Status Report

NASA Hubble Space Telescope Daily Report #5129

By SpaceRef Editor
July 8, 2010
Filed under , ,


Continuing to Collect World Class Science

PERIOD COVERED: 5am June 30 – 5am July 1, 2010 (DOY 181/09:00z-182/09:00z)


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


12319 – REAcq(1,2,1) scheduled at 181/19:43:29z – 19:47:55z required three attempts to achieve FL-DV on FGS-2. The acquisition was successful.

Observations possibly affected: ACS 34, 35, Proposal ID#11669.


12317 – GSAcq(2,1,1) at 172/14:53:57z required two attempts to achieve CT-DV on FGS2. The acquisition was successful.


12318 – GSAcq(2,1,1) at 178/21:01:47z required two attempts to maintain lock. The second attempt was successful.



FGS GSAcq 7 7
FGS REAcq 7 7
OBAD with Maneuver 3 3



ACS/WFC 11996

CCD Daily Monitor (Part 3)

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.

ACS/WFC3 11669

The Origins of Short Gamma-Ray Bursts

During the past decade extraordinary progress has been made in determining the origin of long- duration gamma-ray bursts. It has been conclusively shown that these objects derive from the deaths of massive stars. Nonetheless, the origin of their observational cousins, short-duration gamma-ray bursts (SGRBs) remains a mystery. While SGRBs are widely thought to result from the inspiral of compact binaries, this is a conjecture. SGRBs have been found in elliptical galaxies, Abell Clusters, star-forming dwarfs and even an edge-on spiral. Whether they primarily result from an old population, a young population, or rapid evolution of binaries in globular clusters remains open.

Here we propose to employ two related sets of observations which may dramatically advance our understanding of short bursts. The first is a variant of a technique that we pioneered and used to great effect in elucidating the origins of long-duration bursts. We will examine a statistical sample of hosts and measure the degree to which SGRB locations trace the red or blue light of their hosts, and thus old or young stellar populations. This will allow us to study the demographics of the SGRB population in a manner largely free of the distance dependent selection effects which have so far bedeviled this field. In the second line of attack we will use two targets of opportunity to obtain extremely precise positions of up to two nearby bursts — one on a star-forming galaxy and the other on a elliptical. Observation of the star-formation galaxy could link at least some bursts directly to a young population; however, a discovery in later images of a globular cluster at the site of the explosion in an elliptical would provide revolutionary evidence that SGRBs are formed from compact binaries.

STIS/CC 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

STIS/CC 11847

CCD Bias Monitor-Part 2

Monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1, and 1×1 at gain = 4, to build up high-S/N superbiases and track the evolution of hot columns.

WFC3/ACS/IR 11597

Spectroscopy of IR-Selected Galaxy Clusters at 1 < z < 1.5 We propose to obtain WFC3 G141 and G102 slitless spectroscopy of galaxy clusters at 1 < z < 1.5 that were selected from the IRAC survey of the Bootes NDWFS field. Our IRAC survey contains the largest sample of spectroscopically confirmed clusters at z > 1. The WFC3 grism data will measure H-alpha to determine SFR, and fit models to the low resolution continua to determine stellar population histories for the brighter cluster members, and redshifts for the red galaxies too faint for ground-based optical spectroscopy.


Multiple Stellar Generations in the Unique Globular Clusters NGC 6388 and NGC 6441

