Status Report

NASA Hubble Space Telescope Daily Report #4421

By SpaceRef Editor
August 8, 2007
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NASA Hubble Space Telescope Daily Report #4421

Notice: Due to the conversion of some ACS WFC or HRC observations intoWFPC2, or NICMOS observations after the loss of ACS CCD sciencecapability in January, there may be an occasional discrepancy between aproposal’s listed (and correct) instrument usage and the abstract thatfollows it.

HUBBLE SPACE TELESCOPE DAILY REPORT # 4421- Continuing to collect World Class Science

PERIOD COVERED: UT August 07, 2007 (DOY 219)


ACS/SBC 11225

The Wavelength Dependence of Accretion Disk Structure

We can now routinely measure the size of quasar accretion disks usinggravitational microlensing of lensed quasars. The next step to testingaccretion disk models is to measure the size of accretion disks as afunction of wavelength, particularly at the UV and X-ray wavelengthsthat should probe the inner, strong gravity regime. Here we focus on twofour-image quasar lenses that already have optical {R band} and X-raysize measurements using microlensing. We will combine the HSTobservations with ground-based monitoring to measure the disk size as afunction of wavelength from the near-IR to the UV. We require HST tomeasure the image flux ratios in the ultraviolet continuum near theLyman limit of the quasars. The selected targets have estimated blackhole masses that differ by an order of magnitude, and we should findwavelength scalings for the two systems that are very different becausethe Blue/UV wavelengths should correspond to parts of the disk near theinner edge for the high mass system but not in the low mass system. Theresults will be modeled using a combination of simple thin disk modelsand complete relativistic disk models. While requiring only 18 orbits,success for one system requires observations in both Cycles 16 and 17.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration – CR Persistence Part 5

A new procedure proposed to alleviate the CR-persistence problem ofNICMOS. Dark frames will be obtained immediately upon exiting the SAAcontour 23, and every time a NICMOS exposure is scheduled within 50minutes of coming out of the SAA. The darks will be obtained in parallelin all three NICMOS Cameras. The POST-SAA darks will be non- standardreference files available to users with a USEAFTER date/time mark. Thekeyword ‘USEAFTER=3Ddate/time’ will also be added to the header of eachPOST-SAA DARK frame. The keyword must be populated with the time, inaddition to the date, because HST crosses the SAA ~8 times per day soeach POST-SAA DARK will need to have the appropriate time specified, forusers to identify the ones they need. Both the raw and processed imageswill be archived as POST-SAA DARKs. Generally we expect that all NICMOSscience/calibration observations started within 50 minutes of leaving anSAA will need such maps to remove the CR persistence from the scienceimages. Each observation will need its own CRMAP, as different SAApassages leave different imprints on the NICMOS detectors.

WFPC2 11124

The Origin of QSO Absorption Lines from QSOs

We propose using WFPC2 to image the fields of 10 redshift z ~ 0.7foreground {FG} QSOs which lie within ~29-151 kpc of the sightlines tohigh-z background {BG} QSOs. A surprisingly high fraction of the BG QSOspectra show strong MgII {2796,2803} absorption lines at precisely thesame redshifts as the FG QSOs. The high resolution capabilities of WFPC2are needed to understand the origin of these absorption systems, in twoways. First, we wish to explore the FG QSO environment as close aspossible to the position of the BG QSO, to search for interloping groupor cluster galaxies which might be responsible for the absorption, orirregularly shaped post-merger debris between the FG and BG QSO whichmay indicate the presence of large amount of disrupted gas along asightline. Similarly, high resolution images are needed to search forsigns of tidal interactions between any galaxies which might be foundclose to the FG QSO. Such features might provide evidence of youngmerging events causing the start of QSO duty cycles and producingoutflows from the central AGN. Such winds may be responsible for theobserved absorption lines. Second, we seek to measure the intrinsicparameters of the FG QSO host galaxy, such as luminosity and morphology,to correlate with the properties of the MgII absorption lines. We wishto observe each field through the F814W filter, close to the rest-frameB-band of the FG QSO. These blue data can reveal enhanced star formationregions close to the nucleus of the host galaxy, which may be indicativeof galaxy mergers with the FG QSO host. The FG QSO environment offersquite a different set of phenomena which might be responsible for MgIIabsorption, providing an important comparison to studies of MgIIabsorption from regular field galaxies.

WFPC2 11178

Probing Solar System History with Orbits, Masses, and Colors ofTransneptunian Binaries

The recent discovery of numerous transneptunian binaries {TNBs} opens awindow into dynamical conditions in the protoplanetary disk where theyformed as well as the history of subsequent events which sculpted theouter Solar System and emplaced them onto their present day heliocentricorbits. To date, at least 47 TNBs have been discovered, but only about adozen have had their mutual orbits and separate colors determined,frustrating their use to investigate numerous important scientificquestions. The current shortage of data especially cripples scientificinvestigations requiring statistical comparisons among the ensemblecharacteristics. We propose to obtain sufficient astrometry andphotometry of 23 TNBs to compute their mutual orbits and system massesand to determine separate primary and secondary colors, roughly triplingthe sample for which this information is known, as well as extending itto include systems of two near-equal size bodies. To make the mostefficient possible use of HST, we will use a Monte Carlo technique tooptimally schedule our observations.

WFPC2 11307

Completing the ACS Nearby Galaxy Survey with WFPC2

We are requesting 25 orbits of Director’s Discretionary Time to completethe primary science goals of our highly-ranked ACS Nearby Galaxy SurveyTreasury program {ANGST}. Our program lost ~2/3 of its orbits due to theACS failure. Roughly half of these were restored as a result of anappeal to the Telescope Time Review Board which re-scoped the program.The Board’s response to our appeal was explicit in terms of whichtargets were to be observed and how. We were directed to requestDirector’s discretionary time for the components of the appeal whichwere not granted by the Review Board, but which were vital to thesuccess of the program. The observing strategy for ANGST is two-fold: toobtain one deep field per galaxy which enables derivation of an accurateancient star formation history, and to obtain radial tilings sufficientfor recovering the full star formation history. The Review Board grantedWFPC2 observations for deep fields in 7 galaxies, but no time for radialtilings. However, recovering the full star formation history of a galaxyis not possible without additional radial coverage. We have searched thearchives for observations which may be used in place of the tilings{conceding some of the Treasury goals, but providing significantconstraints on the full star formation history}, and have identifiedsuitable observations for all but two of the galaxies. Here we requestDD time for radial tilings for those last two galaxies.


Cycle 15 Focus Monitor

The focus of HST is measured primarily with ACS/HRC over full CVZ orbitsto obtain accurate mean focus values via a well sampled breathing curve.Coma and astigmatism are also determined from the same data in order tofurther understand orbital effects on image quality and opticalalignments. To monitor the stability of ACS to WFPC2 relative focii,we’ve carried over from previous focus monitor programs parallelobservations taken with the two cameras at suitable orientations ofpreviously observed targets, and interspersed them with the HRC CVZvisits.


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

HSTARS: (None)



                       SCHEDULED      SUCCESSFUL

FGS GSacq               06                 06  
FGS REacq               08                 08  
OBAD with Maneuver      30                 30        


SpaceRef staff editor.