%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%    phase14-GO.tex  (use only for General Observer and Snapshot proposals; 
%                      use phase14-AR.tex for Archival Research and
%                      Theory proposals use phase14-DD.tex for GO/DD proposals).
%
%    HUBBLE SPACE TELESCOPE
%    PHASE I OBSERVING PROPOSAL TEMPLATE 
%    FOR CYCLE 14 (2004)
%
%    Version 1.0, October 01, 2004.
%
%    Guidelines and assistance
%    =========================
%    Two documents are of particular importance for the preparation and
%    submission of HST proposals. The `Call for Proposals' discusses
%    policies and procedures, and explains how to submit a Phase I
%    proposal. The `HST Primer' provides a basic introduction to the
%    technical aspects of HST and its instruments, and explains how to
%    calculate the appropriate number of orbits for your Phase I observing
%    time requests. Both documents are available electronically from the
%    STScI World-Wide Web site at the Cycle 14 Announcement Web Page:
%
%         http://www.stsci.edu/hst/proposing/docs/cycle14announce 
%
%    Please contact the STScI Help Desk if you need assistance with any
%    aspect of proposing for and using HST. Either send e-mail to
%    help@stsci.edu, or call 1-800-544-8125; from outside the United
%    States, call [1] 410-338-1082.
%
%    What/How to submit
%    ==============
%    Cycle 14 proposals must be submitted electronically. Starting in 
%    Cycle 12, a java-based software tool, APT (the Astronomer's 
%    Proposal Tool see: http://apt.stsci.edu is the new interface for 
%    all Phase I and Phase II proposal submissions for HST.
%
%	THE PHASE I LATEX TEMPLATES THAT HAVE BEEN IN USE
%	FOR MANY YEARS WILL NOT BE ACCEPTED IN CYCLE 14.
%
%	A Phase I proposal consists of two parts: 
%
%	*	a completed APT proposal form; and 
%	*	an attached PDF file (see Chapter 9). 
%
%	Both get submitted to STScI directly from within APT. 

%
%	Please study Chapter 7, Chapter 8 and Chapter 9 of the Cycle 14 
%	Call for Proposals at: 
%         http://www.stsci.edu/hst/proposing/docs/cycle14announce 
%	carefully. Please do so well before the submission deadline, to 
%	give the STScI Help Desk ample time to answer any questions that you 
%	may have about the new procedures. 
%
%    LaTeX info
%    ==========
%    Most of the input you will be asked to provide must be given within
%    the curly braces "{}" following the Template-keywords (a Template-
%    keyword is preceded by a backslash: "\"). The LaTeX comment
%    character is the percent sign "%" -- anything you type that has a
%    percent sign to the left of it on the same line will be ignored. If
%    you need to have a percent sign appear in your text, use "\%"
%    instead. Experienced LaTeX users may be tempted to alter styles and
%    fonts to squeeze more text into the allowed space;
%    --- PLEASE DO NOT DO THIS! ---
%
%    Since this is a LaTeX document, you can use the special LaTeX
%    characters you may need. In addition, a number of astronomical
%    symbols have been defined for you in the style file. A complete
%    list of those symbols can be found at the URL:
%
%         http://www.stsci.edu/hst/proposing/docs/symbols.pdf
%
%    Encapsulated PostScript
%    =======================
%    Many LaTeX users will be familiar with ways to incorporate
%    encapsulated PostScript graphics into a document. If you are using
%    this form to prepare output for your POSTSCRIPT/PDF Submission, then
%    feel free to use any of these methods to add figures to your scientific
%    justification or to any of the questions that follow the scientific
%    justification. Information on how to encapsulate figures is
%    available at the URL:
%
%         http://www.stsci.edu/hst/proposing/docs/postscript-guidelines/
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% The template begins here. Do not alter the two lines that follow.

\documentstyle[phase14,12pt,times]{article}
\begin{document}

\def\gs{\mathrel{\raise0.27ex\hbox{$>$}\kern-0.70em % Greater/squiggles
\lower0.71ex\hbox{{$\scriptstyle \sim$}}}}
\def\ls{\mathrel{\raise0.27ex\hbox{$<$}\kern-0.70em % Less than/squiggles
\lower0.71ex\hbox{{$\scriptstyle \sim$}}}}
\def\etal{{\it et al.}}
\def\VEV#1{\left\langle #1\right\rangle}

%   1. SCIENTIFIC JUSTIFICATION
%       (see Section 9.1 of the Call for Proposals)
%
%       Present the SCIENTIFIC JUSTIFICATION for the proposed program.
%       This section should present a balanced discussion of background
%       information, the program's goals, its significance to astronomy in
%       general, and its importance for the specific subfield of astronomy
%       that it addresses. The members of the review panels will span a broad
%       range of scientific expertise, so you should write this section for
%       a general audience of scientists.
%
%       There are page limits on the size of your PDF attachment. 
%
%        For Large GO proposals, Treasury GO proposals the page limits are: 
%        -  No more than 13 pages total. 
%        -  Any text in the `Scientific Justification' section,
%	      may not extend beyond page 6. 
%	   -  the increased limits allow 2 pages for a new section, Two Gyro 
%		Mode Observations (see Section 9.3). This section must be used 
%		to describe the science impact of two-gyro operations and, if 
%		necessary, to outline an alternative observing strategy.
%
%       For all other Regular GO and Snap proposals the limits are: 
%       -  No more than 9 pages total. 
%       -  Any text in the `Scientific Justification' section may not extend 
%          beyond page 3. 
%	  -  the increased limits allow 1 page for a new section, Two Gyro Mode
%		Observations (see Section 9.3). This section must describe the science
%		impact of two-gyro operations and, if necessary, to outline an
%		alternative observing strategy.
%
%       In relation to these page limits, note the following: 
%
%       -  Any pages beyond the page limits will be discarded by STScI 
%          and will not be available to reviewers. 
%       -  The figures and tables must appear after the text of the Science 
%          Justification. There are no limits on the numbers of figures, tables 
%          and references in the PDF attachment. However, the total page limit 
%          must be obeyed.
%       -  The section on previous observations does not count towards the total
%           page limit.
%        -  Your PDF attachment must be prepared with a font size of 12pt. 
%           Do not change the font size or layout in any of the templates that 
%           are provided by STScI. 
%
%       See Section 7.1.3 of the Call for Proposals for further information
%       on Page Limits.
%
\justification          % Do not delete this command.
% Enter your scientific justification here. 

\newcommand\SECTION[1]{\par\vskip 0.07truein\noindent{\bf{#1}}\par}
\newcommand\SUBSECTION[1]{\par\noindent{\bf{#1}}}

\SECTION{Using Type Ia Supernovae in Early-type Galaxies to Measure Cosmology}

The signature goal of the most ambitious cosmology projects being designed
or built this decade (LSST/LST/Panstarrs, Dark Energy Camera,
JDEM/SNAP/Destiny, and the South Pole Telescope and other SZ experiments) is
the detailed, accurate measurement of the universe's expansion history, from
deceleration through acceleration, to look for clues of the properties and
identity of dark energy.  Of the small handful of known measurement techniques
(SN Ia, cluster counts, S-Z, weak lensing, and baryon oscillations), only Type
Ia supernovae (SNe Ia) have actually been developed to the point of routine
use.  Only HST observations can provide the required signal-to-noise for those
supernovae at $z\gs 1$, where the transition from deceleration to acceleration
can be studied.  Initial studies of the decelerating universe from both the
Higher-Z Team (Riess \etal\ 2004) and the Supernova Cosmology Project (Fadeyev,
Aldering \etal\ 2004) clearly point to the limiting factor for both statistical
and systematic uncertainties: extinction correction of the host galaxy.


We propose a new approach to the measurements in this difficult decelerating
redshift range.  By studying ``clean'' supernovae discovered specifically in
galaxy-cluster ellipticals, we can remove this primary statistical and
systematic uncertainty  --- and do so with a dramatically more efficient use of
HST time (see Obs.\ Strategy section).


The resulting data set also provides a deep z-band survey of $z \gs 1$ rich
clusters, allowing us to take important steps in understanding other
cosmological measurement techniques.  In particular, cluster counting is an
extremely sensitive measure of expansion history if their masses can be
estimated with reasonable precision.  We propose to measure cluster masses
via weak lensing from the same HST images, as well as calibrate
Sunyaev-Zel'dovich distance measurements to those same clusters.
%
Finally, this data set will be used to study galaxy cluster assembly and star
formation rates.  We have intentionally included clusters that are
X-ray-selected, optically-selected, and IR-selected for this purpose.

\SUBSECTION{How problematic is the extinction correction uncertainty at $z\gs 1$?}
The correction for the extinction of SNe from dust in the host galaxies is
currently the single dominant source of both statistical and systematic error
for SNe distances and the derived cosmological parameters.  This is already true
at $z \sim 0.5$, even with HST photometry, as shown in Knop \etal\ (2003), and
is dramatically worse at $z >1$ as shown in Figure 1.   The typical color
uncertainties for  HST-studied $z>1$ SNe is 0.08 -- 0.1 in $B-V$, leading to
uncertainties in extinction correction (after accounting for intrinsic color
uncertainty) of $>$0.4 mag!   This dispersion grows worse, $\sigma \approx
0.5$, after accounting for the uncertainty in the dust reddening coefficient,
$R_B \equiv {A_B / E(B-V)}$, which Draine (2003) notes can vary from the
fiducial value 4.1 by $\pm0.5$.   (Note that the actual dispersion about the
Hubble-line fit for $z>1$ SNe Ia corrected for extinction matches this 0.5 mag
value.)  Figure 2a shows the resulting poor constraints on  the dark-energy
equation-of-state parameter and its time variation, $w_0$ vs. $w^\prime$.
These constraints do not allow distinguishing between almost any current dark
energy model.

These large dispersions in extinction correction have been dealt with, e.g.\ in
Riess \etal\ (2004), by applying a strong Bayesian prior to the distribution,
assuming knowledge of the dust and SN distribution in the $z>1$ host galaxies
(shaded contour of Fig.~2b).   However, such Bayesian priors are
necessarily one-sided (no negative reddening) and hence are known to introduce
systematic biases when the error bars are larger at high-redshift than
low-redshift (Perlmutter \etal\ 1999).   This bias can be seen in Fig.~2b as the
difference between the long-dashed contour and the solid contour.   This approach
to the extinction analysis is also subject to other obvious sources of
systematic biases, for example if the mean value of $R_V$ drifts from low to
high redshift, as shown by the short-dashed contour of Fig.~2b.


