NuSTAR and the Cosmic X-ray Background
The cosmic X-ray background (CXB) was first discovered in
the early 1960's, several years before the detection of the
cosmic microwave background (CMB). However, unlike the CMB, it
appears that the CXB is dominated by the emission from
high-energy distant point sources: Active Galactic Nuclei
(AGNs), the sites of intense black-hole growth that reside at
the centres of galaxies. A key goal of high-energy
astrophysics is to determine the composition of the CXB.
Huge strides in revealing the composition of the CXB have
been made over the past decade, with sensitive surveys
undertaken by the Chandra and XMM-Newton observatories,
revealing a plethora of obscured and unobscured AGNs out to
z~5-6. However, Chandra and XMM-Newton are only sensitive to
sources emitting at ~0.5-10 keV, far from the peak of the CXB
at ~20-30 keV. Previous generation observatories have only
resolved ~1-2% of the CXB at the 20-30 keV peak and therefore
provide a very limited view of the source populations that
dominate the CXB.
The great breakthrough in resolving the peak of the CXB is
NuSTAR. NuSTAR was successfully launched on June 13th 2012 and
is the first >10 keV observatory with focusing optics. The
focusing optics on NuSTAR provide a ~1-2 orders of magnitude
improvement in sensitivity and angular resolution over
previous-generation >10 keV observatories, a genuine leap
forward in performance. One of the primary tasks of NuSTAR is
to complete a sensitive extragalactic survey and identify the
source populations that produce the peak of the CXB.
NuSTAR Extragalactic Survey
The NuSTAR extragalactic survey is comprised of three
components (see Table~6 of
Harrison et al. 2013): a deep small-area survey in the
Extended Chandra Deep Field-South (E-CDF-S), a medium
wider-area survey in the Cosmic Evolution Survey (COSMOS) and
a large area (typically shallow) serendipitous survey
conducted in the fields of other NuSTAR targets, including
~100 Swift-BAT identified AGNs.
Durham is leading the execution of the deep E-CDF-S survey,
is leading the shallow serendipitous survey, and is making
significant contributions to the execution of the medium
COSMOS survey. Durham is responsible for providing the NuSTAR
data products and data catalogues for the E-CDF-S and
serendipitous surveys within the NuSTAR extragalactic survey
team.
Publications for the extragalactic survey:
1. - THE NUSTAR EXTRAGALACTIC SURVEY: A FIRST LOOK AT THE DISTANT HIGH-ENERGY COSMIC X-RAY BACKGROUND POPULATION; Alexander, D.M., Stern, D., Del Moro, A., Lansbury, G.B., Assef, R.J., Aird, J., Ajello, M., Ballantyne, D.R., Bauer, F.E., Boggs, S.E., Brandt, W.N., Christensen, F.E., Civano, F., Comastri, A., Craig, W.W., Elvis, M., Grefenstette, B.W., Hailey, C.J., Harrison, F.A., Hickox, R.C., Luo, B., Madsen, K.K., Mullaney, J.R., Perri, M., Puccetti, S., Saez, C., Treister, E., Urry, C.M., Zhang, W.W., Bridge, C.R., Eisenhardt, P.R.M., Gonzalez, A.H., Miller, S.H., Tsai, C.W. 2013, ApJ, 773, 125.
2. - NUSTAR J033202-2746.8: DIRECT CONSTRAINTS ON THE COMPTON REFLECTION IN A HEAVILY OBSCURED QUASAR AT Z~2; Del Moro, A., Mullaney, J.R., Alexander, D.M., Comastri, A., Bauer, F.E., Treister, E., Stern, D., Civano, F., Ranalli, P., Vignali, C., Aird, J.A., Ballantyne, D.R., Balokovic, M., Boggs, S.E., Brandt, W.N., Christensen, F.E., Craig, W.W., Gandhi, P., Gilli, R., Hailey, C.J., Harrison, F.A., Hickox, R.C., LaMassa, S.M., Lansbury, G.B., Luo, B., Puccetti, S., Urry, C.M., Zhang, W.W. 2014, 786, 16.
3. - THE NUSTAR EXTRAGALACTIC SURVEY: EXTENDED CHANDRA DEEP FIELD SOUTH CATALOGS; J. Mullaney et al., in prep.
4. - THE NUSTAR EXTRAGALACTIC SURVEY: COSMIC EVOLUTION SURVEY CATALOGS; F. Civano et al., in prep.