NASA Hubble Space Telescope Daily Report #5049
HUBBLE SPACE TELESCOPE DAILY REPORT #5049
Continuing to Collect World Class Science
PERIOD COVERED: 5am March 9 – 5am March 10, 2010 (DOY 068/10:00z-069/10:00z)
OBSERVATIONS SCHEDULED
ACS/WFC/WFC3/UV 11633
A Precision White Dwarf Cooling Age for NGC 6397
We propose to obtain second epoch imaging of the globular cluster NGC 6397, which has the deepest ACS/WFC dataset (126 orbits in Cycle 13) ever obtained in a globular cluster. These additional 14 orbits would enable the construction of a proper motion – cleaned white dwarf cooling sequence reaching fainter than the observed truncation point of the white dwarf luminosity function; a byproduct will be absolute proper motions (relative to the extragalactic reference frame) of the rich spheroid field population. Our data shows the long sought “blue hook”, a feature in the WD cooling sequence predicted in theoretical white dwarf models; the improved photometry and statistics afforded by the second epoch observations are needed to confirm the blue hook and to test other aspects of white dwarf cooling models that contribute to a 0.5 Gyr or greater uncertainty in the age. The proposed observations will provide formal constraints on the age and formation timescale of NGC 6397 that will be smaller than 1 Gyr and place the cluster’s formation epoch relative to the end of reionization. The final proper motion-purified white dwarf sequence will be a powerful constraint for white dwarf cooling models and atmospheres, the basis for white dwarf-based globular cluster age determinations, and also constrain the fraction of binary white dwarfs.
COS/NUV 11894
NUV Detector Dark Monitor
The purpose of this proposal is to measure the NUV detector dark rate by taking long science exposures with no light on the detector. The detector dark rate and spatial distribution of counts will be compared to pre-launch and SMOV data in order to verify the nominal operation of the detector. Variations of count rate as a function of orbital position will be analyzed to find dependence of dark rate on proximity to the SAA. Dependence of dark rate as function of time will also be tracked.
NIC3/WFC3/IR 11149
Characterizing the Stellar Populations in Lyman-Alpha Emitters and Lyman Break Galaxies at 5.7
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.
STIS/CC/MA 11516
COS-GTO: Cold ISM
With the COS, we will be able to observe interstellar spectra in a new regime, translucent clouds, for atomic, ionic, and molecular lines and bands, and extinction curves. The COS will allow us to observe stars with total visual extinctions up to 10 magnitudes, and the grain size indicator Rv up to 4.5. In translucent clouds we expect to see the transition from neutral and ionized carbon to mostly C I, and then from there, we should expect to see carbon increasingly locked up in molecular form, as CO. Other species are expected to make similar transitions, so we should find detectable abundances of molecules such as H2O, OH, CS, CH2, SiO, and others; also, lower ionization fractions of the metallic elements – and higher depletions of those elements as well. Given that we expect to find higher depletions, we should see an altered grain size distribution, which may show up in the extinction curves, probably as lower far-UV extinction than in diffuse clouds. Finally, we will search for neutral PAHs in absorption, as diffuse bands in the UV, paralleling the optical DIBs (which are thought by some scientists to be formed by singly-ionized PAHs). In translucent clouds, models show that the PAHs will be neutral, not in cationic form.
STIS/CCD/MA1/MA2 11860
MAMA Spectroscopic Sensitivity and Focus Monitor
The purpose of this proposal is to monitor the sensitivity of each MAMA grating mode to detect any change due to contamination or other causes, and to also monitor the STIS focus in a spectroscopic and an imaging mode.
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/IR 11664
The WFC3 Galactic Bulge Treasury Program: Populations, Formation History, and Planets
Exploiting the full power of the Wide Field Camera 3 (WFC3), we propose deep panchromatic imaging of four fields in the Galactic bulge. These data will enable a sensitive dissection of its stellar populations, using a new set of reddening-free photometric indices we have constructed from broad-band filters across UV, optical, and near-IR wavelengths. These indices will provide accurate temperatures and metallicities for hundreds of thousands of individual bulge stars. Proper motions of these stars derived from multi-epoch observations will allow separation of pure bulge samples from foreground disk contamination. Our catalogs of proper motions and panchromatic photometry will support a wide range of bulge studies.
Using these photometric and astrometric tools, we will reconstruct the detailed star-formation history as a function of position within the bulge, and thus differentiate between rapid- and extended-formation scenarios. We will also measure the dependence of the stellar mass function on metallicity, revealing how the characteristic mass of star formation varies with chemistry. Our sample of bulge stars with accurate metallicities will include 12 candidate hosts of extrasolar planets. Planet frequency is correlated with metallicity in the solar neighborhood; our measurements will extend this knowledge to a remote environment with a very distinct chemistry.
Our proposal also includes observations of six well-studied globular and open star clusters; these observations will serve to calibrate our photometric indices, provide empirical population templates, and transform the theoretical isochrone libraries into the WFC3 filter system. Besides enabling our own program, these products will provide powerful new tools for a host of other stellar-population investigations with HST/WFC3. We will deliver all of the products from this Treasury Program to the community in a timely fashion.
WFC3/UVIS 11628
Globular Cluster Candidates for Hosting a Central Black Hole
We are continuing our study of the dynamical properties of globular clusters and we propose to obtain surface brightness profiles for high concentration clusters. Our results to date show that the distribution of central surface brightness slopes do not conform to standard models. This has important implications for how they form and evolve, and suggest the possible presence of central intermediate-mass black holes. From our previous archival proposals (AR-9542 and AR- 10315), we find that many high concentration globular clusters do not have flat cores or steep central cusps, instead they show weak cusps. Numerical simulations suggest that clusters with weak cusps may harbor intermediate-mass black holes and we have one confirmation of this connection with omega Centauri. This cluster shows a shallow cusp in its surface brightness profile, while kinematical measurements suggest the presence of a black hole in its center. Our goal is to extend these studies to a sample containing 85% of the Galactic globular clusters with concentrations higher than 1.7 and look for objects departing from isothermal behavior. The ACS globular cluster survey (GO-10775) provides enough objects to have an excellent coverage of a wide range of galactic clusters, but it contains only a couple of the ones with high concentration. The proposed sample consists of clusters whose light profile can only be adequately measured from space-based imaging. This would take us close to completeness for the high concentration cases and therefore provide a more complete list of candidates for containing a central black hole. The dataset will also be combined with our existing kinematic measurements and enhanced with future kinematic studies to perform detailed dynamical modeling.
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 11912
UVIS Internal Flats
This proposal will be used to assess the stability of the flat field structure for the UVIS detector throughout the 15 months of Cycle 17. The data will be used to generate on-orbit updates for the delta-flat field reference files used in the WFC3 calibration pipeline, if significant changes in the flat structure are seen.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
HSTARS:
For DOY 055
12213 – Review of the 053 SMS PTAS lg2 file found that GSAcq(2,1,1) at 055/21:59:00z took two attempts to achieve Coarse Track Data Valid. The acquisition was eventually successful and finished well within the time allotted so there was no effect on the science observation.
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL
FGS GSAcq 7 7
FGS REAcq 7 7
OBAD with Maneuver 6 6
SIGNIFICANT EVENTS: (None)
