NASA Hubble Space Telescope Daily Report # 4484
Notice: Due to the conversion of some ACS WFC or HRC observations into WFPC2, or NICMOS observations after the loss of ACS CCD science capability in January, there may be an occasional discrepancy between a proposal’s listed (and correct) instrument usage and the abstract that follows it.
HUBBLE SPACE TELESCOPE DAILY REPORT # 4484
– Continuing to collect World Class Science
PERIOD COVERED: UT November 06, 2007 (DOY 310)
OBSERVATIONS SCHEDULED
ACS/SBC 11215
New Sightlines for the Study of Intergalactic Helium: Dozens of High-Confidence, UV- Bright Quasars from SDSS/GALEX The reionization of IGM helium is thought to have occurred at redshifts of z=3 to 4. Detailed study of HeII Lyman-alpha absorption toward a handful of QSOs at 2.7< z<3.3 demonstrated the high potential of such IGM probes, but the critically small sample size limits confidence in cosmological inferences. The requisite unobscured sightlines to high-z are extremely rare, but SDSS provides 5800, z>3.1 QSOs potentially suitable for HeII studies. We’ve cross-correlated SDSS quasars with GALEX UV sources to obtain dozens of new, high confidence, candidate sightlines {z=3.1-4.9} potentially useful for detailed HeII studies with HST. We propose brief, 2-orbit reconnaissance ACS SBC prism exposures toward each of the best dozen new quasars, to definitively verify UV flux down to HeII. Our combined SDSS/GALEX selection insures a high confirmation rate, as the quasars are already known to be UV bright in GALEX. Our program will provide a statistical sample of HeII sightlines extending to high redshift, enabling future long exposure follow-up spectra with the SBC prism, or superb quality COS or STIS spectra after SM4. Stacks of our prism spectra will also directly yield ensemble information. Ultimately, the new sightlines will enable confident measures of the spectrum and evolution of the ionizing background, the evolution of HeII opacity, the epoch of helium reionization, and the density of IGM baryons.
NIC1/NIC2/NIC3 8794
NICMOS Post-SAA calibration – CR Persistence Part 5
A new procedure proposed to alleviate the CR-persistence problem of NICMOS. Dark frames will be obtained immediately upon exiting the SAA contour 23, and every time a NICMOS exposure is scheduled within 50 minutes of coming out of the SAA. The darks will be obtained in parallel in all three NICMOS Cameras. The POST-SAA darks will be non- standard reference files available to users with a USEAFTER date/time mark. The keyword ‘USEAFTER=date/time’ will also be added to the header of each POST-SAA DARK frame. The keyword must be populated with the time, in addition to the date, because HST crosses the SAA ~8 times per day so each POST-SAA DARK will need to have the appropriate time specified, for users to identify the ones they need. Both the raw and processed images will be archived as POST-SAA DARKs. Generally we expect that all NICMOS science/calibration observations started within 50 minutes of leaving an SAA will need such maps to remove the CR persistence from the science images. Each observation will need its own CRMAP, as different SAA passages leave different imprints on the NICMOS detectors.
NIC2 11197
Sweeping Away the Dust: Reliable Dark Energy with an Infrared Hubble Diagram
We propose building a high-z Hubble Diagram using type Ia supernovae observed in the infrared rest-frame J-band. The infrared has a number of exceptional properties. The effect of dust extinction is minimal, reducing a major systematic that may be biasing dark energy measurements. Also, recent work indicates that type Ia supernovae are true standard candles in the infrared meaning that our Hubble diagram will be resistant to possible evolution in the Phillip’s relation over cosmic time. High signal-to-noise measurements of 16 type Ia events at z~0.4 will be compared with an independent optical Hubble diagram from the ESSENCE project to test for a shift in the derived dark energy equation of state due to a systematic bias. In Cycle 15 we obtained NICMOS photometry of 8 ESSENCE supernovae and are awaiting template observations to place them on the IR Hubble diagram. Here we request another 8 supernovae be studied in the final season of the ESSENCE search. Because of the bright sky background, H-band photometry of z~0.4 supernovae is not feasible from the ground. Only the superb image quality and dark infrared sky seen by HST makes this test possible. This experiment may also lead to a better, more reliable way of mapping the expansion history of the universe with the Joint Dark Energy Mission.
NIC3 11334
NICMOS Cycle 16 Spectrophotometry
Observation of the three primary WD flux standards must be repeated to refine the NICMOS absolute calibration and monitor for sensitivity degradation. So far, NICMOS grism spectrophotometry is available for only ~16 stars with good STIS spectra at shorter wavelengths. There are more in the HST CALSPEC standard star data base with good STIS spectra that would also become precise IR standards with NICMOS absolute SED measurements. Monitoring the crucial three very red stars (M, L, T) for variability and better S/N in the IR. Apparent variability was discovered at shorter wavelengths during the ACS cross-calibration work that revealed a ~2% discrepancy of the cool star fluxes with respect to the hot primary WD standards. About a third of these stars are bright enough to do in one orbit, the rest require 2 orbits.
