This program comprises basic tests for measuring the read noise and dark current of the ACS WFC and for tracking the growth of hot pixels. The recorded frames are used to create bias and dark reference images for science data reduction and calibration. This program will be executed four days per week (Mon, Wed, Fri, Sun) for the duration of Cycle 17. To facilitate scheduling, this program is split into three proposals. This proposal covers 308 orbits (19.25 weeks) from 21 June 2010 to 1 November 2010.
How Galaxies Acquire their Gas: A Map of Multiphase Accretion and Feedback in Gaseous Galaxy Halos
We propose to address two of the biggest open questions in galaxy formation - how galaxies acquire their gas and how they return it to the IGM - with a concentrated COS survey of diffuse multiphase gas in the halos of SDSS galaxies at z = 0.15 - 0.35. Our chief science goal is to establish a basic set of observational facts about the physical state, metallicity, and kinematics of halo gas, including the sky covering fraction of hot and cold material, the metallicity of infall and outflow, and correlations with galaxy stellar mass, type, and color - all as a function of impact parameter from 10 - 150 kpc. Theory suggests that the bimodality of galaxy colors, the shape of the luminosity function, and the mass-metallicity relation are all influenced at a fundamental level by accretion and feedback, yet these gas processes are poorly understood and cannot be predicted robustly from first principles. We lack even a basic observational assessment of the multiphase gaseous content of galaxy halos on 100 kpc scales, and we do not know how these processes vary with galaxy properties. This ignorance is presently one of the key impediments to understanding galaxy formation in general. We propose to use the high-resolution gratings G130M and G160M on the Cosmic Origins Spectrograph to obtain sensitive column density measurements of a comprehensive suite of multiphase ions in the spectra of 43 z < 1 QSOs lying behind 43 galaxies selected from the Sloan Digital Sky Survey. In aggregate, these sightlines will constitute a statistically sound map of the physical state and metallicity of gaseous halos, and subsets of the data with cuts on galaxy mass, color, and SFR will seek out predicted variations of gas properties with galaxy properties. Our interpretation of these data will be aided by state-of-the-art hydrodynamic simulations of accretion and feedback, in turn providing information to refine and test such models. We will also use Keck, MMT, and Magellan (as needed) to obtain optical spectra of the QSOs to measure cold gas with Mg II, and optical spectra of the galaxies to measure SFRs and to look for outflows. In addition to our other science goals, these observations will help place the Milky Way's population of multiphase, accreting High Velocity Clouds (HVCs) into a global context by identifying analogous structures around other galaxies. Our program is designed to make optimal use of the unique capabilities of COS to address our science goals and also generate a rich dataset of other absorption-line systems.
CCD Dark Monitor Part 2
Monitor the darks for the STIS CCD.
CCD Bias Monitor-Part 2
Monitor the bias in the 1x1, 1x2, 2x1, and 2x2 bin settings at gain=1, and 1x1 at gain = 4, to build up high-S/N superbiases and track the evolution of hot columns.
