Status Report

NASA Hubble Space Telescope Daily Report #4256

By SpaceRef Editor
December 11, 2006
Filed under , ,
NASA Hubble Space Telescope Daily Report #4256


– Continuing to collect World Class Science

PERIOD COVERED: UT December 08,09,10, 2006 (DOY 342,343,344)


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.

ACS/HRC 11053

Earth Flats

Sky flats will be obtained by observing the bright Earth with the HRC and WFC. These observations will be used to verify the accuracy of the latest pipeline flats and to monitor any changes. Weekly coronagraphic monitoring is required to assess the changing position of the spots.

ACS/HRC 11041

ACS CCDs daily monitor

This program consists of a set of basic tests to monitor, the read noise, the development of hot pixels and test for any source of noise in ACS CCD detectors. The files, biases and dark will be used to create reference files for science calibration. This programme will be for the entire lifetime of ACS. For cycle 15 the program will cover 18 months 12.1.06->05.31.08 and it has been divied into three different proposal each covering six months. The three proposals are 11041-11042-11043.

WFPC2 10915

ACS Nearby Galaxy Survey

Existing HST observations of nearby galaxies comprise a sparse and highly non-uniform archive, making comprehensive comparative studies among galaxies essentially impossible. We propose to secure HST’s lasting impact on the study of nearby galaxies by undertaking a systematic, complete, and carefully crafted imaging survey of ALL galaxies in the Local Universe outside the Local Group. The resulting images will allow unprecedented measurements of: {1} the star formation history {SFH} of a >100 Mpc^3 volume of the Universe with a time resolution of Delta[log{t}]=0.25; {2} correlations between spatially resolved SFHs and environment; {3} the structure and properties of thick disks and stellar halos; and {4} the color distributions, sizes, and specific frequencies of globular and disk clusters as a function of galaxy mass and environment. To reach these goals, we will use a combination of wide-field tiling and pointed deep imaging to obtain uniform data on all 72 galaxies within a volume-limited sample extending to ~3.5 Mpc, with an extension to the M81 group. For each galaxy, the wide-field imaging will cover out to ~1.5 times the optical radius and will reach photometric depths of at least 2 magnitudes below the tip of the red giant branch throughout the limits of the survey volume. One additional deep pointing per galaxy will reach SNR~10 for red clump stars, sufficient to recover the ancient SFH from the color-magnitude diagram. This proposal will produce photometric information for ~100 million stars {comparable to the number in the SDSS survey} and uniform multi-color images of half a square degree of sky. The resulting archive will establish the fundamental optical database for nearby galaxies, in preparation for the shift of high-resolution imaging to the near-infrared.


Morphologies of the Most Extreme High-Redshift Mid-IR-Luminous Galaxies

The formative phase 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, restricting us to the study of 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 bright at mid-IR wavelengths {F[24um]>0.8mJy}, but deep ground based imaging suggests extremely faint {and in some cases extended} optical counterparts {R~24-27}. Deep K-band images show barely resolved galaxies. Mid-infrared spectroscopy with Spitzer/IRS reveals that they have redshifts z ~ 2-2.5, suggesting bolometric luminosities ~10^{13-14}Lsun! We propose to obtain deep ACS F814W and NIC2 F160W images of these sources and their environs in order to determine kpc-scale morphologies and surface photometry for these galaxies. The proposed observations will help us determine whether these extreme objects are merging systems, massive obscured starbursts {with obscuration on kpc scales!} or very reddened {locally obscured} AGN hosted by intrinsically low-luminosity galaxies.

ACS/WFC 10886

The Sloan Lens ACS Survey: Towards 100 New Strong Lenses

As a continuation of the highly successful Sloan Lens ACS {SLACS} Survey for new strong gravitational lenses, we propose one orbit of ACS-WFC F814W imaging for each of 50 high- probability strong galaxy-galaxy lens candidates. These observations will confirm new lens systems and permit immediate and accurate photometry, shape measurement, and mass modeling of the lens galaxies. The lenses delivered by the SLACS Survey all show extended source structure, furnishing more constraints on the projected lens potential than lensed-quasar image positions. In addition, SLACS lenses have lens galaxies that are much brighter than their lensed sources, facilitating detailed photometric and dynamical observation of the former. When confirmed lenses from this proposal are combined with lenses discovered by SLACS in Cycles 13 and 14, we expect the final SLACS lens sample to number 80–100: an approximate doubling of the number of known galaxy-scale strong gravitational lenses and an order-of-magnitude increase in the number of optical Einstein rings. By virtue of its homogeneous selection and sheer size, the SLACS sample will allow an unprecedented exploration of the mass structure of the early-type galaxy population as a function of all other observable quantities. This new sample will be a valuable resource to the astronomical community by enabling qualitatively new strong lensing science, and as such we will waive all but a short {3-month} proprietary period on the observations.

