Notice:
Due to the conversion of some ACS WFC or HRC observations into
WFPC2,
or NICMOS observations after the loss of ACS CCD science
capability
in January, there may be an occasional discrepancy between a
proposal's
listed (and correct) instrument usage and the abstract that
follows
it.
HUBBLE
SPACE TELESCOPE - Continuing to collect World Class Science
DAILY
REPORT # 4474
PERIOD
COVERED: UT October 23, 2007 (DOY 296)
OBSERVATIONS
SCHEDULED
WFPC2
10795
The
Largest Galaxies in the Local Universe: New Light on Disk Galaxy
Formation?
In
the standard scenario of disk galaxy formation in a hierarchical
Universe,
large disks form late via the accretion of either hot or cold
gas.
Direct observational evidence for such late accretion-driven disk
formation
has not been forthcoming. In this proposal, we describe the
discovery
of a rare new type of galaxy that may be examples of massive
disks
in the process of assembly. We have identified a sample of three
such
galaxies selected from the SDSS DR4. They are extremely large
{diameters
over 100 kpc} and highly luminous systems with amorphous
structures
{no obvious spiral arms or bulges}. They are larger than the
largest
normal spirals in the survey, and have significantly bluer
colors,
lower metallicities, lower dust extinctions, higher UV
luminosities
and higher total star formation rates than the most massive
ordinary
spirals. We request HST images in the rest-frame near-UV and
red
to provide detailed maps of the underlying structure of these
galaxies
as well as the distribution of the young stars. The
interstellar
medium of these galaxies is evidently quite different from
that
of normal large spirals and starburst galaxies and they may be
experiencing
a different mode of star formation. We believe they are
worthy
of further investigation with the high-resolution imaging
capabilities
of HST.
FGS
11211
An
Astrometric Calibration of Population II Distance Indicators
In
2002 HST produced a highly precise parallax for RR Lyrae. That
measurement
resulted in an absolute magnitude, M{V}= 0.61+/-0.11, a
useful
result, judged by the over ten refereed citations each year
since.
It is, however, unsatisfactory to have the direct,
parallax-based,
distance scale of Population II variables based on a
single
star. We propose, therefore, to obtain the parallaxes of four
additional
RR Lyrae stars and two Population II Cepheids, or
stars.
The Population II Cepheids lie with the RR Lyrae stars on a
common
K-band Period-Luminosity relation. Using these parallaxes to
inform
that relationship, we anticipate a zero-point error of 0.04
magnitude.
This result should greatly strengthen confidence in the
Population
II distance scale and increase our understanding of RR Lyrae
star
and Pop II Cepheid astrophysics.
NIC1/NIC2/NIC3
8794
NICMOS
Post-SAA calibration - CR Persistence Part 5
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 DARKs. 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.
NIC3
11082
NICMOS
Imaging of GOODS: Probing the Evolution of the Earliest Massive
Galaxies,
Galaxies Beyond Reionization, and the High Redshift Obscured
Universe
(uses
ACS/SBC and WFPC2)
Deep
near-infrared imaging provides the only avenue towards
understanding
a host of astrophysical problems, including: finding
galaxies
and AGN at z > 7, the evolution of the most massive galaxies,
the
triggering of star formation in dusty galaxies, and revealing
properties
of obscured AGN. As such, we propose to observe 60 selected
areas
of the GOODS North and South fields with NICMOS Camera 3 in the
F160W
band pointed at known massive M > 10^11 M_0 galaxies at z > 2
discovered
through deep Spitzer imaging. The depth we will reach {26.5
AB
at 5 sigma} in H_160 allows us to study the internal properties of
these
galaxies, including their sizes and morphologies, and to
understand
how scaling relations such as the Kormendy relationship
evolved.
Although NIC3 is out of focus and undersampled, it is currently
our
best opportunity to study these galaxies, while also sampling enough
area
to perform a general NIR survey 1/3 the size of an ACS GOODS field.
These
data will be a significant resource, invaluable for many other
science
goals, including discovering high redshift galaxies at z > 7,
the
evolution of galaxies onto the Hubble sequence, as well as examining
obscured
AGN and dusty star formation at z > 1.5. The GOODS fields are
the
natural location for HST to perform a deep NICMOS imaging program,
as
extensive data from space and ground based observatories such as
Chandra,
GALEX, Spitzer, NOAO, Keck, Subaru, VLT, JCMT, and the VLA are
currently
available for these regions. Deep high-resolution
near-infrared
observations are the one missing ingredient to this
survey,
filling in an important gap to create the deepest, largest, and
most
uniform data set for studying the faint and distant universe. The
importance
of these images will increase with time as new facilities
come
on line, most notably WFC3 and ALMA, and for the planning of future
JWST
observations.
