NASA Hubble Space Telescope Daily Status Report # 4404
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 DAILY REPORT # 4404
– Continuing to collect World Class Science
PERIOD COVERED: UT July 13,14,15, 2007 (DOY 194,195,196)
OBSERVATIONS SCHEDULED
NIC1/NIC2/NIC3 8793
NICMOS Post-SAA calibration – CR Persistence Part 4
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.
WFPC2 11178
Probing Solar System History with Orbits, Masses, and Colors of Transneptunian Binaries
The recent discovery of numerous transneptunian binaries {TNBs} opens a window into dynamical conditions in the protoplanetary disk where they formed as well as the history of subsequent events which sculpted the outer Solar System and emplaced them onto their present day heliocentric orbits. To date, at least 47 TNBs have been discovered, but only about a dozen have had their mutual orbits and separate colors determined, frustrating their use to investigate numerous important scientific questions. The current shortage of data especially cripples scientific investigations requiring statistical comparisons among the ensemble characteristics. We propose to obtain sufficient astrometry and photometry of 23 TNBs to compute their mutual orbits and system masses and to determine separate primary and secondary colors, roughly tripling the sample for which this information is known, as well as extending it to include systems of two near-equal size bodies. To make the most efficient possible use of HST, we will use a Monte Carlo technique to optimally schedule our observations.
WFPC2 11175
UV Imaging to Determine the Location of Residual Star Formation in Galaxies Recently Arrived on the Red Sequence
We have indentified a sample of low-redshift {z = 0.04 – 0.10} galaxies that are candidates for recent arrival on the red sequence. They have red optical colors indicative of old stellar populations, but blue UV-optical colors that could indicate the presence of a small quantity of continuing or very recent star formation. However, their spectra lack the emission lines that characterize star-forming galaxies. We propose to use ACS/SBC to obtain high-resolution imaging of the UV flux in these galaxies, in order to determine the spatial distribution of the last episode of star formation. WFPC2 imaging will provide B, V, and I photometry to measure the main stellar light distribution of the galaxy for comparison with the UV imaging, as well as to measure color gradients and the distribution of interstellar dust. This detailed morphological information will allow us to investigate the hypothesis that these galaxies have recently stopped forming stars and to compare the observed distribution of the last star formation with predictions for several different mechanisms that may quench star formation in galaxies.
NIC2 11157
NICMOS Imaging Survey of Dusty Debris Around Nearby Stars Across the Stellar Mass Spectrum
Association of planetary systems with dusty debris disks is now quite secure, and advances in our understanding of planet formation and evolution can be achieved by the identification and characterization of an ensemble of debris disks orbiting a range of central stars with different masses and ages. Imaging debris disks in starlight scattered by dust grains remains technically challenging so that only about a dozen systems have thus far been imaged. A further advance in this field needs an increased number of imaged debris disks. However, the technical challege of such observations, even with the superb combination of HST and NICMOS, requires the best targets. Recent HST imaging investigations of debris disks were sample-limited not limited by the technology used. We performed a search for debris disks from a IRAS/Hipparcos cross correlation which involved an exhaustive background contamination check to weed out false excess stars. Out of ~140 identified debris disks, we selected 22 best targets in terms of dust optical depth and disk angular size. Our target sample represents the best currently available target set in terms of both disk brightness and resolvability. For example, our targets have higher dust optical depth, in general, than newly identified Spitzer disks. Also, our targets cover a wider range of central star ages and masses than previous debris disk surveys. This will help us to investigate planetary system formation and evolution across the stellar mass spectrum. The technical feasibility of this program in two-gyro mode guiding has been proven with on-orbit calibration and science observations during HST cycles 13, 14 and 15.
WFPC2 11079
Treasury Imaging of Star Forming Regions in the Local Group: Complementing the GALEX and NOAO Surveys
We propose to use WFPC2 to image the most interesting star-forming regions in the Local Group galaxies, to resolve their young stellar populations. We will use a set of filters including F170W, which is critical to detect and characterize the most massive stars, to whose hot temperatures colors at longer wavelengths are not sensitive. WFPC2’s field of view ideally matches the typical size of the star-forming regions, and its spatial resolution allows us to measure indvidual stars, given the proximity of these galaxies. The resulting H-R diagrams will enable studies of star- formation properties in these regions, which cover largely differing metallicities {a factor of 17, compared to the factor of 4 explored so far} and characteristics. The results will further our understanding of the star-formation process, of the interplay between massive stars and environment, the properties of dust, and will provide the key to interpret integrated measurements of star-formation indicators {UV, IR, Halpha} available for several hundreds more distant galaxies. Our recent deep surveys of these galaxies with GALEX {FUV, NUV} and ground-based imaging {UBVRI, Halpha, [OIII] and [SII]} provided the identification of the most relevant SF sites. In addition to our scientific analysis, we will provide catalogs of HST photometry in 6 bands, matched corollary ground-based data, and UV, Halpha and IR integrated measurements of the associations, for comparison of integrated star-formation indices to the resolved populations. We envisage an EPO component.
