Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.stsci.edu/hst/udf/UDFPlanning2 Äàòà èçìåíåíèÿ: Sat Aug 4 05:17:52 2012 Äàòà èíäåêñèðîâàíèÿ: Tue Oct 2 04:15:23 2012 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: zodiacal light

Planning of the ACS Ultradeep Field
Shardha Jogee, Harry Ferguson, Massimo Stiavelli,
Nino Panagia, and Adam Riess
i

Contents
1 Introduction 1
2 Depth of the UDF 1
3 Filter Selection 2
4 CVZ targets: UV and narrowband observations 4
5 Searches and Followups of Type Ia Supernovae 6
6 Searches and Rates of Type Ia and Type II Supernovae 6
7 Acknowledgments 8
List of Tables
1 Comparison of UDF, GOODS, and HDF limiting magnitudes 9
2 WFC/narrowband imaging during bright CVZ time . . . . . . 10
3 Limiting redshifts, bands of max. flux, expected SNIa & SNII
rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
List of Figures
1 ACS UDF Depth and Exposure Time Tradeo# (WFC) . . . . 12
2 SBC/UV, HRC/UV, WFC/HRC­UV observations in bright
CVZ time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3 E#ect of Sky Background on SBC and WFC Depths . . . . . . 14
4 Limiting Magnitude of HST Imaging Surveys: . . . . . . . . . . 15
5 Surface density vs Lyman # line flux of reionization sources: . 16
6 Redshifted spectra of SNIa and SNII and 4­orbit limiting
fluxes: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7 Redshifted spectra of SNIa and SNII and 8­orbit limiting
fluxes: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8 UV Light curves of SNIa 1992A and SNII 1979C . . . . . . . . 19
9 Color selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
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1 Introduction
The Advanced Camera for Surveys (ACS) Ultra Deep field (UDF) is expected to use
# 300­400 orbits of Director's Discretionary (DD) time, most likely spread out between
Cycle 11 and 12. It o#ers an array of potential scientific returns such as probing the
tail of the reionization epoch, studying the faint end of the galaxy luminosity function,
assessing surface brightness bias in the SFR history derived from the Hubble Deep Field
(HDF), and studying galaxy morphology and structure with images of unprecedented
depth and resolution. Several questions pertinent for the planning of the UDF merit
discussion:
1. Which scientific goals should the the UDF focus on?
2. How many and which filters should be used for the UDF?
3. Should one or two fields be selected? Which one (s)?
4. What are the benefits and limitations of choosing a UDF field which lies in the
continuous viewing zone (CVZ) ?
5. What are the recommended strategies for searches and followups of type Ia and
type II supernovae?
6. Should a slitless grism image be included?
This draft presents material related to some of these questions, particularly items
(2) (4) and (5). We refer the SAC to complementary reports which cover in more detail
other issues such as field selection (report by M. Stiavelli, H. Ferguson, & N. Panagia),
and grism/prism observations (report by J. Rhoads, S. Malhotra, & Z. Tsvetanov).
2 Depth of the UDF
Estimates of the potential depth of the UDF were done with a customized idl
routine The depth or limiting 10 # AB magnitude for extended sources is computed
by summing the counts in a 0.2 square arcsecond square aperture, equivalent to a 0.5 ##
diameter circular aperture. Updated zero point AB magnitudes from the STSDAS
synphot package are used and adopted parameters include 2 readouts (i.e. 1 CR­split
or a 2­point dither) per orbit, a WFC detector dark current of 2.2 x 10 -3 electrons
s -1 pix -1 , a readnoise of 5 electrons and a default gain of 1. The impact of di#erent
sky background levels were considered. At # > 3000 š A, Earthshine (scattered Earth
light) and Zodiacal light tend to dominate the sky background while airglow lines and
geocoronal lines are important in the ultraviolet. Results were cross­checked with ETC
for consistency.
