Galaxy Evolution and Supernovae
from a Deep-Wide WFC3 Survey
• WFC3 IR observations of 5 well-studied reference
fields at high galactic latitude:
– The GOODS fields
• Encompass the deepest fields from HST, Spitzer, Chandra, the
VLA, and soon Herschel
– The Extended Groth Strip
– A small portion of the COSMOS field
– The UKIRT Ultradeep Survey Field
• Optimized for studies of galaxy evolution at z~2-10
• Optimized for supernova cosmology
Theories crumble, but good observations never fade.— Harlow Shapley
Merger of two similar proposals
• Sandy Faber’s team proposed a ‘wedding
cake’ strategy with 2-orbit depth in the three
non-GOODS fields, and 50% of GOODS to
15-orbit depth.
• Our team proposed to cover both GOODS
fields to intermediate depth and to measure
supernovae spectra and light curves. We also
proposed UV observations for GOODS-N.
• The TAC liked the wedding cake, the
supernova followup and the UV observations.
• Teams were merged and told to try to
preserve these features.
90 Co-investigators
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Supernova Cosmology
• Refine the only constraints we have on the time variation of w,
on a path to more than doubling the strength of this crucial test
of a cosmological constant by the end of HST’s life.
Supernova Cosmology
• Obtain a direct, explosion-model-independent measure of the
evolution of Type Ia supernovae as distance indicators at z >
1.5, independent of dark energy.
Supernova Cosmology
• Provide the first measurement of the SN Ia rate at z>1.5 to
distinguish between prompt and delayed SN Ia production and
their corresponding progenitor models.
Supernova Cosmology
• Refine the only constraints we have on the time variation of w,
on a path to more than doubling the strength of this crucial test
of a cosmological constant by the end of HST’s life.
Supernova Cosmology
Cosmic Dawn
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• Greatly improve the estimates of the evolution of stellar
mass, dust and metallicity at z = 4-8 by combining WFC3
data with very deep Spitzer observations.
Cosmic Dawn
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• Improve by ~10x the constraints on the bright end of the
luminosity function at z~7 and 8, and make z~6 measurements
robust using proper 2-color Lyman break selection.
Cosmic Dawn
• Measure fluctuations in the near-IR background light, at
sensitivities sufficiently faint and angular scales
sufficiently large to constrain re-ionization models.
Extragalatic background:
Bock et al. 2006
• Integrated galaxy counts
below previous detection
limits form a lower EBL bound
• Gamma-Ray bursts (e.g
Aharonian et al. 2005) form
upper bound
• Direct detections are difficult
due to the EBL’s faint intensity
• Detections currently conflict
WFC3 Fluctuation Measurements
•
•
•
Reionization Simulation from Trac and Cen 2007
Large θ   Small θ
The large angle (θ ~ 1/30 °) peak
(green curve) is a linear-theory
prediction of clustering of
reionization sources.
Small scale power is sensitive to
the slope and normalization of the
luminosity function.
large area surveys with WFC3 can
(barely) reach large angle peak
Cosmic high-noon
• Test models for the co-evolution of black holes and bulges via the most
detailed census of interacting pairs, mergers, AGN, and bulges, aided
by the most complete and unbiased census of AGN from Herschel,
improved Chandra observations, and optical variability.
Cosmic high-noon
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• Detect individual galaxy subclumps and measure their stellar mass,
constraining the timescale for their dynamical-friction migration to the
center leading to bulge formation.
• Reveal the presence of fully formed passively evolving bulges out to z >
3, measure the bulge/disk ratio, and provide constraints on the relative
ages of the bulge and disk populations.
• Measure the rest-frame optical morphologies of passive galaxies up to
z~2 and beyond, and combine with ACS data to quantify UV-optical color
(age) gradients.
Cosmic variance
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Observing strategy
• Wide fields:
–
–
–
–
~750 sq. arcmin
2/3 orbits J (debating F125W vs. F110W)
4/3 orbits H (F160W)
Half the GOODS area covered this way
• GOODS Deep:
– ~130 sq. arcmin
– 12 orbit depth 4+4+4 in F105W+F125W+F160W
– At least 12 orbits new ACS F814W
• UV (GOODS-N):
– ~70 sq. arcmin
– Primary science is Lyman-escape fractions at z~2.5
– 3:1 ratio in F275W:F336W; leaning toward binning 2x2
Technical Issues
• We need to reprocess and stack all the existing ACS
data on these fields (for high-z galaxies):
– With better geometric distortion corrections and astrometry
than the original GOODS stacks
– With CTE corrections (Anderson algorithm?)
– Need alignment to WFC3 to within 0.1 pixel
– Correcting crosstalk for the EBL fluctuations project
• We are looking closely at image subtraction and
galaxy morphology versus number & size of dithers
• We need to worry about scattered earthshine for the
CVZ orbits
• Persistence, blobs, etc. will be a challenge for the
EBL fluctuations measurement.