ACS/HRC 10878

An ACS Prism Snapshot Survey for z~2 Lyman Limit Systems

We propose to conduct a spectroscopic survey of Lyman limit absorbers at redshifts 1.7 < z < 2.2, using ACS/HRC and the PR200L prism. We have selected 100 quasars at 2.3 < z < 2.6 from the Sloan Digital Sky Survey Spectroscopic Quasar sample, for which no BAL signature is found at the QSO redshift and no strong metal absorption lines are present at z > 2.3 along the lines of sight. The survey has three main observational goals. First, we will determine the redshift frequency dN/dz of the LLS over the column density range 16.3 < log N_HI < 20.3 cm^-2. Second, we will measure the column density frequency distribution f{N} for the partial Lyman limit systems {PLLS} over the column density range 16.3 < log N_HI < 17.5 cm^-2. Third, we will identify new sightlines for measurements of the primordial D/H ratio. With this survey, we will also constrain two key quantities of cosmological relevance: First, the measurements of dN/dz for optically thick LLS and f{N} for the PLLS are critical to estimating the attenuation of extragalactic ionizing sources {e.g. QSOs}. Currently, uncertainties in dN/dz and f{N} are the greatest sources of uncertainty for inferring the shape and intensity of the UV background radiation field. Second, we will estimate the amount of metals in the LLS using the f{N} and ground based observations of metal line transitions. It is possible that a significant fraction of the "missing metals" at z~2 are associated with these highly ionized absorbers. Third, analysis of the LLS lends to investigations of the interface between galaxies {i.e. the damped Lyman alpha systems} and the intergalactic medium {i.e. the Lyman alpha forest}. This survey is ideal for a snapshot observing program, because the on-object integration times are less than 10 minutes, and the targets cover the majority of the northern sky.

ACS/HRC 10877

A Snapshot Survey of the Sites of Recent, Nearby Supernovae

During the past few years, robotic {or nearly robotic} searches for supernovae {SNe}, most notably our Lick Observatory Supernova Search {LOSS}, have found hundreds of SNe, many of them in quite nearby galaxies {cz < 4000 km/s}. Most of the objects were discovered before maximum brightness, and have follow-up photometry and spectroscopy; they include some of the best-studied SNe to date. We propose to conduct a snapshot imaging survey of the sites of some of these nearby objects, to obtain late-time photometry that {through the shape of the light and color curves} will help reveal the origin of their lingering energy. The images will also provide high-resolution information on the local environments of SNe that are far superior to what we can procure from the ground. For example, we will obtain color-color and color-magnitude diagrams of stars in these SN sites, to determine the SN progenitor masses and constraints on the reddening. Recovery of the SNe in the new HST images will also allow us to actually pinpoint their progenitor stars in cases where pre- explosion images exist in the HST archive. This proposal is an extension of our successful Cycle 13 snapshot survey with ACS. It is complementary to our Cycle 15 archival proposal, which is a continuation of our long-standing program to use existing HST images to glean information about SN environments.

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.

ACS/HRC 10867

SAINTS – Supernova 1987A INTensive Survey

SAINTS is a program to observe SN 1987A, the brightest supernova in 383 years, as it morphs into the youngest supernova remnant at age 19. HST is a unique tool for spatially-resolved observations of the many physical components of SN 1987A. A violent encounter is now underway between the fastest-moving debris and the circumstellar ring: the collision excites “hotspots” that light up suddenly. The optical, infrared and X-ray fluxes are rising rapidly and vary significantly on 6-month time scales: regularly-spaced HST, SPITZER, and CHANDRA observations are needed to understand the physics of these shocked regions. In Cycle 15, the many separate hotspots may begin to fuse as the shock fully enters the circumstellar ring. Photons from these shocks may excite previously invisible gas outside the ring, revealing the true extent of the mass loss that preceded the explosion of Sanduleak -69 202. The inner debris of the explosion itself, still excited by radioactive isotopes produced in the explosion, is now resolved by ACS and seen to be aspherical, providing direct evidence on the asymmetry of the explosion. Many questions about SN 1987A remain unanswered despite our diligent efforts at observation and analysis since the launch of HST. How did the enigmatic three rings form? Precisely what took place in the core during the core collapse and bounce? Is a black hole or a neutron star left behind in the debris? The rich and deep data set from SAINTS will be a resource for current use and for future reference to help answer these central questions of supernova science.

