HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT       #4816

PERIOD COVERED: 5am March 20 - 5am March 23, 2009 (DOY

                           079/0900z-082/0900z)

OBSERVATIONS SCHEDULED

WFPC2 11987

The Recent Star Formation History of SINGS Galaxies

The Spitzer Legacy project SINGS provided a unique view of the current

state of star formation and dust in a sample of galaxies of all Hubble

types. This multi-wavelength view allowed the team to create current

star formation diagnostics that are independent of the dust content and

increased our understanding of the dust in galaxies. Even so, using the

SINGS data alone we can only make rough estimates of the recent star

formation history of these galaxies. The lack of U-band observations

means that it is impossible to estimate the ages of young clusters. In

addition, the low resolution of the Spitzer and ground-based

observations means that what appear to be individual Spitzer sources can

actually be composed of many individual clusters with varying ages. In

this proposal we plan to address this missing area in SINGS by obtaining

high-resolution WFPC2 UBVI observations to accurately find and determine

the ages of the young stellar clusters in a subset of the SINGS

galaxies. These observations will greatly enhance the legacy value of

the SINGS observations while also directly answering questions

pertaining to star formation in galaxies.

WFPC2 11986

Completing HST's Local Volume Legacy

Nearby galaxies offer one of the few laboratories within which stellar

populations can be tied to multi-wavelength observations. They are thus

essential for calibrating and interpreting key astrophysical

observables, such as broad-band luminosities, durations and energy input

from starbursts, and timescales of UV, H-alpha, and FIR emission. The

study of stellar populations in nearby galaxies requires high-resolution

observations with HST, but HST's legacy for this limited set of galaxies

remains incomplete.

As a first attempt to establish this legacy, The ACS Nearby Galaxy

Survey Treasury (ANGST) began observations in late 2006. ANGST was

designed to carry out a uniform multi-color survey of a volume-limited

sample of ~70 nearby galaxies that could be used for systematic studies

of resolved stellar populations. The resulting data provide nuanced

constraints on the processes which govern star formation and galaxy

evolution, for a well-defined population of galaxies. All photometry for

the survey has been publicly released.

However, the failure of ACS 4.5 months after ANGST began taking data led

to a drastic reduction in the planned survey. The loss is two-fold.

First, the goals of completeness and uniformity were greatly

compromised, impacting global comparison studies. Second, the variety of

observed star formation histories was reduced. Given that we have never

found two galaxies with identical star formation histories, and fully

sampling the population allows us to catch those few systems whose star

formation rates and metallicities place the strongest constraints on key

astrophysical processes.

Here we propose WFPC2 observations of all remaining galaxies within the

Local Volume (D<3.5Mpc) for which current HST observations are

insufficient for meaningful stellar population studies. We will use

these observations for research on the star formation histories of

individual galaxies and the Local Volume, detailed calibrations of star

formation rate indicators, and the durations of starbursts. We will also

make them publicly available through the ANGST archive to support future

research. The proposed observations will finally complete a lasting

legacy of HST

ACS/SBC 11980

Deep FUV Imaging of Cooling Flow Clusters

We propose to take deep ACS FUV images of a carefully selected sample of

19 bright central galaxies in nearby galaxy clusters. This program is

the last critical element of a comprehensive investigation of the impact

of stellar and AGN feedback on the local galaxy cluster environment. The

HST images will complement new, high-resolution, Halpha images obtained

with the recently commissioned Maryland-Magellan Tunable Filter (MMTF)

on the Baade 6.5m telescope, archival Chandra, VLA, and GALEX data, and

on-going H2/NIR observations. The MMTF data have revealed unsuspected

filamentary complexes in several systems. The GALEX data often show

hints of extended NUV and FUV emission on a similar scale, but their

poor spatial resolution prevents meaningful comparison with the MMTF

data. The HST data will provide this much needed gain in resolution. The

combined radio-H2-Halpha-FUV-X-ray dataset will allow us to derive with

unprecedented precision the role of the AGN, hot stars, shocks, and

relativistic particles on the excitation and thermodynamics of the

multi-phase intracluster and interstellar media in these systems. This

is an important question since the formation and evolution of most

cluster galaxies have likely been affected by these processes.

