The Discovery of a High-Redshift Quasar without Emission Lines from Sloan Digital Sky Survey Commissioning Data.
We report observations of a luminous unresolved object at redshift z=4.62, with a featureless optical spectrum redward of the Lyalpha forest region, discovered from Sloan Digital Sky Survey commissioning data. The redshift is determined by the onset of the Lyalpha forest at lambda approximately 6800 Å and a Lyman limit system at lambda=5120 Å. A strong Lyalpha absorption system with weak metal absorption lines at z=4.58 is also identified in the spectrum. The object has a continuum absolute magnitude of -26.6 at 1450 Å in the rest frame (h0=0.5, q0=0.5) and therefore cannot be an ordinary galaxy. It shows no radio emission (the 3 sigma upper limit of its flux at 6 cm is 60 µJy), indicating a radio-to-optical flux ratio at least as small as that of the radio-weakest BL Lacertae objects known. It is also not linearly polarized to a 3 sigma upper limit of 4% in the observed I band. Therefore, it is either the most distant BL Lac object known to date, with very weak radio emission, or a new type of unbeamed quasar, whose broad emission line region is very weak or absent.
Fan
X
Strauss
MA
Gunn
JE
Lupton
RH
Carilli
CL
Rupen
MP
Schmidt
GD
Moustakas
LA
Davis
M
Annis
J
Bahcall
NA
Brinkmann
J
Brunner
RJ
Csabai
I
Doi
M
Fukugita
M
Heckman
TM
Hennessy
GS
Hindsley
RB
Ivezic
Z
Knapp
GR
Lamb
DQ
Munn
JA
Pauls
AG
Pier
JR
Rockosi
CM
Schneider
DP
Szalay
AS
Tucker
DL
York
DG