NIC3 10861

An ACS Treasury Survey of the Coma cluster of galaxies

We propose to use the unique spatial resolution of HST and ACS to construct a Treasury imaging survey of the core and infall region of the richest local cluster, Coma. We will observe samples of thousands of galaxies down to magnitude B=27.3 with the aim of studying in detail the dwarf galaxy population which, according to hierarchical models of galaxy formation, are the earliest galaxies to form in the universe. Our initial scientific objectives are: 1} A study of the structure of the dwarf galaxies, including scaling laws, nuclear structure and morphology, to compare with hierarchical and evolutionary models of their formation. 2} A study of the stellar populations from colors and color gradients, and how the internal chemical evolution of galaxies is affected by interaction with the cluster gaseous and galaxy environment. 3} To determine the effect of the cluster environment upon morphological features, disks, bulges and bars, by comparing these structure in the Coma sample with field galaxy samples. 4} Identification of dwarf galaxy samples for further study with the new generation of multi-object and integral-field spectrographs on 8-10 metre class telescopes such as Keck, Subaru, Gemini, and GTC. This is the first such survey of a nearby rich cluster. It will provide a key database for studies of galaxy formation and evolution, and a very needed reference for comparison with similar galaxy surveys both in lower density environments in the nearby universe, and in high density environments at high redshifts.

ACS/HRC 10860

The largest Kuiper belt object

The past year has seen an explosion in the discoveries of Pluto-sized objects in the Kuiper belt. With the discoveries of the methane-covered 2003 UB313 and 2005 FY9, the multiple satellite system of 2003 EL61, and the Pluto-Charon analog system of Orcus and its satellite, it is finally apparent that Pluto is not a unique oddball at the edge of the solar system, but rather one of a family of similarly large objects in the Kuiper belt and beyond. HST observations over the past decade have been critical for understanding the interior, surface, and atmosphere of Pluto and Charon. We propose here a comprehensive series of observations designed to similarly expand our knowledge of these recently discovered Pluto-sized and near-Pluto-sized Kuiper belt objects. These observations will measure objects’ sizes and densities, explore the outcome of collisions in the outer solar system, and allow the first ever look at the interior structure of a Kuiper belt object. Our wide field survey that discovered all of these objects is nearly finished, so after five years of continuous searching we are finally almost complete in our tally of these near-Pluto-sized objects. This large HST request is the culmination of this half-decade search for new planetary-sized objects. As has been demonstrated repeatedly by the approximately 100 previous orbits devoted to the study of Pluto, only HST has the resolution and sensitivity for detailed study of these distant objects.

ACS/WFC 10809

The nature of “dry” mergers in the nearby Universe

Recent studies have shown that “dry” mergers of red, bulge-dominated galaxies at low redshift play an important role in shaping today’s most massive ellipticals. These mergers have been identified in extremely deep ground-based images of red sequence galaxies at z ~ 0.1. The ground-based images reach surface brightness limits of AB ~ 29, but lack the resolution to study the morphologies of the galaxies inside the effective radius. Here we propose to obtain ACS images of a representative sample of 40 of these red sequence galaxies: 15 ongoing dry mergers, 15 remnants, and 10 undisturbed objects. We will measure the isophote shapes and ellipticities of the galaxies, their dust content, morphological fine structure {shells and ripples}, AGN content, and their location on the Fundamental Plane. By comparing galaxies in different stages of the merging process we can constrain the amount of gas associated with these red mergers, the effect of active nuclei, and track structural changes. As two galaxies can be observed in a single orbit 20 orbits are requested to observe the 40 galaxies.

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.

NIC2, ACS/WFC 10802

SHOES-Supernovae, HO, for the Equation of State of Dark energy

The present uncertainty in the value of the Hubble constant {resulting in an uncertainty in Omega_M} and the paucity of Type Ia supernovae at redshifts exceeding 1 are now the leading obstacles to determining the nature of dark energy. We propose a single, integrated set of observations for Cycle 15 that will provide a 40% improvement in constraints on dark energy. This program will observe known Cepheids in six reliable hosts of Type Ia supernovae with NICMOS, reducing the uncertainty in H_0 by a factor of two because of the smaller dispersion along the instability strip, the diminished extinction, and the weaker metallicity dependence in the infrared. In parallel with ACS, at the same time the NICMOS observations are underway, we will discover and follow a sample of Type Ia supernovae at z > 1. Together, these measurements, along with prior constraints from WMAP, will provide a great improvement in HST’s ability to distinguish between a static, cosmological constant and dynamical dark energy. The Hubble Space Telescope is the only instrument in the world that can make these IR measurements of Cepheids beyond the Local Group, and it is the only telescope in the world that can be used to find and follow supernovae at z > 1. Our program exploits both of these unique capabilities of HST to learn more about one of the greatest mysteries in science.

