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Daily Report #4558
HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science
DAILY REPORT***** # 4558 PERIOD COVERED: UT February 29,March 01,02, 2008 (DOY 060,061,062) OBSERVATIONS SCHEDULED NIC1/NIC2/NIC3 8795 NICMOS Post-SAA calibration - CR Persistence Part 6 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 11289 SL2S: The Strong Lensing Legacy Survey Recent systematic surveys of strong galaxy-galaxy lenses {CLASS, SLACS, GOODS, etc.} are producing spectacular results for galaxy masses roughly below a transition mass M~10^13 Mo. The observed lens properties and their evolution up to z~0.2, consistent with numerical simulations, can be described by isothermal elliptical potentials. In contrast, modeling of giant arcs in X-ray luminous clusters {halo masses M ~10^13 Mo} favors NFW mass profiles, suggesting that dark matter halos are not significantly affected by baryon cooling. Until recently, lensing surveys were neither deep nor extended enough to probe the intermediate mass density regime, which is fundamental for understanding the assembly of structures. The CFHT Legacy Survey now covers 125 square degrees, and thus offers a large reservoir of strong lenses probing a large range of mass densities up to z~1. We have extracted a list of 150 strong lenses using the most recent CFHTLS data release via automated procedures. Following our first SNAPSHOT proposal in cycle 15, we propose to continue the Hubble follow-up targeting a larger list of 130 lensing candidates. These are intermediate mass range candidates {between galaxies and clusters} that are selected in the redshift range of 0.2-1 with no a priori X-ray selection. The HST resolution is necessary for confirming the lensing candidates, accurate modeling of the lenses, and probing the total mass concentration in galaxy groups up to z~1 with the largest unbiased sample available to date. NIC2 11237 The origin of the break in the AGN luminosity function We propose to use NICMOS imaging to measure rest-frame optical luminosities and morphological properties of a complete sample of faint AGN host galaxies at redshifts z ~ 1.4. The targets are drawn from the VLT-VIMOS Deep Survey, and they constitute a sample of the lowest luminosity type 1 AGN known at z 1. The spectroscopically estimated black hole masses are up to an order of magnitude higher than expected given their nuclear luminosities, implying highly sub-Eddington accretion rates. This exactly matches the prediction made by recent theoretical models of AGN evolution, according to which the faint end of the AGN luminosity function is populated mainly by big black holes that have already exhausted a good part of their fuel. In this proposal we want to test further predictions of that hypothesis, by focussing on the host galaxy properties of our low-luminosity, low- accretion AGN. If the local ratio between black hole and bulge masses holds at least approximately at these redshifts, one expects most of these low-luminosity AGN to reside in fairly big ellipticals with stellar masses around and above 10^11 solar masses (in contrast to the Seyfert phenomenon in the local universe). With NICMOS imaging we will find out whether that is true, implying also a sensitive test for the validity of the M_BH/M_bulge relation at z ~ 1.4. FGS 11211 An Astrometric Calibration of Population II Distance Indicators In 2002 HST produced a highly precise parallax for RR Lyrae. That measurement resulted in an absolute magnitude, M{V}= 0.61+/-0.11, a useful result, judged by the over ten refereed citations each year since. It is, however, unsatisfactory to have the direct, parallax-based, distance scale of Population II variables based on a single star. We propose, therefore, to obtain the parallaxes of four additional RR Lyrae stars and two Population II Cepheids, or W Vir stars. The Population II Cepheids lie with the RR Lyrae stars on a common K-band Period-Luminosity relation. Using these parallaxes to inform that relationship, we anticipate a zero-point error of 0.04 magnitude. This result should greatly strengthen confidence in the Population II distance scale and increase our understanding of RR Lyrae star and Pop II Cepheid astrophysics. FGS 11210 The Architecture of Exoplanetary Systems Are all planetary systems coplanar? Concordance cosmogony makes that prediction. It is, however, a prediction of extrasolar planetary