Daily # 3986

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 3986

PERIOD COVERED: UT November 10, 2005 (DOY 314)

OBSERVATIONS SCHEDULED

ACS/HRC 10556

Neutral Gas at Redshift z=0.5

Damped Lyman-alpha systems {DLAs} are used to track the bulk of the
neutral hydrogen gas in the Universe. Prior to HST UV spectroscopy,
they could only be studied from the ground at redshifts z1.65.
However, HST has now permitted us to discover 41 DLAs at z1.65 in our
previous surveys. Followup studies of these systems are providing a
wealth of information about the evolution of the neutral gas phase
component of the Universe. But one problem is that these 41
low-redshift systems are spread over a wide range of redshifts
spanning nearly 70% of the age of the Universe. Consequently, past
surveys for low-redshift DLAs have not been able to offer very good
precision in any small redshift regime. Here we propose an ACS-HRC-
PR200L spectroscopic survey in the redshift interval z=[0.37, 0.7]
which we estimate will permit us to discover another 41 DLAs. This
will not only allow us to double the number of low-redshift DLAs, but
it will also provide a relatively high-precision regime in the
low-redshift Universe that can be used to anchor evolutionary studies.
Fortunately DLAs have high absorption equivalent width, so
ACS-HRC-PR200L has high-enough resoultion to perform this proposed
MgII-selected DLA survey.

ACS/WFC 10523

The Halo Shape and Metallicity of Massive Spiral Galaxies

We propose to resolve the stellar populations of the halos of seven
nearby, massive disk galaxies using a SNAP survey with WFC/ACS. These
observations will provide star counts and color-magnitude diagrams 2-3
magnitudes below the tip of the Red Giant Branch along the two
principal axes and one intermediate axis of each galaxy. We will
measure the metallicity distribution functions and stellar density
profiles from star counts down to very low average surface
brightnesses, equivalent to ~31 V-mag per square arcsec. This proposal
will create a unique sampling of galaxy halo properties, as our
targets cover a range in galaxy mass, luminosity, inclination, and
morphology. As function of these galaxy properties this survey will
provide:- the first systematic measurement of radial light profiles
and axial ratios of the diffuse stellar halos and outer disks of
spiral galaxies- a comprehensive analysis of halo metallicity
distributions as function of galaxy type and position within the
galaxy- an unprecedented study of the stellar metallicity and age
distribution in the outer disk regions where the disk truncations
occur- the first comparative study of globular clusters and their
field stellar populations We will use these fossil records of the
galaxy assembly process to test halo formation models within the
hierarchical galaxy formation scheme.

ACS/WFC 10586

The Rosetta Stone without a Distance: Hunting for Cepheids in the
Primordial Galaxy I Zw 18

The Blue Compact Dwarf galaxy I Zw 18 is one of the most intriguing
objects in the Local Universe. It has the lowest nebular metallicity
of all known galaxies {Z=1/32 solar}. It has long been regarded as a
possible example of a galaxy undergoing its first burst of star
formation. However, its real evolutionary state continues to be
controversial. The WFPC2 and NICMOS detection of AGB stars by our
group and others suggested the presence of an underlying older
population. However, deeper ACS observations by Izotov & Thuan {2004}
recently failed to detect the signature of RGB stars. This was
interpreted as confirmation that I Zw 18 is in fact a galaxy "in
formation", a local analog of primordial galaxies in the distant
Universe. This result was widely reported in the international news
media. However, an alternative possibility is that I Zw 18 is somewhat
further away than previously believed, so that Red Giant Branch stars
were too faint to detect. Quoted distances in the literature have
ranged from 10 to 20 Mpc. We intend to resolve this controversy by
direct determination of the distance to 1 Mpc accuracy using Cepheids.
For this we request 12 visits of two orbits each, to execute at
carefully planned intervals. We will obtain V and I band ACS/WFC
photometry in each visit. The new data will be combined with archival
data, but we show that the archival data by themselves are
insufficient to achieve our science goals. The distance will allow us
to place I Zw 18 into its proper place in the evolutionary sequence of
galaxy formation.

ACS/WFC 10596

AGNs with Intermediate-mass Black Holes: A Test of the Black
Hole-Bulge Paradigm

The recent progress in the study of central black holes in galactic
nuclei has led to a general consensus that supermassive {10^6-10^9
solar mass} black holes are closely connected with the formation and
evolutionary history of large galaxies, especially their bulge
component. Two outstanding issues, however, remain unresolved. Can
central black holes form in the absence of a bulge? And does the mass
function of central black holes extend below 10^6 solar masses?
Intermediate-mass black holes {10^4-10^6 solar masses}, if they exist,
may offer important clues to the nature of the seeds of supermassive
black holes. In a first systematic search using the Sloan Digital Sky
Survey, we have recently discovered 19 Type 1 AGNs with candidate
intermediate-mass black holes that reside in low-luminosity,
presumably late-type host galaxies. Follow-up observations with Keck
indicate that these objects obey the low-mass extension of the
well-known correlation between black hole mass and bulge stellar
velocity dispersion. However, very little is known about the host
galaxies themselves, including the crucial question of whether they
have bulges or not. We propose to obtain ACS/WFC images of this unique
sample of AGNs in order to investigate the detailed structural
properties of the host galaxies. We are particularly keen to determine
whether the hosts contain bulges, and if so, where they lie on the
fundamental plane of spheroids compared to the bulges of supermassive
black holes. We will also be able to measure an accurate optical
luminosity for the AGN, which is an essential ingredient to improve
the current mass estimates.