WFPC2
11126
Resolving
the Smallest Galaxies
An
order of magnitude more dwarf galaxies are expected to inhabit the
Local
Group, based on currently accepted galaxy formation models, than
have
been observed. This discrepancy has been noted in environments
ranging
from the field to rich clusters, with evidence emerging that
lower
density regions contain fewer dwarfs per giant than higher density
regions,
in further contrast to model predictions. One possible
explanation
for this involves the effects of reionization on the forming
galaxies
and naturally explains both the dearth of dwarf galaxies and
the
apparent environmental dependence. However, before such theories can
be
fully tested, we require a better understanding of the distribution
of
dwarf galaxies. Currently, there is no complete census of the
faintest
dwarf galaxies in any environment. The discovery of the
smallest
and faintest dwarfs is hampered by the limitations in detecting
such
faint and low surface brightness galaxies, and this is compounded
by
the great difficulty in determining accurate distances to, or
ascertaining
group membership for, such faint objects. The M81 group
provides
a unique means for establishing membership for galaxies in a
low
density region complete to magnitudes as faint as M_R ~ -7. With a
distance
modulus of 27.8, the tip of the red giant branch {TRGB} appears
at
I ~ 24, just within the reach of ground based surveys. We currently
have
surveyed a 30 square degree region around M81 with the
CFHT/Megacam.
From these images we have detected 15 new candidate dwarf
galaxies.
We propose to use the HST with WFPC2 to image these 15
galaxies
in F606W and F814W bands in order to construct a
color-magnitude
diagram down to I = 25.5 from which to measure accurate
TRGB
distances to these candidate galaxies and determine star formation
and
metallicity histories. The overall project will provide a survey of
the
dwarf galaxies in the M81 group environment with unprecedented
completeness
to a limit of M_R < -7.
WFPC2
11194
Beyond
the Bullet: Direct Detection of Dark Matter in Merging Galaxy
Clusters
Our
comparison of the distribution of baryons {stars and gas} and mass
{from
weak lensing} in the "Bullet" Cluster has recently yielded
concrete
evidence for dark matter independent of basic assumptions
regarding
the nature of the gravitational force. The one incomplete
aspect
of the argument relates to potential, although highly unlikely,
coincidences
{special alignments along the line of sight, and/or
fortuitous
canceling in non-standard gravitational models} that can
always
be invoked against results derived from the study of one object.
Therefore,
we propose to complete this line of investigations by
increasing
the size of our sample with observations of an additional
cluster.
Here we propose to obtain HST WFPC2 imaging mosaics around the
cores
of the cluster to detect at high significance if the weak
gravitational
lensing mass peaks are routinely displaced from the X-ray
plasma
clouds and aligned with the galaxy concentrations in interacting
clusters.
With a relatively modest allocation of time, we seek to
complete
a significant step toward the eventual resolution of the dark
matter
question.
FLIGHT
OPERATIONS SUMMARY:
Significant
Spacecraft Anomalies: (The following are preliminary reports
of
potential non-nominal performance that will be investigated.)
HSTARS:
11036 – ACS 779 Fold Mechanism Move was
Blocked
ACS 779 Status Buffer Message
("Fold Mechanism Move was Blocked") was
received following the failure of the REacq(2,1,2) at
296/10:41:59
(HSTAR 11035), which caused the Take Data Flag to be down
when the Fold
mechanism move to the SBC position was commanded. Flight
Software Error
Count (JERRCNT) incremented to 31. OPS Note 1645-3 executed
to change
JERRCNT limit to 31.
11035
- REacq(2,1,2) failed to RGA hold during LOS
REacq(2,1,2) failed to RGA control during LOS. Upon
acquisition of
signal at 296/11:07:19 the vehicle was not guiding and there
were no
flags set. Two ACS 779 status buffer messages indicating that
take data
flag was down. OBAD prior to the REacq had an RSS value of 5.69
arcseconds.
COMPLETED
OPS REQUEST: (None)
COMPLETED
OPS NOTES:
1645-3
- Change JERRCNT Limit @296/1142z
SCHEDULED
SUCCESSFUL
FGS
GSacq
08
08
FGS
REacq
07
06
OBAD
with Maneuver 30
30
SIGNIFICANT
EVENTS: (None)