The James Webb Space Telescope (JWST), due to launch in 2014, shall provide an unprecedented wealth of information in the near and mid-infrared wavelengths, thanks to its high-sensitivity instruments and its 6.5 m primary mirror, the largest ever lau
nched into space. NIRSpec and MIRI, the two spectrographs onboard JWST, will play a key role in the study of the spectral features of Active Galactic Nuclei in the 0.6-28 micron wavelength range. This talk aims at presenting an overview of the possibilities provided by these two instruments, in order to prepare the astronomical community for the JWST era.
AIMS: We present a sample of candidate quasars selected using the KX-technique. The data cover 0.68 deg^2 of the X-ray Multi-Mirror (XMM) Large-Scale Structure (LSS) survey area where overlapping multi-wavelength imaging data permits an investigation
of the physical nature of selected sources. METHODS: The KX method identifies quasars on the basis of their optical (R and z) to near-infrared (Ks) photometry and point-like morphology. We combine these data with optical (u*,gr,i,z) and mid-infrared (3.6-24 micron) wavebands to reconstruct the spectral energy distributions (SEDs) of candidate quasars. RESULTS: Of 93 sources selected as candidate quasars by the KX method, 25 are classified as quasars by the subsequent SED analysis. Spectroscopic observations are available for 12/25 of these sources and confirm the quasar hypothesis in each case. Even more, 90% of the SED-classified quasars show X-ray emission, a property not shared by any of the false candidates in the KX-selected sample. Applying a photometric redshift analysis to the sources without spectroscopy indicates that the 25 sources classified as quasars occupy the interval 0.7 < z < 2.5. The remaining 68/93 sources are classified as stars and unresolved galaxies.