ACS/WFC 10626

A Snapshot Survey of Brightest Cluster Galaxies and Strong Lensing to
z = 0.9

We propose an ACS/WFC snapshot survey of the cores of 150 rich galaxy
clusters at 0.3 z 0.9 from the Red Sequence Cluster Survey {RCS}.
An examination of the galaxian light in the brightest cluster
galaxies, coupled with a statistical analysis of the strong-lensing
properties of the sample, will allow us to contrain the evolution of
both the baryonic and dark mass in cluster cores, over an
unprecedented redshift range and sample size. In detail, we will use
the high- resolution ACS images to measure the metric {10 kpc/h}
luminosity and morphological disturbances around the brightest
clusters galaxies, in order to calibrate their accretion history in
comparison to recent detailed simulations of structure formation in
cluster cores. These images will also yield a well-defined sample of
arcs formed by strong lensing by these clusters; the frequency and
detailed distribution {size, multiplicity, redshifts} of these strong
lens systems sets strong constraints on the total mass content {and
its structure} in the centers of the clusters. These data will also be
invaluable in the study of the morphological evolution and properties
of cluster galaxies over a significant redshift range. These analyses
will be supported by extensive ongoing optical and near-infrared
imaging, and optical spectroscopy at Magellan, VLT and Gemini
telescopes, as well as host of smaller facilities.

ACS/WFC/WFPC2 10585

NGC 4449: a Testbed for Starbursts in the Low- and High-Redshift
Universe

We will obtain deep ACS/WFC broad-band imaging in F435W, F555W, and
F814W of the Magellanic irregular galaxy NGC 4449 in order to infer
the properties of the resolved {young and old} stellar population,
compare the current strong star-formation activity to that at earlier
epochs, trace the major episodes of star formation over cosmic time,
and relate them to the past history of interaction/merging of this
galaxy. NGC 4449 is one of the closest { 5 Mpc} global starbursts
with a widespread star-formation activity that could have been
triggered by interaction or accretion. It is, therefore, the perfect
laboratory where to address issues related to star formation in
extreme environments and investigate processes connected to the
formation and evolution of galaxies in the early universe. At a
distance of 4.2 Mpc, the stellar content in NGC 4449 can easily be
resolved with HST. Yet, up to date no comprehensive dataset has been
collected that is suited to infer a global star-formation history of
the galaxy and to better understand its evolution. ACS/WFC provides
the angular resolution and sensitivity to easily reach magnitude
limits necessary for the detection of individual stars at the tip of
the red giant branch {i.e., with ages from 1 Gyr up to 12 Gyr} with
the required accuracy. A mosaic of 2 pointings along the major axis
will give a good coverage of the galaxy and will allow us to infer a
star- formation history unbiased by local properties of peculiar
regions. Narrow-band imaging in F658N {Halpha} will provide a map of
the ionized gas. Finally, WFPC2 parallel observations in F555W and
F814W will allow to search deep in the HI halo of NGC 4449 for
evidence of stars belonging to tidal streams. Our investigation of NGC
4449 will benefit from the wealth of observations already available
over almost the whole electromagnetic spectrum and will be crucial in
better understanding how starbursts can be influenced by merging
phenonema in both the low- and high-redshift universe.

FGS 10432

Precise Distances to Nearby Planetary Nebulae

We propose to carry out astrometry with the FGS to obtain accurate and
precise distances to four nearby planetary nebulae. In 1992, Cahn et
al. noted that ``The distances to Galactic planetary nebulae remain a
serious, if not THE most serious, problem in the field, despite
decades of study.'' Twelve years later, the same statement still
applies. Because the distances to planetary nebulae are so uncertain,
our understanding of their masses, luminosities, scale height, birth
rate, and evolutionary state is severely limited. To help remedy this
problem, HST astrometry can guarantee parallaxes with half the error
of any other available approach. These data, when combined with
parallax measurements from the USNO, will improve distance
measurements by more than a factor of two, producing more accurate
distances with uncertainties that are of the order of ~6%. Lastly,
most planetary nebula distance scales in the literature are
statistical. They require several anchor points of known distance in
order to calibrate their zero point. Our program will provide "gold
standard" anchor points by the end of 2006, a decade before any
anticipated results from future space astrometry missions.

