NASA Hubble Space Telescope Daily Report #5181

Status Report From: Space Telescope Science Institute
Posted: Sunday, September 19, 2010

HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science


PERIOD COVERED: 5am September 14 - 5am September 15, 2010 (DOY 257/09:00z-258/09:00z)


Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)

HSTARS: (None)


18917-0 - Set STIS Event Flags 2 and 3 to inhibit further MAMA ops @ 257/18:59z


FGS GSAcq 9 9
FGS REAcq 6 6
OBAD with Maneuver 5 5


Ops Request 18917-0 at approximately 257/19:00 UTC, set the STIS event flags 2 and 3 in the NSSC-1 to prevent MAMA Low Voltage from being enabled.


ACS/WFC 12209

A Strong Lensing Measurement of the Evolution of Mass Structure in Giant Elliptical Galaxies

The structure and evolution of giant elliptical galaxies provide key quantitative tests for the theory of hierarchical galaxy formation in a cold dark matter dominated universe. Strong gravitational lensing provides the only direct means for the measurement of individual elliptical galaxy masses beyond the local universe, but there are currently no large and homogeneous samples of strong lens galaxies at significant cosmological look-back time. Hence, an accurate and unambiguous measurement of the evolution of the mass-density structure of elliptical galaxies has until now been impossible. Using spectroscopic data from the recently initiated Baryon Oscillation Spectroscopic Survey (BOSS) of luminous elliptical galaxies at redshifts from approximately 0.4 to 0.7, we have identified a large sample of high-probability strong gravitational lens candidates at significant cosmological look-back time, based on the detection of emission-line features from more distant galaxies along the same lines of sight as the target ellipticals. We propose to observe 45 of these systems with the ACS-WFC in order to confirm the incidence of lensing and to measure the masses of the lens galaxies. We will complement these lensing mass measurements with stellar velocity dispersions from ground-based follow-up spectroscopy. In combination with similar data from the Sloan Lens ACS (SLACS) Survey at lower redshifts, we will directly measure the cosmic evolution of the ratio between lensing mass and dynamical mass, to reveal the structural explanation for the observed size evolution of elliptical galaxies (at high mass). We will also measure the evolution of the logarithmic mass-density profile of massive ellipticals, which is sensitive to the details of the merging histories through which they are assembled. Finally, we will use our lensing mass-to-light measurements to translate the BOSS galaxy luminosity function into a mass function, and determine its evolution in combination with data from the original Sloan Digital Sky Survey.

ACS/WFC 12210

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.


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.

FGS 12316

HST/FGS Astrometric Search for Young Planets Around Beta Pic and AU Mic

AU Mic is a nearby Vega-type debris disk stars. Its disk system has been spatially resolved in exquisite detail, predominantly via the ACS coronagraph and WFPC-2 cameras onboard HST. These images exhibit a wealth of morphological features which provide compelling indirect evidence that AU Mic likely harbors short-period planetary body(ies). We propose to use the superlative astrometric capabilities of HST/FGS to directly detect these planets, hence provide the first direct planet detection in a Vega-type system whose disk has been imaged at high spatial resolution.

S/C 12046

COS FUV DCE Memory Dump

Whenever the FUV detector high voltage is on, count rate and current draw information is collected, monitored, and saved to DCE memory. Every 10 msec the detector samples the currents from the HV power supplies (HVIA, HVIB) and the AUX power supply (AUXI). The last 1000 samples are saved in memory, along with a histogram of the number of occurrences of each current value.

In the case of a HV transient (known as a "crackle" on FUSE), where one of these currents exceeds a preset threshold for a persistence time, the HV will shut down, and the DCE memory will be dumped and examined as part of the recovery procedure. However, if the current exceeds the threshold for less than the persistence time (a "mini-crackle" in FUSE parlance), there is no way to know without dumping DCE memory. By dumping and examining the histograms regularly, we will be able to monitor any changes in the rate of "mini-crackles" and thus learn something about the state of the detector.

STIS/CCD 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

STIS/CCD 11847

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 11999

JWST Calibration from a Consistent Absolute Calibration of Spitzer & Hubble

Recently, Gordon, Bohlin, et al. submitted a successful Spitzer proposal for cross calibration of HST and Spitzer. The cross-calibration targets are stars in three categories: WDs, A-stars, and G-stars. Traditionally, IR flux standards are extrapolations of stellar models that are tied to absolute fluxes at shorter wavelengths. HST absolute flux standards are among the best available with a solid basis that uses pure hydrogen models of hot WD stars for the SED slopes and is tied to Vega at 5556A via precise Landolt V-band photometry. Consistently matching models to our three categories of HST observations along with Spitzer photometry and the few existing absolute IR flux determinations will provide a solid basis for JWST flux calibration over its 0.8-30micron range. The goal of this proposal is to complete the HST observations of the set of HST/Spitzer cross-calibration stars. Using a variety of standard stars with three different spectral types will ensure that the final calibration is not significantly affected by systematic uncertainties.

WFC3/ACS/IR 11563

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.

WFC3/IR/S/C 11929

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).

WFC3/UV 12324

The Temperature Profiles of Quasar Accretion Disks

We can now routinely measure the size of quasar accretion disks using gravitational microlensing of lensed quasars. At optical wavelengths we observe a size and scaling with black hole mass roughly consistent with thin disk theory but the sizes are larger than expected from the observed optical fluxes. One solution would be to use a flatter temperature profile, which we can study by measuring the wavelength dependence of the disk size over the largest possible wavelength baseline. Thus, to understand the size discrepancy and to probe closer to the inner edge of the disk we need to extend our measurements to UV wavelengths, and this can only be done with HST. For example, in the UV we should see significant changes in the optical/UV size ratio with black hole mass. We propose monitoring 5 lenses spanning a broad range of black hole masses with well-sampled ground based light curves, optical disk size measurements and known GALEX UV fluxes during Cycles 17 and 18 to expand from our current sample of two lenses. We would obtain 5 observations of each target in each Cycle, similar to our successful strategy for the first two targets.

WFC3/UVIS 11905

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).

WFC3/UVIS/IR 11702

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 6.520deg) 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.

// end //

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