4.2. Upcoming and Planned X-ray Missions
In the future, both large
(
US
$1 billion, or
600 billion
Chilean pesos; see Figure 14) and
small-to-medium class
(
US $120-180
million) X-ray missions should substantially advance
the AGN X-ray survey work described above. Constellation-X, for
example, should
enable high-quality X-ray spectroscopy for some of the remarkable brighter
sources found in X-ray surveys. XEUS should be able to generate
hundreds
of fields that are as sensitive as the deepest Chandra surveys, while
also providing superior photon statistics to those available presently.
Fitting of high-quality XEUS spectra should allow direct redshift
determination in many cases. Ultimately, Generation-X will
reach flux limits ~ 100 times better than
those of Chandra and XEUS (see
Figure 14). This improved
sensitivity should allow detection and study of ~ 1000
M
"proto-quasars" at
z 10-15,
enabling investigation of how the stellar-mass black holes
made by the deaths of the first stars grew to make the first AGN.
 |
Figure 14. Flux limit from 0.5-2 keV versus
faint-source positional accuracy for some past, present, and future
X-ray missions (the locations in the diagram and launch dates for
future missions are approximate). With a 5-10 Ms exposure,
Chandra can achieve sensitivities comparable to those discussed
for XEUS. Furthermore, Chandra positions are likely to be
the best available for
|
Future small-to-medium class X-ray missions, at least one to be launched
soon, will sensitively survey large areas of sky at high X-ray energies;
some will access the poorly explored
10-200 keV band covering
the peak of the XRB. After its 2004-2005 launch, for example, Swift
will serendipitously conduct the most sensitive
10-150 keV
survey to date with its Burst Alert Telescope. A large fraction of the
sky should be covered over the lifetime of Swift, and
200-400
AGN should be detected. In the 2007-2010 timeframe, proposed missions
such as the Dark Universe Observatory (DUO) and the
Nuclear Spectroscopic Telescope Array (NuSTAR) will also
hopefully conduct sensitive surveys in the 0.3-8 keV and
6-80 keV bands, respectively. DUO would detect ~ 160,000
AGN in its surveys of the North Galactic Cap (the SDSS area) and South
Galactic Pole, while NuSTAR would carry the first highly
sensitive, focusing telescope for > 10 keV X-rays.
Other planned small-to-medium class missions include
Japan's Monitor of All-sky X-ray Image (MAXI) and
New X-ray Telescope (NeXT)
as well as Europe's LOBSTER and ROSITA.
The Black Hole Finder Probe, defined as part of NASA's Beyond
Einstein program, should ultimately obtain an all-sky census of
accreting black holes using a wide-field imaging telescope in the
10-600 keV band.
Acknowledgments
We gratefully acknowledge support from NSF CAREER award AST-9983783, CXC grant GO2-3187A, the Royal Society (DMA), the PPARC (FEB), and Italian Space Agency contract ASI/I/R/057/02 (CV). We thank all of our collaborators.