Daily Report #4587

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT***** # 4587

PERIOD COVERED: UT April 10, 2008 (DOY 101)

OBSERVATIONS SCHEDULED

NIC1/NIC2/NIC3 11318

NICMOS Cycle 16 Multiaccum Darks

The purpose of this proposal is to monitor the dark current, read
noise, and shading profile for all three NICMOS detectors throughout
the duration of Cycle 16. This proposal is a slightly modified version
of proposal 10380 of cycle 13 and 9993 of cycle12 and is the same as
Cycle 15. Covers the period from April 08 to November 08 (inclusive).

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA calibration - CR Persistence Part 6

A new procedure proposed to alleviate the CR-persistence problem of
NICMOS. Dark frames will be obtained immediately upon exiting the SAA
contour 23, and every time a NICMOS exposure is scheduled within 50
minutes of coming out of the SAA. The darks will be obtained in
parallel in all three NICMOS Cameras. The POST-SAA darks will be
non-standard reference files available to users with a USEAFTER
date/time mark. The keyword 'USEAFTER=date/time' will also be added to
the header of each POST-SAA DARK frame. The keyword must be populated
with the time, in addition to the date, because HST crosses the SAA ~8
times per day so each POST-SAA DARK will need to have the appropriate
time specified, for users to identify the ones they need. Both the raw
and processed images will be archived as POST-SAA DARKSs. Generally we
expect that all NICMOS science/calibration observations started within
50 minutes of leaving an SAA will need such maps to remove the CR
persistence from the science images. Each observation will need its
own CRMAP, as different SAA passages leave different imprints on the
NICMOS detectors.

NIC2 11155

Dust Grain Evolution in Herbig Ae Stars: NICMOS Coronagraphic Imaging
and Polarimetry

We propose to take advantage of the sensitive coronagraphic
capabilities of NICMOS to obtain multiwavelength coronagraphic imaging
and polarimetry of primordial dust disks around young
intermediate-mass stars {Herbig Ae stars}, in order to advance our
understanding of how dust grains are assembled into larger bodies.
Because the polarization of scattered light is strongly dependent on
scattering particle size and composition, coronagraphic imaging
polarimetry with NICMOS provides a uniquely powerful tool for
measuring grain properties in spatially resolved circumstellar disks.
It is widely believed that planets form via the gradual accretion of
planetesimals in gas-rich, dusty circumstellar disks, but the
connection between this suspected process and the circumstellar disks
that we can now observe around other stars remains very uncertain. Our
proposed observations, together with powerful 3-D radiative transfer
codes, will enable us to quantitatively determine dust grain
properties as a function of location within disks, and thus to test
whether dust grains around young stars are in fact growing in size
during the putative planet-formation epoch. HST imaging polarimetry of
Herbig Ae stars will complement and extend existing polarimetric
studies of disks around lower-mass T Tauri stars and debris disks
around older main-sequence stars. When combined with these previous
studies, the proposed research will help us establish the influence of
stellar mass on the growth of dust grains into larger planetesimals,
and ultimately to planets. Our results will also let us calibrate
models of the thermal emission from these disks, a critical need for
validating the properties of more distant disks inferred on the basis
of spectral information alone.

NIC2 11208

The co-evolution of spheroids and black holes in the last six billion
years

The masses of giant black holes are correlated with the luminosities,
masses, and velocity dispersions of the bulges of their host galaxies.
This empirical correlation of phenomena on widely different scales
{from pcs to kpcs} suggests that the formation and evolution of
galaxies and central black holes are closely linked. In Cycle 13, we
have started a campaign to map directly the co-evolution of spheroids
and black-holes by measuring in observationally favorable redshift
windows the empirical correlations connecting their properties. By
focusing on Seyfert 1s, where the nucleus and the stars contribute
comparable fractions of total light, black hole mass and bulge
dispersion are obtained from Keck spectroscopy. HST is required for
accurate measurement of the non stellar AGN continuum, the morphology
of the galaxy, and the structural parameters of the bulge. The results
at z=0.36 indicate a surprisingly fast evolution of bulges in the past
4 Gyrs {significant at the 95%CL}, in the sense that bulges were
significantly smaller for a given black hole mass. Also, the large
fraction of mergers and disturbed galaxies {4+2 out of 20} identifies
gas-rich mergers as the mechanisms responsible for bulge-growth. Going
to higher redshift -- where evolutionary trends should be stronger --
is needed to confirm these tantalizing results. We propose therefore
to push our investigation to the next suitable redshift window z=0.57
{lookback-time 6 Gyrs}. Fifteen objects are the minimum number
required to map the evolution of the empirical correlations between
bulge properties and black- hole mass, and to achieve a conclusive
detection of evolution {99%CL}.

NIC2/NIC1/NIC3 11159

The True Galactic Bulge Luminosity Function

We propose to obtain second epoch imaging of the deep Galactic bulge
field observed using NICMOS by Zoccali et al. (2000). The bulge
luminosity and mass function suffered from 30-50% contamination by
foreground disk stars, which was impossible to correct for in the
original study. Revisiting the field after 9 years, we propose to
segregate the foreground disk stars because they have large transverse
velocities, thus revealing the luminosity function of Galactic bulge
low mass stars to near the hydrogen burning limit. The slope of the
mass function has implications for galaxy formation and for
understanding the nature of microlensing in the Galactic bulge.