\SUBSECTION{How is this problem solved using SNe Ia in ellipticals?}
In Sullivan \etal\ (2003), we showed that the dispersion (including 
ground-based measurement error) about the Hubble diagram
for elliptical-hosted SNe is 0.16 mag --- three times smaller than just the measurement uncertainty for extinction-corrected SNe Ia at $z>1$ ---
primarily due to the absence of dust.   Thus, SNe Ia in ellipticals
are statistically each worth \emph{nine times} that of SNe in spirals when
making cosmological measurements -- and without the aforementioned systematics
associated with extinction correction.  We therefore propose to collect a sample 
of $\sim$10 SNe Ia
at $z \gs 1$ entirely in cluster elliptical host galaxies, to achieve the statistical
constraints of $\sim$90 SNe in later-type hosts.  This would yield the
stronger constraints on $w$ vs. $w^\prime$ shown in Fig. 2c --- without 
extinction prior systematics.


The $z=0.9 - 1.7$ redshift range provides key leverage of the
cosmological model, especially constraints on the dark energy time
variation $w'$.  Furthermore, this regime is when cluster potentials
first begin responding to the accelerating effects of dark energy.


\SUBSECTION{How is it known that the targeted $z \gs 1$ cluster ellipticals are
dust-free?}
%Nearby elliptical galaxies are well known to be almost entirely free of dust,
%with very few exceptions (like the disk in the center of Cen A).
The clearest line of evidence for the lack of a significant role for dust in
elliptical galaxies comes from the tightness of the color-magnitude relation.
The dispersion in the colors of early-type galaxies has long been known to be
very small in clusters ranging from Coma to intermediate redshifts (Bower
\etal\ 1992; Ellis \etal\ 1997; Stanford, Eisenhardt \& Dickinson 1998;
van Dokkum \etal\ 2001; Blakeslee \etal\ 2003).  In fact, this relation
has recently been shown by Hogg \etal\ (2004) to be universal for early-type
galaxies in clusters and in lower-density environments using an
enormous sample from SDSS.

Recent results from ACS imaging show the same strikingly small dispersion in
color extends to redshifts $z \gs 1$ (Figure 4).  ACS imaging of RDCS1252-29
at $z=1.24$ by Blakeslee \etal\ (2003) found an intrinsic dispersion of $0.024
\pm 0.008$ mag for 30 ellipticals in the F775W - F850LP color, which
approximates rest-frame $U-B$.  This dispersion is comparable to that found by
Bower \etal\ in Coma.  Given the high likelihood of at least some age (and
color) variation in the stellar populations of the member galaxies, the maximum
amount of dust that could be in these ellipticals must be still smaller than
this dispersion -- unless a conspiracy gives all these ellipticals the same
amount of dust along the line of sight.
%Note that this test can be performed for each cluster in which we find a SN
%Ia.
%
%The Bower et al. number for the dispersion in U-V for Coma early-types was
%0.04.


%In addition, the HST images themselves will provide another sanity check.
%Elliptical galaxies are well-fit by 2-dimensional de Vaucouleur profiles.
%Subtracting such model fits from ellipticals reveal when dust lanes
%are present (as in the rare examples like Cen A).


\SUBSECTION{Why is this cluster search much more efficient at finding (and
studying) SNe Ia at $z \gs 1$ than the previous HST searches in the GOODS
fields?}
This search centered on rich clusters is expected to yield twice as
many $z \gs 1$ supernovae in total as the previous blank-field searches (such
as the two SN teams' previous GOODS searches), and \emph{five times} as many
supernovae in elliptical hosts.  The number of Type Ia supernovae scales with
luminosity, with a rate of approximately one per year per $10^{12} L_{\odot}$
in rest-frame B-band luminosity.  Fig.~3a shows that
compared to an average GOODS field, our cluster fields generally contain more
than five times the rest-frame B-band luminosity from early type galaxies at $z
\gs 1$ -- hence the factor of 5 increase in the elliptical-hosted SN Ia rate.
Since we still
find (and study) the field SNe not in clusters, the total discovery rate will
more than double.  Note that these cluster SN rates are consistent with the
rate seen in previous searches of clusters below $z=1$, including one we (SCP)
performed with ground-based telescopes (Perlmutter \etal\ 1995; Pain 1997
[which ref???]), and the search of archival HST data by Gal-Yam \etal\ (2002,
who rediscovered one of our cluster SNe).


In addition to discovering more SNe Ia per HST orbit, there is another set of
major efficiency gains in the {\it follow-up} of these SNe due to the knowledge
that the host is elliptical, our knowledge of the redshift of the cluster, and
the higher rate per field.   First, the follow-up observations need
significantly less signal-to-noise and fewer bands, since the extinction
correction no longer dominates the requirements, and the bands can be
pre-chosen to match each cluster's known redshift.  Second, the higher
discovery rate allows pre-scheduling observations for each cluster
with a cadence guaranteed to well sample the lightcurves for every supernova
discovered.   For all but the highest redshift clusters, this eliminates the
need for expensive TOO follow-up in obtaining the fundamental lightcurve data!
Finally, these $z \gs 1$ clusters' old stellar populations will only host
SNe Ia, so much spectroscopy can be saved as well.


%\SUBSECTION{What is the optimal redshift range, and what limits on $w_0$
%and $w^\prime$ are expected?}
%The two key goals of the SN Ia work at these redshifts is (1) to map the
%expansion history back in time to the epoch in which matter dominated over dark
%energy and the universe was decelerating, and (2) to use this epoch to begin to
%constrain the time derivative of the equation-of-state of dark energy,
%$w^\prime$, together with its value today, $w_0$.  These measurements are most
%sensitive beyond $z \gs 1$, but not much more is gained above $z \sim 1.7$
%since then the matter density completely dominates.  In this $z=0.9-1.7$
%redshift range, gravitational lensing enters as a systematic.  Mass fluctuations
%along the light path amplify and deamplify the magnitude distribution of
%standard candles, distorting the Hubble diagram.  Holz \& Linder (2005) show
%this is not a dominant source of error currently, but the sample observed here
%will serve as a valuable testbed for Monte Carlo techniques treating the
%influence of gravitational lensing on the derived cosmological model (due to
%the non-Gaussianity of the lensing effect, one cannot simply average SNe flux
%over large redshift bins).  We have therefore chosen the richest clusters in
%this redshift range for this search, and with the resulting $\sim$10 cluster
%SNe Ia the statistical and systematic uncertainties due to extinction can be
%reduced to the level that the dashed contours of Fig.\ 1 can be ``recovered.''


\SECTION{Developing other Dark Energy Techniques using these Cluster Data}

The number of clusters of galaxies as a function of mass and redshift provides
a powerful alternative probe of the cosmology thanks to its sensitivity to the
comoving volume {\it and} the growth of large scale structure. The rare,
massive clusters at high redshifts provide most of the discriminating power of
the experiment, requiring large surveys of the sky to search for these systems.
A number of large cluster surveys are
underway (e.g., Red-sequence Cluster Survey) or being built in the near future
(e.g., South Pole Telescope Sunyaev-Zel'dovich Survey, Dark Energy Survey) with
this dark energy measurement as a key goal.
However, these surveys, which detect clusters through a variety of techniques, all
require estimates for the cluster masses in order to succesfully constrain
cosmological parameters.

%None of the observables (richness, luminosity, temperature, etc.)
%measure mass directly, although masses can be inferred under certain
%assumptions (e.g., hydrostatic equibrium, spherical
%geometry). Nevertheless, m
Many cluster properties correlate with mass, but
%Unfortunately 
it is not (yet) possible to predict these relations to
the required level of accuracy, because of the complex nature of
cluster formation. This is more of an issue at higher redshifts, where
clusters are dynamically young.  Instead the mass-observable relations
-- and their evolution --
need to be calibrated empirically. 
%Moreover, it is important to
%measure the {\it evolution} in these relations.

\SUBSECTION{Weak lensing estimates of cluster masses.}
Weak gravitational lensing of background galaxies
is now a well-established technique for providing a {\it
direct} measurement of the projected cluster mass, without any
assumptions about the geometry or dynamical state of the cluster.  
%The
%proposed observations enable us to determine masses of clusters in a
%redshift range which is virtually unexplored. In conjunction with the
%X-ray, SZ and optical properties, the proposed observations enable us
%to extend the mass calibrations out to high redshifts. In addition,
%such a comparison will provide invaluable insights on cluster
%formation, at an era when clusters were young.
The next generation cluster surveys will yield samples of order $10^4$
clusters out to high redshifts. It will be impossible to obtain weak
lensing masses for all of them. Fortunately, recent work by Majumdar
\& Mohr (2003; 2004) on ``self-calibration'' has shown that follow-up
studies of only a moderate sample of clusters are sufficient to allow
these surveys to constrain $w$ better than $5-10\%
$. The main
requirement of such a sample is that the observations can constrain the
evolution in cluster properties.

Out to $z = 0.7$, large ground based projects (e.g., Canadian Cluster
Calibration Project, CFHT Legacy Survey, Subaru observations) will
provide a detailed study of the mass-observable relation and its
scatter using $\sim 10^3$ clusters. Members of our team are leading
some of these efforts. At higher redshifts, space-based observations
are needed, driven by the need to measure the shapes of resolved {\it
background} galaxies. 
Note that Holz \& Linder (2005) show that gravitational lensing 
at these redshifts is not a major source of error for the supernova 
Hubble diagram with current measurements  (though the observations 
can serve as a valuable testbed for 
Monte  Carlo techniques treating the influence of the lensing effect).
The proposed observations target a redshift
range which is virtually unexplored. Without the proposed
observations, our knowledge of the cluster properties at $z>1$ will be
too limited to use these systems for cosmology. Consequently,
observations in this regime are desparately needed if cluster
abundance studies are to succeed.

