HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5169

PERIOD COVERED: 5am August 26 - 5am August 27, 2010 (DOY 238/09:00z-239/09:00z)

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               03           03

FGS REAcq               12           12

OBAD with Maneuver 03           03

SIGNIFICANT EVENTS: (None)

OBSERVATIONS SCHEDULED:

STIS/CCD 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

STIS/CCD 11847

CCD Bias Monitor-Part 2

Monitor the bias in the 1x1, 1x2, 2x1, and 2x2 bin settings at gain=1,

and 1x1 at gain = 4, to build up high-S/N superbiases and track the

evolution of hot columns.

WFC3/IR 11708

Determining the Sub-stellar IMF in the Most Massive Young Milky Way

Cluster, Westerlund 1

Despite over 50 years of active research, a key question in galactic

astronomy remains unanswered: is the initial mass function (IMF) of

stars and sub-stellar objects universal, or does it depend on initial

conditions? The answer has profound consequences for the evolution of

galaxies as well as a predictive theory of star formation. Work to date

suggests that certain environments (high densities, e.g. Elmegreen 2004;

low metallicity, e.g. Larson 2005) should produce a top-heavy IMF, and

there are hints from unresolved star-bursts that this might be the case.

Yet, there is no clear evidence for an IMF that differs from that

characterizing the Galactic field stars in a resolved stellar population

down to one solar mass. Westerlund 1 is the most massive young star

cluster known in the Milky Way. With an estimated mass of 5x10^4 Msun,

an age of 3-5 Myr, and located at a distance of 3-4 kpc, it presents a

unique opportunity to test whether the IMF in such a cluster deviates

from the norm well down into the brown dwarf regime. We propose WFC3

near-IR imaging to probe the IMF down to 40 Jupiter masses. The data

will enable use to: 1) provide a stringent test of the universality of

the IMF under conditions approximating those of star-bursts; 2) search

for primordial or dynamic mass segregation in the clusters; and 3)

assess whether the cluster is likely to remain bound (as a massive open

cluster) or disperse into the field. We will obtain images in the F125W,

F160W, and F139M filters. The F139M filter covers a strong water

absorption feature and the color F125W/F139M is a powerful temperature

diagnostic in the range 2800-4000 K. This information will enable us to:

a) confirm membership for low mass stars suspected on the basis of their

position in the color-magnitude diagram; b) place the members in the HR

diagram; and c) estimate the masses and ages of cluster members for

low-mass stars and sub-stellar objects. This new capability offered with

the WFC3 (through a novel combination of filter complement, high spatial

resolution, and large field of view) will enable us to make a

fundamental test of whether the IMF is universal on a unique resolved

stellar population, as well as assess the clusters structure, dynamics,

and ultimate fate.

WFC3/UV 11638

Illuminating the HI Structure of a Proto-cluster Region at z=2.84

We propose very deep intermediate-band Lyman alpha imaging in the field

of a newly-discovered proto-cluster region surrounding the extremely

luminous QSO HS1549+19 at z=2.844. The large structure, initially

discovered in a spectroscopic survey of galaxies in fields surrounding

the brightest QSOs at z=2.5-2.8, represents an ideal laboratory for

studying the response of the intergalactic medium to a source of

ionizing photons that exceeds the UV background by factors >1000. Within

a single pointing of WFC3-UVIS there are already more than 45 known

Lyman alpha emitters, most of which are already spectroscopically

confirmed, and at least 3 of which are giant “Lyman alpha blobs''. Many

of the objects have properties similar to those expected from the

process of fluorescence, in which Lyman alpha emission is induced by the

UV radiation field of the QSO in any HI gas that dense enough to remain

partially self-shielded. Fortuitously, the F467M filter (Stromgren "b")

in WFC3-UVIS is a perfect match to Lyman alpha at z=2.844. In

combination with an equally deep broad-band continuum image, the

observations will allow the construction of a Lyman alpha map tracing

dense gas throughout the inner parts of a proto-cluster region at

sub-kpc resolution. The ability to measure the spatial sub-structure and

surface brightness distribution of Lya emission, relative to known

protocluster galaxies and AGN, will illuminate the "cosmic web'' in a

dense region caught in a violent stage of formation.

WFC3/UVIS 11905

WFC3 UVIS CCD Daily Monitor

The behavior of the WFC3 UVIS CCD will be monitored daily with a set of

full-frame, four-amp bias and dark frames. A smaller set of 2Kx4K

subarray biases are acquired at less frequent intervals throughout the

cycle to support subarray science observations. The internals from this

proposal, along with those from the anneal procedure (Proposal 11909),

will be used to generate the necessary superbias and superdark reference

files for the calibration pipeline (CDBS).