NIC3 11120

A Paschen-Alpha Study of Massive Stars and the ISM in the Galactic
Center

The Galactic center (GC) is a unique site for a detailed study of a
multitude of complex astrophysical phenomena, which may be common to
nuclear regions of many galaxies. Observable at resolutions
unapproachable in other galaxies, the GC provides an unparalleled
opportunity to improve our understanding of the interrelationships of
massive stars, young stellar clusters, warm and hot ionized gases,
molecular clouds, large scale magnetic fields, and black holes. We
propose the first large-scale hydrogen Paschen alpha line survey of
the GC using NICMOS on the Hubble Space Telescope. This survey will
lead to a high resolution and high sensitivity map of the Paschen
alpha line emission in addition to a map of foreground extinction,
made by comparing Paschen alpha to radio emission. This survey of the
inner 75 pc of the Galaxy will provide an unprecedented and complete
search for sites of massive star formation. In particular, we will be
able to (1) uncover the distribution of young massive stars in this
region, (2) locate the surfaces of adjacent molecular clouds, (3)
determine important physical parameters of the ionized gas, (4)
identify compact and ultra-compact HII regions throughout the GC. When
combined with existing Chandra and Spitzer surveys as well as a wealth
of other multi-wavelength observations, the results will allow us to
address such questions as where and how massive stars form, how
stellar clusters are disrupted, how massive stars shape and heat the
surrounding medium, and how various phases of this medium are
interspersed.

NIC3 11149

Characterizing the Stellar Populations in Lyman-Alpha Emitters and
Lyman Break Galaxies at 5.7z7 in the Subaru Deep Field

The epoch of reionization marks a major phase transition of the
Universe, during which the intergalactic space became transparent to
UV photons. Determining when this occurred and the physical processes
involved represents the latest frontier in observational cosmology.
Over the last few years, searches have intensified to identify the
population of high-redshift (z6) galaxies that might be responsible
for this process, but the progress is hampered partly by the
difficulty of obtaining physical information (stellar mass, age, star
formation rate/history) for individual sources. This is because the
number of z6 galaxies that have both secure spectroscopic redshifts
and high-quality infrared photometry (especially with Spitzer/IRAC) is
still fairly small. Considering that only several photometric points
are available per source, and that many model SEDs are highly
degenerate, it is crucial to obtain as many observational constraints
as possible for each source to ensure the validity of SED modeling. To
better understand the physical properties of high-redshift galaxies,
we propose here to conduct HST/NICMOS (72 orbits) and Spitzer/IRAC
(102 hours) imaging of spectroscopically confirmed, bright (z26 mag
(AB)) Ly-alpha emitters (LAEs) and Lyman-break galaxies (LBGs) at
5.7z7 selected from the Subaru Deep Field. Spectroscopic redshifts
remove one critical free parameter from SED modeling while bright
source magnitudes ensure high-quality photometric data. By making
accurate determinations of stellar masses, ages, and star-formation
histories, we will specifically address the following major questions:
(1) Do LAEs and LBGs represent physically different galaxy populations
at z6 as suggested recently? (2) Is Ly-alpha emission systematically
suppressed at z6 with respect to continuum emission? (i.e., are we
reaching the epoch of incomplete reionization?), and (3) Do we see any
sign of abnormally young stellar population in any of the z6
galaxies?

WFPC2 10841

A Proper Motion Search for Intermediate Mass Black Holes in Globular
Clusters {2nd Epoch Observations}

Establishing the presence or absence of intermediate-mass black holes
{IMBH} in globular clusters is crucial for understanding the evolution
of dense stellar systems. Observationally, this search has been
hampered by the low number of stars with known velocities in the
central few arcseconds. This limits our knowledge of the velocity
dispersion in the region where the gravitational influence of any IMBH
would be felt. In Cycle 13, we successfully obtained ACS/HRC images of
the centers of five carefully chosen Galactic globular clusters
{GO-10401} for a new proper motion study. Although the science case
was approved and the first epoch images obtained, the requested future
cycle observations were not granted {due to a general policy decision
based on the strong uncertainties at the time concerning the immediate
future of HST}. We have now assessed the quality of the first epoch
observations. The HRC resolution reveals many isolated stars in to the
very center of each cluster that remained blended or unresolved in
previous WFPC2 data. Given a two year baseline, we are confident that
we can achieve the proper motion precision required to place strict
limits on the presence of an IMBH. Therefore, we request the
second-epoch, follow-up observations to GO-10401 in order to measure
the proper motions of stars in our target clusters. These velocity
measurements will allow us to: {i} place constraints on the mass of a
central black hole in each cluster; {ii} derive the internal velocity
dispersion as a function of cluster radius; {iii} verify or reject
previous reports of cluster rotation; and {iv} directly measure
velocity anisotropy as a function of radius. If no second epoch data
are obtained then the observing time already invested in the first
epoch will have been wasted.

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.

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**************** 06*************** 06
FGS REacq**************** 08*************** 08
OBAD with Maneuver* *** * 28*************** 28

SIGNIFICANT EVENTS: (None)