Our calculations of the expected uncertainties in the mass
measurements show that we can achieve a $\sim 30\%$ accuracy for an
individual cluster of mass $M=5\times 10^{14} M_\odot$ ($\sim$ average
mass in our sample). More importantly , the observations allow us to
determine the zero-point of the mass-observable better than $15\%$ in
each of four independent redshift bins. The proposed observations
allow us for the first time to accurately constrain the evolution in
cluster properties at these redshifts, especially once tied to the
ongoing work at lower redshifts.


The proposed sample is larger by a factor of 4 from previous work,
and targets clusters at higher redshifts. In
addition, the clusters have been selected based on either their X-ray
emission or the overdensity of red galaxies. The accuracy in the mass
determination of individual clusters is sufficient to address the
important question whether different detection methods select
different populations of galaxy clusters. We will complement the
sample proposed here with data already in the HST archive to extend
the range in mass and redshift. In combination with our ground based
efforts we will be able to study the evolution in the properties of
galaxy clusters from the present day out to $z\sim 1.4$, thus paving
the way for cluster abundance studies in an era of precision
cosmology.


\SUBSECTION{Cluster masses from X-rays.}
The observed X-ray luminosity function of clusters (e.g., Gioia 1991;
Vikhlinin et al. 1998; Rosati et al.2001; Nichols et al. 1999) or the
distribution of the X-ray gas temperature (Henry \& Arnaud 1991; Eke
eta l. 1998; Donahue \& Voit 1999; Henry 2000) can be tied to
cosmological models by detailed observation of the intra-cluster
medium.  The latter X-ray observations provide good estimates the
virialized masses of clusters, but are observationally very expensive.
We thus rely on X-ray observations of a subsample of clusters as
important calibrators for this method. Obtaining accurate X-ray
observations for all the clusters in our proposed sample is a major
goal, as are Sunyaev-Zeldovich measurements. In combination with
the weak lensing measurements, we will be able to study the properties
of the intra-cluster medium at this high redshifts for the first time
with sufficient detail. 


Currently, 4 of our proposed
X-ray selected clusters and 5 of our optically selected clusters have
available or scheduled X-ray measurements via XMM or Chandra that are
sufficient to determine cluster temperatures and masses to $15\%$
accuracy.  We will vigorously pursue additional observations to create
a calibration sample spanning our complete redshift and mass range.

%Chandra observations of cluster morphology  also provide
%important information about the core mass distributions and
%dynamical state of the clusters. These observations are important
%in the interpretation of strong lensing results, and investigating
%any discrepanies between weak lensing and virial mass
%estimators. The dynamical state of the cluster may also provide an important
%parameter in understanding the cluster galaxy stellar populations
%(e.g. Biviano \etal\ 2003) and the history of star formation as
%cluster-scale stuctures are assembled.


\SUBSECTION{Sunyaev-Zeldovich estimates of cluster masses and $D_A$.}
Using Sunyaev-Zel'dovich (SZ) observations along with X-ray observations of a
single galaxy cluster, one can decouple the dependence of the signals on
electron density and determine the angular diameter distance ($D_A$) to the
cluster.  To date, the method has been used to determine distances to 26
different clusters.  A fit to the sample of SZE and X-ray determined distances
yields a Hubble constant $H_0 = 60 \pm 3$ (statistical) $\pm 18$ (systematic) km/s/Mpc, 
(for $\Omega_M=0.3$, $\Omega_{\Lambda}=0.7$) (Reese \etal, 2002).

The SZ Array (SZA) is one instrument in the next generation of dedicated
telescopes for observing galaxy clusters and determining SZ
cosmological-distance measurements.  However, this method has never been
calibrated against other distance measurements.  The SN Ia measurements
described in this proposal will provide a sample of distance-calibrated high
redshift galaxy clusters which will be be targeted in future SZA observations
to allow a first cross-calibration.
%The sample is being studied extensively in X-ray observations, which will be
%used in conjunction with the SZ measurements to provide an independent distance
%measurement to the cluster.
%%Comparing the SZ/X-ray distance measurements to
%%the SNe distance measurements, we can determine the extent of systematic
%%uncertainties in the two methods.


\SECTION{Galaxy Cluster Science at $z \gs 1$}


(Note that our present ignorance of some cluster properties does not
impact upon the main science driver with SNe.)

%%%%%%%%%%%%%%%%%%%% The following is from Adam Stanford
% Peter Eisenhardt cut at this topic
Quantifying and interpreting the assembly and star formation history of massive
elliptical galaxies is one of the principal objectives of galaxy evolution
research.  Whether they form via monolithic collapse (Eggen, Lynden-Bell \&
Sandage 1962) or hierarchical assembly (White \& Frenk 1991), such galaxies
account for a substantial fraction of the stellar mass in the Universe (Hogg
\etal\ 2002), and are found in highly overdense regions (Hogg \etal\ 2003) -
i.e., galaxy clusters.  The slope, scatter, and intercept of the cluster
elliptical galaxy color magnitude relation at $z < 1$ are surprisingly well
matched by a simple star formation history consisting of a burst at $z > 3$
followed by passive evolution (Stanford \etal\ 1998), and their luminosity
functions also are fit by such models (de Propris \etal\ 1999), arguing for
little assembly at $z < 1$.   ACS imaging of more distant clusters will
determine how far this implausibly simple scenario can be pushed, by enabling
measurements of the fractions of mergers and ellipticals, and their luminosity
functions.

The ACS GTO team (including co-I's on this proposal) has made significant
progress in understanding $z \sim 1$ galaxy clusters.  Postman \etal\ (2005)
present results based on morphological analyses of ACS imaging of 7 clusters at
$0.8 < z < 1.3$.  They
%confirm previous work by Smith \etal\ (2004 -- REF???) that a
%morphology--density relation exists at $z \sim 1$, but that the slope of this
%relation flattens from the present epoch out to high redshift.  Moreover,
%Postman \etal\ 
find that the fraction of ellipticals does not change up to $z \sim 1.25$, and
that the fraction of S0s remains roughly constant at the 20\% level seen in
$0.4 < z < 0.5$ clusters.  Hence, the formation of all massive cluster
ellipticals, and a significant fraction of the lenticulars as well, must be
occuring at $z > 1.25$.

This proposal will take the next step beyond the limits of the GTO program in
terms of small sample size and redshift to probe the regime in which massive
cluster galaxies are being formed.  The GTO program has three clusters as
$z>1$, while our sample has 16.  The highest redshift of the clusters is pushed
from $z=1.26$ to $z=1.6$.

In conjunction with data we have obtained on our sample clusters from Chandra,
XMM, Keck, the VLT, Magellan, and Spitzer, the ACS data to be obtained in this
proposal will provide the ability to
%: {\bf 1)}
determine the epochs of the assembly of ellipticals and the origin of S0s, 
%{\bf 2)} measure the mass function of distant clusters 
and calibrate the relation between mass and X-ray luminosity and temperature,
as well as future SZ mass determinations, at unprecedented redshifts. 
%and {\bf 3)} compare the properties of clusters selected in the optical, NIR,
%and X-ray at redshifts $z > 1$ where clusters are first forming.


%\SUBSECTION{Galaxy Evolution and Clusters}
%
%Progress in understanding galaxy evolution in clusters is being driven
%by the need to reproduce simultaneously the lower number fractions of
%early-types towards higher-$z$ (Dressler et al.\ 1997; van Dokkum et
%al.\ 2001; Postman et al.\ 2005), strong homogeneity and slow
%evolution in the stellar populations of ellipticals and S0s in
%moderate redshift clusters ( Aragon-Salamanca et al.\ 1993; Ellis et
%al.\ 1997; Stanford, Eisenhardt, \& Dickinson 1998; van Dokkum et 
%al. 1998a; Kelson et al.\ 2000; van Dokkum \& Stanford 2003; Blakeslee
%et al.\ 2003; Holden et al.\ 2004; Postman et al.\ 2005), the
%morphology-density relation (Postman et al.\ 2005), and galaxy
%downsizing (Kodama et al.).
%
%
%A self-consistent explanation of these results can be achieved by
%invoking an observational bias: the progenitors of the youngest,
%low-redshift early-types drop out of samples constructed in high
%redshift clusters.  van Dokkum \& Franx (2001) have shown the way that
%morphological evolution at $z \lesssim 2$ coupled with star formation
%at $z \sim 2-3$ ($\Omega_m = 0.3$, $\Lambda = 0.7$) can explain the
%results seen in Figure 2.  More complex semi-analytic models of
%galaxy formation and evolution set in a CDM universe naturally predict
%the morphological evolution that is a central tenet in the paradigm of
%cluster galaxy evolution discussed here: ellipticals are formed by
%mergers at higher redshift (e.g., van Dokkum et al.\ 1999), and the
%Butcher-Oemler effect is the result of spirals being converted into
%S0s at moderate redshifts (Dressler et al.\ 1997).  The models of
%Kauffman \& Charlot (1998) are able to match the small scatter in the
%color-mag relation of the early-types, and even the $M/L$ evolution
%found by e.g.\ van Dokkum et al.\ (1998) can be predicted (Diaferio et
%al.\ 2000).
%
%However the accuracy of this scenario for galaxy evolution in clusters
%is open to debate.  In the case of early-types, the ideas are based
%heavily on observations of only a few high-z clusters (e.g., MS1054
%and RDCS0848+4453).  For disk galaxies, the details of when field
%spirals fall in to a cluster and have their star formation stopped are
%essentially unknown.  Several types of critical tests must be
%performed on multiple, well-defined cluster samples that span a range
%of cluster mass at high redshift (mainly $z > 1$), where qualitative changes in the
%cluster galaxy population seem to be occuring: 1) determine the
%relative fractions of ellipticals and S0s (separately), and of disk
%galaxies to investigate dependencies
%on cluster mass, position within the cluster, and redshift; 2) measure
%the early-type $M/L$ ratios (now possible up to $z \sim 1.3$ [van
%Dokkum \& Stanford 2003; Holden et al.\ 2005] in conjunction with Keck+VLT
%spectroscopy) using the intercept of the fundamental plane (FP) in
%order to determine if there is variation in the galaxy $M/L$ ratios at the
%same redshift; and 3) precisely measure the slope and intrinsic scatter in the
%color-mag relation in a larger number of high-$z$ clusters to
%determine if there are any variations with respect to cluster mass or
%dynamical state .