FGS 10614

Internal Structure and Figures of Binary Asteroids

The goal of this proposal is to obtain very important information on the internal structure of a number of asteroids, and insight on the gravitational reaccumulation-process after a catastrophic disruptive collision. High resolutions observations with the HST/FGS interferometer are proposed to obtain high precision data for the topographic shape and size of a number of selected asteroids. Here we focus on objects with satellites, hence with known masses, so that the bulk density and porosity will be derived in the most accurate manner. This will yield plausible estimates on the internal properties of the objects, test wether they are close or not to figures of equilibrium {in terms of shape and adimensional rotational frequency}, and provide estimates of their relative density. The HST/FGS in interferometric mode is an ideal facility to carry out this program.

ACS/WFC 10237

Low-Ionization BALs: Evolution or Orientation?

We propose to test the hypothesis that Low-Ionization Broad Absorption Line Quasars {LoBALs} represent a special stage of quasar evolution: young quasars in systems with strong interaction and star-formation. We will carry out high resolution imaging using ACS/WFC and NICMOS to measure the properties of the host galaxies of four LoBAL quasars at z = 0.9 – 2.0 that show strong overlapping FeII absorption troughs. The ACS imaging will be carried out in the passband with the strongest BAL absorption, acting as a natural coronagraph. This results in a reduction of quasar light by a factor of 15 – 26 in these passbands, providing arguably the best view of the host galaxies of luminous, high-redshift quasars. This method allows efficient detection and detailed modeling of the host galaxy morphology in the rest-frame ultraviolet, which is most sensitive to star formation and galaxy interaction. We will also use NICMOS imaging to measure the rest-frame light from the host galaxy to probe the old stellar populations where the host galaxy is likely to be brighter. It has been suggested that LoBALs might not be explained simply as an orientation effect but rather as an early phase of quasar evolution. Such a phase is typically associated with large amounts of dust and gas, and young galaxies with strong star formation. With HST observations, we will study the color and morphology of the FeLoBAL quasar host galaxies, and measure the age of their dominant stellar populations. We will also measure the density of close companions, and, in particular, look for signs of ongoing or recent mergers. These measurements will be compared to those of control samples of normal quasars at similar redshift. If LoBALs are indeed young systems, then their host galaxies are expected to show stronger interactions and merger activity, younger stellar ages, and regions with strong star formation. If the LoBAL host galaxies show no significant difference from those of normal quasars, it will support the view that LoBAL quasars are not a distinct population and that all quasars have BAL outflows along some lines of sight.


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


10550 – GSAcq(2,3,2) failed to RGA Hold (Gyro Control) Upon acquisition of signal at 342/10:31:46, the GSAcq(2,3,2) scheduled at 342/08:57:20 -09:05:25 was observed to have failed to RGA Hold due to search radius limit exceeded on FGS-2. One 486 ESB “a05” (FGS Coarse Track failed – Search Radius Limit Exceeded) was received. Pre-acquisition OBADs (RSS) attitude error corrections values not available pending future ETR Dump due to LOS.

10551 – GSAcq (2,1,2) failed due to Scan Step Limit Exceeded on FGS At AOS 342/20:03:25 GSAcq (2,1,2) scheduled from 342/19:44:42-19:51:57 failed to RGA control due to scan step limit exceeded on FGS 2. OBAD #1: V1 15.18, V2 -2510.66, V3 542.69, RSS 2569.75 OBAD #2: V1, -2.28, V2 12.47, V3 2.90, RSS 13.01 OBAD MAP: V1 0.62, V2 5.71, V3 -3.33, RSS 6.64

10552 – GSAcq(2,1,2) Loss of Lock While HST was guiding under two FGSs following successful GSAcq(2,1,2) of 343/00:59:25 FGS-1 the Sub-dominant guider lost lock at 343/03:07:25 following a Type 3 Slew scheduled at 343/02:57:56 – 02:58:06. The mnemonic QDVFGSM0 (FGS Attitude Error Angle) broke limit at 343/03:07:22 with a value of -0.000601679 radians. The spacecraft entered M2G_MODE at 343/03:07:32. The TERM EXP was not scheduled until 343/04:52:25.

10553 – REacq(1,2,2) failed due to scan step limit exceeded. REacq(1,2,2) scheduled at 344/14:51:03 failed due to scan step limit exceeded on FGA 1. OBAD1 showed errors of V1= -49.56, V2=-3489.72, V3=-42.59, RSS=3490.33. OBAD2 showed errors of V1=-3.26, V2=-6.41, V3=-2.85, and RSS=7.74.

The REacq(1,2,2) at 344/16:26:58 also failed due to scan step limit exceeded on FGS 1 at 16:30:18. OBAD1 was during LOS. OBAD2 showed errors of V1=-0.26, V2=-1.32, V3=2.56, RSS= 2.89.



                         SCHEDULED      SUCCESSFUL
FGS GSacq               21                     19
FGS REacq               20                      18
OBAD with Maneuver  84                      84


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