system architecture as yet untested by direct observation for main sequence stars other than the Sun. To provide such a test, we propose to carry out FGS astrometric studies on four stars hosting seven companions. Our understanding of the planet formation process will grow as we match not only system architecture, but formed planet mass and true distance from the primary with host star characteristics for a wide variety of host stars and exoplanet masses. We propose that a series of FGS astrometric observations with demonstrated 1 millisecond of arc per-observation precision can establish the degree of coplanarity and component true masses for four extrasolar systems: HD 202206 {brown dwarf+planet}; HD 128311 {planet+planet}, HD 160691 = mu Arae {planet+planet}, and HD 222404AB = gamma Cephei {planet+star}. In each case the companion is identified as such by assuming that the minimum mass is the actual mass. For the last target, a known stellar binary system, the companion orbit is stable only if coplanar with the AB binary orbit. WEPC2 11196 An Ultraviolet Survey of Luminous Infrared Galaxies in the Local Universe At luminosities above 10^11.4 L_sun, the space density of far-infrared selected galaxies exceeds that of optically selected galaxies. These Luminous Infrared Galaxies {LIRGs} are primarily interacting or merging disk galaxies undergoing starbursts and creating/fueling central AGN. We propose far {ACS/SBC/F140LP} and near {WFPC2/PC/F218W} UV imaging of a sample of 27 galaxies drawn from the complete IRAS Revised Bright Galaxy Sample {RBGS} LIRGs sample and known, from our Cycle 14 B and I-band ACS imaging observations, to have significant numbers of bright {23 B 21 mag} star clusters in the central 30 arcsec. The HST UV data will be combined with previously obtained HST, Spitzer, and GALEX images to {i} calculate the ages of the clusters as function of merger stage, {ii} measure the amount of UV light in massive star clusters relative to diffuse regions of star formation, {iii} assess the feasibility of using the UV slope to predict the far-IR luminosity {and thus the star formation rate} both among and within IR-luminous galaxies, and {iv} provide a much needed catalog of rest- frame UV morphologies for comparison with rest-frame UV images of high-z LIRGs and Lyman Break Galaxies. These observations will achieve the resolution required to perform both detailed photometry of compact structures and spatial correlations between UV and redder wavelengths for a physical interpretation our IRX-Beta results. The HST UV data, combined with the HST ACS, Spitzer, Chandra, and GALEX observations of this sample, will result in the most comprehensive study of luminous starburst galaxies to date. NIC3 11195 Morphologies of the Most Extreme High-Redshift Mid-IR-luminous Galaxies II: The `Bump' Sources The formative phase of some of the most massive galaxies may be extremely luminous, characterized by intense star- and AGN-formation. Till now, few such galaxies have been unambiguously identified at high redshift, and thus far we have been restricted to studying the low-redshift ultraluminous infrared galaxies as possible analogs. We have recently discovered a sample of objects which may indeed represent this early phase in galaxy formation, and are undertaking an extensive multiwavelength study of this population. These objects are optically extremely faint {R26} but nevertheless bright at mid-infrared wavelengths {F[24um] 0.5 mJy}. Mid-infrared spectroscopy with Spitzer/IRS reveals that they have redshifts z~2, implying luminosities ~1E13 Lsun. Their mid-IR SEDs fall into two broad, perhaps overlapping, categories. Sources with brighter F[24um] exhibit power-law SEDs and SiO absorption features in their mid-IR spectra characteristic of AGN, whereas those with fainter F[24um] show a "bump" characteristic of the redshifted 1.6um peak from a stellar population, and PAH emission characteristic of starformation. We have begun obtaining HST images of the brighter sources in Cycle 15 to obtain identifications and determine kpc-scale morphologies for these galaxies. Here, we aim to target the second class {the "bump" sources} with the goal of determining if these constitute morphologically different objects, or simply a "low-AGN" state of the brighter class. The proposed observations will help us determine whether these objects are merging systems, massive obscured starbursts {with obscuration on kpc scales!