\SUBSECTION{Supernovae rates and star formation}
The rate of supernovae in galaxy clusters will address outstanding questions
about the intracluster medium (ICM).  Specifically, the high metal abundances
and the high energetics of the ICM are as-yet unexplained.  The metals seen in
luminous elliptical galaxies is explained by Type Ia supernovae rates and mass
loss from evolving stars (which were originally enriched by Type II
supernovae).

However, the mystery arises when one looks at the iron abundances
in the ICM.  The iron produced from Type II SNe of a Salpeter IMF
do not produce enough iron, nor do Type I SNe.
It has been suggested by Brighenti \& Mathews 1999 that a higher
rate for Type Ia supernovae can explain the ICM metal abundances
as well as the ``entropy floor'' seen in the X-ray gas
(e.g., Lloyd-Davies, Ponman \& Cannon 2000).

The only observational measures of SN rates in $z \sim 1$ clusters
is from the work of Gal-Yam \etal\ (2002).
Searching the HST archive for repeated WFPC2 pointings of
galaxy clusters, they identified 2 or 3 supernovae in 18 pointings
(with overlaps of 1.3 to 4.7 square arcminutes).
The derived SNe rate of $0.41^{+1.23}_{-0.39} h^2_{50}$ SNu in
clusters at $z\sim 1$ argues against SNe Ia being the
dominant source of iron in the ICM.  However, these statistics
from a mere 2 or 3 detections 
%could clearly use improvement, and
must be extended and improved for $z >1$.
%%Our proposal would allow an improvement at the level of ...[QUANTIFY?].


\SUBSECTION{Strong lenses at $z \gs 1$, and
the possibility of finding strongly lensed supernovae}
Massive clusters are rich test grounds for understanding of structure
formation and cosmological geometry through gravitational lensing of
background galaxies.  The probability of formation of giant arcs has
been found to be greatly enhanced, beyond expected, around clusters
(see, e.g., Gladders \etal\ 2003; Ho \& White 2004),
showing the need for increased understanding of their mass distribution.
As one eye-opening example, Broadhurst \etal\ (2004)
find over 130 images of 35 multiply lensed galaxies behind Abell 1689 using
ACS imaging.  This includes radial arcs and near-central images.
Our target list includes one already known high redshift lensing cluster,
RCS2319+0038 at z=0.91
(Gladders \etal\ 2003), exhibiting three dramatic giant arcs.  With
deeper z-band imaging, and the advantage of ACS for observing long,
thin, low surface brightness giant arcs, this cluster will
likely become the poster child for high-redshift cluster lensing.

Higher redshift cluster lensing will
be even more useful in constraining cluster mass profiles and
using arcs for geometric measures of cosmological distances.
Availability of X-ray and other wavelength
imaging of these clusters would provide much needed information for
understanding the role of clusters in cosmology. 
[[[BUT THIS IS NOT DONE BY THIS PROPOSAL -- should this point be taken out?]]]
Finally, cluster lenses act as natural
gravitational telescopes which facilitate the detection and study of
faint, high redshift galaxies (e.g., Metcalfe \etal\ 2003; Pello \etal\ 2004).
In particular, if our z-band images are combined with deep
i-band data, the i-z color can be used to search gravitationally
lensed high redshift galaxies out to $z\sim 7$.
Such lensing leads to the
possibility of finding strongly lensed supernovae and
extremely distant supernovae, otherwise too faint
to be detected (Gunnarsson \& Goobar 2003).
%By combining the observed (lensed) supernova brightness with the weak and
%strong lensing cluster information, important bounds may be set on
%both cosmological parameters and the mass profile of the lensing
%cluster.


\SECTION{Conclusions}

The observations proposed here initiate a new approach to SN measurements 
and will provide a first 
significant, {\it and unbiased} measurement of $w_0$ vs. $w^\prime$.  They
will  then comprise a springboard for a wide array of
astrophysical investigations: high redshift supernovae, cluster profiles,
gravitational lensing, and multiwavelength studies of large scale structure and
cosmology.  The emphasis on high redshift and attention to systematics are
the opening steps in bringing to maturity cosmological methods of the next
generation, and the cluster data will serve as a bedrock scientific legacy for
extragalactic astronomy.


\SECTION{References}
{\scriptsize
Blakeslee, J.~P.\ \etal\ 2003, ApJL, 596, 143 \\
Bower \etal\ 1992 {\bf ???} \\
Brighenti, F.\ \& Mathews, W.~G.\ 1999, ApJ, 515, 542 \\
Broadhurst, T.\ \etal\ 2004, ApJ  [astro-ph/0409132] \\
Brodwin, M. 2004, PhD thesis \\
%Cardelli, J.A., Clayton, G.C. \& Mathis, J.S. 1988, ApJ, 329, 33 \\
%Dalal, N., Holder, G., \& Hennawi, J.\ 2004, ApJ, 609, 50 \\
Donahue \& Voit 1999 {\bf ???} \\
Draine, B.~T.\ 2003, ARA{\&}A 41, 241 [astro-ph/0304489] \\
Ebeling, H., Edge, A.~C., \& Henry, J.~P.\ 2001, ApJ, 553, 668 \\
Eggen, Lynden-Bell \& Sandage 1962 ??? \\
Eisenhardt \etal\ 2004 {\bf ???} \\ % Array Camera Shallow Survey (IRAC)
Eke \etal\ 1998 {\bf ???} \\
Ellis \etal\ 1997 {\bf ???} \\
Fadeyev, Alderring \etal\ 2004 {\bf ???} \\
%Fontana, A. \etal\ 2000, AJ, 120, 2206 \\
Gal-Yam, A., Maoz, D., \& Sharon, K.\ 2002, MNRAS, 332, 37 \\
Gioia 1991 {\bf ???} \\
Gladders, M.~D., Hoekstra, H., Yee, H.~K.~C., Hall, P.~B.,
  \& Barrientos, L.~F.\ 2003, ApJ, 593, 48 [astro-ph/0303041] \\
Gladders \& Yee 2004 {\bf ???} \\ % RCS cluster survey
Gunnarsson, C.\ \& Goobar, A.\ 2003, A{\&}A, 405, 859 \\
%Haiman, Mohr \& Holder 2001 \\
%Hennawi, J. \etal\ 2005, in prep. \\
Gunnerson \& Goobar 2003 {\bf ???} \\
Henry 2000 {\bf ???} \\
Henry \& Arnaud 1991 {\bf ???} \\
Heymans, C.\ \etal\ 2004, MNRAS, submitted [astro-ph/0411324] \\
%Holz, D.E. \& Linder, E.V. 2005, submitted to ApJ [astro-ph/0412173] \\
Ho, S.\ \& White, M.\ 2004, ApJ, submitted [astro-ph/0408245] \\
Hoekstra, H., Franx, M., \& Kuijken, K.\ 2000, ApJ, 532, 88 \\
Hogg, D.~W.\ \etal\ 2002 ??? \\
Hogg, D.~W.\ \etal\ 2003 ??? \\
Hogg, D.~W.\ \etal\ 2004, ApJ, 601, 29 \\
Jee, M.~J., White, R.~L., Benitez, N., Ford, H.~C., Blakeslee, J.~P.,
  Rosati, P., Demarco, R. \& Illingworth, G.~D.\ 2005, ApJ, 618, 46 \\
Knop, R.\ \etal\ 2003 {\bf ???} \\
Kolatt, T.~S.\ \& Bartelmann, M.\ 1998, MNRAS, 296, 763 \\
Krist, J.~E. \& Hook, R.~N.\ 2004, the Tiny Tim User's Manual, version 6.3 \\
Linder, E.~V.\ \& Miquel, R.\ 2004, Phys.\ Rev.\ D, 70, 123516 [astro-ph/0409411]  {\bf ???} \\
Lloyd-Davies, E.~J., Ponman, T.~J. \& Cannon, D.~B.\ 2000, MNRAS, 315, 689 \\
Lombardi, M.\ \etal\ 2005, ApJ, in press, astro-ph/0501150 \\
Metcalfe, L.\ \etal\ 2003, A{\&}A, 407, 791 \\
Majumdar, S.\ \& Mohr, J.~J.\ 2003, ApJ, 586, 603 \\
Majumdar, S.\ \& Mohr, J.~J.\ 2004, ApJ, 613, 41 \\
Nichols \etal\ 1999 {\bf ???} \\
Pain, R.\ \etal\  {\bf ???} \\
Pell{\' o}, R., Schaerer, D., Richard, J., Le Borgne, J.-F., \& Kneib,
  J.-P.\ 2004, A{\&}A, 416, L35 \\
Perlmutter, S.\ \etal\ 1995, ApJ, 440, 41 \\
Perlmutter, S.\ \etal\ 1999 {\bf ???} \\
Pierre \etal\ 2004 {\bf ???} \\
Postman, M.\ \etal\ 2005, ApJ, in press [astro-ph/0501224] \\
Sullivan, M.\ \etal\  {\bf ???} \\
Reese, E.~D., Carlstrom, J.~E., Joy, M., Mohr, J.~J., Grego, L.,
  \& Holzapfel, W.~L.\ 2002, ApJ, 581, 53 \\
Riess, A.\ \etal\  2004 {\bf ???} \\
Rosati \etal\ 1998 {\bf ???} \\ % RDCS survey
Rosati \etal\ 2001 {\bf ???} \\
Stanford, S.~A., Eisenhardt, P.~R., \& Dickinson, M.\ 1998 ApJ, 492, 461 \\
Tripp, T.\ 1998, A{\&}A, 331, 815 \\
van Dokkum \etal\ 2001 {\bf ???} \\
Vikhlinin \etal\ 1998 {\bf ???} \\
White \& Frenk 1991 {\bf ???} \\
}

