NASA Hubble Space Telescope Daily Report #4150
HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science
DAILY REPORT # 4150
PERIOD COVERED: UT July 6, 2006 (DOY 187)
OBSERVATIONS SCHEDULED
ACS/HRC 10545
Icy planetoids of the outer solar system
Early HST studies of satellites of Kuiper belt object focussed on the 50-200 km objects that were the largest known at the time. In the past 3 years we have discovered a population of much more rare and much larger {500-2000+ km} icy planetoids in the Kuiper belt. These objects are the largest and brightest known in the Kuiper belt and, in the era when we now know of more than 1000 Kuiper belt objects, these few planetoids are likely to be the focus of much of the research on physical properties of the outer solar system for years to come. We are currently engaged in an intensive program involving Spitzer, Keck, and other telescopes to study the physical and dynamical properties of this new population. HST is uniquely capable of addressing one parameter fundamental to completing the physical picture of these planetoids: the existence and size of any satellites. The detection and characterization of satellites to these large planetoids would allow us to address unique issues critical to the formation and evolution of the outer solar system, including the measurement of densities, internal properties, sizes and shapes of these objects, the study of binary formation as a function of primary size, and the context of the Pluto-Charon binary. For these bright objects, a satellite search takes less than a full orbit, allowing the opportunity for a new project on UV spectroscopy of the planetoids to piggyback at no added time cost. This poorly explored spectral range has the potential to show unique signatures of trapped gasses, cosmochemically important ices, and complex organic materials.
ACS/HRC 10556
Neutral Gas at Redshift z=0.5
Damped Lyman-alpha systems {DLAs} are used to track the bulk of the neutral hydrogen gas in the Universe. Prior to HST UV spectroscopy, they could only be studied from the ground at redshifts z>1.65. However, HST has now permitted us to discover 41 DLAs at z<1.65 in our previous surveys. Followup studies of these systems are providing a wealth of information about the evolution of the neutral gas phase component of the Universe. But one problem is that these 41 low-redshift systems are spread over a wide range of redshifts spanning nearly 70% of the age of the Universe. Consequently, past surveys for low-redshift DLAs have not been able to offer very good precision in any small redshift regime. Here we propose an ACS-HRC-PR200L spectroscopic survey in the redshift interval z=[0.37, 0.7] which we estimate will permit us to discover another 41 DLAs. This will not only allow us to double the number of low-redshift DLAs, but it will also provide a relatively high-precision regime in the low-redshift Universe that can be used to anchor evolutionary studies. Fortunately DLAs have high absorption equivalent width, so ACS- HRC-PR200L has high-enough resoultion to perform this proposed MgII-selected DLA survey.
ACS/HRC 9746
Binary systems in the Kuiper Belt
The properties of the orbits of Kuiper belt object {KBO} satellites hold keys to fundamental insight into masses and densities of KBOs, the interaction history of the early solar system, the internal structure of distant ice-rock bodies, and even the genesis of the Pluto- Charon binary. Within the past 18 months, 9 KBO satellite systems have been discovered, allowing for the first time the possibility of characterizing a sample of KBO satellite orbital properties. We propose HRC observations to determine satellite orbits in the 6 best cases. We have carefully devised a strategy for each of these 6 systems to make maximum use of ground-based observations, previous HST observations, and the smallest possible number of new HST observations. Our proposed observations will efficiently provide highly reliable orbital solutions which are critical to achieving the scientific promise available from the study of these systems. Our strategy relies heavily on extensive Monte Carlo simulations to define optimal times of observing such that each new point obtained gives maximum leverage for refining the orbital solution. We find that with this strategy we can provide mass solutions for all 6 systems to an accuracy of better than 10% using only 25 new HST observations. This highly efficient program provides extreme scientific output with optimal use of scarce resources.
ACS/WFC 10503
The Star Formation Histories of Early Type Dwarf Galaxies in Low Density Environments: Clues from the Sculptor Group
We seek HST ACS/WFC time to conduct a detailed study of the stellar populations of 5 early-type {dE, dE/dIrr} dwarf galaxies in the nearby {~1.5 to 4 Mpc} Sculptor group. Four of these systems have been recently found to contain modest amounts of HI, and existing ground-based and HST snapshot data point to the potential presence of small populations of young {blue} stars in at least three of these systems. Consequently, they resemble the Local Group ‘transition’ objects Phoenix and LGS3. The relative number of such transition systems is thus substantially larger in the low density environment of the Scl group than for the Local Group. Detailed stellar populations studies will allow estimation of the star formation histories, via stellar population modelling of the color-magnitude diagrams, of the target dwarfs, which in turn will connect to gas consumption and retention rates. For the two nearer dwarfs we aim to reach below the horizontal branch {a first for any system beyond the Local Group} equivalent to a main sequence turnoff age of ~1 Gyr. The observations of these two systems will also allow detection of RR Lyrae variables and thus direct confirmation of the presence of old populations. For the other three dwarfs will we cover the first 2.5 mags of the red giant branch, equivalent to the main sequence termination for a ~300 Myr population. The results will have implications for theories of galaxy formation and evolution, particularly with regard to the evolutionary relation between low luminosity dEs and dwarf irregulars.
