I. Matute, J. Masegosa, I. Márquez, A. Fernández-Soto, C. Husillos, A. del Olmo, J. Perea, M. Pović, B. Ascaso, E. J. Alfaro, M. Moles, J. A. L. Aguerri, T. Aparicio--Villegas, N. Benítez, T. Broadhurst, J. Cabrera--Cano, F. J. Castander, J. Cepa, M. Cerviño, D. Cristóbal-Hornillos, L. Infante, R. M. González Delgado, V. J. Martínez, A. Molino, F. Prada, J. M. Quintana
We aim to illustrate the potentiality of the Advanced Large, Homogeneous Area, Medium-Band Redshift Astronomical (ALHAMBRA) survey to investigate the high redshift universe through the detection of quasi stellar objects (QSOs) at redshifts larger than 5. The search for z>5 QSOs candidates was done by fitting an extensive library of spectral energy distributions --including active and non-active galaxy templates as well as stars-- to the photometric database of the ALHAMBRA survey (composed of 20 optical medium-band plus the 3 broad-band JHKs filters). Our selection over ~1 square degree of ALHAMBRA data (~1/4 of the total area covered by the survey), combined with GTC/OSIRIS spectroscopy, has yielded the identification of an optically faint QSO at very high redshift (z = 5.41). The QSO has an absolute magnitude of ~-24 at the 1450{\AA} continuum, a bolometric luminosity of ~2x10^46 erg/s and an estimated black hole mass of ~10^8 Msolar. This QSO adds itself to a reduced number of known UV faint sources at these redshifts. The preliminary derived space density is compatible with the most recent determinations of the high-z QSO luminosity functions (QLF). This new detection shows how ALHAMBRA, as well as forthcoming well designed photometric surveys, can provide a wealth of information on the origin and early evolution of this kind of objects.
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http://arxiv.org/abs/1307.5117
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