%%%%%% FIGURES %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}
\plottwo{ms_hubble_type2.eps}{hubble2.ps}
\caption{
 {\em (a) Left Panel:}  The SCP SN Ia Hubble diagram broken into host galaxy
types from Sullivan et al.\ (2003).  The SNe in elliptical hosts (filled red
circles) show significantly less dispersion, $\sigma = 0.16$ mag, including
measurement error.   (This ground-based measurement error for this $z \sim 0.5$
sample is quite close to the HST measurement error at $z>1$ in this proposal.)
{\em (b) Right Panel:}    The comparison of the Hubble diagram, before and
after extinction correction, for a mixture of SNe Ia in all host types shows
the dramatic increase in error bars due to the uncertainty in $B - V$ color
being multiplied by $R_B \approx 4$ and by the uncertainty in $R_B$.   The data
shown is from the SCP (Knop et al.\ 2003) and the Riess et al.\ 2004 GOODS
search samples.  For the SNe at redshifts $z > 1$ this yields an uncertainty of
$\sim$0.5 mag, which is consistent with the measured dispersion of 0.5 mag.
The ratio of this dispersion to the elliptical-hosted dispersion of panel (a)
makes the elliptical-hosted SNe  each worth 9 of the
extinction-corrected others.  } \end{figure}

%\begin{figure}
%%\plotone{bias.eps}
%{\plotfiddle{bias.eps}{2.0truein}{0}{40}{40}{0}{0}}
%\caption{ 
%\end{figure}

\begin{figure}
\plotone{wwPrimeHSTclusterFig2.eps}
\caption{ 
{\em (a)  Left Panel:}  Confidence region on the $w^\prime$ vs $w_0$ plane for
a simulation matched to the current literature supernovae sample but with
underlying cosmology ($w_0 = -1$; $w^\prime =0$).   The parameters are quite
poorly constrained because uncertainties in color measurement are magnified by
$R_B \approx  4$.  {\em (b) Middle Panel:}   To remedy this problem, one might
try using a prior on the extinction distribution to be less sensitive to the
color measurement and hence its large uncertainty as shown by the solid red
contour.   However this introduces systematic biases  in the extinction
correction, shown by the shift from the underlying cosmology (dashed contour),
if the uncertainties are higher at  high redshift than at low redshift as is
the case with the actual data.   The filled gray contour is the result reported
in Riess et al 2004 using this extinction-prior approach.   The short-dashed
contour shows that this approach is also sensitive to shifts in the value of
$R_B$ with redshift; the example shifts from 4.1 to 3.5. {\em (c)
Right Panel:}   The goal of this proposal is shown as a confidence region for a
simulated new sample of $\sim10$ $z \gs 1$ SNe Ia found in cluster ellipticals,
together with 5 in ellipticals from the past and ongoing GOODS searches, as
well as 120 SNe Ia in ellipticals at the lower redshifts now being produced by
the ground-based CFHT SN Legacy Survey, the CTIO Essence survey, and (at $z<
0.1$) the Nearby SN Factory.   A SN Hubble diagram in ellipticals avoids  the
large statistical error problem of panel (a) and the large systematics problem
of panel (b).  } \end{figure}

\begin{figure}
%{\plotfiddle{od_new.eps}{2.0truein}{0}{40}{40}{0}{-50}}
\plottwo{od_new.eps}{histomad.ps}
\caption{
 {\em (a) Left Panel:} Elliptical host supernovae at $z \gs 1$ will be found
much more frequently in our cluster sample than in the field.  The ratio
$L_B/<L_B>$ of rest frame blue luminosity for early type galaxies with $z > 1$
within an ACS FOV, relative to the average field value of this quantity, is
plotted for clusters in our sample from the optically selected Red-sequence
Cluster Survey (RCS - Gladders \& Yee 2004), the x-ray selected ROSAT Deep
Cluster Survey (RDCS - Rosati et al.\ 1998), and the 4.5 micron selected Infrared
Array Camera Shallow Survey (IRAC - Eisenhardt et al.\ 2004).  } \end{figure}


\begin{figure}
%\plottwo{rdcs1252_acs_iz.eps}{cl1252_cmr.eps}
%\plottwo{r1252cmd.eps}{cmd_scatter_vs_z.eps}
\plottwo{r1252cmd.eps}{scat_vs_z.ps}
\caption {
{\em (a) Left Panel:} The dust-free nature of ellipticals (filled circles)
and S0 galaxies (filled squares) in RX1252-29 at $z=1.23$ is supported by
the small scatter of the color-magnitude relation.
The relation for the Coma cluster, 
transformed to the observed bands with no evolution
correction, is shown as a dot-dash line.  The solid line
is this relation at the redshift of RX1252 assuming WMAP
cosmology and $-1.4$ mag of luminosity evolution. \newline
{\em (b) Right Panel:} 
Scatter in rest frame $U-B$ CM relation for early-type galaxies in clusters as
a function of redshift.  In order of increasing redshift the points are from
Bower et al.\ (1992), van Dokkum et al. (1998), Ellis et al.\  (1998), van
Dokkum et al.\ (2000), Blakeslee et al.\ (2003), and van Dokkum et al.\ (2001).
The dashed line is the average value, indicating no change with redshift in the
scatter.
}
\end{figure}

%\begin{figure}
%{\plotfiddle{cmd_scatter_vs_z.eps}{2.0truein}{0}{100}{100}{0}{0}}
%%\plotone{cmd_scatter_vs_z.eps}
%\caption{ 
%}
%\end{figure}



%\begin{figure}
%{\plotfiddle{sn_z.eps}{2.0truein}{0}{50}{50}{0}{-100}}
%\caption
%{{\it upper panel:} Relative uncertainty in the weak lensing mass estimate as a
%function of cluster redshift for a cluster with M=$5\times
%10^{14}M_\odot$ and $10^{15}M_\odot$. The calculations assume that we
%can only use the shape measurements at $r>60"$, because of
%substructure in the cluster core. For some clusters we might be able
%to use the lensing signal at smaller radii, thus reducing the
%uncertainties. The average mass of the clusters in our sample is
%thought to be $\sim 5\times 10^{14} M_\odot$. The most massive
%clusters ($\sim 10^{15} M_\odot$) in the sample can be detected with
%high significance out to $z=1.4$. {\it lower panel:} Relative error in
%the zero-point of the mass-observable (i.e., $M-T_X$, $M-L_X$,
%$M-$richness) relation in four independent redshift bins. The relative
%errors are $<15\%$, allowing us to constrain the evolution in cluster
%properties, especially once tied to the ongoing work at lower
%redshifts. The resulting accuracy is sufficient to enable cluster
%abundance studies out to $z\sim1.4$!}
%\end{figure}


\begin{figure}
\plotone{followup.eps}
\caption{
The simulated data set for this proposal, with signal-to-noise at
a given redshift and SN epoch based on actual data from our previous SN
photometry with HST  ACS and NICMOS.
The simulated data was fit with the lightcurve-fitting program of our actual analysis to test the feasibility of the chosen cadences. Even after propagating the uncertainty in the lightcurve timescale stretch used for correction, we obtain typical errors of 0.07 to 0.13 mag for a redshift range between 0.9 and 1.5.
The bars at the top of the
figure show the observing time period covered for each cluster, and the symbols
show when observations are scheduled (with slightly different cadences
depending on the redshift of the cluster).   The same symbols are used for the
observations on the lightcurves, to show where a supernova might be discovered
and followed in its cluster's time window.   Note that the observations are
well spread throughout the year (allowing easy HST scheduling, with flexibility
since there are other clusters to study if one is difficult to schedule).
There are therefore SNe to be observed in our ground-based observing program at
almost any time during the year, in addition to the host galaxies that can be
observed  any time after the supernova is observed. } \end{figure}


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%   2. DESCRIPTION OF THE OBSERVATIONS
%       (see Section 9.2 of the Call for Proposals)
%
%      Please provide a short description of the proposed observations. 
%      Explain the amount of exposure time and number of orbits requested 
%      (e.g., number of objects, examples of exposure-time calculations and 
%      orbit estimates for some typical observations). You should summarize 
%      your target acquisition strategies and durations where relevant. For CVZ 
%      targets, state the number of CVZ opportunities available in the cycle. 
%
%      Discuss and justify any non-standard calibration requirements. You should 
%      estimate the number of orbits required for these special calibrations, and
%      include them in the Observation Summary section of APT. 
%
%      Depending on the type of proposal, the following items should also be 
%      included: 
%
%     *	Long-term projects should provide summary information for the entire 
%               project, along with a cycle-by-cycle breakdown of the requested 
%               spacecraft orbits. 
%     *	Treasury Programs should discuss the data products that will be made 
%               available to the community, the method of dissemination, and a realistic 
%               time line. It is a requirement that data products be delivered to STScI in 
%               suitable digital formats for further dissemination via the HST Data Archive 
%               or related channels. Any required technical support from STScI and 
%               associated costs should be described in detail. 
%
%		Proposers submitting Large and Treasury Programs should discuss
%		how they have designed their program with regard to schedulability.
%
%		- All proposers should include the number and durations of the
%		schedulability windows for each observation.
%		- Proposers of programs with timing constraints and timing relationships
%		between observations should describe those constraints,
%		including allowable flexibility.
%		- Proposers of programs containing large blocks of orbits at constrained
%		orientation angles, such as mosaics and surveys, should
%		describe those constraints and allowable flexibility.
%		- Proposers requesting large blocks of orbits with a single target
%		should estimate how many orbits/day will be required for their
%		programs, during the scheduling windows that meet their timing
%		and orientation restrictions.
%		- If a target visibility other than that indicated on the Large Program
%		web page is used, state the value used and explain why you used
%		that value.
%    *		Calibration proposals should present a detailed justification of how they 
%               will achieve the goals of the program, and if applicable, a description of 
%               the conditions under which these goals will be achieved. 
%    *		Calibration proposals should discuss what documentation, and data 
%               products and/or software will be made available to STScI to support 
%               future observing programs. 
%    *		Proposers submitting Large and Treasury programs are asked to
%		include additional technical detail to provide information on the
%		scheduling aspects of their program.
%
\describeobservations   % Do not delete this command.
% Enter your observing description here.

