Status Report

NASA Hubble Space Telescope Daily Report #4443

By SpaceRef Editor
September 10, 2007
Filed under , ,
NASA Hubble Space Telescope Daily Report #4443

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.


– Continuing to collect World Class Science

PERIOD COVERED: UT September 07,08,09, 2007 (DOY 250, 251, 252) OBSERVATIONS SCHEDULED

WFPC2 11312

The Local Cluster Substructure Survey {LoCuSS}: Deep Strong Lensing Observations with WFPC2

LoCuSS is a systematic and detailed investigation of the mass, substructure, and thermodynamics of 100 X-ray luminous galaxy clusters at 0.15< z<0.3. The primary goal is to test our recent suggestion that this population is dominated by dynamically immature disturbed clusters, and that the observed mass-temperature relation suffers strong structural segregation. If confirmed, this would represent a paradigm shift in our observational understanding of clusters, that were hitherto believed to be dominated by mature, undisturbed systems. We propose to complete our successful Cycle 15 program {SNAP:10881} which prior to premature termination had delivered robust weak-lensing detections in 17 clusters, and candidate strongly-lensed arcs in 11 of these 17. These strong and weak lensing signals will give an accurate measure of the total mass and structure of the dark matter distribution that we will subsequently compare with X-ray and Sunyaev Zeldovich Effect observables. The broader applications of our project include 1} the calibration of mass-temperature and mass-SZE scaling relations which will be critical for the calibration of proposed dark energy experiments, and 2} the low redshift baseline study of the demographics of massive clusters to aid interpretation of future high redshift {z>1} cluster samples. To complete the all-important high resolution imaging component of our survey, we request deep WFPC2 observations of 20 clusters through the F606W filter, for which wide-field weak-lensing data are already available from our Subaru imaging program. The combination of deep WFPC2 and Subaru data for these 20 clusters will enable us to achieve the science program approved by the Cycle 15 TAC.

WFPC2 11229

SEEDS: The Search for Evolution of Emission from Dust in Supernovae with HST and Spitzer

The role that massive stars play in the dust content of the Universe is extremely uncertain. It has long been hypothesized that dust can condense within the ejecta of supernovae {SNe}, however there is a frustrating discrepancy between the amounts of dust found in the early Universe, or predicted by nucleation theory, and inferred from SN observations. Our SEEDS collaboration has been carefully revisiting the observational case for dust formation by core-collapse SNe, in order to quantify their role as dust contributors in the early Universe. As dust condenses in expanding SN ejecta, it will increase in optical depth, producing three simultaneously observable phenomena: {1} increasing optical extinction; {2} infrared {IR} excesses; and {3} asymmetric blue-shifted emission lines. Our SEEDS collaboration recently reported all three phenomena occurring in SN2003gd, demonstrating the success of our observing strategy, and permitting us to derive a dust mass of up to 0.02 solar masses created in the SN.  To advance our understanding of the origin and evolution of the interstellar dust in galaxies, we propose to use HST’s WFPC2 and NICMOS instruments plus Spitzer’s photometric instruments to monitor ten recent core- collapse SNe for dust formation and, as a bonus, detect light echoes that can affect the dust mass estimates. These space-borne observations will be supplemented by ground- based spectroscopic monitoring of their optical emission line profiles. These observations would continue our 2-year HST and Spitzer monitoring of this phenomena in order to address two key questions: Do all SNe produce dust? and How much dust do they produce? As all the SN are witin 15 Mpc, each SN stands an excellent chance of detection with HST and Spitzer and of resolving potential light echoes.

FGS 11213

Distances to Eclipsing M Dwarf Binaries

We propose HST FGS observations to measure accurate distances of 5 nearby M dwarf eclipsing binary systems, from which model-independent luminosities can be calculated. These objects have either poor or no existing parallax measurements. FGS parallax determinations for these systems, with their existing dynamic masses determined to better than 0.5%, would serve as model-independent anchor points for the low-mass end of the mass-luminosity diagram.

FGS 11212

Filling the Period Gap for Massive Binaries

The current census of binaries among the massive O-type stars is seriously incomplete for systems in the period range from years to millennia because the radial velocity variations are too small and the angular separations too close for easy detection. Here we propose to discover binaries in this observational gap through a Faint Guidance Sensor SNAP survey of relatively bright targets listed in the Galactic O Star Catalog. Our primary goal is to determine the binary frequency among those in the cluster/association, field, and runaway groups.  The results will help us assess the role of binaries in massive star formation and in the processes that lead to the ejection of massive stars from their natal clusters. The program will also lead to the identification of new, close binaries that will be targets of long term spectroscopic and high angular resolution observations to determine their masses and distances. The results will also be important for the interpretation of the spectra of suspected and newly identified binary and multiple systems.

