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stead recent massive formation.
The detection
of infrared contin­
uum would help constrain char­
acteristics total mass stellar
populations through comparison with
population synthesis models.
References
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co 1999, preprint astroph/
9811399v2 Jan 1999).
Thompson Djorgovski
S., Trauger
VLT Spectroscopy the 4.11 Radio Galaxy
TN J1338--1942
DE BREUCK
, W. VAN BREUGEL MINNITI 2,3
MILEY
1 RæTTGERING
1 S.A. STANFORD
2 and C. CARILLI
4
Sterrewacht Leiden, The Netherlands (debreuck,miley,rottgeri@strw.leidenuniv.nl)
Institute Geophysics and Planetary Physics, Lawrence Livermore
National Laboratory, Livermore, U.S.A. (wil,adam@igpp.llnl.gov)
Universidad CatÑlica, Santiago, Chile (dante@astro.puc.cl)
National Radio Astronomy Observatory, Socorro, USA (ccarilli@nrao.edu)
High­redshift galaxies (HzRGs)
play important cosmology. They
to
of oldest and massive galaxies
at
shifts, therefore constrain
epoch which the generation
stars were formed. The near­IR Hub­
K
-- diagram powerful radio
galaxies shows
a remarkably cor­
relation from present
= despite significant K­correc­
tions (van Breugel 1998, 1999).
This indicates follow
evolution
of hosts HzRGs from
near their formation epoch
to
redshift where powerful radio
sources inhabit massive elliptical gal­
axies (e.g. Lilly
& Longair 1984; Best,
Longair RÆttgering 1998). exam­
ple,
~ observe change
observed K­band morphologies
HzRGs large­scale low­sur­
face brightness emission bright
radio­aligned clumps
at
<
~
3 smooth,
compact structures, sometimes show­
elliptical shapes, like their ocal
Universe counterparts (van Breugel
1998). These surrounding clumps
have properties similar drop­
galaxies similar redshifts (Pen­
tericci
et 1999), indicate that
HzRGs often reside
in (proto­)cluster
environments. evolution picture
seems consistent hierarchical
clustering formation models Kauff­
mann
et 1999), where massive
jects form accretion
of smaller sys­
tems located
in over­dense regions.
Figure VLT spectrum
of J1338--1942.
The panel has boxcar smoothed
factor
9 better show shape
Lya forest Lyman limit.
E­mail: kudritzki@usm.uni­muenchen.de

Detailed studies HzRG can
compared predictions the
hierarchical clustering scenarios.
Using newly available surveys,
have begun
a systematic search
>
3 radio galaxies Breuck
et
2000),
to
be followed more detailed
studies selected objects.
During second VLT
Antu operations
in 1999, used
FORS1 obtain
a spectrum the
second highest redshift radio galaxy
from sample, J1338--1942
at
z
4.11. We discovered object
March ESO 3.6­m tele­
scope Breuck 1999a). The
purpose these observations was
study emission and UV­
continuum. used 600R grism 1.3²
wide and integrated
47 The
spectrum, shown Figures
1
dominated bright Lya
â
s
--2 rest­frame
equivalent width 210±50å,
a typical
value HzRGs.
Most notable from Figure
2
is the
large asymmetry emission pro­
consistent with
a very wide 1400
km/s) blueward depression over the
entire spatial extent emission
(~10 kpc). Similar asymmetries have
been detected
in other HzRGs, and
have been interpreted ab­
sorption cold
in
a halo sur­
rounding galaxy (e.g. Ojik
1997; Dey 1999). The profile
fit
a simple model consisting
Gaussian emission profile and
single absorption function (see
Figure This model constrains
column density range
--
20
--2
. From
derive total mass absorber
--
â
7 , which is compara­
slightly than the
mass, as derived from the Lya emis­
sion Breuck 1999b). These
results show that J1338--1942
surrounded

large
reservoir

gas. We also detect continuum emission TN J1338--1942, second
time this is reported in the spectrum of
>
4 radio galaxy. continuum,
shown
in bottom panel
of Figure
shows
a discontinuity across Lya
line,
a tentative detection the
Lyman deficit bluewards
Lya interpreted
HI absorp­
along cosmological sight,
and described parameter
A
=
(Oke Korycanski 1982).
J1338--1942, measure
A
= 0.37
similar
to
A
=
± 0.1
measured
= radio galaxy
1435+64 (Spinrad
et
al. 1995). Both
these values
>
4 radio
galaxies significantly lower than
D values found quasars
these redshifts (Schneider 1991).
Although based only measure­
ments, results suggest
ground absorption
A
)
in quasars
could have been overestimated
cause highest redshift
>
4)
found from samples
optical colour selection, thereby
excluding quasars with relatively small
breaks across
It therefore particularly important
to expand number objects
z selected
by techniques other
optical colours. Radio galaxies
brightest objects
at
shifts which not out­shined
central AGN quasars. Using
high sensitivity
of VLT instru­
ments, able study
same origin and evolution
luminous halos
or ionised
and neutral
HI surrounding
them.
Acknowledgements. The work
C.D.B., W.v.B., S.A.S.
IGPP/LLNL performed under
auspices Department
Energy under contract W­7405­ENG­
D.M.
is supported Fondecyt
grant 01990440 DIPUC.
supported
by
Formation Evolution Galaxies
network European
Commission under contract
FMRX­CT96­086 TMR
gramme.
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Figure spectrum around Lya The model consisting
of
Gaussian emission profile (dashed line) Voigt absorption profile with indicated
rameters.