Figure 1 shows the WFC depth for extended sources as a function of on­source ex­
posure time, assuming dark sky conditions (equivalent to Zodiac=Low, Earthsine=low
1

in ETC). Table 1 and Fig. 4 show some of values and comparisons with other HST sur­
veys such as the ACS Great Observatories Origins Deep Survey (GOODS; Giavalisco
et al. 2001), and the WFPC2 HDF (Williams et al. 1996). Note the following points :
. For a 4­band imaging strategy with # 100 orbits per optical broadband filter
(such as F435W, F606W, F775W), the UDF reaches # 1.3 mag deeper than the
HDF (Table 1). The gain of 3.3 in flux is coupled with the factor of 1.8 increase
in field of view (202 ## â 202 ## vs. 150 ## â 150 ## ) and 2 in angular resolution (0.05 ##
vs. 0.1 ## ), leading to a six­fold increase in e#ective surveying power in the optical
regime (Figs. 1 and 3). The corresponding depth increase w.r.t GOODS is # 2
mag.
. In going from 100 to 200 orbits per WFC broadband filter, the gain in depth is
# 0.4 mag. This would be the tradeo# between a 2­bands versus a 3­bands or
4­bands optical imaging strategy (Fig. 1 and Table 1).
. If the UDF field is chosen to lie in the CVZ, UV observations or narrowband
optical observations during the daytime part of 400 CVZ orbits can be obtained
for free (i.e. without significant loss of the darktime for broadband optical
imaging). In particular, WFC/F892N observations (§ 4, option I) can probe
# 6.3 Ly# emitters with a limiting flux below the unlensed flux of the highest
redshift galaxy reported to date (Hu et al. 2002). The large ACS/WFC field of
view o#ers the potential of detecting several tens of such sources.
3 Filter Selection
The choice of filters is guided by (i) the targeted science, (ii) a tradeo# between depth
and color information, and (iii) optimal use of unique ACS capabilities not provided by
WFPC2 or the upcoming WFC3 in 2005. It is beyond the scope of this draft to discuss
all possible filter combinations, but we summarize here some factors to consider and
the most promising options.
. Ideally an ACS UDF would make use of the F850LP filter which is a unique ACS
capability. It o#ers a larger wavelength resolution in the red than WFPC2 broad
filters such as F814W. When used with two adjacent filters, F850LP enables
high redshifts systems close to the epoch of reionization (# 7) to be separated
out using the Lyman break technique. For instance, in the (F606W, F775W,
F850LP) color­color plane (Fig. 9), z # 4--6 targets can be selected as F606W
dropouts (e.g., F606W­F775W > 1.4) and z # 6--8 targets as F775W dropouts
(e.g., F775W­F850LP > 3), with possible significant contamination from lower
redshift systems.
. With the expected depth of the UDF, ground­based follow ups to get col­
ors/redshifts of targets are not viable. Therefore, the required color information
has to come from the ACS observations themselves. Color information from only
2

2 bands has a small dynamic range: at least 3 bands are needed for the Lyman
break technique and 4 filters give robust photometric redshifts enabling objects
at intermediate and high redshifts to be selected. Below are possible 3­band and
4­band filter combinations.
. (F435W+F606W+F775W+F850LP) combination : The WFC/F606W
filter is the most sensitive for optical imaging and significantly more sensitive
(by # 0.5 mag) than F555W, the Sloan Digitized Sky Survey (SDSS) r filter
(Fig. 1). Given that color identification of objects (dropouts) works best with
four adjacent filters with little overlap, a multi­band imaging program using
F606W should exclude F475W (SDSS g)and F555W (SDSS r) as they overlap
significantly with F606W. Instead, F435W on the blue side of F606W and either
(F775W+F850LP) or F814W on the red side could be selected. The use of
F775W+F850LP rather than F814W gives extra wavelength resolution allowing
redshifts close to the epoch of reionization to be separated out. This leads us to a
choice of (F435W+F606W+F775W+F850LP), which is also used by the GOODS
program. With this filter set galaxies at z= 2--4, z=4--6.1, and potentially z=6--8
can be selected, respectively as F435W, F606W, and F775W dropouts (see Fig.