WFPC2 11201

Systemic and Internal motions of the Magellanic Clouds: Third Epoch Images

In Cycles 11 and 13 we obtained two epochs of ACS/HRC data for fields in the Magellanic Clouds centered on background quasars. We used these data to determine the proper motions of the LMC and SMC to better than 5% and 15% respectively. These are by far the best determinations of the proper motions of these two galaxies. The results have a number of unexpected implications for the Milky Way-LMC-SMC system. The implied three-dimensional velocities are larger than previously believed, and are not much less than the escape velocity in a standard 10^12 solar mass Milky Way dark halo. Orbit calculations suggest the Clouds may not be bound to the Milky Way or may just be on their first passage, both of which would be unexpected in view of traditional interpretations of the Magellanic Stream. Alternatively, the Milky Way dark halo may be a factor of two more massive than previously believed, which would be surprising in view of other observational constraints. Also, the relative velocity between the LMC and SMC is larger than expected, leaving open the possibility that the Clouds may not be bound to each other. To further verify and refine our results we now request an epoch of WFPC2/PC data for the fields centered on 40 quasars that have at least one epoch of ACS imaging. We request execution in snapshot mode, as in our previous programs, to ensure the most efficient use of HST resources. A third epoch of data of these fields will provide crucial information to verify that there are no residual systematic effects in our previous measurements. More importantly, it will increase the time baseline from 2 to 5 yrs and will increase the number of fields with at least two epochs of data. This will reduce our uncertainties correspondingly, so that we can better address whether the Clouds are indeed bound to each other and to the Milky Way. It will also allow us to constrain the internal motions of various populations within the Clouds, and will allow us to determine a distance to the LMC using rotational parallax.

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.

WFPC2 11115

Photometric Imaging of Asteroid 2 Pallas

We propose to conduct the first HST imaging of Asteroid 2 Pallas with WFPC2-PC over 4 HST orbits. We will image the asteroid in five filters: F336w, F439w, F555w, F675w and F814w. We will utilize these observations to drastically improve the knowledge of Pallas’ shape, spin pole position and surface properties, including roughness and albedo, parameters that are poorly determined by previous study.  These observations will result in high signal-to-noise, high resolution surface maps from the visible to the UV. A satellite search will also be conducted for objects within the stability field of up to 21st magnitude, or about 900m in diameter. It is demonstrated in our proposal that significant scientific opportunity exists in Cycle 16 because Pallas is at both a low-phase, 3.9 degree opposition and near its closest approach to Earth, conditions that do not occur simultaneously in the next twenty years. This window represents the best chance to answer long standing, fundamental questions about Pallas, the main asteroid belt, and the formation of the solar system.

WFPC2 11084

Probing the Least Luminous Galaxies in the Local Universe

We propose to obtain deep color-magnitude data of eight new Local Group galaxies which we recently discovered: Andromeda XI, Andromeda XII, and Andromeda XIII {satellites of M31}; Canes Venatici I, Canes Venatici II, Hercules, and Leo IV {satellites of the Milky Way}; and Leo T, a new “free-floating” Local Group dwarf spheroidal with evidence for recent star formation and associated H I gas. These represent the least luminous galaxies known at *any* redshift, and are the only accessible laboratories for studying this extreme regime of galaxy formation. With deep WFPC-2 F606W and F814W pointings at their centers, we will determine whether these objects contain single or multiple age stellar populations, as well as whether these objects display a range of metallicities.

WFPC2 11037

Red Filters Closeout

This calibration program observes three very red stars {M, L, T dwarfs} in the five reddest broad and medium filters {F785LP, F791W, F814W, F850LP, and F1042M} on WF3 in order to allow cross-calibration to ACS, and in future WFC3. The far-red QE curves will also be tested. Similar observations on PC1 were made in WFPC2/CAL 10078 and 10366.

WFPC2 11034

WFPC2 Closeout Photometric Characterization

The standard star GRW+70D5829 is observed in filter and chip combinations that were not included in photometric calibration programs from 2005, 2006, and 2007. These observations are needed to complete a library of recent standard star observations taken in all filter and chip combinations before WFPC2 is decommissioned in SM4. {Linear Ramp and Polarizer filters are covered in a separate proposal.} These observations, along with other recent standard star observations, will be used to study long-term throughput.

WFPC2 11022

WFPC2 Cycle 15 Decontaminations and Associated Observations

This proposal is for the WFPC2 decons. Also included are instrument monitors tied to decons: photometric stability check, focus monitor, pre- and post-decon internals {bias, intflats, kspots, & darks}, UV throughput check, VISFLAT sweep, and internal UV flat check.

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.

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 Milky 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.


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


10988 – GSACQ(2,1,2) failed, Search Radius Limit Exceeded on FGS 2 GSACQ(2,1,2) at 251/11:44:35 failed at 11:50:07 with search radius limit exceeded on FGS 2. OBADs prior to GSACQ had RSS errors of 1793.72 and 10.09 arcseconds, OBAD map after acquisition had error 17.96 arcseconds.

REACQ(2,1,2) at 13:16:32 also failed at 13:22:01

10897 – Unplanned HST communications outage

HST experienced an unplanned communication outage beginning at about 15:46 GMT on Friday, September 7. Communication was restored via LGAs at ~17:53 GMT following a telemetry switch to A-format (4kps). All spacecraft systems were verified nominal and communications were re-configured back to HST high-gain antennas. There were no hardware anomalies and normal science activities continued throughout the period without loss of science data.

Analysis confirmed that the S/C communications equipment was left in coherent mode following a planned 2-way tracking event. This permitted capture of the HST MA transponder by a ground station overflight of the USN station at South Point, Hawaii. Per the hardware’s design, detection of the ground signal by the HST transponder resulted in a transition to GSTDN-mode baseband RF signal. The two subsequent TDRSS passes were



                       SCHEDULED      SUCCESSFUL 
FGS GSacq               18                 17 
FGS REacq               25                 24 
OBAD with Maneuver      88                 88 


SpaceRef staff editor.