Matute, I.; Masegosa, J.; Márquez, I.; Fernández-Soto, A.; Husillos, C.; del Olmo, A.; Perea, J.; Pović, M.; Ascaso, B.; Alfaro, E. J.; Moles, M.; Aguerri, J. A. L.; Aparicio-Villegas, T.; Benítez, N.; Broadhurst, T.; Cabrera-Cano, J.; Castander, F. J.; Cepa, J.; Cerviño, M.; Cristóbal-Hornillos, D.; Infante, L.; González Delgado, R. M.; Martínez, V. J.; Molino, A.; Prada, F.; Quintana, J. M.
Bibliographical reference
Astronomy and Astrophysics, Volume 557, id.A78, 6 pp.
Description
Aims: 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 higher than 5.
Methods: We searched for QSOs candidates at high redshift 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 near-infrared filters). Results:
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 identification of an optically faint QSO at
very high redshift (z = 5.41). The QSO has an absolute magnitude of ~-24
at the 1450 Å continuum, a bolometric luminosity of ≈2 ×
1046 erg s-1, and an estimated black hole mass of
≈108 M⊙. 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. 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 object.
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