HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT       #4818

PERIOD COVERED: 5am March 24 - 5am March 25, 2009 (DOY

                           083/0900z-084/0900z)

OBSERVATIONS SCHEDULED

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.

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.

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 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

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary reports

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

HSTARS: (None)

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

                      SCHEDULED      SUCCESSFUL

FGS GSAcq               05                 05                         

FGS REAcq               10                 10                          

OBAD with Maneuver 30                 30              

SIGNIFICANT EVENTS: (None)