} or very reddened {locally obscured} AGN hosted by intrinsically low-luminosity 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 challenge 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. NIC3 11153 The Physical Nature and Age of Lyman Alpha Galaxies In the simplest scenario, strong Lyman alpha emission from high redshift galaxies would indicate that stellar populations younger than 10 Myrs dominate the UV. This does not, however, constrain the stellar populations older than 100 Myrs, which do not contribute to UV light. Also, the Lyman alpha line can be boosted if the interstellar medium is both clumpy and dusty. Different studies with small samples have reached different conclusions about the presence of dust and old stellar populations in Lyman alpha emitters. We propose HST- NICMOS and Spitzer-IRAC photometry of 35 Lyman-alpha galaxies at redshift 4.5z6.5, in order to determine their spectral energy distribution {SED} extending through rest-frame optical. This will allow us to measure accurately {1} The total stellar mass in these objects, including old stars which may have formed at redshifts {z 8} not easily probed by any other means. {2} The dust extinction in the rest-frame UV, and therefore a correction to their present star-formation rates. Taken together, these two quantities will yield the star-formation histories of Lyman alpha galaxies, which form fully half of the known galaxies at z=4-6. They will tell us whether these are young or old galaxies by straddling the 4000A break. Data from NICMOS is essential for these compact and faint {i=25-26th magnitude AB} high redshift galaxies, which are too faint for good near-IR photometry from the ground. WFPC2 11146 The Role of Stellar Feedback in Galaxy Evolution Stellar feedback - the return of mass and energy from star formation to the interstellar medium - is one of the primary engines of galaxy evolution. Yet, the observational canvass of feedback is incomplete. We propose to investigate this fundamental aspect of star formation on one local actively star-forming galaxy, He2-10, selected to occupy an unexplored niche in the key parameter space of stellar mass. The WFPC2 narrow-band observations in the light of H-beta, [OIII], H-alpha, and [SII] will: {1} discriminate the feedback-induced shock fronts from the photoionized regions; {2} map, and provide a complete census of, the shocks inside and around the starburst regions; and {3} measure the energy budget of the star-formation-produced shocks. These observations, joined by our previous data and studies on starbursts, will yield: {1} the efficiency of the feedback, i.e. the fraction of the star formation's mechanical energy transported out of the starburst volume rather than radiated away, in the dual-parameter space of host's stellar mass and star formation intensity; {2} the conditions under which feedback morphs from a localized process to a galactic scale mechanism. The high angular resolution of HST is crucial for separating the spatially narrow shock fronts {~10 pc=0.2" at 10 Mpc} from the more extended photoionization fronts. This project will provide the most comprehensive quantitative foundation of stellar feedback and a gauge for determining the role of feedback in the energetics, structure and star formation history of galaxies. NIC2 11142 Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3 We aim to determine physical properties of IR luminous galaxies at 0.3z2.7 by requesting coordinated HST/NIC2 and MIPS 70um observations of a unique, 24um flux-limited sample with complete Spitzer mid-IR spectroscopy. The 150 sources investigated in this program have S{24um} 0.8mJy and their mid-IR spectra have already provided the majority targets with spectroscopic redshifts {0.3z2.7}. The proposed 150~orbits of NIC2 and 66~hours of MIPS 70um will provide the physical measurements of the light distribution at the rest-frame ~8000A and better estimates of the bolometric luminosity. Combining these parameters together with the rich suite of spectral diagnostics from the mid-IR spectra, we will {1} measure how common mergers are among LIRGs and ULIRGs at 0.3z2.7, and establish if major mergers are the drivers of z1 ULIRGs, as in the local Universe. {2} study the co-evolution of star formation and blackhole accretion by investigating the relations between the fraction of starburst/AGN measured from mid-IR spectra vs. HST