Over the last few years HST observations have resulted in one of the most exciting and unexpected developments in stellar population studies: the discovery of multiple generations of stars in several globular clusters. The finding of multiple main sequences in the massive clusters NGC 2808 and Omega Centauri, and multiple subgiant branches in NGC 1851, M54, and NGC 6388 has challenged the long-held paradigm that globular clusters are simple stellar populations. Even more surprising, given the spectroscopic and photometric constraints, the only viable explanation for the main sequence splitting appears to be Helium enrichment, up to an astonishingly high Y=0.4. The conditions under which certain globulars experience the formation of multiple stellar generations remain mysterious, and even more so the helium-enrichment phenomenon. Such an enrichment has important implications for chemical-enrichment, star-formation, and stellar-evolution scenarios, in star clusters and likely elsewhere. To properly constrain the multiple main sequence phenomenon, it is important to determine its extent among GCs: is it limited to Omega Cen and NGC2808, or is it more common? We propose deep WFC3 optical/IR imaging of NGC 6388 and 6441, the two globular clusters that are most likely to host multiple, helium-enriched populations. Our simulations of WFC3 performance suggest that we will be able to detect even the main sequence splittings caused by small He differences (Delta Y <0.03). WFC3/UVIS 11697 Proper Motion Survey of Classical and SDSS Local Group Dwarf Galaxies Using the superior resolution of HST, we propose to continue our proper motion survey of Galactic dwarf galaxies. The target galaxies include one classical dwarf, Leo II, and six that were recently identified in the Sloan Digital Sky Survey data: Bootes I, Canes Venatici I, Canes Venatici II, Coma Berenices, Leo IV, and Ursa Major II. We will observe a total of 16 fields, each centered on a spectroscopically-confirmed QSO. Using QSOs as standards of rest in measuring absolute proper motions has proven to be the most accurate and most efficient method. HST is our only option to quickly determine the space motions of the SDSS dwarfs because suitable ground-based imaging is only a few years old and such data need several decades to produce a proper motion. The two most distant galaxies in our sample will require time baselines of four years to achieve our goal of a 30-50 km/s uncertainty in the tangential velocity; given this and the finite lifetime of HST, it is imperative that first-epoch observations be taken in this cycle. The SDSS dwarfs have dramatically lower surface brightnesses and luminosities than the classical dwarfs. Proper motions are crucial for determining orbits of the galaxies and knowing the orbits will allow us to test theories for the formation and evolution of these galaxies and, more generally, for the formation of the Local Group. 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 11911 UVIS L-Flats and Geometric Distortion Multiple pointing observations of the globular cluster Omega Centauri (NGC 5139) will be used to measure the filter-dependent low frequency flat field (L-flat) corrections and stability for a key set of 10 broadband filters used by GO programs. The selected filters are F225W, F275W, F336W, F390W, F438W, F555W, F606W, F775W, F814W and F850LP. By measuring relative changes in brightness of a star over different portions of the detector, we will determine local variations in the UVIS detector response. The broad wavelength range covered by these observations will allow us to derive the L-flat correction for the remaining wide, medium and narrow-band UVIS filters. The same data will also be used to determine and correct the geometric distortion that affects UVIS data. The broad wavelength range covered by these observations will allow us to measure the geometric distortion dependence with wavelength and filters and to provide the most appropriate correction over the entire wavelength range provided by UVIS. WFC3/UVIS/IR 11662 Improving the Radius-Luminosity Relationship for Broad-Lined AGNs with a New Reverberation Sample The radius-luminosity (R-L) relationship is currently the fundamental basis for all techniques used to estimate black hole masses in AGNs, in both the nearby and distant universe. However, the current R-L relationship is based on 34 objects that cover a limited range in black hole mass and luminosity. To improve our understanding of black hole growth and evolution, the R-L relationship must be extended to cover a broader range of black hole masses using the technique known as reverberation mapping. To this end, we have been awarded an unprecedented 64 nights on the Lick Observatory 3-m telescope between March 24 and May 31, 2008, to spectroscopically monitor 12 AGNs in order to measure their black hole masses. To properly determine the luminosities of these 12 AGNs, we must correct them for their host-galaxy starlight contributions using high-resolution images. Previous work by Bentz et al. (2006) has shown that the starlight correction to AGN luminosity measurements is an essential component to interpreting the R-L relationship. The correction will be substantial for each of the 12 sources we will monitor, as the AGNs are relatively faint and embedded in nearby, bright galaxies. Starlight corrections are not possible with ground-based images, as the PSF and bulge contributions become indistinguishable under typical seeing conditions, and adaptive optics are not yet operational in the spectral range where the corrections are needed. In addition, spectral decompositions are very model-dependent and are limited by the degree of accuracy to which we understand emission processes and stellar populations in galaxies. Without correcting for starlight, we will be unable to apply the results of our Spring 2008 campaign to the body of knowledge from previous reverberation mapping work. Therefore, we propose to obtain high resolution, high dynamic range images of the host galaxies of the 12 AGNs in our ground-based monitoring sample, as well as one white dwarf which will be used as a PSF model. WFC3/UVIS/IR 11700 Bright Galaxies at z>7.5 with a WFC3 Pure Parallel Survey

The epoch of reionization represents a special moment in the history of the Universe as it is during this era that the first galaxies and star clusters are formed. Reionization also profoundly affects the environment where subsequent generations of galaxies evolve. Our overarching goal is to test the hypothesis that galaxies are responsible for reionizing neutral hydrogen. To do so we propose to carry out a pure parallel WFC3 survey to constrain the bright end of the redshift z>7.5 galaxy luminosity function on a total area of 176 arcmin^2 of sky. Extrapolating the evolution of the luminosity function from z~6, we expect to detect about 20 Lyman Break Galaxies brighter than M_* at z~8 significantly improving the current sample of only a few galaxies known at these redshifts. Finding significantly fewer objects than predicted on the basis of extrapolation from z=6 would set strong limits to the brightness of M_*, highlighting a fast evolution of the luminosity function with the possible implication that galaxies alone cannot reionize the Universe. Our observations will find the best candidates for spectroscopic confirmation, that is bright z>7.5 objects, which would be missed by small area deeper surveys. The random pointing nature of the program is ideal to beat cosmic variance, especially severe for luminous massive galaxies, which are strongly clustered. In fact our survey geometry of 38 independent fields will constrain the luminosity function like a contiguous single field survey with two times more area at the same depth. Lyman Break Galaxies at z>7.5 down to m_AB=26.85 (5 sigma) in F125W will be selected as F098M dropouts, using three to five orbits visits that include a total of four filters (F606W, F098M, F125W, F160W) optimized to remove low-redshift interlopers and cool stars. Our data will be highly complementary to a deep field search for high- z galaxies aimed at probing the faint end of the luminosity function, allowing us to disentangle the degeneracy between faint end slope and M_* in a Schechter function fit of the luminosity function. We waive proprietary rights for the data. In addition, we commit to release the coordinates and properties of our z>7.5 candidates within one month from the acquisition of each field.

SpaceRef staff editor.