Daily Report #4586
Cooper, Joe
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 images. 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)