\SECTION{The supernova observing strategy}

The high rate of SNe Ia produced by the clusters {\it in addition} to the SNe
Ia in the fore/background field galaxies makes possible an elegantly simple
combined search-and-follow-up scheduling strategy.   Generally, we observe each
cluster with the ACS F850LP filter every $\sim$24 days for $\sim$8 visits, with
the exact cadence depending on the cluster redshift and the exact number of
visits depending on HST observing constraints for the cluster.  This means that
every supernova that appears in these clusters during the entire period, modulo
small end effects, will have a lightcurve measured --- without the need for
expensive Target of Opportunity (ToO) observations.  We obtain ground-based
spectroscopy of the supernovae's host galaxies after the fact, for precise
redshifts and confirmation of elliptical galaxy type, which also confirms the
SN Ia identification.  For only the two highest redshift SNe, we supplement
this basic lightcurve with an additional ($>$2-week-advance-notice) ToO
follow-up observation sequence with NIC2 F110W, to provide restframe $B$ band
lightcurve data --- since the NICMOS fields are too small to be used in the
pre-scheduled search. (The very lowest redshift clusters are observed as part
of the pre-scheduled cadence in ACS 814W to match the restframe B band.)

Figure 5 shows this strategy.  Note that this is a dramatically more
efficient approach than the previous ACS/GOODS searches, performed by both our
team and the Riess et al.\ team, for several reasons.   First, there is a large
net savings in the number of search-plus-follow orbits necessary to study
$\sim$10 SNe Ia; the previous method required $\sim$35\% more orbits.  Second,
the number of required ToO's is reduced from 10 to 3 per SN,
in itself equivalent to
many orbits of observing time, and that these are ToO's with more than two
weeks advance notice and hence much less disruptive to schedule.  Third, the
resulting data has much smaller statistical uncertainties, since the large
contribution from extinction correction is removed, making each of these SNe
worth $\sim$10 SNe not found in ellipticals.  Fourth, not only will the
$\sim$10 cluster SNe be supplemented by $\sim$10 SNe from the field that would
have been studied in the GOODS searches, but there is still an additional
population of useful SNe that have their lightcurves obtained, which previously
could not be followed given the limited number of ToO's.  (Including the
cluster and the field, each cluster target field will thus be expected to yield
on average one SN Ia in the $z>1$ range and more at $z<1$ -- all with z-band
lightcurves.)


This observing strategy is also considerably simpler to schedule than the
previous GOODS searches.  The observing simulations show that there is
flexibility in the exact choice of repetition dates; the cluster observations
can be at any orient (unlike the contiguous GOODS tiles); there are clusters on
the target list observable at different times of the year, and they do not all
need to be observed in the same cadence like the GOODS tiles, so the observing
load is spread.



The observing requirements for this program are based on our experience with
ACS and NICMOS measurements of supernovae in precisely this redshift range
(with even a few in ellipticals), so we have direct tests of our exposure time,
filter, and cadence requirements.    For the bulk of the target clusters,
between $z = 1.1$ and 1.4, we require a single ACS orbit with the 850LP filter
every 24 observer days (i.e., $\sim$10.5 SN-restframe days) over the
lightcurve.   After propagating errors for the fit of the lightcurve timescale
(used to calibrate the peak magnitude), this yields a SN Hubble-diagram point
with uncertainty below the $\sim$0.15 mag intrinsic SN Ia uncertainty (in fact,
$90\%$ of the SNe will have distance modulus uncertainties below 0.10 mag).  At
redshift smaller than 1.1 one can afford to increase the cadence to 28 observer
days and still be left with an
uncertainty in the distance modulus of less than 0.1 mag.  Correspondingly,
for redshifts $z>1.4$ we choose a shorter cadence of 20 days to compensate
for the increase of the photometric errors.   The fluxes/magnitudes, cadences
and error bars shown in Fig.~5 demonstrate the range that are expected for
this program.

[CHECK ALL THE NUMBERS IN THIS PARAGRAPH -- they are currently estimates.]  For
an elliptical host galaxy, with its symmetric smooth morphology, the images
before and/or after the SN lightcurve generally provide a fit of the host
galaxy light that gets subtracted from each image of the SN-plus-galaxy.
However, for $\sim$2 of the targeted $\sim$10 SNe Ia we expect the SN to be so
close to the core of a bright host that we will need an additional final image
the following year, with a 3-orbit depth so as not to degrade the
signal-to-noise after subtraction.   
%More than offsetting this requirement for
%6 additional orbits is the probability of cancelling the final cadence
%observations for clusters that have not produced a SN in time to be followed
%for sufficient lightcurve points.
Offsetting this requirement for
6 additional orbits is the probability of cancelling the final cadence
observations for clusters that have not produced a SN in time to be followed
for sufficient lightcurve points.  This should happen often enough that
we can reschedule these cancelled final observations to provide the
following-year visit for the cases that require them.
%This will happen, on average, for 15 of the
%25 clusters, saving 15 orbits from the total required.  
(The cancellations would be three weeks in advance, so will not introduce
scheduling complications.) 

For the highest redshift clusters probability distributions for the photometric
redshifts and SED fits (Brodwin 2004, PhD thesis) are available for all sources
in the field down to the IRAC $4.5\mu$m selection limit (which corresponds to
$\sim L^* + 0.5$.)  Only SNe associated with hosts with $>90\%$ probability of
having both $1.3 < z < 1.6$ and an SED type earlier than Sbc at $z=0$
(corresponding to a $z_f = 3$ passively evolving elliptical at $z=1.6$) will be
targeted for NICMOS followup. 
%%end new part
[Issues to decide:   Do we want full lightcurve follow-up of $z>1.3$ SNe, or
just at max?   Do we want an additional point in a NICMOS color at max for a
number of $z ~ 1.1$ SNe to check the intrinsic color (which would help the
measurements of spiral-hosted SNe)?   What about a point in the CMAGIC period
of the lightcurve?]


The fundamental dataset of F850LP-band lightcurves for every SN shown (and
more!) in Figure 5 will be obtained without need of any ToO's.   However, for
specific cluster redshift ranges the science will be greatly enhanced by
strategic use of additional low-impact ToO orbits.  Primarily, these consist of
a simple single-orbit or two-orbit observation in an additional NICMOS F110W
filter {\em that can be scheduled over two weeks in advance}.

A short cadence of $\sim 24$ days for redshifts $z \approx$ 1 -- 1.5 will allow
prompt detection of SNe while still on the rise.  Single-orbit NICMOS F110W
follow-up observations will lead to a SN observation within $\pm$5 days
(rest-frame) around maximum light.
For three of the SNe ($z \approx$ 1.25 -- 1.5
clusters), these near-maximum orbits  will provide the restframe B-band point
(with an error of $\sim$ 0.07 magnitudes) to tie these SNe to the same
restframe-B Hubble diagram as the others.   (Restframe U in 850LP will provide
the lightcurve date and timescale ``stretch'' measurement, as for previous
very-high-redshift SNe.)  For 6 of the SNe ($z \approx$ 1 -- 1.25 clusters),
these observations provide a color measurement at maximum light to calibrate
the intrinsic SN Ia colors at high-redshift.  Note that these ToO's are much
less expensive in orbits and disruption to the HST calendar than the
fast-run-around $\sim$20-orbit-timeseries ToO's needed for every one of the
GOODS supernova discoveries by the two SN research teams.  For only two of our
ToO's, for a SN at $z \gs 1.4$ will this time series of 8 orbits be needed to
provide the restframe B lightcurve, when the F850LP lightcurve is too far into
the restframe UV of the SN to provide significant signal-to-noise.

\SECTION{Observing requirements for the cluster science}

The primary requirement for achieving our objectives on the evolution and
formation of galaxies in clusters is to obtain reliable visual classifications
of galaxies down to 2 magnitudes below $L^\ast$ at $z \sim 1.2$ using the
standard system of elliptical, lenticular, and spiral/irregular over an area
reaching out to $r_{200}$.  The secondary requirement is to measure galaxy
sizes, in particular $r_e$, with sufficient accuracy to enable estimates of
$M/L$ ratios for early-type galaxies when coupled with velocity dispersions
being obtained with ground-based facilities.  These requirements can be met
with 8 orbit exposures in the F850LP band of the central $\sim$200 arcsec area
of our target clusters, as shown  by Postman \etal\ (2005) and by Holden \etal\
(2005). In order to determine the morphologies of galaxies in the high redshift
galaxies, HST images are necessary. Ground-based images even with 0.5 arcsec
seeing are incapable of yielding high enough spatial resolution to reliably
determine e.g.  whether a galaxy is an elliptical or a lenticular (crucial to
understanding the origins of these two kinds of galaxies) in clusters at $z
\sim 1$ and greater.


\SECTION{Observing requirements for the weak lensing studies}

Most current weak lensing studies of galaxy clusters with HST use a
mosaic of observations in order to extend the measurement of the
lensing signal out to larger radii, thus improving the accuracy of the
mass measurement. Typically the motivation for this is the need to
break the mass-sheet degeneracy; in practice this is not feasible, and
instead we intend to fit parameterized mass models (e.g., the NFW
profile predicted by cold dark matter simulations) to the data. This
approach still benefits from covering a large area, but our detailed
calculations show that the gain is minimal for clusters beyond $z=1$
(where the FOV of ACS is well matched to the cluster). We find that
we obtain more accurate masses by obtaining deeper observations
instead, thus increasing the number density background galaxies and
the accuracy in the shape measurements.

Hence the observing strategy for the SNe search is well matched to the
requirements of the weak lensing mass determination. For clusters
below $z=1$ and clusters that show evidence of a complicated mass
distribution we might consider mosaiced observations (with a large
overlap in the centre), but most of the clusters will be observed to
an $\sim 8$ orbit depth.

We estimated the expected accuracy in the weak lensing mass
measurements but considering a cluster described by a singular
isothermal sphere. We furthermore adopted a photometric redshift
distribution for the background galaxies based on UDF observations. As
we propose observations of high redshift clusters, some of which are
known to have a complex mass distribution in their cores (e.g.,
Hoekstra \etal\ 2000; Jee \etal\ 2005), we also assume that we can only
use the shape measurements at $r>60"$. For some clusters we might be
able to use the lensing signal at smaller radii, thus reducing the
uncertainties. We compared the outcome of our model calculations to
actual published results (Jee \etal\ 2005; Lombardi \etal\ 2005) and
find very good agreement.

