galaxy clusters, the radiative cooling time of the X-ray-emitting gas is much shorter than the age of the system. Despite this, the gas there is still hot. Mechanical power from the central AGN acting through jets is thought to somehow compensate for the energy lost across scales of tens to hundreds of kpc. IXO will map the gas velocity across dozens of galaxy clusters to an accuracy of tens of km/s, revealing how the mechanical energy is spread and dissipated.

Selected References

A.M.Bykov, Yu.A.Uvarov, J.B.G.M.Bloemen, J.W. den Herder, J.S.Kaastra, "A Model of Polarized X-ray Emission from Twinkling Synchrotron Supernova Shells", MNRAS (in press), 2009. Download PDF

For more information, refer to IXO Astro 2010 Decadal White Papers:

• Cosmic Feedback from Massive Black Holes, A. Fabian et al.
• Fundamental Accretion and Ejection Astrophysics, Miller et al.