ABSTRACT (c4.abs)

We propose to use COB or IRIM on the 4-meter to image the fields of 21
radio-loud quasars with 1.4$<$z$<$2.0 to K$_s$=21.6, $\sim$2 magnitudes
below the no-evolution K$_*$ at z=2.
Fourteen of the quasars' spectra show
z$_{abs}\sim$z$_{em}$ CIV $\lambda\lambda$1548,1550 
``associated'' absorption-line systems of various strengths, and imaging of
these objects, seven others that do not show such absorption, and three blank 
control fields will allow us to test the hypothesis that clusters of galaxies 
are responsible for the associated absorption.  
These data will also enable us to study 
the environments of radio-loud quasars in this redshift range.

SCIENTIFIC JUSTIFICATION (c4.just)

The study of galaxies at high redshift is interesting because galaxies seen at 
z$>$1 are billions of years younger than nearby galaxies.
It has proved very difficult to discover galaxies at z$>$1 in field surveys,
but we know that metal-enriched gas and thus galaxies of some sort
exist at high z in some areas 
of the sky because we see such gas in absorption in quasar spectra.  
Searching for the galaxies responsible for these high-z absorption lines,
and galaxies clustered with them,
should be an efficient way to discover high-z galaxies.
% 
In addition to the general population of intervening absorbers, 
there exists an excess of CIV absorption-line systems with z$_{abs}$ 
within a few thousand km/s of the quasar z$_{em}$.
%
These so-called ``associated'' absorption systems may arise from gas 
expelled at high velocity from the quasars
or from clusters which are either very near in redshift space to the quasars 
or contain the quasars. 
%
If associated absorption does arise from galaxies in a cluster 
at or near the quasar redshift, then imaging to K$_s$=21.6 
will enable us to detect such galaxies even at z=2.
These galaxies should be detectable as an excess above the background galaxy
counts, concentrated around the quasar on the sky.
K-band galaxy counts extending to K$_s$$>$22 (Gardner et al. 1993)
can be used to estimate the background counts.
Zeropoint differences between our K$_s$ filter and that used for the deep 
counts might affect our background estimates, but can be calibrated with 3 hrs 
observation of blank fields to obtain our own counts to K$_s$=21.5 over an area
equal to that of the the published K$_s$$>$22 counts.

Studying the fields of 21 radio-loud quasars with 1.4$<$z$<$2 in this manner
will enable us to test the hypothesis of a cluster origin for associated 
absorption, as well as to detect clusters associated with the quasars 
themselves.
Our quasars are almost all drawn from the unpublished `Radio-Loud Survey' 
of Foltz et al., which contains $\sim$100 quasars 
with 1.25$<$z$_{em}$$<$2.4, S(11 cm)$>$100 mJy, and V$<$18.5.  
Seven of our 21 quasars show strong (rest-frame EW$>$1.5~A)
associated absorption, 7 weaker absorption, and 7 no absorption.
Each subsample will be comparable to the others in their range of z$_{em}$, 
absorber EW, M$_{\rm B}$, and radio properties.  We will attempt to avoid 
objects with strong high-z intervening absorption, to avoid confusion
about which system any galaxies we might detect are associated with.
%
Comparison of the subsamples should enable us to discern whether galaxies 
detected near associated-absorption quasars are associated with the 
absorption systems or with the quasars themselves.
For example, if the same fraction of quasars in each subsample shows
excess galaxies, then the galaxies are very likely associated
with the quasars, not the absorption systems.

If excess galaxies are detected around only a few of our quasars, 
we will be able to rule out a cluster origin for associated 
absorption systems and place upper limits of $\sim$2 magnitudes
below K$_*$ on the magnitudes of the absorbing galaxies.
%
If excess galaxies are detected around many of our quasars, we will be able
to statistically compare their M$_K$ magnitudes and impact parameters 
to those of galaxies responsible for lower-z absorption systems.
%
In either case, we will also obtain information about the environments 
of RLQs at z=1.4-2.0.  
%
Unfortunately, it will probably not be possible to determine B$_{\rm gq}$ 
(a standard measure of the cluster richness) for any clusters we might
detect, because the derivation of B$_{\rm gq}$ assumes spherically symmetric 
clusters and a constant physical clustering scale, 
assumptions which no longer hold at z=1.5-2, where clusters are in the early
stages of formation. %(Evrard \& Charlot, preprint).
%
Also, the analysis assumes knowledge of the K-band
galaxy luminosity function at z$>$1, knowledge which exists only via
extrapolation from z$<$1 at the present (Cowie \& Songailia 1993).
%
We will still attempt to calculate B$_{\rm gq}$ for any clusters discovered, 
to see if we can obtain physically realistic results to compare with 
published z$<$1 B$_{\rm gq}$'s, but we are likely to be severely limited 
in this attempt as discussed above.

We are aware of two other groups imaging CIV absorption systems in the IR.
Aragon-Salamanca et al. (preprint) have imaged 11 QSOs to K=20.3
to study galaxies that produce intervening CIV absorption.
Some of their quasars also show associated absorption; thus,
our results should help test the reliability of their identification 
of the faint excess galaxies they detected with the intervening absorption
systems, rather than the associated systems and/or the quasars.
%
Yee, Ellingson, \& Nadeau are proposing to use the CFHT to image 20-30 
quasars with 1.5$<$z$<$2.5 in the IR. %(Yee 1993, personal communication).
Although they have included some objects with associated absorption,
their main goal is study the environments of the quasars, whereas ours is to 
determine the origin of associated absorption, although we will obtain 
information on quasar environments as well.
Since our sample is drawn mostly from unpublished data,
it should have only a few objects in common with theirs, 
and so the data sets will be complementary.

