Notice: For the foreseeable future, the daily reports may contain

apparent discrepancies between some proposal descriptions and the listed

instrument usage. This is due to the conversion of previously approved

ACS WFC or HRC observations into WFPC2, or NICMOS observations

subsequent to the loss of ACS CCD science capability in late January.

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT       # 4365

PERIOD COVERED: UT May 17, 2007 (DOY 137)

OBSERVATIONS SCHEDULED

WFPC2 10832

Solving the microlensing puzzle: An HST high-resolution imaging approach

We propose to use the HST Advanced Camera for Surveys High Resolution

Channel to obtain high resolution imaging data for 10 bona-fide LMC

microlensing events seen in the original MACHO survey. The purpose of

this survey will be to assess whether or not the lens and source stars

have separated enough to be resolved since the original microlensing

event took place - about a decade has passed since the original MACHO

survey and the HST WFPC2 follow-up observations of the microlensing

events. If the components of the lensing event are resolved, we will

determine the apparent magnitude and color of both the lens and the

source stars. These data, in combination with Spitzer/IRAC data and

Magellan near-IR JHK data, will be used to ascertain the basic

properties of the lens stars. With the majority of the microlensing

events in the original MACHO survey observed at the highest spatial

resolution currently possible, we will be able to draw important

conclusions as to what fraction of these events have lenses which belong

to some population of dwarf stars in the disk and what fraction must be

due to lenses in the halo or beyond. These data will greatly increase

our understanding of the structure of the Galaxy by characterizing the

stellar population responsible for the gravitational microlensing.

ACS/SBC 10862

Comprehensive Auroral Imaging of Jupiter and Saturn during the

International Heliophysical Year A comprehensive set of observations of

the auroral emissions from Jupiter and Saturn is proposed for the

International Heliophysical Year in 2007, a unique period of especially

concentrated measurements of space physics phenomena throughout the

solar system. We propose to determine the physical relationship of the

various auroral processes at Jupiter and Saturn with conditions in the

solar wind at each planet. This can be accomplished with campaigns of

observations, with a sampling interval not to exceed one day, covering

at least one solar rotation. The solar wind plasma density approaching

Jupiter will be measured by the New Horizons spacecraft, and a separate

campaign near opposition in May 2007 will determine the effect of

large-scale variations in the interplanetary magnetic field {IMF} on the

Jovian aurora by extrapolation from near-Earth solar wind measurements.

A similar Saturn campaign near opposition in Jan. 2007 will combine

extrapolated solar wind data with measurements from a wide range of

locations within the Saturn magnetosphere by Cassini. In the course of

making these observations, it will be possible to fully map the auroral

footprints of Io and the other satellites to determine both the local

magnetic field geometry and the controlling factors in the

electromagnetic interaction of each satellite with the corotating

magnetic field and plasma density. Also in the course of making these

observations, the auroral emission properties will be compared with the

properties of the near-IR ionospheric emissions {from ground-based

observations} and non thermal radio emissions, from ground-based

observations for Jupiter?s decametric radiation and Cassini plasma wave

measurements of the Saturn Kilometric Radiation {SKR}.

WFPC2 10880

The host galaxies of QSO2s: AGN feeding and evolution at high

luminosities

Now that the presence of supermassive black holes in the nuclei of

galaxies is a well established fact, other questions related to the AGN

phenomena still have to be answered. Problems of particular interest are

how the AGN gets fed, how the black hole evolves and how the evolution

of the black hole is related to the evolution of the galaxy bulge. Here

we propose to address some of these issues using ACS/WFC + F775W

snapshot images of 73 QSO2s with redshifts in the range 0.3<z<0.4. These

observations will be combined with similar archival data of QSO1s and

ground based data of Seyfert and normal galaxies. First, we will

intestigate whether interactions are the most important feeding

mechanism in high luminosity AGNs. This will be done in a quantitative

way, comparing the asymmetry indices of QSO2 hosts with those of lower

luminosity AGNs and normal galaxies. Second, we will do a detailed study

of the morphology of the host galaxies of both QSO types, to determine

if they are similar, or if there is an evolutionary trend from QSO2s to

QSO1s. The results from this project will represent an important step in

the understanding of AGN evolution, and may also introduce a substantial

modification to the Unified Model.

WFPC2 10889

The Nature of the Halos and Thick Disks of Spiral Galaxies

We propose to resolve the extra-planar stellar populations of the thick

disks and halos of seven nearby, massive, edge-on galaxies using ACS,

NICMOS, and WFPC2 in parallel. These observations will provide accurate

star counts and color-magnitude diagrams 1.5 magnitudes below the tip of

the Red Giant Branch sampled along the two principal axes and one

intermediate axis of each galaxy. We will measure the metallicity

distribution functions and stellar density profiles from star counts

down to very low average surface brightnesses, equivalent to ~32 V-mag

per square arcsec. These observations will provide the definitive HST

study of extra-planar stellar populations of spiral galaxies. Our

targets cover a range in galaxy mass, luminosity, and morphology and as

function of these galaxy properties we will provide: - The first

systematic study of the radial and isophotal shapes of the diffuse

stellar halos of spiral galaxies - The most detailed comparative study

to date of thick disk morphologies and stellar populations - A

comprehensive analysis of halo and thick disk metallicity distributions

as a function of galaxy type and position within the galaxy. - A

sensitive search for tidal streams - The first opportunity to directly

relate globular cluster systems to their field stellar population We

will use these fossil records of the galaxy assembly process preserved

in the old stellar populations to test halo and thick disk formation

models within the hierarchical galaxy formation scheme. We will test

LambdaCDM predictions on sub-galactic scales, where it is difficult to

test using CMB and galaxy redshift surveys, and where it faces its most

serious difficulties.

WFPC2 10903

Resolving the LMC Microlensing Puzzle: Where are the Lensing Objects?

We are requesting 12 HST orbits to continue to investigate the nature of

the population that gives rise to the microlensing seen towards the LMC.

This proposal builds on the cycle 14 HST program {10583} and will

complement the study with 12 yet-to-be discovered microlensing

candidates from Fall 2006. Our SuperMacho project is an ongoing ground-

based survey on the CTIO 4m that has demonstrated the ability to detect

LMC microlensing events via frame subtraction. The combination of high

angular resolution and photometric accuracy with HST will allow us to 1}

confrim that the detected flux excursions arise from LMC stars, rather

than background supernovae or AGN, and 2} obtain reliable baseline flux

measurements for the objects in their unlensed state. This latter

measurement in important in determining the microlensing optical depth

towards the LMC.

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               08                  08            

FGS REacq               04                  04               

OBAD with Maneuver 24                  24              

SIGNIFICANT EVENTS: (None)