Galaxies at z~7-10 in the Reionization Epoch: Luminosity Functions to <0.2L* from Deep IR Imaging of the HUDF and HUDF05 Fields
The first generations of galaxies were assembled around redshifts z~7-10+, just 500-800 Myr after recombination, in the heart of the reionization of the universe. We know very little about galaxies in this period. Despite great effort with HST and other telescopes, less than ~15 galaxies have been reliably detected so far at z>7, contrasting with the ~1000 galaxies detected to date at z~6, just 200-400 Myr later, near the end of the reionization epoch. WFC3 IR can dramatically change this situation, enabling derivation of the galaxy luminosity function and its shape at z~7-8 to well below L*, measurement of the UV luminosity density at z~7-8 and z~8-9, and estimates of the contribution of galaxies to reionization at these epochs, as well as characterization of their properties (sizes, structure, colors). A quantitative leap in our understanding of early galaxies, and the timescales of their buildup, requires a total sample of ~100 galaxies at z~7-8 to ~29 AB mag. We can achieve this with 192 WFC3 IR orbits on three disjoint fields (minimizing cosmic variance): the HUDF and the two nearby deep fields of the HUDF05. Our program uses three WFC3 IR filters, and leverages over 600 orbits of existing ACS data, to identify, with low contamination, a large sample of over 100 objects at z~7-8, a very useful sample of ~23 at z~8-9, and limits at z~10. By careful placement of the WFC3 IR and parallel ACS pointings, we also enhance the optical ACS imaging on the HUDF and a HUDF05 field. We stress (1) the need to go deep, which is paramount to define L*, the shape, and the slope alpha of the luminosity function (LF) at these high redshifts; and (2) the far superior performance of our strategy, compared with the use of strong lensing clusters, in detecting significant samples of faint z~7-8 galaxies to derive their luminosity function and UV ionizing flux. Our recent z~7.4 NICMOS results show that wide-area IR surveys, even of GOODS-like depth, simply do not reach faint enough at z~7-9 to meet the LF and UV flux objectives. In the spirit of the HDF and the HUDF, we will waive any proprietary period, and will also deliver the reduced data to STScI. The proposed data will provide a Legacy resource of great value for a wide range of archival science investigations of galaxies at redshifts z~2-9. The data are likely to remain the deepest IR/optical images until JWST is launched, and will provide sources for spectroscopic follow up by JWST, ALMA and EVLA.
IR Dark Current Monitor
Analyses of ground test data showed that dark current signals are more reliably removed from science data using darks taken with the same exposure sequences as the science data, than with a single dark current image scaled by desired exposure time. Therefore, dark current images must be collected using all sample sequences that will be used in science observations. These observations will be used to monitor changes in the dark current of the WFC3-IR channel on a day-to-day basis, and to build calibration dark current ramps for each of the sample sequences to be used by Gos in Cycle 17. For each sample sequence/array size combination, a median ramp will be created and delivered to the calibration database system (CDBS).
Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey -- GOODS-South Field, Early Visits of SNe Search
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 10^9 M_Sun out to z~8.
We adopt a two-tiered strategy with a "Wide" component (roughly 2 orbits deep over ~0.2 sq. degrees) and a "Deep" component (roughly 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 in COSMOS, EGS, and UKIDSS/UDS. Each of these consists of roughly 3x15 WFC3/IR tiles. Each WFC3 tile will be observed for 2 orbits, with single orbits separated in time to allow a search for high-redshift Type Ia SNe. The co-added exposure times will be 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 roughly 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 fields cover roughly half of each GOODS field, with exact areas and placements to be determined as part of the Phase-2 process. Each WFC3/IR tile within the Deep regions will receive approximately 12 orbits of exposure time split 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 also 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.
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 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< z<2. The observing configuration for the follow up will depend on the redshift of the supernova, and will likely include a grism observation with either ACS G800L, WFC3-IR G102, or G141, and light curves observed with F850LP, WFC3-IR F125W, and F160W.
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< z<1.5 will be used to measure the evolution of dark energy.
This program takes full advantage of MCTP mode to fulfill Hubble's legacy for deep extragalactic science and prepare the way for JWST.
WFC3 UVIS CCD Daily Monitor
The behavior of the WFC3 UVIS CCD will be monitored daily with a set of full-frame, four-amp bias and dark frames. A smaller set of 2Kx4K subarray biases are acquired at less frequent intervals throughout the cycle to support subarray science observations. The internals from this proposal, along with those from the anneal procedure (Proposal 11909), will be used to generate the necessary superbias and superdark reference files for the calibration pipeline (CDBS).
Cycle 17: UVIS Bowtie Monitor
Ground testing revealed an intermittent hysteresis type effect in the UVIS detector (both CCDs) at the level of ~1%, lasting hours to days. Initially found via an unexpected bowtie-shaped feature in flatfield ratios, subsequent lab tests on similar e2v devices have since shown that it is also present as simply an overall offset across the entire CCD, i.e., a QE offset without any discernable pattern. These lab tests have further revealed that overexposing the detector to count levels several times full well fills the traps and effectively neutralizes the bowtie. Each visit in this proposal acquires a set of three 3x3 binned internal flatfields: the first unsaturated image will be used to detect any bowtie, the second, highly exposed image will neutralize the bowtie if it is present, and the final image will allow for verification that the bowtie is gone.
