SLACS for the Masses: Extending Strong Lensing to Lower Masses and Smaller Radii
Strong gravitational lensing provides the most accurate possible measurement of mass in the central regions of early-type galaxies (ETGs). We propose to continue the highly productive Sloan Lens ACS (SLACS) Survey for strong gravitational lens galaxies by observing a substantial fraction of 135 new ETG gravitational-lens candidates with HST-ACS WFC F814W Snapshot imaging. The proposed target sample has been selected from the seventh and final data release of the Sloan Digital Sky Survey, and is designed to complement the distribution of previously confirmed SLACS lenses in lens-galaxy mass and in the ratio of Einstein radius to optical half-light radius. The observations we propose will lead to a combined SLACS sample covering nearly two decades in mass, with dense mapping of enclosed mass as a function of radius out to the half-light radius and beyond. With this longer mass baseline, we will extend our lensing and dynamical analysis of the mass structure and scaling relations of ETGs to galaxies of significantly lower mass, and directly test for a transition in structural and dark-matter content trends at intermediate galaxy mass. The broader mass coverage will also enable us to make a direct connection to the structure of well-studied nearby ETGs as deduced from dynamical modeling of their line-of-sight velocity distribution fields. Finally, the combined sample will allow a more conclusive test of the current SLACS result that the intrinsic scatter in ETG mass-density structure is not significantly correlated with any other galaxy observables. The final SLACS sample at the conclusion of this program will comprise approximately 130 lenses with known foreground and background redshifts, and is likely to be the largest confirmed sample of strong-lens galaxies for many years to come.
The Cosmological Impact of AGN Outflows: Measuring Absolute Abundances and Kinetic Luminosities
AGN outflows are increasingly invoked as a major contributor to the formation and evolution of supermassive black holes, their host galaxies, the surrounding IGM, and cluster cooling flows. Our HST/COS proposal will determine reliable absolute chemical abundances in six AGN outflows, which influences several of the processes mentioned above. To date there is only one such determination, done by our team on Mrk 279 using 16 HST/STIS orbits and 100 ksec of FUSE time. The advent of COS and its high sensitivity allows us to choose among fainter objects at redshifts high enough to preclude the need for FUSE. This will allow us to determine the absolute abundances for six AGN (all fainter than Mrk 279) using only 40 HST COS orbits. This will put abundances studies in AGN on a firm footing, an elusive goal for the past four decades. In addition, prior FUSE observations of four of these targets indicate that it is probable that the COS observations will detect troughs from excited levels of C III. These will allow us to measure the distances of the outflows and thereby determine their kinetic luminosity, a major goal in AGN feedback research.
We will use our state of the art column density extraction methods and velocity-dependent photoionization models to determine the abundances and kinetic luminosity. Previous AGN outflow projects suffered from the constraints of deciding what science we could do using ONE of the handful of bright targets that were observable. With COS we can choose the best sample for our experiment. As an added bonus, most of the spectral range of our targets has not been observed previously, greatly increasing the discovery phase space.
Probing the Outer Regions of M31 with QSO Absorption Lines
We propose HST-COS spectroscopy of 10 quasars behind M31. Absorption lines due to MgII, FeII, CIV, and a variety of other lines will be searched for and measured. Six quasars lie between 1 and 4.2 Holmberg radii near the major axis on the southwest side, where confusion with Milky Way gas is minimized. Two lie even farther out on the southwest side of the major axis. One lies within 1 Holmberg radius. Two of the 10 pass through M31's high velocity clouds seen in a detailed 21 cm emission map. Exposure time estimates were based on SDSS magnitudes and available GALEX magnitudes. Thus, using the most well-studied external spiral galaxy in the sky, our observations will permit us to check, better than ever before, the standard picture that quasar metal-line absorption systems such as MgII and CIV arise in an extended gaseous halo/disk of a galaxy well beyond its observable optical radius. The observations will yield insights into the nature of the gas and its connection to the very extended stellar components of M31 that have recently been studied. Notably the observations have the potential of extending M31's rotation curve to very large galactocentric distances, thereby placing new constraints on M31's dark matter halo.
Finally, we also request that the coordinated parallel orbits be allocated to this program so that we may image the resolved stellar content of M31's halo and outer disk.