morphologies, L{bol} and z. {3} obtain the current best estimates of the far-IR emission, thus L{bol} for this sample, and establish if the relative contribution of mid-to-far IR dust emission is correlated with morphology {resolved vs. unresolved}. WFPC2 11138 The Physics of the Jets of Powerful Radio Galaxies and Quasars We propose to obtain HST polarimetry of the jets of the quasars 1150+497 and PKS 1136-135. Our goal is to solve the riddle of their high-energy emission mechanism, and tackle issues such as particle acceleration and jet dynamics. Our targets are the optically brightest quasar jets, and they span the range of luminosities and beaming parameters seen in these objects. Recent observations with Spitzer, HST and Chandra have shed new light on the spectral morphology of quasar jets, throwing wide open the question of the nature of their optical and X-ray emission. Three mechanisms are possible, including synchrotron emission as well as two Comptonization processes. Polarimetry can uniquely determine which of these mechanisms operates in the optical. We will compare the optical polarimetry to in- hand radio polarimetry as well as in-hand and new Spitzer, HST and Chandra imaging to gain new insights on the structure of these jets, as well as particle acceleration mechanisms and jet dynamics. WFPC2 11134 WFPC2 Tidal Tail Survey: Probing Star Cluster Formation on the Edge The spectacular HST images of the interiors of merging galaxies such as the Antennae and NGC 7252 have revealed rich and diverse populations of star clusters created over the course of the interaction. Intriguingly, our WFPC2 study of tidal tails in these and other interacting pairs has shown that star cluster birth in the tails does not follow a similarly straightforward evolution. In fact, cluster formation in these relatively sparse environments is not guaranteed -- only one of six tails in our initial study showed evidence for a significant population of young star clusters. The tail environment thus offers the opportunity to probe star cluster formation on the edge of the physical parameter space {e.g., of stellar and gas mass, density, and pressure} that permits it to occur. We propose to significantly extend our pilot sample of optically bright, gas-rich tidal tails by a factor of 4 in number to include a more diverse population of tails, encompassing major and minor mergers, gas-rich and gas-poor tails, as well as early, late, and merged interaction stages. With 21 orbits of HST WFPC2 imaging in the F606W and F814W filters, we can identify, roughly age-date, and measure sizes of star clusters to determine what physical parameters affect star cluster formation. WFPC2 imaging has been used effectively in our initial study of four mergers, and it will be possible in this program to reach similar limits of Mv=-8.5 for each of 16 more tails. With the much larger sample we expect to isolate which factors, such as merger stage, HI content, and merger mass ratio, drive the formation of star clusters. WFPC2 11130 AGNs with Intermediate-mass Black Holes: Testing the Black Hole-Bulge Paradigm, Part II The recent progress in the study of central black holes in galactic nuclei has led to a general consensus that supermassive {10^6-10^9 solar mass} black holes are closely connected with the formation and evolutionary history of large galaxies, especially their bulge component. Two outstanding issues, however, remain unresolved. Can central black holes form in the absence of a bulge? And does the mass function of central black holes extend below 10^6 solar masses? Intermediate-mass black holes {10^6 solar masses}, if they exist, may offer important clues to the nature of the seeds of supermassive black holes. Using the SDSS, our group has successfully uncovered a new population of AGNs with intermediate-mass black holes that reside in low-luminosity galaxies. However, very little is known about the detailed morphologies or structural parameters of the host galaxies themselves, including the crucial question of whether they have bulges or not. Surprisingly, the majority of the targets of our Cycle 14 pilot program have structural properties similar to dwarf elliptical galaxies. The statistics from this initial study, however, are really too sparse to reach definitive conclusions on this important new class of black holes. We wish to extend this study to a larger sample, by using the Snapshot mode to