HUBBLE
SPACE TELESCOPE - Continuing to collect World Class Science
DAILY
REPORT # 4586
PERIOD
COVERED: UT April 09, 2008 (DOY 100)
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 i
mages.
Each observation will need its own CRMAP, as different SAA
passages
leave different imprints on the NICMOS detectors.
NIC2
11150
Beta
Pic Polarimetry with NICMOS
Debris
disk stars host transient dust grains that comprise a collisional
cascade
with sizes ranging from planetesimals to the sub-micron. In
addition
to the gravity of the host star and any planets present, these
grains
are subject to size-dependent non-gravitational forces, e.g.,
corpuscular
drag and radiation pressure. When a steep spectrum of grain
sizes
prevails, such as the Dohnanyi distribution, scattered light
images
preferentially trace grains with dimensionless size parameter of
order
unity. Thus images in scattered starlight provide unique windows
on
the balance of forces acting on grains at a specific size. Therefore,
in
an A star system such as beta Pic, the near-IR is dominated by grains
close
to the blow out size and therefore NICMOS traces dust on
hyperbolic
orbits.
Scattering
is fundamentally polarization sensitive, and measurements
that
record intensity literally see only half the picture. If linear
polarization
is measured then the elements of the complex scattering
matrix
can be reconstructed. These matrix elements provide fundamental
constraints
on the size, composition and structure of the scatterers.
Notably,
polarimetry can be used to break the degeneracy between
scattering
asymmetry, g, and the radial dust gradient, which are
otherwise
covariant in an edge-on disk. Thus, we can use polarimetry to
localize
the parent bodies in the beta Pic disk.
In
beta Pic, dust is thought to originate mainly from the sublimation of
cometary
bodies near periastron. The irradiation of cometary material
leads
to sublimation and photodissociation of ices forming porous grains
consisting
of a matrix of refractory material. Such grains have a
characteristic
scattering signature in polarized light that can be
distinguished
from compact grains that arise from collisional erosion of
asteroidal
material.
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 5.7<z<7 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 (z>6) 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 z>6
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 (z<26 mag (AB)) Ly-alpha emitters
(LAEs)
and Lyman-break galaxies (LBGs) at 5.7<z<7 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 z>6 as suggested recently?
(2)
Is Ly-alpha emission systematically suppressed at z>6 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 z>6 galaxies?
WFPC2
11099
A
"silver bullet" for the sources of reionization
Recent
discoveries of z>6 galaxies have given us the first glimpse of
the
Universe shortly after the era of reionization. The questions arose
whether
these first galaxies can be made responsible for the
reionization
process, and how long did it last. Neither observations nor
theory
provide a clean answer. In particular observations give results
that
are barely mutually consistent and need to be further tested.
Observing
high redshift (z>7) sources is in general difficult, mostly
due
to the high luminosity distance to these objects, and partly due to
the
lower expected stellar masses compared to objects at moderate
redshifts.
We
propose to use one of the most massive, merging cluster 1E0657-56
(z=0.295)
as a cosmic telescopes to efficiently probe the high-redshift
universe.
The gravitational potential well of this cluster provides
several
magnitudes of magnification, enabling study of intrinsically
lower
luminosity galaxies.As we discuss in the proposal, due to its
highly
elongated mass distribution and ideal redshift the bullet cluster
is
a prime candidate for this study. We propose deep NICMOS and WFPC2
observations;
with much reduced observing time compared to e.g. NICMOS
UDF
we expect an order of magnitude more (~5 candidates) z>7 objects.
They
will also likely be multiply imaged, and since the geometry of
images
depends upon the redshift, we will be able to confirm their
nature,
thereby not requiring (often prohibitive at these magnitudes)
spectroscopic
follow-up. This will enable us to count high-redshift
sources
and constrain their luminosity function; a task made possible
with
the help of gravitational lensing even in the pre-JWST era.
WFPC2
11113
Binaries
in the Kuiper Belt: Probes of Solar System Formation and
Evolution
The
discovery of binaries in the Kuiper Belt and related small body
populations
is powering a revolutionary step forward in the study of
this
remote region. Three quarters of the known binaries in the Kuiper
Belt
have been discovered with HST, most by our snapshot surveys. The
statistics
derived from this work are beginning to yield surprising and
unexpected
results. We have found a strong concentration of binaries
among
low-inclination Classicals, a possible size cutoff to binaries
among
the Centaurs, an apparent preference for nearly equal mass
binaries,
and a strong increase in the number of binaries at small
separations.
We propose to continue this successful program in Cycle 16;
we
expect to discover at least 13 new binary systems, targeted to
subgroups
where these discoveries can have the greatest impact.
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
05
05
FGS
REacq
09
09
OBAD
with Maneuver
28
28
SIGNIFICANT
EVENTS: (None)