WFPC2 11976

Particle Separation in and Expansion of the Dust Arcs of the Young Star

V1331 Cyg

HST-WFPC2 imaging of the young star V1331 Cyg revealed several dust arcs

seen in scattered light which were caused by short-lived strong winds

arising from FU Ori-like outbursts. Most notably the brightest outer arc

is encircled by an expanding CO ring which implies that the otherwise

extremely well mixed gas and dust components were separated according to

particle mass. This is presumably due to the dependence of the wind ram

pressure on the ratio of particle cross section and mass as well as the

brief acceleration period. Thus, we suspect that a FU Ori outburst acts

as a cosmic mass spectrometer. In order to verify this hypothesis, we

apply for 2nd epoch imaging to reveal the color gradient across the

bright dust arc which will be induced by the grain sorting. Furthermore,

the current imagery will allow us to prove directly the expansion of the

arc by measuring its proper motion. The proposed observations represent

new diagnostics for what concerns studies of young stellar objects.

WFPC2 11975

UV Light from Old Stellar Populations: a Census of UV Sources in

Galactic Globular Clusters

In spite of the fact that HST has been the only operative

high-resolution eye in the UV-window over the last 18 years, no

homogeneous UV survey of Galactic globular clusters (GGCs) has been

performed to date. In order to fill this gap in the stellar population

studies, we propose a program that exploits the unique capability of the

WFPC2 and the SBC in the far-/mid- UV for securing deep UV imaging of 46

GGCs. The proposed observations will allow to study with unprecedented

accuracy the hottest GGC stars, comprising the extreme horizontal branch

(HB) stars and their progeny (the so-called AGB-manque', and Post-early

AGB stars), and "exotic stellar populations" like the blue straggler

stars and the interacting binaries. The targets have been selected to

properly sample the GGC metallicity/structural parameter space, thus to

unveil any possible correlation between the properties of the hot

stellar populations and the cluster characteristics. In addition, most

of the targets have extended HB "blue tails", that can be properly

studied only by means of deep UV observations, especially in the far-UV

filters like the F160BW, that is not foreseen on the WFC3. This data

base is complemented with GALEX observations in the cluster outermost

regions, thus allowing to investigate any possible trend of the

UV-bright stellar types over the entire radial extension of the

clusters. Although the hottest GGC stars are just a small class of

"special" objects, their study has a broad relevance in the context of

structure formation and chemical evolution in the early Universe,

bringing precious information on the basic star formation processes and

the origin of blue light from galaxies. Indeed, the proposed

observations will provide the community with an unprecedented data set

suitable for addressing a number of still open astrophysical questions,

ranging from the main drivers of the HB morphology and the mass loss

processes, to the origin of the UV upturn in elliptical galaxies, the

dating of distant systems from integrated light, and the complex

interplay between stellar evolution and dynamics in dense stellar

aggregates. In the spirit of constructing a community resource, we

entirely waive the proprietary period for these observations.

WFPC2 11944

Binaries at the Extremes of the H-R Diagram

We propose to use HST/Fine Guidance Sensor 1r to survey for binaries

among some of the most massive, least massive, and oldest stars in our

part of the Galaxy. FGS allows us to spatially resolve binary systems

that are too faint to observe using ground-based, speckle or optical

long baseline interferometry, and too close to resolve with AO. We

propose a SNAP-style program of single orbit FGS TRANS mode observations

of very massive stars in the cluster NGC 3603, luminous blue variables,

nearby low mass main sequence stars, cool subdwarf stars, and white

dwarfs. These observations will help us to (1) identify systems suitable

for follow up studies for mass determination, (2) study the role of

binaries in stellar birth and in advanced evolutionary states, (3)

explore the fundamental properties of stars near the main sequence-brown

dwarf boundary, (4) understand the role of binaries for X-ray bright

systems, (5) find binaries among ancient and nearby subdwarf stars, and

(6) help calibrate the white dwarf mass - radius relation.

FGS 11943

Binaries at the Extremes of the H-R Diagram

We propose to use HST/Fine Guidance Sensor 1r to survey for binaries

among some of the most massive, least massive, and oldest stars in our

part of the Galaxy. FGS allows us to spatially resolve binary systems

that are too faint for ground-based, speckle or optical long baseline

interferometry, and too close to resolve with AO. We propose a

SNAP-style program of single orbit FGS TRANS mode observations of very

massive stars in the cluster NGC 3603, luminous blue variables, nearby

low mass main sequence stars, cool subdwarf stars, and white dwarfs.