9).
. (F606W+F775W+F850LP) combination: This filter selection is suitable
for identifying z # 6 objects close to the tail of the reionization epoch, via the
Lyman Break technique, making optimal use of F850LP (see Fig. 9). In the
(F606W, F775W, F850LP) color­color plane (Fig. 9), z # 4 - -6 targets can
be selected as F606W dropouts (e.g., F606W­F775W > 1.4) and z # 6 - -8
targets as F775W dropouts (e.g., F775W­F850LP > 3), with possible significant
contamination from lower redshift systems. The (F606W+F775W+F850LP)
combination does not enable reliable color identification of lower redshift (z < 3)
objects in the HDF to address surface brightness bias issue in the SF history at
z # 1--3 derived from HDF. due to the loss of wavelength resolution in the red.
. (F475W+ F555W+F775W+F850LP) combination : This combination
corresponds to the SDSS g, r, i, z set. Similar considerations apply as above.
We are more sensitive by # 0.2 mag in the blue with F475W, but lose sensitivity
in the red by by giving up F606W.
. For CVZ targets :(any of the above in darktime) + (WFC/narrowband
filter or WFC/UV broadband filter or SBC/F150LP in bright time):
If the UDF targets a CVZ field, then WFC/narrowband optical observations
or SBC/UV or WFC/UV broadband observations could be taken `for free'
during the daytime part of the orbit, with little loss of the darktime available
for broadband optical imaging at night. The best alternative for daytime
observations seems to be WFC/F892N (§ 4).
For further information or clarification: please contact Shardha Jogee, Harry
Ferguson, & Massimo Stiavelli.
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4 CVZ targets: UV and narrowband observations
Most targets are occulted in part of every HST orbit except for targets which lie in
the continuous viewing zone. CVZ targets can be observed without occultation for a
fraction of time during the 56 day HST precessional cycle. Depending on the telescope
position and the target, there may be up to 7 CVZ intervals with durations ranging
between 1 to 105 orbits. Observing e#ciency of targets in the CVZ is about twice that
of non­CVZ observations. For instance, a non­CVZ target has a visibility time (amount
of unocculted time per orbit) typically ranging from 44 m to 55 m. For CVZ targets the
corresponding visibility time is the entire orbital time of 96 m. A significant fraction of
this time (typically 30 to 40% or 28 to 40m) has a large optical sky background produced
mostly by Earthshine, particularly during the daytime part of the CVZ observations.
Earthshine is a strong function of the angle A e of the observations with respect to
the Earth bright limb. For instance, Earthshine can vary from V=18.0 to 23.4 mag
arcsecs -2 as A e changes from 16 to 52 # . The bright sky background strongly impacts
broadband optical imaging, but can have minimal e#ect on narrowband optical imaging
and select ultraviolet observations as shown in Fig. 3. The advantage of CVZ fields
is that the bright time can be optimally used for low background observations namely,
select UV observations or optical narrowband observations, with only minimal loss in
the available dark time for broadband optical observations. This advantage was one of
the prime factors for the selection of the HDF­N field to be in the CVZ.
We have explored three types of observations (I, II, III below) that can be carried
out in CVZ bright time. Option I seem to be the most promising as it covers the entire
WFC fov in one pointing and provides limiting fluxes probing an interesting redshift
regime. Options II and III both cover a small fraction (3% to 36 %) of the entire WFC
fov and require a tradeo# between coverage and depth.
