Abstract
The majority of known very high-redshift (z>=3.4) quasi-stellar objects (QSOs) have relatively bright apparent magnitudes1,2, R<=18, and recent systematic surveys for fainter high-redshift QSOs3 have failed to find such objects, perhaps implying that the epoch of QSO formation is luminosity dependent. The z=4.01 QSO recently reported4 is quite faint, and was selected by colour rather than spectrum, raising the possibility that previous slitless spectroscopic surveys have been biased against high-redshift QSOs. Here we report the discovery of a faint, red QSO (B>= 21, R ˜ 19) at z = 3.56, selected by 'traditional' low dispersion spectroscopic methods. The surface density of very faint, high-redshift QSOs may not be negligible, with a variety of lines of evidence suggesting that there are at least ˜ 0.2 deg−2 objects with z>= 3.4.
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Anderson, S., Margon, B. Surface density of faint high-redshift quasi-stellar objects. Nature 327, 125–127 (1987). https://doi.org/10.1038/327125a0
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DOI: https://doi.org/10.1038/327125a0
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