IAU Focus Meetings (GA)

FM 6: X-ray Surveys of the Hot and Energetic Cosmos

Start date/time

August 5, 2015

End date/time

August 6, 2015


United States


Andrea Comastri

Event website


Coordinating Division

Division D High Energy Phenomena and Fundamental Physics

Other Divisions:


Co-Chairs of SOC:
Andrea Comastri (INAF-OABO )
C. Megan Urry (Yale University)


  • Super Massive Black Hole (SMBH) demography and growth: uncovering the entire AGN population.
  • The light-up and early evolution of the first SMBH.
  • SMBH accretion physics and nuclear environment physics.
  • Connections between AGN activity and host galaxies and large-scale structures.
  • X-raying AGN feedback.
  • Resolving the X-ray background.
  • Cosmic evolution of hard X-ray sources in starburst and normal galaxies.
  • X-ray clusters as cosmological probes.
  • Physics of groups and clusters.
  • Future prospects for X-ray survey missions/instruments.


X-ray surveys are playing a key role in our understanding of the hot and energetic component of our Universe. Since their launch, in 1999, both XMM-Newton and Chandra surveys have transformed our understanding of the sources of the Cosmic X-ray Background, including their cosmological evolution and the physical processes shaping their properties. Combining data from deep and wide surveys covering a wide portion of the luminosity redshift plane, the most reliable and unbiased census of AGN is obtained. Furthermore a large number of starburst and normal galaxies, as well as galaxy clusters and groups are routinely detected.

Detailed investigations of the physics and evolution of X-ray selected sources were addressed thanks to massive observations along the entire electromagnetic spectrum (COSMOS, ECDFS, AEGIS, etc). The X-ray survey science is still actively pursued by the scientific community and well received by XMM and Chandra Time Allocation Committee who have recently granted major programs (i.e. the Chandra Ultradeep 7Ms Survey in the CDFS and the 3Ms COSMOS Legacy Survey; and the Large area surveys with XMM: XXL and Stripe82X).

The launch of NuSTAR in 2012, with its imaging capabilities at > 8 keV, is providing a unique opportunity to map the third dimension of the luminosity-redshift-obscuration space at limiting fluxes more than two orders of magnitude fainter than those reached by non imaging Swift/BAT and INTEGRAL surveys. The key goal of NuSTAR surveys is to resolve a significant fraction of the hard X-ray background close to its peak in the energy density at 25-30 keV, and elucidate whether it is due to the most heavily obscured Compton-thick AGN. eROSITA, due for launch in 2015, will survey the entire sky. In the soft X-ray band (0.5-2 keV), this will be about 20 times more sensitive than the ROSAT all sky survey, while in the hard band (2-10 keV) it will provide the first ever imaging survey of the sky at those energies. Such a sensitive all-sky survey will revolutionize our view of the high-energy sky. The detection of very large samples (~10^5 objects) of galaxy clusters out to redshifts z>1, in order to study the large scale structure in the Universe, test and characterize cosmological models including Dark Energy will provide a major breakthrough. eROSITA is also expected to yield a sample of around 3 millions Active Galactic Nuclei, providing a unique view of theevolution of supermassive black holes within the emerging cosmic structure.

Last but not least, the ESA SPC has recommended the science theme: "The hot and the energetic Universe" for the next Large mission (L2) foreseen for a 2028 launch. The Athena mission concept, with its high spectral resolution Integral Field Unit, and the Wide Field Imager at the focus of a 2 square meters effective area X-ray telescope, will guarantee major breakthroughs and provide transformational science.

The science drivers of the proposed focused meeting revolves around the inter relation between black hole growth and the evolving large scale structure as traced by X-ray surveys complemented by multi-wavelength follow-up programs. The aim of the meeting will be to review and discuss these observational advances, alongside progress in theory/simulation. Synergies with future multi-band surveys (i.e. EUCLID, LSST, SKA) will also be discussed.


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