The average mass of the clusters in our sample is thought to be $\sim
5\times 10^{14} M_\odot$. Our calculations suggest that we obtain a
$\sim 30\%$ accuracy in the mass measurement of our "average" cluster.
More importantly, the observations allow us to determine the
zero-point of the mass-observable (i.e., $M-T_X$, $M-L_X$,
$M-$richness) relation in four independent redshift bins, with a
relative error $<15\%$ in each bin. This enables us to constrain the
evolution in cluster properties, especially once tied to the ongoing
work at lower redshifts. The resulting accuracy is sufficient to
enable cluster abundance studies out to $z\sim1.4$!

COSMOS and GEMS (Heymans \etal\ 2004) observations show the ACS PSF undergoes
cyclic variation with a period of 15-20 caused by thermal fluctuations within
the telescope.  However, we have extensive experience in correcting for such
effects.
Using the program TinyTim (Krist \& Hook 2004) we can create
models of the PSF for the entire range of allowed focus values. Then,
the $\sim 20$ stars in each exposure suitable for PSF measurement
can be used to determine the focus value for that exposure. The
appropriate TinyTim model can then be used for PSF correction.

We should also note that because of the nature of this program, the
clusters will be observed with different roll angles, thus partly
averaging out some of the PSF effects. In addition, studies of galaxy
clusters are less sensitive to residual systematics compared to cosmic
shear measurements.

\SECTION{Ground-base observations}
Extensive ground-based observations of the target clusters have been carried
out and will continue to be performed at Keck, Magellan, and the VLT.  Deep
multiband imaging exists for all target clusters, including in most cases
optical and NIR bands.  An abundant amount of multiwavelength data has already
been published for the three X-ray clusters (Stanford et al.\ 1997, Rosati et
al.\ 1999, Stanford et al.\ 2001, Stanford et al.\ 2002, Rosati et al.\ 2004,
Lidman et al.\ 2004, Holden et al.\ 2004).   In particular, we have
spectroscopic redshifts for the brightest $\sim$ 20 member galaxies on average
for each of these RDCS clusters so the redshifts of the likely host galaxies
for SNe to be found in this HST program are already known.  For the IRAC
clusters, we have begun a program of slitmask spectroscopy at Keck to obtain
redshifts for the brightest galaxies which should provide spectroscopic-$z$ for
galaxies containing $\sim$50\% of the total cluster luminosity within the next
$\sim$2 years.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%   3. Two-Gyro Mode Observations
%       (see Section 9.3 of the Call for Proposals)
%
%		This new section has been added to take account of the possible 
%		transition from standard three-gyro operations with HST to the 
%		Two-Gyro Science Mode currently under development by the 
%		HST project. This is likely to result in reduced scheduling flexibility 
%		(fewer orbits available for a given target), lower observational 
%		efficiency (longer overheads per target) and, possibly, degraded 
%		scientific performance. Those issues are discussed
%		thoroughly in The HST Two-Gyro Science Handbook.
%
%		Based on the information in the HST Two-Gyro Handbook, 
%		proposers should address the following issues:
%
%		� Are the scientific goals of this proposal attainable with observations
%		undertaken in two-gyro mode?
%		� How will the observations be modified to take account of two-gyro
%		operations? Modifications might include increased integration times
%		and/or fewer instrumental configurations for GO and SNAP Programs;
%		GO Programs might envisage a reduced number of targets
%		and/or increased orbit allocations.
%		� In the case of Large, Treasury and Long-Term GO Programs, what
%		are the scientific implications if only a subset of the data are obtained
%		in normal three-gyro mode?
%
\describetwogyro   % Do not delete this command.
% Enter your Strategy for Two-Gyro Mode Observations here.
Because of the continuous time series of observations required by this proposal
it would be important not to change the observing plan if only a subset of the
data were obtained in normal three-gyro mode.   Fortunately, there are
sufficient numbers of rich $z > 1$ clusters to target that we can choose a
target set that works for either two or three gyro mode with no change in our
observing plan.   We have checked that all of the observations can be made in
two-gyro mode for the time window requested.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%   4. SPECIAL REQUIREMENTS
%       (see Section 9.4 of the Call for Proposals)
%
%       List and justify any special scheduling requirements, including
%       requests for: 
%
%         - Target of Opportunity (TOO) observations: 
%              estimate the TOO's probability of occurrence during Cycle�14, and 
%              state how soon HST must begin observing after the occurrence 
%         - Continuous Viewing Zone (CVZ) observations
%         - Shadow time (SHD) or Low-sky (LOW) observations 
%         - Time-critical observations
%         - Early acquisition observations
%         - Coordinated Parallel (CPAR) or Pure Parallel (PPAR) observations
%         - Target acquisitions that use the `Reuse target offset' function
%         - Real-time interactions
%         - Scheduling of STIS/MAMA and STIS/CCD observations 
%              (other than target acquisitions) in the same visit
%         - Scheduling of coronographic observations in the same 
%              orbit with a roll of the spacecraft between observations
%         - Requests for expedited data access
%         - Other special scheduling requirements (e.g., requests for
%             non-SAA impacted orbits
%
%       Also, if applicable, discuss the benefits of or need for a 
%       non-default proprietary period request.
%
\specialreq             % Do not delete this command.
% Justify your special requirements here, if any.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%   5. COORDINATED OBSERVATIONS
%       (see Section 9.5 of the Call for Proposals)
%
%       If you have plans for conducting coordinated observations with 
%       other facilities that affect the HST scheduling, please describe 
%       them here (examples are coordinated or simultaneous observations 
%       with other spacecraft or ground-based observatories). Describe how 
%       those observations will affect the scheduling. 
%
%       If you have plans for supporting observations that do not affect 
%       HST scheduling, then don't describe them here. If they improve 
%       your science case, then describe them in the `Scientific Justification' 
%       section of the proposal (see Section 9.1). 
%
%       A limited feasibility check on coordinated observations between 
%      HST and a few other observations (Chandra, XTE, and FUSE) may 
%      be performed via the Visual Observation Layout Tool (VOLT), developed 
%      at the Goddard Space Flight Center. See the VOLT web site at
%           http://pioneer.gsfc.nasa.gov/public/volt/home.html
%      for more information. Note that VOLT cannot be used for detailed
%      (Phase II) scheduling of HST observations. 
%
%      Joint HST-Chandra Observations 
%
%      Proposers requesting joint HST-Chandra observations must provide a 
%      full and comprehensive technical justification for the Chandra portion 
%      of their program. This justification must include: 
%
%	*	the choice of instrument (and grating, if used), 
%	*	the requested exposure time, justification for the exposure time, target
%		 count rate(s) and assumptions made in its determination, 
%	*	information on whether the observations are time-critical; indicate 
%		whether the observations must be coordinated in a way that affects the 
%		scheduling (of either the Chandra or HST observations), 
%	*	the exposure mode and chip selection (ACIS) or instrument configuration 
%		(HRC), 
%	*	information about nearby bright sources that may lie in the field of view, 
%	*	a demonstration that telemetry limits will not be violated, 
%	*	a description of how pile-up effects will be minimized (ACIS only). 
%
%	Technical documentation about Chandra is available from the 
%	Chandra X-ray Center (CXC) Web Page at: http://asc.harvard.edu/
%	which also provides access to the Chandra Help Desk. The primary document 
%	is the Proposer's Observatory Guide, available from the Chandra User 
%	Documents Web Page and the Chandra Proposer Web Page. Full specification 
%	of approved observations will be requested during the Chandra Cycle 7 
%	period when detailed feasibility checks will be made. 
%
%	Proposers requesting joint HST-Chandra observations must specify 
%	whether they were awarded Chandra time in a previous Chandra or HST 
%	cycle for similar or related observations. 
%
%	Joint HST-Spitzer Observations
%
%      Proposers requesting joint HST-Spitzer observations must provide a full 
%	and comprehensive technical justification for the Spitzer portion of their 
%	program. This justification must include:
%
%	� the choice of instrument and Astronomical Observation Template(s),
%	� the requested observing time, justification for the requested time, target
%	fluxes, required sensitivity and assumptions made in its derivation,
%	� information on whether the observations are time-critical; indicate
%	whether the observations must be coordinated in a way that affects
%	scheduling of either HST or Spitzer observations.
%
%	Technical documentation about the Spitzer Space Telescope is available
%	from the Spitzer Science Center (SSC) Web Page, which also provides
%	access to the Spitzer Help desk (help@spitzer.caltech.edu). The primary
%	document is the Spitzer Observer�s Manual, available, together with other
%	relevant documents, from the Proposal Kit Web Page. The SSC strongly
%	recommends that observers proposing Spitzer observations estimate the
%	required observing time using Spot, the Spitzer proposal planning software,
%	also available from the online proposal kit.
%
%	Proposers for Collaborative HST-Spitzer Programs must also complete the
%	Spitzer proposal submission process by the HST Cycle 14 deadline. Both
%	submissions should include the same PDF attachment. Detailed
%	instructions for the Spitzer submission are in the Spitzer Cycle 2 Call for
%	Proposals. In the case of Regular HST-Spitzer Programs, full specification
%	of the Spitzer observations will be requested by Spitzer after the proposals
%	are selected, at which time detailed feasibility checks will be made.
%
%	Proposers requesting joint HST-Spitzer observations must specify whether
%	they were awarded Spitzer time in a previous cycle for similar or related
%	observations.
%
%	Joint HST-NOAO Observations 
%
%	Proposers requesting joint HST-NOAO observations must provide a full 
%	and comprehensive technical justification for the NOAO portion of their 
%	program. This justification must include: 
%
%	*	the telescope(s) and instrument(s) on which time is requested, 
%	*	the requested observing time per telescope/instrument, a specification 
%		of the number of nights for each semester during which time will be 
%		required, a breakdown into dark, grey and bright time, and an 
%		explanation of how the required exposure time was estimated, 
%	*	information on whether the observations are time-critical; indicate 
%		whether the observations must be coordinated in a way that affects 
%		the scheduling (of either the NOAO or the HST observations), 
%	*	a description of any special scheduling or implementation requirements, 
%
%	Successful proposers will be asked to supply additional details about 
%	the observations, i.e., the same details required for NOAO proposals for 
%	the particular telescope/instrument. This "Phase II - NOAO" information 
%	must be submitted by the April 30, 2005 NOAO deadline for the Fall 2005 
%	semester. Submission instructions will be forthcoming following notification 
%	of the results of the HST review. 
%
%	Technical documentation about the NOAO facilities is available from the 
%	NOAO Web Page at:  http://www.noao.edu/. 	Questions may be directed to
%	 the NOAO Proposal Help Desk by email to noaoprop-help@noao.edu. 
%	NOAO will perform feasibility checks on any approved proposals. 
%
%	Proposers requesting joint HST-NOAO observations must specify whether 
%	they were recently (in the last two years) awarded NOAO time for similar or 
%	related observations. 
%
%	A full and comprehensive scientific justification for the requested NOAO 
%	observing time and facilities must be given in the `Scientific Justification'
%	 section of the proposal.       
%
\coordinatedobs          % Do not delete this command.
% Enter your coordinated observing plans here, if any.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%   6. JUSTIFY DUPLICATIONS
%       (see Section 9.6 of the Call for Proposals)
%
%       Justify, on a target-by-target basis, any potential duplication with 
%	previously accepted GO or GTO observing programs. Use the
%	`Duplication' checkbox in the OS to identify the duplicating observations.
%
\duplications           % Do not delete this command.
% Enter your duplication justifications here, if any.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%   7. PREVIOUS RELATED HST PROGRAMS
%       (see Section 9.9 of the Call for Proposals)
%
%       Please list the program number and status of the data for all 
%	accepted GO/SNAP/AR programs of the PI which are relevant to 
%	the current proposal. Include a list of major publications resulting 
%	from the previous HST observations and provide a sentence or two 
%	describing the significance of each paper. Related publications based 
%	on theory and/or data from other telescopes should be included. 
%	Unpublished data from early cycles should be explained. A significant 
%	publication record will be regarded by the Review Panels and TAC as 
%	a strong plus. GTO programs and publications may be included at the 
%	PI's discretion. 