ACS/WFC/HRC 11005
Funcional test – MEB2 switch
This is a functional test to be executed after the switch to MEB2.
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 DARKSs. 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 10510
Morphology of massive early-type galaxies at z>1.2: constraining galaxy formation models
We ask for NICMOS-NIC2 H-band imaging of a sample of 10 massive early-type galaxies spectroscopically identified at 1.2 < z < 1.7. Our aim is to look for possible relics of merging events of their formation/evolution in their morphology. The requested observations, sampling their rest-frame at lambda>6500A, would map the mass distribution of the bulk of their stellar content. The targets have been revealed by our group on the basis of near-IR spectroscopy obtained in the framework of a spectroscopic survey of a complete sample of bright EROs {Ks<18.5}. Optical and near-IR photometry is available for all the targets, and low resolution near-IR spectra have allowed their identification and redshift measurement. Spectroscopic and photometric data in our hands show that they have already assembled stellar masses greater than 3 10^11 solar masses, and that the mean age of their stellar population is estimated older than 2-3 Gyr for 6 of them and about 1 Gyr for the other 4 galaxies. Thus, they are among the most luminous and massive evolved galaxies detected so far at z>1. Other data are needed to infer how they have assembled such high stellar masses, i.e. to trace back their evolution. The requested observations would allow us to reveal signs of past interaction/merger event. A smooth r^{1/m} profile, coupled with no other signs of interaction/merger {disturbed morphology}, would place the possible merger event of formation 1-2 Gyr before their redshift z pprox 1.5, i.e. at z > 2- 3. On the other hand, if signs of recent merger events will be found, the last merger event forming the local massive spheroids will be constrained at 1.5 < z < 2. Thus, the requested HST observations will allow for the first time to see how massive early-type galaxies at z pprox 1.5 look like, constraining in any case the redshift of the possible merging event of their formation.
NIC2 10849
Imaging Scattered Light from Debris Disks Discovered by the Spitzer Space Telescope around 21 Sun-like Stars
We propose to use the high-contrast capability of the NICMOS coronagraph to image a sample of newly discovered circumstellar disks associated with Sun-like stars. These systems were identified by their strong thermal infrared {IR} emission with the Spitzer Space Telescope as part of the Spitzer Legacy Science program titled “The Formation and Evolution of Planetary Systems” {FEPS, P.I.: M.Meyer}. Modeling of the thermal excess emission from the spectral energy distributions alone cannot distinguish between narrowly confined high-opacity disks and broadly distributed, low-opacity disks. By resolving light scattered by the circumstellar material, our proposed NICMOS observations can break this degeneracy, thus revealing the conditions under which planet formation processes are occuring or have occured. For three of our IR-excess stars that have known radial-velocity planets, resolved imaging of the circumstellar debris disks may further offer an unprecedented view of planet-disk interactions in an extrasolar planetary system. Even non-detections of the light scattered by the circumstellar material will place strong constraints on the disk geometries, ruling out disk models with high optical depth. Unlike previous disk imaging programs, our program contains a well-defined sample of ~1 solar mass stars covering a range of ages from 3 Myr to 3 Gyr, thus allowing us to study the evolution of disks from primordial to debris for the first time. The results from our program will greatly improve our understanding of the architecture of debris disks around Sun-like stars, and will create a morphological context for the existence of our own solar system. This proposal is for a continuation of an approved Cycle 14 program {GO/10527, P.I.: D. Hines}.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
HSTARS:
10344 – GSAcq(2,3,2) Failed to RGA Control @ 187/2026z
The GSAcq(2,3,2) scheduled for 187/20:26:03 – 20:34:08 failed to RGA hold due to stop flag (QF2STOPF) indication on FGS-2. Pre-acquisition OBADs had (RSS) attitude error corrections values of 3017.15 and 9.93 arcseconds. Post-acquisition OBAD/MAP at 187/20:34:07 had (RSS) error correction of 3.55 arcseconds. Possible Observations affected: ACS 194 thru 196. REacqs(2,3,2) scheduled for 187/22:00:01, 187/23:36:00, both failed to RGA Hold due to stop flag on FGS-2. However the REacq at 188/01:12:29 was successful.
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL FAILURE TIMES
FGS GSacq 9 8 187/2026z (HSTAR 10344)
FGS REacq 6 4 187/2200z, 187/2336z (HSTAR 10344)
OBAD with Maneuver 31 31
SIGNIFICANT EVENTS: (None)