ACS/SBC/WFPC2 10904
Star formation in extended UV disk {XUV-disk} galaxies
The Galaxy Evolution Explorer {GALEX} has discovered the existence of extended UV-disk {XUV-disk} galaxies. This class of intriguing spiral galaxies is distinguished by UV-bright regions of star formation located at extreme galactocentric radii, commonly reaching many times the optical extent of each target. XUV-disks represent a population of late-type galaxies still actively building, or significantly augmenting, their stellar disk in the outer, low-density environment. Prior to GALEX, such regions were considered to be far more stable against star formation than now realized. Our work on these targets has led to the recognition of the XUV phenomenon as probing a diverse population of galaxies which, although having certain commonality in terms of their present XUV star formation, have apparently experienced different star formation histories {as judged by their outer disk UV-optical colors and morphology}. In ordinary spirals, disk formation occurred at a much earlier epoch, making today’s XUV-disks useful templates for commonplace, high z galaxies. The diverse XUV-disks in our sample may represent snapshots of different phases in the disk building process. We seek to characterize the demographics of star forming regions occupying this environmental range, especially in contrast to their inner disk counterparts. HST imaging is needed to accurately characterize the massive stars and clusters which have, in fact, managed to form. The GALEX observations are limited by 5″ resolution. Deep ACS FUV, B, V, I, and H-alpha imaging {along with parallel WFPC2 data} will allow: {1} photometric classification of the OB star population, {2} constraint on the cluster mass function and age distribution, {3} critical accounting for possible leakage of Lyman continuum photons in a porous ISM or an IMF change, and {4} population synthesis modeling of the field SFH on Gyr timescales. We benefit from extensive archival HST observations of our target galaxies, although the outer disk has yet to be probed.
WFPC2 10884
The Dynamical Structure of Ellipticals in the Coma and Abell 262 Clusters
We propose to obtain images of 13 relatively luminous early type galaxies in the Coma cluster and Abell 262 for which we have already collected ground based major and minor axis spectra and images. The higher resolution HST images will enable us to study the central regions of these galaxies which is crucial to our dynamical modelling. The complete data set will allow us to perform a full dynamical analysis and to derive the dark matter content and distribution, the stellar orbital structure, and the stellar population properties of these objects, probing the predictions of galaxy formation models. The dynamical analysis will be performed using an up-to- date axi-symmetric orbit superposition code.
NIC3 10874
Search for Extremely Faint z>7 Galaxy Population with Cosmic Lenses
Deep UDF/NICMOS observations find a significant decrease in the number of galaxy candidates between redshift z=6 and 7, but the sample at z>7 is too small to draw conclusions. From our observations of 15 clusters we have found a number of bright z-dropouts, aided by the lensing amplification. We propose deep NICMOS observations of the best cases of cluster centers where a rare combination of a significant lensing effect and the richness in z-band dropouts in background may dramatically increase the discovery rate. The NICMOS images will reach an unprecendented depth of AB~27.8, or AB~30 in nonlensed intrinsic magnitude, and may find many faint {~0.05L*} galaxies at z=7-10, at a level that the UDF reaches for z~6 objects. We produce precision mass distribution maps from weak-lensing models, which enable us to derive the candidates’ intrinsic magnitudes and their luminosity function. The knowledge of such faint galaxy population at z>7 will facilitate the models of the IGM reionization and future JWST planning.
WFPC2 10818
Very Young Globular Clusters in M31 ?
We propose to use HST’s unique high spatial resolution imaging capabilities to conclusively confirm or refute the presence of alleged very young globular clusters in M31. Such young globular clusters with ages < 3 Gyr are not present in our galaxy, and, if real, would lead to a striking difference in the age distribution of the GCs between M31 and the Millky Way. If the apparent presence of very young globular clusters in M31 is confirmed through our proposed ACS imaging {now WFPC2 imaging} with HST, this would suggest major differences in the history of assembly of the two galaxies, with probable substantial late accretion into M31 which did not occur in our own galaxy.