A Dynamical-Compositional Survey of the Kuiper Belt: A New Window Into the Formation of the Outer Solar System
The eight planets overwhelmingly dominate the solar system by mass, but their small numbers, coupled with their stochastic pasts, make it impossible to construct a unique formation history from the dynamical or compositional characteristics of them alone. In contrast, the huge numbers of small bodies scattered throughout and even beyond the planets, while insignificant by mass, provide an almost unlimited number of probes of the statistical conditions, history, and interactions in the solar system. To date, attempts to understand the formation and evolution of the Kuiper Belt have largely been dynamical simulations where a hypothesized starting condition is evolved under the gravitational influence of the early giant planets and an attempt is made to reproduce the current observed populations. With little compositional information known for the real Kuiper Belt, the test particles in the simulation are free to have any formation location and history as long as they end at the correct point. Allowing compositional information to guide and constrain the formation, thermal, and collisional histories of these objects would add an entire new dimension to our understanding of the evolution of the outer solar system. While ground based compositional studies have hit their flux limits already with only a few objects sampled, we propose to exploit the new capabilities of WFC3 to perform the first ever large-scale dynamical-compositional study of Kuiper Belt Objects (KBOs) and their progeny to study the chemical, dynamical, and collisional history of the region of the giant planets. The sensitivity of the WFC3 observations will allow us to go up to two magnitudes deeper than our ground based studies, allowing us the capability of optimally selecting a target list for a large survey rather than simply taking the few objects that can be measured, as we have had to do to date. We have carefully constructed a sample of 120 objects which provides both overall breadth, for a general understanding of these objects, plus a large enough number of objects in the individual dynamical subclass to allow detailed comparison between and within these groups. These objects will likely define the core Kuiper Belt compositional sample for years to come. While we have many specific results anticipated to come from this survey, as with any project where the field is rich, our current knowledge level is low, and a new instrument suddenly appears which can exploit vastly larger segments of the population, the potential for discovery -- both anticipated and not -- is extraordinary.
Search for Very High-z Galaxies with WFC3 Pure Parallel
WFC3 will provide an unprecedented probe to the early universe beyond the current redshift frontier. Here we propose a pure parallel program using this new instrument to search for Lyman-break galaxies at 6.5< z<8.8 and to probe the epoch of reionization, a hallmark event in the history of the early universe. We request 200 orbits, spreading over 30 ~ 50 high Galactic latitude visits (|b|>20deg) that last for 4 orbits and longer, resulting a total survey area of about 140~230 square arcminute. Based on our understanding of the new HST parallel observation scheduling process, we believe that the total number of long-duration pure parallel visits in Cycle 17 should be sufficient to accommodate our program. We waive all proprietary rights to our data, and will also make the enhanced data products public in a timely manner.
(1) We will use both the UVIS and the IR channels, and do not need to seek optical data from elsewhere.
(2) Our program will likely triple the size of the probable candidate samples at z~7 and z~8, and will complement other targeted programs aiming at the similar redshift range.
(3) Being a pure parallel program, our survey will only make very limited demand on the scarce HST resources. More importantly, as the pure parallel pointings will be at random sight-lines, our program will be least affected by the bias due to the large scale structure ("cosmic variance").
(4) We aim at the most luminous LBG population, and will address the bright-end of the luminosity function at z~8 and z~7. We will constrain the value of L* in particular, which is critical for understanding the star formation process and the stellar mass assembly history in the first few hundred million years of the universe.
(5) The candidates from our survey, most of which will be the brightest ones that any surveys would be able to find, will have the best chance to be spectroscopically confirmed at the current 8--10m telescopes.
(6) We will also find a large number of extremely red, old galaxies at intermediate redshifts, and the fine spatial resolution offered by the WFC3 will enable us constrain their formation history based on the study of their morphology, and hence shed light on their connection to the very early galaxies in the universe.