Probing Warm-Hot Intergalactic Gas at 0.5 < z < 1.3 with a Blind Survey for O VI, Ne VIII, Mg X, and Si XII Absorption Systems
Currently we can only account for half of the baryons (or less) expected to be found in the nearby universe based on D/H and CMB observations. This "missing baryons problem" is one of the highest-priority challenges in observational extragalatic astronomy. Cosmological simulations suggest that the baryons are hidden in low-density, shock-heated intergalactic gas in the log T = 5 - 7 range, but intensive UV and X-ray surveys using O VI, O VII, and O VIII absorption lines have not yet confirmed this prediction. We propose to use COS to carry out a sensitive survey for Ne VIII and Mg X absorption in the spectra of nine QSOs at z(QSO) > 0.89. For the three highest-redshift QSOs, we will also search for Si XII. This survey will provide more robust constraints on the quantity of baryons in warm-hot intergalactic gas at 0.5 < z < 1.3, and the data will provide rich constraints on the metal enrichment, physical conditions, and nature of a wide variety of QSO absorbers in addition to the warm-hot systems. By comparing the results to other surveys at lower redshifts (with STIS, FUSE, and from the COS GTO programs), the project will also enable the first study of how these absorbers evolve with redshift at z < 1. By combining the program with follow-up galaxy redshift surveys, we will also push the study of galaxy-absorber relationships to higher redshifts, with an emphasis on the distribution of the WHIM with respect to the large-scale matter distribution of the universe.
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.
STIS CCD Hot Pixel Annealing
This purpose of this activity is to repair radiation induced hot pixel damage to the STIS CCD by warming the CCD to the ambient instrument temperature and annealing radiation-damaged pixels.
Radiation damage creates hot pixels in the STIS CCD Detector. Many of these hot pixels can be repaired by warming the CCD from its normal operating temperature near -83 deg. C to the ambient instrument temperature (~ +5 deg. C) for several hours. The number of hot pixels repaired is a function of annealing temperature. The effectiveness of the CCD hot pixel annealing process is assessed by measuring the dark current behavior before and after annealing and by searching for any window contamination effects.
MAMA NUV Flats
This program will obtain NUV-MAMA observations of the STIS internal Deuterium lamp to construct an NUV flat applicable to all NUV modes.
Infrared Survey of Star Formation Across Cosmic Time
We propose to use the unique power of WFC3 slitless spectroscopy to measure the evolution of cosmic star formation from the end of the reionization epoch at z>6 to the close of the galaxy-building era at z~0.3.Pure parallel observations with the grisms have proven to be efficient for identifying line emission from galaxies across a broad range of redshifts. The G102 grism on WFC3 was designed to extend this capability to search for Ly-alpha emission from the first galaxies. Using up to 250 orbits of pure parallel WFC3 spectroscopy, we will observe about 40 deep (4-5 orbit) fields with the combination of G102 and G141, and about 20 shallow (2-3 orbit) fields with G141 alone.
Our primary science goals at the highest redshifts are: (1) Detect Lya in ~100 galaxies with z>5.6 and measure the evolution of the Lya luminosity function, independent of of cosmic variance; 2) Determine the connection between emission line selected and continuum-break selected galaxies at these high redshifts, and 3) Search for the proposed signature of neutral hydrogen absorption at re-ionization. At intermediate redshifts we will (4) Detect more than 1000 galaxies in Halpha at 0.5
To identify single-line Lya emitters, we will exploit the wide 0.8--1.9um wavelength coverage of the combined G102+G141 spectra. All [OII] and [OIII] interlopers detected in G102 will be reliably separated from true LAEs by the detection of at least one strong line in the G141 spectrum, without the need for any ancillary data. We waive all proprietary rights to our data and will make high-level data products available through the ST/ECF.
Formation and Evolution of Massive Galaxies in the Richest Environments at 1.5 < z < 2.0
We propose to image seven 1.5
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).
Differentiation in the Kuiper belt: a Search for Silicates on Icy Bodies.
We currently have a large on-going program (Go Program 11644, 120 orbits) to exploit the superb stability and photometric characteristics of HST and the broad range in wavelength coverage of the WFC3 to make broad-band vis/IR spectral observations of a large sample of Kuiper belt objects. Though the survey is currently only ~50% complete, the quality and unprecedented signal-to-noise of these observations has revealed the existence of a previously undiscovered spectral variability not explainable within our current understanding of these objects.
A possible explanation for this variability is that with this faint set of Kuiper belt objects, we are beginning to see the difference between larger differentiated objects and smaller non-differentiated objects. Its seems that the small and likely undifferentiated objects are exhibiting silicate features that affect our photometry - features not exhibited by the icy mantles of larger icy bodies.
We propose a small add-on survey to dramatically increase the scientific results of our large program. The proposed observations will use the proven capabilities of WFC3 to make broad and narrow-band photometric observations to detect spectral features in the 1.0-1.3 micron range of a small subset of our sources. The 13 targets have been carefully selected to cover the range of spectral variability detected in our large program as well as sample the entire dynamical range and physical sizes of these targets. These observations will allow the identification of undifferentiated Kuiper belt objects by detection of their silicate features. As a probe for differentiation, these observations could constrain the natal locations of different Kuiper belt classes, a constraint currently unavailable to formation models. This small set of observations will allow the calibration of the spectral variability seen in our large program, and drastically enhance the scientific output of our full Cycle 17 sample.
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.