TECHICAL JUSTIFICATION (c4.tech)

The June 1993 NOAO Newsletter states that IRIM is capable of detections 
to K$\sim$22 in 2 hours on the 4-meter.
This agrees with calculations of IRIM's sensitivity using parameters provided
in the preliminary IRIM manual, assuming that the detection is 3$\sigma$ in
a circular aperture of radius 2 pixels (1.2'').
Using K$_*$=-25.1 (from Mobasher 1993), an unevolved K$_*$ galaxy would
have K$\sim$18 at z=1.5 and K$\sim$19 at z=2, with a range of +/-1 magnitude
for different cosmological models.  
Imaging to a 3$\sigma$\ limit of K=21.6 in an r=1.2'' aperture (1 hour 
integration with IRIM) thus allows us to probe from 1-3 magnitudes below 
L$_*$ even at z=2.  Such deep imaging is necessary so that each individual 
quasar will show a statistically significant excess of galaxies. 
Some of our target galaxies may be extended, but one hour of integration
will still allow detection down to K$_s$=20.8 in a r=2.4'' aperture.
COB has about twice the QE of IRIM at K and half the linear pixel size, 
so the time necessary for a detection of the same SNR and aperture on the sky
will be half that required with IRIM.

IRIM's 2.5' FOV corresponds to $\sim$1.2 Mpc in our redshift range, so it
is clearly preferable for studying the overall environments of our quasars
and for obtaining extensive control field data in only 3 hours.
However, COB's 0.3'' pixel scale is better for resolving objects very 
close to the quasar sightline, which are more likely to be responsible for the 
associated absorption.  COB's 1.25' FOV still covers a useful 0.6 Mpc 
projected distance at z=1.5-2, and we could still obtain enough control
field data in 3 hours to be able to compare our K$_s$ calibration to that of the
published deep counts.
Thus, either IRIM, COB, or ideally some combination thereof
would be acceptable for our project.  
Observations we make with COB will help characterize its performance 
in detecting objects at very faint flux levels.

Objects with moderate or strong absorption which are
observable for at least a few hours in the spring include
1206+43 (z=1.40), 
0919+218 (1.42),
1416+159 (1.47), 
0326+277 (1.53), 
1323+65 (1.62),
1556+335 (1.64),
1343+38 (1.84),
0033+098 (1.92),
0256-005 (1.99), 
1157+01 (1.99), 
and 
1456+09 (1.99).
Other objects with weaker absorption, and ones with no detected absorption,
will be observed as well.

Since we will spend $\sim$1 hour of integration on each object, and we have
21 objects and 3 control fields in our sample, we request 4 nights of bright 
4-meter time to image all our targets, allowing 25\% overhead time for 
standard star observations, target acquisition, etc.

\kxdtext

KPNO form (c4.tex)

% *** How much more observing time do you need ?
Most of this thesis will be done using Steward Observatory telescopes.
The only other part of the thesis where KPNO time may be requested in the 
future is for 1.3m time to study low redshift objects where IRIM or SQIID's 
fields of view, and SQIID's simultaneous JHK capability, would 
prove useful.

For the part of the thesis proposed in this project, we anticipate that 4 
nights of 4-m time will be sufficient.  If the weather is good, this should 
be the only proposal we will need to submit for the project.  
If we lose some time to weather, we would ask for 2, 3, or 4 nights next fall,
as appropriate, to complete observations of a useful number of objects.

If we detect objects near some of our quasars in K$_s$, several followup 
studies might be worthwhile, two of which would likely require 4-m time.
The first is to obtain infrared colors, and since near real-time data reduction 
is possible, we might be able to image a few fields in J or H as well as 
K$_s$ during our initial run, if the primary project objectives had been 
largely completed.
The second is narrowband imaging with COB at the wavelengths of strong optical 
emission lines at the quasar and/or absorber redshifts, both to study the 
galaxies' star-formation properties and to help confirm the association of the 
galaxies with the quasars and/or the absorbers.  
However, it is premature to 
speculate on such projects until some galaxies are actually detected, and in 
any case the projects might not be attemptable soon enough to be included in 
this thesis.

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\leavevmode\hangindent=14pt\hbox{9) }\ksmrm If the facilities of other
observatories are being used for this project, please give details.
If you have access to a telescope through your home institution, indicate why
KPNO facilities are better suited to this project.\par

\vbox to 2.2in{
\kbgntext

% *** Do you have other access, and why are we better ?

The SO NICMOS3 array cannot be used on the MMT; otherwise it would be suitable
for this project.  It can be used on the SO 90'', but in 1 hour at the 90''
our observations have reached only K=20 (3$\sigma$\ in r=2").  Thus not only 
is the 90'' collecting area too small for this project, but the 4-m has been 
better optimized for faint IR observations.  The 90'' is suitable for studying
objects out to z$\sim$1.25, and we are using it to do just that.

The only IR array available for use on the MMT is a 128x128 NICMOS2 array.
Its FOV is $<$1' across, and its QE is substantially lower than the NICMOS3
chips.  We estimate that in 1 hour integration we could also reach only K=20.
This agrees with estimates provided by users of the 128x128 array.

Thus, no SO facility is able to probe 2 magnitudes fainter than K$_*$ at 
z$\sim$2, which is essential for this project.