Title: Deep near-infrared survey and high redshift supernovae (final title pending)
PI: Sandra Faber
PI Institution: University of California - Santa Cruz
co-PI: Harry Ferguson
co-PI Institution: Space Telescope Science Institute
Science Category: Unresolved Stellar Populations and Galaxy Structure
Allocation: 902 orbits
This survey will document the first third of galactic evolution from z=8 to 1.5 and
test for evolution in the properties of Type Ia supernovae to z~2 by imaging
more than 250,000 galaxies with WFC3/IR and ACS. Five premier multi-wavelength
regions are selected from within the Spitzer SEDS survey, providing complementary
IRAC data down to 26.5 AB mag, a unique resource for stellar masses at high redshifts.
The use of five widely separated fields mitigates cosmic variance and yields
statistically robust samples of galaxies down to 109 solar masses out to z~8.
This proposal represents the merged science plans from two different MCT proposals.
We recognize the need to communicate as precise information as possible for Cycle 18
proposers, but plans are not yet final owing to difficulties in merging two large and
complex science programs. The following description represents our best thinking at the
present time, and future developments will be posted (with version numbers) ASAP on
the new project website.
The program incorporates a two-tiered strategy using a "Wide" component
(2 orbits deep over ~0.2 sq. degrees) and a "Deep" component (12 orbits deep over
~0.04 sq. degrees). Combining these with ultra-deep imaging from the Cycle 17
HUDF09 program yields a three-tiered strategy for efficient sampling of
both rare/bright and faint/common objects.
Three of the Wide-survey fields are located within the SEDS regions in
COSMOS, EGS, and UKIDSS/UDS (see csmct.ucolick.org),
with exact areas and placements to be determined as part of the Phase-2
process. Each contiguous Wide mosaic consists of roughly 3x15 WFC3/IR tiles observed
for 2 orbits each, with single orbits separated in time to allow a search for
high-redshift Type Ia SNe. The co-added exposure times are approximately
2/3 orbit in J (F125W) and 4/3 orbit in H (F160W). ACS parallels overlap most of
the WFC3 area and will consist of 2/3 orbits in V (F606W) and 4/3 orbit in I (F814W).
Because of the larger area of ACS, this results in effective exposures that
are twice as long (4/3 in V, 8/3 in I), making a very significant improvement to
existing ACS mosaics in COSMOS and EGS and creating a new ACS mosaic in UDS/UKIDSS
where none now exists. Other Wide-survey components are located in the GOODS fields
(North and South) surrounding the Deep-survey areas.
The Deep-survey mosaics cover approximately half of each GOODS field, with exact
areas and placements again to be determined as part of the Phase-2 process. The location
relative to the ERS2 field in GOODS-S is TBD. Each WFC3/IR tile within the Deep regions
will receive 12 orbits of effective exposure time split equally between Y (F105W),
J (F125W), and H (F160W). Multi-epoch imaging will provide an efficient search for
high-redshift Type Ia SNe here also. ACS parallels are taken in the Deep regions with
the goal of assembling enough total exposure time in F850LP and other filters to identify
high redshift z>6 galaxies in concert with WFC3/IR data using the Lyman break technique.
Shallow borders to 2-orbit depth using the Wide WFC3 filter strategy are added around
both Deep areas to increase the depth of ACS parallels on top of the Deep area and enlarge
the total GOODS area covered.
A portion of the GOODS-N campaign will take place while the field is in the HST
Continuous Viewing Zone (CVZ). The bright time in those orbits will be used to
obtain UV imaging with WFC3 in the F275W and F336W filters. The exact number of
orbits will not be known until Phase-2 planning is complete, but we anticipate
that it will be possible to schedule at least 100 orbits, resulting in 5-sigma
point-source depths of 26.6, 26.4 AB mag in F275W and F336W, respectively. The
science goals include measuring the Lyman-continuum escape fractions for galaxies
at z~2.5 and identifying Lyman-break galaxies at z~2-3.
The Type Ia supernova search program in this proposal is integrated
with that in the Postman cluster MCT proposal, with this one stressing
the more distant supernovae. A combined follow-up program will
provide light curves and grism spectra of 15-20 of the best candidates
at redshifts 1
A representative current strawman proposal looks as follows. We
stress that this is not yet final; details may change.
The new data will be used to answer many urgent questions in galaxy evolution and cosmology.
In the reionization era, we will identify hundreds of high-confidence z>7 galaxies in the
Deep regions, in addition to hundreds of highly-luminous candidates in the Wide regions
for detailed follow-up. These samples will be used to construct a unified picture of
star-formation and stellar mass buildup in early galaxies. Extremely deep X-ray data
will reveal distant AGNs to z>6, shedding light on the earliest stages of BH growth.
In the peak star formation/QSO era, z~2, we will document the properties of early disks,
the build-up of bulges, the evolution of mergers, and the nature of AGN hosts to construct
an integrated model for structural evolution, star formation quenching, and AGN triggering.
Finally, the ~8 Type Ia SNe found beyond z>1.5 in the supernova programs will establish
the constancy of these standard candles independent of dark energy and yield the first
measurement of the Type Ia rate at z~2 to distinguish among different progenitor models.
Lower-redshift SNe Ia at 1
This program takes full advantage of MCTP mode to fulfill Hubble's
legacy for deep extragalactic science and prepare the way for JWST.