I. WFC/narrowband optical imaging WFC/narrowband optical imaging o#ers
the option of probing Ly# emitters from redshifts z # 3.1 out to z # 6.3, close to the
tail of the epoch of reionization as shown in Table 2. In particular , a limiting flux
of 3 â 10 -18 erg cm -2 s -1 for z # 6.3 Ly# emitters by observing with WFC/F892N
during the bright time of 400 CVZ orbits assuming 30 m of bright time per orbit. This
limit is a factor of # 10 lower than the observed flux of the lensed galaxy at z # 6.56
reported by Hu et al. (2002) and 2 times lower than its unlensed flux . Furthermore,
the volume probed for Ly­alpha emitters with a single WFC/F892N field is # 2400
Mpc 3 which is # 20 times larger than the region studied by Hu et al. (2002). If the
galaxy observed by Hu et al. (2002) and their density estimates are representative, we
expect to see several tens of such sources in a single ACS/WFC field. This is illustrated
in Fig. 5. Thus, WFC/F892N observations 'for free' during bright CVZ time o#er the
exciting possibility of probing Ly# emitters close to the epoch of reionization. Another
complementary option here is ACS ramp filter imaging down to wavelengths longer
than 1 micron, o#ering the possibility of pushing the redshift limit even further. 2%
bandpass ramp filters, and a 9% FR914M filter are being considered. We also note
that if the dark time of CVZ orbits were to use the (F606W+F775W+F850LP) filter
combination, this would give additional leverage in identifying z # 6 objects.
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II. SBC/UV and HRC/UV imaging The ACS Solar Blind Channel (SBC) MAMA
detector has a high UV quantum e#ciency, high throughput, low detector dark current
(1.2 x 10 -5 electrons s -1 pix -1 ), no read noise and low sky background. A large draw­
back, however, is that the field of view (35 ## â31 ## ) is 40 times smaller than that of WFC.
Figure 2 shows the depth achieved with di#erent SBC UV filters in bright time. The
expected total bright time is 720 kilosec if we assume 30 m of bright time per 96m CVZ
orbit and a total of 400 CVZ orbits. The best SBC filter is F150LP which has a large
throughput and a bandpass that minimizes the airglow and geocoronal lines F150LP
can also provide by far the best constraints on the escaping Lyman­continuum from
galaxies at z # 1. With 400 CVZ orbits, SBC/F150LP observations of a single field,
covering # 3% of the ACS/WFC field, reach 30.42 AB mag (Fig. 2). This is deeper
by 2.92 mag or a factor of 15 in flux compared to very deep STIS far­UV observations
GO­7410 reaching # 27.5 AB mag at 1500 š A (Gardner et al. 2000) HDF/F300W
reached 26.98 AB mag. Covering the entire ACS/WFC field with # 40 SBC pointings
result in a depth of # 27.7 AB mag, not providing significant depth increase w.r.t
HDF/F300W. There is no net gain in considering the HRC which has a similar field of
view and lower sensitivity (Fig. 2).
III. WFC/HRC­filter UV imaging Standard WFC filters are not designed to go
below pivot wavelength of 4300 š Aas the WFC detector quantum e#ciency (DQE) falls
sharply below 4000 š A, reaching values below 10 -26 at 3000 š A. In a non­standard mode
we can use the HRC UV filters HRC--F330W (covering 2950--3750 š A) with the WFC,
but the unvignetted field of view is only # 72 ## â 72 ## or # 36% of the standard WFC
field of view. As illustrated in Fig. 2, this option does not promise any significant
depth increase with respect to the HDF.
CVZ Fields The CVZ is within 24 # of the orbital poles such that CVZ targets lie
in a narrow range of declinations centered about ± 61.5 # . CVZ fields would therefore
exclude HDF­S, equatorial fields, while allowing fields near the HDF­N. The final choice
of a CVZ field would be further guided by a consideration of the scientific drivers, the
need to minimize optical extinction, HI column density, IR cirrus emission, the need
to avoid bright clusters in order to optimize the study of faint objects and minimize
bias (For potential candidate CVZ fields, see report on UDF fields by M. Stiavelli, H.
Ferguson, & N. Panagia).