%
%       The information in this section is not counted against
%       the total page limits for the proposal.
%
\previousprograms        % Do not delete this command.
% Enter your previous HST programs here, if any.
\emph{To be updated}

By combining observations from a series of GO programs over a number of HST
cycles we have obtained a cumulative sample of high redshift SNe which has
yielded new determinations of  cosmological parameters $(\Omega_M,
\Omega_\Lambda, w)$.  Equally important,  these HST observations have been the
basis for studies of possible systematics of the SN technique, such as
host-galaxy extinction or evolution.  Two such multi-cycle HST studies were
published in the past year and both provided confirmation and improved
precision on the earlier ground-based acclerating universe results.  Knop
\etal, 2003  (based on G0-7336, GO-7590, GO-8346) presented an analysis of an
independent set of 11 high redshift SNe.  The high-quality lightcurves
available from photometry on WFPC2 make it possible for this sample alone to
provide measurements of the cosmological parameters comparable in statistical
weight to the previous results.  In addition to high-precision lightcurve
measurements, this data  offered greatly improved  color measurements of the
high-redshift supernovae, and hence improved host-galaxy extinction estimates.
These extinction measurements show no anomalous negative $E(B-V)$ at high
redshift.  The precision of the measurements is such that  it was  possible to
perform (for the first) time a host-galaxy  extinction correction directly for
individual supernovae without any assumptions or priors on the parent $E(B-V)$
distribution.

Sullivan \etal\ 2003 (based on GO-8313, GO-9131) presented
the Hubble diagram of distant type Ia supernovae 
(SNe Ia) segregated according to the type of host galaxy.
This allowed us to confirm our previous  evidence for a cosmological constant by explicitly comparing SNe
residing in galaxies likely to contain negligible dust with the larger sample.
%  These data demonstrate that host galaxy extinction is unlikely to systematically dim 
% distant SNe Ia in a manner
% that would produce a spurious cosmological constant.  
These data provide  a key test of evolutionary systematics.

Other such multi-cycle analyses, described below, are in progess.
In particular, this year we are completing final  observations of host galaxies 
after the SNe faded  for SNe  discovered in GO-9075 and GO-8585.

\noindent
{\bf GO-9727}: This cycle 12 program will begin observations in April 2004 using ACS to do a new search for very high redshift $(1.2 > z > 1.6)$ SNe Ia in the GOODS-N field. 
In coordination with Riess (GO-9728),  images from 15 ACS pointings will be taken 
 approximately every 45 days and searched for candidates. 
 Followup photometry will be obtained with ACS and NICMOS for 
approximately three very high redshift SNe. 

\noindent
{\bf GO-9075}: 
In this program, we pushed our SNe Ia studies to the highest redshifts 
that are feasible for a ground-based discovery and spectroscopic 
identification campaign. 
HST follow-up observations for this program started after servicing 
mission 3B in March 2002 and have been completed for the most 
part --- final reference images are still to be taken.
Coordinated with three large search campaigns using the Subaru 8.2~m and 
also with simultaneous smaller searches using the CTIO 4~m and CFHT 3.6~m, 
we obtained ACS/WFC and NICMOS/NIC2  photometry for multi-epoch lightcurves  
of eight Type Ia  SNe at high  redshift $(0.9 < z < 1.3)$. 
For two of the highest redshift SNe, ACS grism spectra were taken.
Analysis of this ACS data is in progress. 
With the refurbished NICMOS, we obtained final reference images of the host of SN1998eq,
which we had 
previously studied in G0-8088, and these images will allow us to complete that analysis.  

{\bf GO-8585}:
In GO 8585 we observed six Type Ia supernovae with HST using WFPC. The
supernovae were discovered in ground based searches at the CTIO 4-m, CFHT
and Subaru telescopes. We obtained both U- and B-band restframe photometry
(using either F814W or F850LP depending on the redshift) for each
supernova for a period of 2 months. 
%Analysis of this data will be completed when the final reference images are 
% available, 
% scheduled for spring 2003. 
Analysis of this data is presented in the PhD thesis of J.~Raux (Univ. of Paris, 2003), presented at the January 2004 AAS meeting. A publication is in progress. 

{\bf GO-8313}: The objective of this project, which has now been
completed with the publication (Sul03) mentioned above, was to obtain snapshot
unfiltered STIS images of distant galaxies of known redshift which
have hosted supernovae (SNe) of Type Ia found by the SCP, 20 of which
are used in the Hubble diagram of 42 type Ia SNe (Perlmutter \etal\
1999).  
% In Sullivan et al. (2003, Sul03) we present these new results
% on the Hubble diagram of SNe~Ia as a function of host galaxy
% morphology that demonstrates that host galaxy extinction is unlikely
% to systematically dim distant SN~Ia in a manner that would produce a
 %spurious cosmological constant. 
The internal extinction implied is
small, even for late-type systems ($A_{B} < 0.3)$, and the
cosmological parameters derived from those SNe~Ia hosted by (presumed)
dust-free early-type galaxies are consistent with our previous
determination of a non-zero $\Lambda$. The brightness scatter about
the Hubble line for SNe~Ia in these early-type hosts is also
significantly smaller than for the SNe~Ia in late-type galaxies. This
result was based on HST STIS ``snapshot'' images and Keck spectroscopy
of SNe spanning the range $0.3 < z < 0.8$.

{\bf GO-8346}:
We had the unique opportunity of following up SN2000fr, 
which had been  discovered {\it 14 days prior} to maximum light in its
restframe. Because this supernova at z=0.54 was 
discovered so early we were
able to obtain excellent light curves from HST in F555W, F675W and
F814W spanning the period from one week prior to maximum light to 6 weeks after
Several spectra of the supernova were taken at VLT and Keck along with NIR
photometry at VLT. 
% To date, this is still the best observed
% high-redshift supernova and preliminary results were presented in 
% Nobili, S. \etal\, 2001, AAS, 199,1611N.

{\bf DD-8088}: WFPC2 and NICMOS (cycle 7) observations were obtained
for SN1998eq at $z=1.20$ 
%(a record-breaking redshift for a
%spectroscopically confirmed Type~Ia supernova; 
(Aldering, \etal, 1998,IAUC,7046).  The preliminary photometry is consistent with the
previous results for $\Omega_M,\Omega_\Lambda$.  With the final NICMOS
image of the galaxy without the supernova obtained, this analysis can now be completed.

{\bf GO-7850} and balance of {\bf GO-7336} and {\bf DD-7590}:
WFPC2 and NICMOS observations were obtained for 11 Type Ia supernovae in
the redshift range 0.36---0.86.  These observations, including final
references where necessary, are now complete, and the results were 
published in Knop, R., \etal\, 2003 as mentioned above.
% The cosmological results from these  SNe
%  are in close agreement with results from the first supernova
% results (Per99) that gave direct evidence for a
% cosmological constant.
% The lightcurves provided by WFPC2 for these supernovae 
% were excellent; at the higher redshifts, these lightcurves provide a % % 
% substantially
% better measurement of the calibrated supernova magnitude than those for
% comparable supernovae observed only from the ground.  
The color information provided by NICMOS (Burns, S., \etal, 
2001,AAS,199.1610B), was only  possible with HST.
% The improvement of
% the confidence limits on the cosmological parameters $\Omega_M$ and
% $\Omega_\Lambda$  are as good as we had previously predicted.  

{\bf GO-7336} and {\bf DD-7590}:
Perlmutter \etal, 1998, Nature, 391, 51 reported the results of our
HST and ground-based imaging and Keck spectroscopic observations of
SN1997ap.
%then the {\it highest redshift} ($z = 0.83$) {\it
%spectroscopically confirmed} Type~Ia supernova. 
The HST portion is
based on a total of 4 orbits.
Also from this program, HST observations of two $z = 0.83$ SNe~Ia
are included in the analysis in Per99 which reports on the results from our HST and
ground-based imaging and Keck spectroscopic observations of 42 type~Ia
supernovae with $0.18 < z < 0.86$. 
The paper rules out a flat $\Omega_M =
1$ universe and presents very strong evidence for a positive
cosmological constant.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\end{document}          % End of proposal. Do not delete this line.
                        % Everything after this command is ignored.