These observations will help us to (1) identify systems suitable for

follow up studies for mass determination, (2) study the role of binaries

in stellar birth and in advanced evolutionary states, (3) explore the

fundamental properties of stars near the main sequence-brown dwarf

boundary, (4) understand the role of binaries for X-ray bright systems,

(5) find binaries among ancient and nearby subdwarf stars, and (6) help

calibrate the white dwarf mass - radius relation.

FGS 11788

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.

FGS 11704

The Ages of Globular Clusters and the Population II Distance Scale

Globular clusters are the oldest objects in the universe whose age can

be accurately determined. The dominant error in globular cluster age

determinations is the uncertain Population II distance scale. We propose

to use FGS 1r to obtain parallaxes with an accuracy of 0.2

milliarcsecond for 9 main sequence stars with [Fe/H] < -1.5. This will

determine the absolute magnitude of these stars with accuracies of 0.04

to 0.06mag. This data will be used to determine the distance to 24

metal-poor globular clusters using main sequence fitting. These

distances (with errors of 0.05 mag) will be used to determine the ages

of globular clusters using the luminosity of the subgiant branch as an

age indicator. This will yield absolute ages with an accuracy 5%, about

a factor of two improvement over current estimates. Coupled with

existing parallaxes for more metal-rich stars, we will be able to

accurately determine the age for globular clusters over a wide range of

metallicities in order to study the early formation history of the Milky

Way and provide an independent estimate of the age of the universe.

The Hipparcos database contains only 1 star with [Fe/H] < -1.4 and an

absolute magnitude error less than 0.18 mag which is suitable for use in

main sequence fitting. Previous attempts at main sequence fitting to

metal-poor globular clusters have had to rely on theoretical

calibrations of the color of the main sequence. Our HST parallax program

will remove this source of possible systematic error and yield distances

to metal-poor globular clusters which are significantly more accurate

than possible with the current parallax data. The HST parallax data will

have errors which are 10 times smaller than the current parallax data.

Using the HST parallaxes, we will obtain main sequence fitting distances

to 11 globular clusters which contain over 500 RR Lyrae stars. This will

allow us to calibrate the absolute magnitude of RR Lyrae stars, a

commonly used Population II distance indicator.

WFPC2 11343

Identifying the host galaxies for optically dark gamma-ray bursts

We propose to use the high spatial resolution capabilities of Chandra to

obtain precise positions for a sample of Gamma-ray bursts (GRBs) with no

optical afterglows, where the optical light is suppressed relative to

the X-ray flux. These bursts are likely to be highly obscured and may

have different environments from the optically bright GRBs. Our Chandra

observations will (unlike Swift-XRT positions) allow for the unique

identification of a host galaxy. To locate these host galaxies we will

follow up our Chandra positions with deep optical and IR observations

with HST. The ultimate aim is to understand any differences between the

host galaxies of optically dark and bright GRBs, and how these affect

the use of GRBs as tracers of starformation and galaxy evolution at high

redshift.

WFPC2 11316

HST Cycle 16 & Pre-SM4 Optical Monitor

This is a continuation of the Cycle 15 & pre-SM4 Optical Monitor, 11020.

Please see that proposal for a more complete description of the

observing strategy. The 6 visits comprising this proposal observe two

single standard stars with WFPC2/PC in order to establish overall OTA

focal length for the purposes of focus maintenance. The goal of this

monitoring before SM4 is to establish a best estimate of the OTA focus

entering SMOV.

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.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary reports

of potential non-nominal performance that will be investigated.)

HSTARS:

11734 - REAcq(1,2,2) scheduled at 082/04:04:45z failed due to scan step

            limited exceed on FGS1.

            Observation effected WFPC 23-24, Proposal ID# 11975 & 11302.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

                       SCHEDULED      SUCCESSFUL  

FGS GSAcq               15                  15                        

FGS REAcq               23                  22                    

OBAD with Maneuver 76                  76              

SIGNIFICANT EVENTS: (None)