Scheduling Considerations for CVZ (1) HST can typically observe within 15.5
# of the bright Earth limb and 7.6 # of the dark Earth limb. Earthshine is a strong
function of the angle between the viewing direction and the Earth bright limb and
can vary significantly during one orbit of the CVZ. Therefore observations in the UV
and di#erent optical filters must be carefully scheduled on the appropriate part of
the orbits where they are least impacted by the background (see Fig. 3). In the
planning and scheduling of the HDF­N, the SEAM software was used to model the time­
varying zodiacal light and Earthshine during a spacecraft CVZ orbit. This software is
no longer available (Larry Petro; private communication), but an alternative version
can be developed. (2) The maximum no of contiguous uninterrupted orbits which
5

can be scheduled in a row would be 5--6 due to HTS's passage through the South
Atlantic Anomaly (SAA). SAA impacts large non­CVZ programs as well, so this is not
a major overhead. (3) There is somewhat less flexibility in scheduling observations for
supernovae searches, although the suggested SN Ia search strategy of 5 orbit epochs in
di#erent filter with each filter separated by 60 day intervals (§ 5) are not inconsistent
with the SAA constraint and HST precessional cycle of 56 days controlling recurrent
CVZ observations.
For further information or clarification: please contact Shardha Jogee, Harry Ferguson,
& Massimo Stiavelli.
5 Searches and Followups of Type Ia Supernovae
The following factors should be considered in optimizing supernovae searches. Any
multi­orbit deep integration of a high galactic latitude field in a red bandpass is ideal
for searching for distant supernovae as long as the observations are properly sequenced.
The ideal spacing of successive epochs of integration for collecting type Ia supernovae
of cosmological significance is (1+z) â 20 days, where 20 days is the risetime of a SN
Ia (Riess et al. 1999). The redshift, z, is the target redshift and should be matched
to (i.e., less than) the maximum redshift to which an epoch can detect a SN Ia at
peak. Calculations and experience from GOODs indicates that 1 orbit in F850LP can
comfortably reach z=1.5. To reach unique redshifts, `epochs' of the UDF should be
more than 1 orbit. Choosing a target of z=2 would require 5 orbit epochs. Simultaneous
epochs of bluer colors will allow determination of the type of any supernova found.
So to maximize the likelihood of finding SNe Ia at z=2 (e.g., for rates) a sequence
of 5 orbit blasts with each filter separated by 60 day intervals would be ideal. Two
problems immediately arise: (1) The spacing of the search epochs is a factor of 4­5
too long to follow the light curve of a SN Ia discovered (2) it would take 2­3 years to
finish the UDF! An obvious compromise is just do 1 or 2 SN searches (i.e., a 60­120 day
interval for the UDF) and do many shorter 5 orbit epochs in between to follow any
SN discovered. An additional point to note is that a multiple epoch program with #
5--7 orbits would easily allow a range of orientations good for a slitless grism program.
For further information or clarification: please contact Adam Riess
6 Searches and Rates of Type Ia and Type II
Supernovae
RATIONALE ­ Detecting and studying photometrically high­z (say, z > 1.5) SNe
is of fundamental importance because it allows us to study SN rates. Even without
spectroscopy (obtaining detailed spectra would be VERY hard; see below) the SN
characterization can be inferred from imaging alone (see figures), and the redshifts may
6

be measured either from the host­galaxy spectrum (actual spectroscopy or its poor­
child approximation, i.e. photometry) or even from photometry of the SNe themselves.
The rates of SNIa will be able to reveal the nature of their progenitors and/or the
history of star formation for moderate mass stars (3­8 M# ).
The rates of SNII will provide a direct measurement of the cosmic star formation rate
in the redshift interval 1­2.5, i.e. just where the peak of star formation is ''expected''
to occur. We like to stress that the SNII rate is a direct measurement of the death of
stars with masses 8­30 M# (for a Salpeter IMF they include 86% of the stars above 8
M# and 63% of the mass in massive stars), which in steady state (over time intervals
less than 30 Myrs) IS the star formation rate itself. The widely used diagnostic based
on the H# flux is probing only the upper end of the IMF, which includes about 27% of
the massive stars and less than 1/2 of their total mass. Note also that the amount of
processed material that is injected into the ISM/IGM is increasing less than linearly
with the stellar progenitor mass and, therefore, the direct SNII rate measurement is a
much better tool to study the chemical evolution of the Universe.