FGS 10480

Parallaxes of Extreme Halo Subgiants: Calibrating Globular Cluster
Distances and the Ages of the Oldest

The ages of the oldest stars are a key constraint on the evolution of
our Galaxy, the history of star formation, and cosmological models.
These ages are usually determined from globular clusters. However, it
is alternatively possible to determine ages of extreme Population II
subgiants in the solar neighborhood based on trigonometric parallaxes,
without any recourse to clusters. This approach completely avoids the
vexing issues of cluster distances, reddenings, and chemical
compositions. There are 3 known nearby, extremely metal-deficient Pop
II subgiants with Hipparcos parallax errors of 6-11% which are
available for such age determinations. At present, based on the latest
isochrones, the derived ages of these stars {HD 84937, HD 132475, and
HD 140283} are all close to 14 Gyr, uncomfortably close to or higher
than current estimates of the age of the universe. However, the errors
in the Hipparcos parallaxes imply uncertainties of at least 2 Gyr in
the ages of the 3 stars. We propose to measure parallaxes of these
three Pop II subgiants using HST's Fine Guidance Sensor 1R. We expect
to reduce the Hipparcos parallax error bars by factors of 5-6,
providing the most stringent test yet of current theoretical stellar
models of Pop II stars and pushing the age uncertainties to below 0.5
Gyr. These data will also provide a major new constraint on the
distance scale of globular clusters, with wide implications for
stellar evolution and the calibration of Pop II standard candles. The
ages of the oldest stars are a key constraint on the evolution of our
Galaxy, the history of star formation, and cosmological models. These
ages are usually determined from globular clusters. However, it is
alternatively possible to determine ages of extreme Population II
subgiants in the solar neighborhood based on trigonometric parallaxes,
without any recourse to clusters. This approach completely avoids the
vexing issues of cluster distances, reddenings, and chemical
compositions. There are 3 known nearby, extremely metal- deficient Pop
II subgiants with Hipparcos parallax errors of 6-11% which are
available for such age determinations. At present, based on the latest
isochrones, the derived ages of these stars {HD 84937, HD 132475, and
HD 140283} are all close to 14 Gyr, uncomfortably close to or higher
than current estimates of the age of the universe. However, the errors
in the Hipparcos parallaxes imply uncertainties of at least 2 Gyr in
the ages of the 3 stars. We propose to measure parallaxes of these
three Pop II subgiants using HST's Fine Guidance Sensor 1R. We expect
to reduce the Hipparcos parallax error bars by factors of 5-6,
providing the most stringent test yet of current theoretical stellar
models of Pop II stars and pushing the age uncertainties to below 0.5
Gyr. These data will also provide a major new constraint on the
distance scale of globular clusters, with wide implications for
stellar evolution and the calibration of Pop II standard candles.

FGS 10610

Astrometric Masses of Extrasolar Planets and Brown Dwarfs

We propose observations with HST/FGS to estimate the astrometric
elements {perturbation orbit semi-major axis and inclination} of
extra-solar planets orbiting six stars. These companions were
originally detected by radial velocity techniques. We have
demonstrated that FGS astrometry of even a short segment of reflex
motion, when combined with extensive radial velocity information, can
yield useful inclination information {McArthur et al. 2004}, allowing
us to determine companion masses. Extrasolar planet masses assist in
two ongoing research frontiers. First, they provide useful boundary
conditions for models of planetary formation and evolution of
planetary systems. Second, knowing that a star in fact has a plantary
mass companion, increases the value of that system to future
extrasolar planet observation missions such as SIM PlanetQuest, TPF,
and GAIA.

NIC1/NIC2/NIC3 10380

Cycle 13 NICMOS dark current, shading profile, and read noise
monitoring program

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 13. This proposal is an essentially unchanged
continuation of PID 9993 which cover the duration of Cycle 12.

NIC2 10717

Quasar Bolometri Luminosity and Spectral Energy Distributions from
Radio to X-ray

We propose to build the best SED data set spanning from radio to X-ray
wavelengths for 35 quasars. We will use new and archival mid-to-far IR
data from Spitzer as well as other existing multi-wavelength data. We
have unique quasi-simultaneous FUV/UV-optical spectra for our sample,
greatly reducing the uncertainty due to quasar intrinsic time
variability in the UV bump. We will derive accurate bolometric
luminosities for the sample and seek to establish a more reliable and
accurate way to obtain the bolometric luminosity of quasars from their
partial SEDs and/or spectral properties. We will also apply
multivariate analysis to the SEDs, study the quasar multi-wavelength
spectral properties and their dependence on the overall SEDs, and thus
better understand the physical processes quasars employ emitting
across the entire electromagnetic spectrum. HST NICMOS observations
will be used to remove host galaxy contamination from the quasar SEDs.
This is a joint Spitzer-HST project.

NICMOS 8790

NICMOS Post-SAA calibration - CR Persistence Part 1.

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.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.)

HSTARS:

10012 - GSAcq(2,1,1) requires multiple attempts to achieve CT-DV @
307/05:01:59z GSAcq(2,1,1) required six attempts to achieve CT-DV on
FGS2. The acquisition was ultimately successful.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 10 10
FGS REacq 05 05
OBAD with Maneuver 26 26

SIGNIFICANT EVENTS: (None)