obtain WFPC2 F814W images from a parent sample of 175 AGNs with intermediate- mass black holes selected from our final SDSS search. We are particularly keen to determine whether the hosts contain bulges, and if so, how the fundamental plane properties of the host depend on the mass of their central black holes. We will also investigate the environment of this unique class of AGNs. WFPC2 11124 The Origin of QSO Absorption Lines from QSOs We propose using WFPC2 to image the fields of 10 redshift z ~ 0.7 foreground {FG} QSOs which lie within ~29-151 kpc of the sightlines to high-z background {BG} QSOs. A surprisingly high fraction of the BG QSO spectra show strong MgII {2796,2803} absorption lines at precisely the same redshifts as the FG QSOs. The high resolution capabilities of WFPC2 are needed to understand the origin of these absorption systems, in two ways. First, we wish to explore the FG QSO environment as close as possible to the position of the BG QSO, to search for interloping group or cluster galaxies which might be responsible for the absorption, or irregularly shaped post-merger debris between the FG and BG QSO which may indicate the presence of large amount of disrupted gas along a sightline. Similarly, high resolution images are needed to search for signs of tidal interactions between any galaxies which might be found close to the FG QSO. Such features might provide evidence of young merging events causing the start of QSO duty cycles and producing outflows from the central AGN. Such winds may be responsible for the observed absorption lines. Second, we seek to measure the intrinsic parameters of the FG QSO host galaxy, such as luminosity and morphology, to correlate with the properties of the MgII absorption lines. We wish to observe each field through the F814W filter, close to the rest- frame B-band of the FG QSO. These blue data can reveal enhanced star formation regions close to the nucleus of the host galaxy, which may be indicative of galaxy mergers with the FG QSO host. The FG QSO environment offers quite a different set of phenomena which might be responsible for MgII absorption, providing an important comparison to studies of MgII absorption from regular field galaxies. WFPC2 11122 Expanding PNe: Distances and Hydro Models We propose to obtain repeat narrowband images of a sample of eighteen planetary nebulae {PNe} which have HST/WFPC2 archival data spanning time baselines of a decade. All of these targets have previous high signal-to-noise WFPC2/PC observations and are sufficiently nearby to have readily detectable expansion signatures after a few years. Our main scientific objectives are {a} to determine precise distances to these PNe based on their angular expansions, {b} to test detailed and highly successful hydrodynamic models that predict nebular morphologies and expansions for subsamples of round/elliptical and axisymmetric PNe, and {c} to monitor the proper motions of nebular microstructures in an effort to learn more about their physical nature and formation mechanisms. The proposed observations will result in high-precision distances to a healthy subsample of PNe, and from this their expansion ages, luminosities, CSPN properties, and masses of their ionized cores. With good distances and our hydro models, we will be able to determine fundamental parameters {such as nebular and central star masses, luminosity, age}. The same images allow us to monitor the changing overall ionization state and to search for the surprisingly non-homologous growth patterns to bright elliptical PNe of the same sort seen by Balick & Hajian {2004} in NGC 6543. Non-uniform growth is a sure sign of active pressure imbalances within the nebula that require careful hydro models to understand. NIC3 11107 Imaging of Local Lyman Break Galaxy Analogs: New Clues to Galaxy Formation in the Early Universe We have used the ultraviolet all-sky imaging survey currently being conducted by the Galaxy Evolution Explorer {GALEX} to identify for the first time a rare population of low-redshift starbursts with properties remarkably similar to high-redshift Lyman Break Galaxies {LBGs}. These "compact UV luminous galaxies" {UVLGs} resemble LBGs in terms of size, SFR, surface brightness, mass, metallicity, kinematics, dust, and color. The UVLG sample offers the unique opportunity of investigating some very important properties of LBGs that have remained virtually inaccessible at high