OBSERVATIONAL CONSTRAINTS AND RECOMMENDED STRATEGY
Using the observed spectra of SNIa 1992 (Kirshner et al. 1993, ApJ 415, 589) and
SNII 1998S (Lentz et al. 2001, ApJ 547, 406) we computed the expected spectra of
SNIa and SNII at a number of redshifts (series 1: z = 1, 1.5, 2, 2.5; series 2 z = 2,
2.2, 2.4, 2.6) for di#erent choices of the exposure time (1, 2, 4, 8, 16, 32 orbits) in
four adjacent/non­overlapping ACS bands (F475W, F606W, F775W, F850LP). In all
calculations we have assumed B max = ­19.5 and ­17.5 for SNIa and SNII, respectively.
The corresponding flux limits for a S/N=10 are shown in the plots (see Figures 6 and
7).
The 1 orbit exposure time corresponds to the GOODS strategy and indeed we find
that one can detect SNIa up to a maximum of z=1.5 and SNII up to about z=1.7 (cf.
Table 3). It is also apparent that SNe that are detected only in the z­band are likely
to be SNIa, whereas SNe detected in more bands with comparable fluxes are SNII.
We estimated the expected SN rates following the calculations by Madau, Della
Valle & Panagia (1998, MNRAS 297, L12) . [Note that the detection rates of the
ongoing GOODS SN search are perfectly consistent with Madau et al predictions.]
Table 4 reports for SNIa and SNII: the maximum detection redshift, the observing
band where the highest flux is expected and the SN rate, in units of SN/year per ACS
field, for exposure times 1 through 32 orbits.
In our opinion the interesting cases to consider are 8 or 16 orbits per epoch and
per band because they extend the search to redshifts beyond the expected cosmic star
formation peak at about z=1.5­2.
The widths of the light curves (defined as #t(1 mag)) at the appropriate wavelengths
(about 2400 š A and 2800 š A for SNII and SNIa, respectively; see Panagia et al. 1980,
MNRAS 192, 861, Kirshner et al. 1993; Figure 8) are about 15­20 days for both SNII
and SNIa near their limiting detection redshifts.
It follows that if one wants to cover ALL events that occur in a given field one
should make observations at time intervals no longer than 45­60 days.
A possible strategy, then, would be to observe at 8 epochs, at 1.5 mos intervals,
7

which corresponds to a total exposure of either 64 or 128 orbits per band.
From the point of view of maximizing the SN detections, it is apparent that (a)
monitoring TWO fields at 8 epochs with exposures of 8 orbits at each epoch is MUCH
MORE ADVANTAGEOUS than (b) monitoring ONE field at 8 epochs with exposures
of 16 orbits. In the two field option (a) one expects to detect about 17±4 SNII and
4±2 SNIa, whereas in the one field option (b) only 10±3 SNII and 3±1.7 SNIa would
be expected.
POSSIBLE ENHANCEMENTS
. Stacking the observations made at each epoch in two or more bands (most
importantly the V and I bands for SNII, and the I and z bands for SNIa) will provide
even deeper images that can be used to detect SNe that would fall below the detection
limit otherwise.
. Adopting one of the GOODS fields (or similarly deep, multiband fields) would
add the first epoch observation ``for free''.
For further information or clarification: please contact Nino Panagia.
7 Acknowledgments
We are grateful to Ron Gilliland, Mark Clampin, Guido de Marchi, Larry Petro, and
Adam Welty for discussions.