WFPC2 11029
WFPC2 CYCLE 15 Intflat Linearity Check and Filter Rotation Anomaly Monitor
Intflat observations will be taken to provide a linearity check: the linearity test consists of a series of intflats in F555W, in each gain and each shutter. A combination of intflats, visflats, and earthflats will be used to check the repeatability of filter wheel motions. {Intflat sequences tied to decons, visits 1-18 in prop 10363, have been moved to the cycle 15 decon proposal xxxx for easier scheduling.} Note: long-exposure WFPC2 intflats must be scheduled during ACS anneals to prevent stray light from the WFPC2 lamps from contaminating long ACS external exposures.
WFPC2 11038
Narrow Band and Ramp Filter Closeout
These observations are to improve calibration of narrow band and ramp filters. We also test for changes in the filter properties during WFPC2’s 14 years on-board HST.
WFPC2 11202
The Structure of Early-type Galaxies: 0.1-100 Effective Radii
The structure, formation and evolution of early-type galaxies is still largely an open problem in cosmology: how does the Universe evolve from large linear scales dominated by dark matter to the highly non-linear scales of galaxies, where baryons and dark matter both play important, interacting, roles? To understand the complex physical processes involved in their formation scenario, and why they have the tight scaling relations that we observe today {e.g. the Fundamental Plane}, it is critically important not only to understand their stellar structure, but also their dark-matter distribution from the smallest to the largest scales. Over the last three years the SLACS collaboration has developed a toolbox to tackle these issues in a unique and encompassing way by combining new non-parametric strong lensing techniques, stellar dynamics, and most recently weak gravitational lensing, with high-quality Hubble Space Telescope imaging and VLT/Keck spectroscopic data of early-type lens systems. This allows us to break degeneracies that are inherent to each of these techniques separately and probe the mass structure of early-type galaxies from 0.1 to 100 effective radii. The large dynamic range to which lensing is sensitive allows us both to probe the clumpy substructure of these galaxies, as well as their low-density outer haloes. These methods have convincingly been demonstrated, by our team, using smaller pilot-samples of SLACS lens systems with HST data. In this proposal, we request observing time with WFPC2 and NICMOS to observe 53 strong lens systems from SLACS, to obtain complete multi-color imaging for each system. This would bring the total number of SLACS lens systems to 87 with completed HST imaging and effectively doubles the known number of galaxy-scale strong lenses. The deep HST images enable us to fully exploit our new techniques, beat down low-number statistics, and probe the structure and evolution of early-type galaxies, not only with a uniform data-set an order of magnitude larger than what is available now, but also with a fully coherent and self-consistent methodological approach!
WFPC2 11307
Completing the ACS Nearby Galaxy Survey with WFPC2
We are requesting 25 orbits of Director’s Discretionary Time to complete the primary science goals of our highly-ranked ACS Nearby Galaxy Survey Treasury program {ANGST}. Our program lost ~2/3 of its orbits due to the ACS failure. Roughly half of these were restored as a result of an appeal to the Telescope Time Review Board which re-scoped the program. The Board’s response to our appeal was explicit in terms of which targets were to be observed and how. We were directed to request Director’s discretionary time for the components of the appeal which were not granted by the Review Board, but which were vital to the success of the program. The observing strategy for ANGST is two-fold: to obtain one deep field per galaxy which enables derivation of an accurate ancient star formation history, and to obtain radial tilings sufficient for recovering the full star formation history. The Review Board granted WFPC2 observations for deep fields in 7 galaxies, but no time for radial tilings. However, recovering the full star formation history of a galaxy is not possible without additional radial coverage. We have searched the archives for observations which may be used in place of the tilings {conceding some of the Treasury goals, but providing significant constraints on the full star formation history}, and have identified suitable observations for all but two of the galaxies. Here we request DD time for radial tilings for those last two galaxies.
WFPC2/ACS/HRC/WFPC 11020
Cycle 15 Focus Monitor
The focus of HST is measured primarily with ACS/HRC over full CVZ orbits to obtain accurate mean focus values via a well sampled breathing curve. Coma and astigmatism are also determined from the same data in order to further understand orbital effects on image quality and optical alignments. To monitor the stability of ACS to WFPC2 relative focii, we’ve carried over from previous focus monitor programs parallel observations taken with the two cameras at suitable orientations of previously observed targets, and interspersed them with the HRC CVZ visits.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.) HSTARS: (None)
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL FGS GSacq 06 06 FGS REacq 06 06 OBAD with Maneuver 24 24
SIGNIFICANT EVENTS: (None)