redshift: their morphology and the mechanism that drives their star formation. Therefore, in Cycle 15 we have imaged 7 UVLGs using ACS in order to 1} characterize their morphology and look for signs of interactions and mergers, and 2} probe their star formation histories over a variety of timescales. The images show a striking trend of small- scale mergers turning large amounts of gas into vigorous starbursts {a process referred to as dissipational or "wet" merging}. Here, we propose to complete our sample of 31 LBG analogs using the ACS/SBC F150LP {FUV} and WFPC2 F606W {R} filters in order to create a statistical sample to study the mechanism that triggers star formation in UVLGs and its implications for the nature of LBGs. Specifically, we will 1} study the trend between galaxy merging and SFR in UVLGs, 2} artificially redshift the FUV images to z=1-4 and compare morphologies with those in similarly sized samples of LBGs at the same rest-frame wavelengths in e.g. GOODS, UDF, and COSMOS, 3} determine the presence and morphology of significant stellar mass in "pre- burst" stars, and 4} study their immediate environment. Together with our Spitzer {IRAC+MIPS}, GALEX, SDSS and radio data, the HST observations will form a unique union of data that may for the first time shed light on how the earliest major episodes of star formation in high redshift galaxies came about. This proposal was adapted from an ACS HRC+WFC proposal to meet the new Cycle 16 observing constraints, and can be carried out using the ACS/SBC and WFPC2 without compromising our original science goals. WFPC2 11103 A Snapshot Survey of The Most Massive Clusters of Galaxies We propose the continuation of our highly successful SNAPshot survey of a sample of 125 very X-ray luminous clusters in the redshift range 0.3-0.7. As demonstrated by the 25 snapshots obtained so far in Cycle14 and Cycle15 these systems frequently exhibit strong gravitational lensing as well as spectacular examples of violent galaxy interactions. The proposed observations will provide important constraints on the cluster mass distributions, the physical nature of galaxy-galaxy and galaxy-gas interactions in cluster cores, and a set of optically bright, lensed galaxies for further 8-10m spectroscopy. All of our primary science goals require only the detection and characterization of high-surface-brightness features and are thus achievable even at the reduced sensitivity of WFPC2. Because of their high redshift and thus compact angular scale our target clusters are less adversely affected by the smaller field of view of WFPC2 than more nearby systems. Acknowledging the broad community interest in this sample we waive our data rights for these observations. Due to a clerical error at STScI our approved Cycle15 SNAP program was barred from execution for 3 months and only 6 observations have been performed to date - reinstating this SNAP at Cycle16 priority is of paramount importance to reach meaningful statistics. WFPC2 11083 The Structure, Formation and Evolution of Galactic Cores and Nuclei A surprising result has emerged from the ACS Virgo Cluster Survey {ACSVCS}, a program to obtain ACS/WFC gz imaging for a large, unbiased sample of 100 early-type galaxies in the Virgo Cluster. On subarcsecond scales {i.e., 0.1"-1"}, the HST brightness profiles vary systematically from the brightest giants {which have nearly constant surface brightness cores} to the faintest dwarfs {which have compact stellar nuclei}. Remarkably, the fraction of galaxy mass contributed by the nuclei in the faint galaxies is identical to that contributed by supermassive black holes in the bright galaxies {0.2%}. These findings strongly suggest that a single mechanism is responsible for both types of Central Massive Object: most likely internally or externally modulated gas inflows that feed central black holes or lead to the formation of "nuclear star clusters". Understanding the history of gas accretion, star formation and chemical enrichment on subarcsecond scales has thus emerged as the single most pressing question in the study of nearby galactic nuclei, either active or quiescent. We propose an ambitious HST program {199 orbits} that constitutes the next, obvious step forward: high-resolution, ultraviolet {WFPC2/F255W} and infrared {NIC1/F160W} imaging for the complete ACSVCS sample. By capitalizing on HST's unique ability to provide high-resolution images with a sharp