8

Table 1: Comparison of UDF, GOODS, and HDF limiting magnitude
(1) (2) (3) (4) (5)
Imaging Pivot # On­source No of 10 #
mode Time orbits
[ š A] [kilosec] AB mag 1
UDF
WFC/F435W 4311.80 24.0 10.0 27.9286
WFC/F435W 4311.80 120.0 50.0 28.8126
WFC/F435W 4311.80 180.0 75.0 29.0342
WFC/F435W 4311.80 240.0 100.0 29.1913
WFC/F435W 4311.80 480.0 200.0 29.5693
WFC/F606W 5915.38 24.0 10.0 28.2768
WFC/F606W 5915.38 120.0 50.0 29.1569
WFC/F606W 5915.38 180.0 75.0 29.3780
WFC/F606W 5915.38 240.0 100.0 29.5348
WFC/F606W 5915.38 480.0 200.0 29.9121
WFC/F775W 7697.34 24.0 10.0 27.6346
WFC/F775W 7697.34 120.0 50.0 28.5161
WFC/F775W 7697.34 180.0 75.0 28.7374
WFC/F775W 7697.34 240.0 100.0 28.8943
WFC/F775W 7697.34 480.0 200.0 29.2719
WFC/F850LP 9103.29 24.0 10.0 27.1026
WFC/F850LP 9103.29 120.0 50.0 27.9858
WFC/F850LP 9103.29 180.0 75.0 28.2073
WFC/F850LP 9103.29 240.0 100.0 28.3643
WFC/F850LP 9103.29 480.0 200.0 28.7422
GOODS
WFC/F435W 4311.80 7.2 3.0 27.2000
WFC/F606W 5915.38 6.0 2.5 27.5000
WFC/F775W 7697.34 6.0 2.5 26.8000
WFC/F850LP 9103.29 12.0 5.0 26.7000
HDF
WFPC2/F300W 2992.00 153.7 64.0 26.9800
WFPC2/F450W 4556.47 120.6 50.0 27.8600
WFPC2/F606W 6001.06 109.0 45.0 28.2100
WFPC2/F814W 8001.61 123.6 51.0 27.6000
Notes: (1)Column 5 is the limiting 10 # AB magnitude for extended sources assuming a
0.2 square arcsecond square in all three surveys. For the UDF, we assume an exposure
time of 240 kilo seconds (# 100 orbits), 1 CR­split or a 2­point dither per orbit, and
low sky background (Zodiac=Low, Earthshine=Ave)in the optical.
9

Table 2: WFC/narrowband imaging during bright CVZ time
(1) (2) (3) (4)
Imaging mode On­source time z(Ly#) Emission flux 1
[kilosec] erg cm -2 s -1
WFC/F502N 20.0 3.13 2.8e­17
WFC/F502N 100.0 3.13 1.2e­17
WFC/F502N 200.0 3.13 8.4e­18
WFC/F502N 800.0 3.13 4.2e­18
WFC/F658N 20.0 4.41 1.3e­17
WFC/F658N 100.0 4.41 5.6e­18
WFC/F658N 200.0 4.41 4.0e­18
WFC/F658N 800.0 4.41 2.0e­18
WFC/F660N 20.0 4.43 1.7e­17
WFC/F660N 100.0 4.43 7.4e­18
WFC/F660N 200.0 4.43 5.2e­18
WFC/F660N 800.0 4.43 2.6e­18
WFC/F892N 20.0 6.34 2.0e­17
WFC/F892N 100.0 6.34 8.7e­18
WFC/F892N 200.0 6.34 6.1e­18
WFC/F892N 800.0 6.34 3.0e­18
Notes: (1) Column 4 is the limiting 10 # flux for an extended Ly #­emitting source at
a redshift z(Ly#), assuming a 0.2 square arcsecond square aperture.