ACS/SBC 10810
The Gas Dissipation Timescale: Constraining Models of Planet Formation
We propose to constrain planet-formation models by searching for molecular hydrogen emission around young {10-50 Myr} solar-type stars that have evidence for evolved dust disks. Planet formation models show that the presence of gas in disks is crucial to the formation of BOTH giant and terrestrial planets, influences dust dynamics, and through tidal interactions with giant planets leads to orbital migration. However, there is a lack of systematic information on the presence and lifetime of gas residing at planet-forming radii. We will use a newly identified broad continuum emission feature of molecular hydrogen at 1600 Angstrom to search for residual gas within an orbital radius of 5-10 AU around young stars that have evolved beyond the optically thick T Tauri phase. These observations will enable the most sensitive probe to date of remant gas in circumstellar disks, detecting surfaces densites of ~0.0001 g/cm^2, or less than 10^-5 of the theoretical “mininum mass” solar nebula from which our solar system is thought to have formed. Our observations are designed to be synergistic with ongoing searches for gas emission that is being performed using the Spitzer Space Telescope in that the proposed HST observations are ~100 times more sensitive and will have 50 times higher angular resolution. These combined studies will provide the most comprehensive view of residual gas in proto- planetary disks and can set important constraints on models of planet formation.
ACS/HRC 10806
Accretion in the closest binary systems known
Recently, three variable stars have been identified as likely accreting binary systems with ultra- short orbital periods. Optical and X-ray observations have revealed periodicities of 5-10 minutes, making them the closest binaries known as well as strong sources of gravitational wave emission. Such short-period accreting binaries form the cornerstone to our understanding of binary formation and evolution, in particular of the large double white dwarf population in our galaxy, a candidate progenitor population for Type Ia supernovae. We propose to obtain the first UV spectroscopy of these objects using the ACS prisms in order to {i} determine the temperature of the primary and the composition of their donor stars, {ii} correlate the UV variability with other wavebands and determine if the periods are indeed orbital. These UV observations are essential in order to unequivocally determine whether these are indeed the most compact binaries known.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
HSTARS:
#10892 OBAD Failed Quaternion (ESB 1903) & OBAD Too few stars (ESB 1901).
At 194/19:00:38 “OBAD Failed Quaternion”. At 19:01:37 equation F2SOB flagged indicating entering Stuck-on-Bottom. At 19:05:42 F2SOB returned back in bounds due to start of OBAD #2. At 19:08:26 received error “OBAD Too few stars”. At 19:09:31 equation F2SOB flagged indicating Stuck-on-Bottom. Unable to perform OBAD table dumps as forward ended at 19:01:01. OBAD #1: V1 673.57, V2 -1769.09, V3 -336.61, RSS 1922.68 OBAD #2: Same numbers as above OBAD MAP: V1 593.88, V2 -1714.43, V3 -423.05, RSS 1863.05 GSAcq scheduled at 19:10:43 was not attempted.
#10893 GSAcq (1,2,2) failed due to Search Radius Limit Exceeded on FGS 1.
At AOS (195/01:05:57) GSAcq (1,2,2) scheduled from 195/00:00:14-00:07:34 failed due to search radius limit exceeded on FGS 1. OBAD data unavailable due to LOS. OBAD MAP RSS: 49.95
#10894 GSacq(2,1,2) failed, Search Radius Limit exceeded on FGS 2.
Upon acquisition of signal at 195/19:25:25 vehicle was in RGA control with FGS2 Search Radius Limit and Stop flags set. GSacq(2,1,2) scheduled at 19:11:56 failed with search radius limit exceeded on FGS 2. Post-acquisition OBAD/MAP at 19:20:00 had RSS error of 20.16 arcseconds. OBADs prior to GSACQ are not available. REACQ(2,1,2) at 20:44:12 was successful.
#10895 GSaqc(1,2,2) failed to RGA control.
The GSacq(1,2,2) scheduled at 195/22:21:07 failed during LOS due to search radius limit exceeded on FGS 1. The map at 22:28:27 showed errors of V1=o.33, V2=-3.53, V3=61.25, and RSS= 61.35.
#10896 OBAD Failed Identification (ESB 1902).
OBAD1 scheduled at 195/23:47:00 failed during LOS. OBAD2 and the GSacq was successful.
#10897 REacq(1,3,1) failed, Search Radius Limit exceeded on FGS 2.
REacq(1,3,1) at 196/11:07:23 failed at 11:13:04 with search radius limit exceeded on FGS 1. OBADs prior to REacq at 11:03:03 had RSS error of 59.84 arcseconds, Post-acquisition OBAD/MAP at 11:15:27 had RSS error of 62.24 arcseconds.
COMPLETED OPS REQUEST:
#17597-9 FHST Stuck-on-Bottom Macro Execution @ 196/0136z & 196/0322z
SCHEDULED SUCCESSFUL
FGS GSacq 25 21
FGS REacq 18 17
OBAD with Maneuver 86 83
COMPLETED OPS NOTES: (None)
SIGNIFICANT EVENTS: (None)