and stable PSF at UV and IR wavelengths, we will leverage the existing optical HST data to obtain the most complete picture currently possible for the history of star formation and chemical enrichment on these small scales. Equally important, this program will lead to a significant improvement in the measured structural parameters and density distributions for the stellar nuclei and the underlying galaxies, and provide a sensitive measure of "frosting" by young stars in the galaxy cores. By virtue of its superb image quality and stable PSF, NICMOS is the sole instrument capable of the IR observations proposed here. In the case of the WFPC2 observations, high-resolution UV imaging { 0.1"} is a capability unique to HST, yet one that could be lost at any time. WFPC2 11030 WFPC2 WF4 Temperature Reduction #3 In the fall of 2005, a serious anomaly was found in images from the WF4 CCD in WFPC2. The WF4 CCD bias level appeared to have become unstable, resulting in sporadic images with either low or zero bias level. The severity and frequency of the problem was rapidly increasing, making it possible that WF4 would soon become unusable if no work-around were found. Examination of bias levels during periods with frequent WFPC2 images showed low and zero bias episodes every 4 to 6 hours. This periodicity is driven by cycling of the WFPC2 Replacement Heater, with the bias anomalies occurring at the temperature peaks. The other three CCDs {PC1, WF2, and WF3} appear to be unaffected and continue to operate properly. Lowering the Replacement Heater temperature set points by a few degrees C effectively eliminates the WF4 anomaly. On 9 January 2006, the upper set point of the WFPC2 Replacement Heater was reduced from 14.9C to 12.2C. On 20 February 2006, the upper set point was reduced from 12.2C to 11.3C, and the lower set point was reduced from 10.9C to 10.0C. These changes restored the WF4 CCD bias level; however, the bias level has begun to trend downwards again, mimicking its behavior in late 2004 and early 2005. A third temperature reduction is planned for March 2007. We will reduce the upper set point of the heater from 11.3C to 10.4C and the lower set point from 10.0C to 9.1C. The observations described in this proposal will test the performance of WFPC2 before and after this temperature reduction. Additional temperature reductions may be needed in the future, depending on the performance of WF4. Orbits: internal 26, external 1. 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 11028 WFPC2 Cycle 15 UV Earth Flats Monitor flat field stability. This proposal obtains sequences of earth streak flats to improve the quality of pipeline flat fields for the WFPC2 UV filter set. These Earth flats will complement the UV earth flat data obtained during cycles 8-14. WFPC2 11027 Visible Earth Flats This proposal monitors flatfield stability. This proposal obtains sequences of Earth streak flats to construct high quality flat fields for the WFPC2 filter set. These flat fields will allow mapping of the OTA illumination pattern and will be used in conjunction with previous internal and external flats to generate new pipeline superflats. These Earth flats will complement the Earth flat data obtained during cycles 4-14. WFPC2 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: 11203 - GSAcq (2,3,3) failed to RGA Hold (Gyro Control) At 060/14:47:31 GSAcq (2,3,3) scheduled from 060/14:44:08 - 14:51:29 failed due to QF2STOPF and QSTOP flags on FGS-2. OBAD #1 RSS data was unavailable due to LOS. OBAD #2 RSS = 16.84a-s. OBAD MAP RSS = 15.29a-s. Received 486 ESB 1808 (x2) TxG Sanity Check Failed at AOS (060/14:43:00). At 14:47:15 mnemonic F2SSCEA flagged Red High EV=10.16, RV=255, EU UL=10 / LL= -10. 11204 - GSAcq (2,1,2) results in Fine Lock Backup (2,0,2) At AOS (060/18:10:15) GSAcq (2,1,2) scheduled from 060/17:47:29-17:54:48 resulted in Fine Lock Backup (2,0,2) due to QF1STOPF and QSTOP flags on FGS-1. Due to LOS, Pre-acquisition OBAD 1 & 2 data will be unavailable until the next scheduled engineering data dump at 061/13:09:29. Post-acquisition OBAD MAP RSS = 13.35 a-s. COMPLETED OPS REQUEST: (None) COMPLETED OPS NOTES: (None) ********************** SCHEDULED***** SUCCESSFUL FGS GSacq************** 26**************** 25 FGS REacq************** 16**************** 16 OBAD with Maneuver **** 84**************** 84 SIGNIFICANT EVENTS: (None) |
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