10

Table 3: Limiting redshifts, bands of max. flux, expected SNIa & SNII rates
SNIa SNII
Exp. Time z max band(Fmax ) SN/yr z max band(Fmax ) SN/yr
1 orbit 1.5 z­band 1.2 1.5 V­band 3.2
2 orbits 1.6 z­band 1.4 1.8 V­band 5.7
4 orbits 1.7 z­band 1.6 2.0 I­band 6.7
8 orbits 1.8 z­band 1.8 2.2 I­band 8.5
16 orbits 2.0 z­band 2.4 2.5 I­band 10.4
32 orbits 2.1 z­band 2.7 2.7 I­band 11.0
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Figure 1: UDF Depth and Exposure Time Tradeo# (WFC): The limiting 10 #
AB magnitude for extended sources assuming a 0.2 square arcsecond square aperture
is plotted as a function of on­source exposure time T for WFC/broadband optical
imaging. Dark sky conditions (equivalent to Zodiac=Low, Earthshine=Ave in ETC)
and 2 readouts (i.e. 1 CR­split or a 2­point dither) per orbit are assumed. The vertical
dashed lines indicate the number of orbits corresponding to T, assuming 2400 s of
on­source dark time per orbit.
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Figure 2: SBC/UV, HRC/UV, WFC/HRC­UV observations in bright CVZ
time: Plotted are the limiting 10 # AB magnitude for extended sources observed in
bright CVZ time (equivalent to Zodiac=High, Earthshine=High in ETC). 720 kilosec
of bright time is available assuming 30 m of bright time per orbit for a total of 400
CVZ orbits. Note that WFC/HRC­UV setups use HRC filters with the WFC and cover
# 30 % of the standard WFC fov. SBC/UV and HRC/UV cover 3% and 5% of the
standard WFC fov. For reference, the limiting magnitude of the HDF is marked.
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Figure 3: E#ect of Sky Background on SBC and WFC Depths: Plotted are
the limiting 10 # AB magnitude for extended sources observed with the SBC/UV,
WFC/HRC­F330W, and WFC/broadband optical filters under low, average and
bright sky conditions. An on­source exposure time of 240 kilosec is assumed. Note
that the limiting depths of the SBC/F150LP, SBC/F165LP, and WFC/HRC­F330W
configurations are nearly independent of the sky background.
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Figure 4: Limiting Magnitude of HST Imaging Surveys: Plotted are the limiting
10 # AB magnitude for extended sources in di#erent HST surveys, assuming a 0.2
square arcsec aperture. For the UDF, plotted values assume an exposure time of 240
kilosec (# 100 orbits), 1 CR­split or a 2­point dither per orbit, low sky background
in the optical and high sky background in the UV. For point sources, the limiting
magnitude is # 0.8 mag fainter as shown by the arrows. Note that the SBC covers
only 3% of the WFC field of view.
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Figure 5: Surface density vs Lyman # line flux of reionization sources: The
solid bar represents the density estimated from the detection at z = 6.56 by Hu et al.
(2002) while the two points with down­pointing arrows represent their upper limits.
The thin dotted line indicates the locus of identical sources for z reion < 10. The (0.1,
30) model combines a 10 % escape of Lyman continuum photons with a standard value
for the clumpiness of neutral hydrogen (after Stiavelli et al. 2002, ApJ submitted).
The dashed lines show the cumulative Lyman # luminosity function of reionization
sources for the (0.1, 30) model and M # ­17.5. As an illustration, we also show as solid
lines show the cumulative Lyman # luminosity function for a model with M # = -10
rescaled to pass through the Hu et al. data point. The upper and lower line in each
pair are for for z reion = 6.2 and 9, respectively. The shaded area represents models that
would imply a mean metallicity of the Universe at reionization higher than 0.01 Z# .
The thick corner marker identifies identifies the area probed by a narrow band excess
survey with ACS+F892N at z = 6.33.
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Figure 6: Redshifted spectra of SNIa and SNII and 4­orbit limiting fluxes:
The redshifted spectra of SNIa 1992A (red curve) and SNII 1998S (blue curve) are
compared with the limiting fluxes for an exposure time of 4 orbits.
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Figure 7: Redshifted spectra of SNIa and SNII and 8­orbit limiting fluxes:
The redshifted spectra of SNIa 1992A (red curve) and SNII 1998S (blue curve) are