HUBBLE
SPACE TELESCOPE - Continuing to collect World Class Science
DAILY
REPORT # 4533
PERIOD
COVERED: UT January 24, 2007 (DOY 024)
OBSERVATIONS
SCHEDULED
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
10889
The
Nature of the Halos and Thick Disks of Spiral Galaxies
We
propose to resolve the extra-planar stellar populations of the thick
disks
and halos of seven nearby, massive, edge-on galaxies using ACS,
NICMOS,
and WFPC2 in parallel. These observations will provide accurate
star
counts and color-magnitude diagrams 1.5 magnitudes below the tip of
the
Red Giant Branch sampled 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 ~32 V-mag
per
square arcsec. These observations will provide the definitive HST
study
of extra-planar stellar populations of spiral galaxies. Our
targets
cover a range in galaxy mass, luminosity, and morphology and as
function
of these galaxy properties we will provide: - The first
systematic
study of the radial and isophotal shapes of the diffuse
stellar
halos of spiral galaxies - The most detailed comparative study
to
date of thick disk morphologies and stellar populations - A
comprehensive
analysis of halo and thick disk metallicity distributions
as
a function of galaxy type and position within the galaxy. - A
sensitive
search for tidal streams - The first opportunity to directly
relate
globular cluster systems to their field stellar population We
will
use these fossil records of the galaxy assembly process preserved
in
the old stellar populations to test halo and thick disk formation
models
within the hierarchical galaxy formation scheme. We will test
LambdaCDM
predictions on sub-galactic scales, where it is difficult to
test
using CMB and galaxy redshift surveys, and where it faces its most
serious
difficulties.
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.
NIC3/WFPC2
11195
Morphologies
of the Most Extreme High-Redshift Mid-IR-luminous Galaxies
II:
The `Bump' Sources
The
formative phase of some of the most massive galaxies may be
extremely
luminous, characterized by intense star- and AGN-formation.
Till
now, few such galaxies have been unambiguously identified at high
redshift,
and thus far we have been restricted to studying the
low-redshift
ultraluminous infrared galaxies as possible analogs. We
have
recently discovered a sample of objects which may indeed represent
this
early phase in galaxy formation, and are undertaking an extensive
multiwavelength
study of this population. These objects are optically
extremely
faint {R>26} but nevertheless bright at mid-infrared
wavelengths
{F[24um] > 0.5 mJy}. Mid-infrared spectroscopy with
Spitzer/IRS
reveals that they have redshifts z~2, implying luminosities
~1E13
Lsun. Their mid-IR SEDs fall into two broad, perhaps overlapping,
categories.
Sources with brighter F[24um] exhibit power-law SEDs and SiO
absorption
features in their mid-IR spectra characteristic of AGN,
whereas
those with fainter F[24um] show a "bump" characteristic of the
redshifted
1.6um peak from a stellar population, and PAH emission
characteristic
of starformation. We have begun obtaining HST images of
the
brighter sources in Cycle 15 to obtain identifications and determine
kpc-scale
morphologies for these galaxies. Here, we aim to target the
second
class {the "bump" sources} with the goal of determining if these
constitute
morphologically different objects, or simply a "low-AGN"
state
of the brighter class. The proposed observations will help us
determine
whether these objects are merging systems, massive obscured
starbursts
{with obscuration on kpc scales!} or very reddened {locally
obscured}
AGN hosted by intrinsically low-luminosity galaxies.
S/C
11163
Accreting
Pulsating White Dwarfs in Cataclysmic Variables
Recent
ground-based observations have increased the number of known
pulsating
white dwarfs in close binaries with active mass transfer
{cataclysmic
variables} from 5 to 11 systems. Our past Cycles 8 and 11
STIS
observations of the first 2 known, followed by our Cycle 13 SBC
observations
of the next 3 discovered, revealed the clear presence of
the
white dwarf and increased amplitude of the pulsations in the UV
compared
to the optical. The temperatures derived from the UV spectra
show
4 systems are much hotter than non-interacting pulsating white
dwarfs.
A larger sample is needed to sort out the nature of the
instability
strip in accreting pulsators i.e. whether effects of
composition
and rotation due to accretion result in a well- defined
instability
strip as a function of Teff.
WFPC2/NIC2
10890
Morphologies
of the Most Extreme High-Redshift Mid-IR-Luminous Galaxies
The
formative phase of the most massive galaxies may be extremely
luminous,
characterized by intense star- and AGN-formation. Till now,
few
such galaxies have been unambiguously identified at high redshift,
restricting
us to the study of low-redshift ultraluminous infrared
galaxies
as possible analogs. We have recently discovered a sample of
objects
which may indeed represent this early phase in galaxy formation,
and
are undertaking an extensive multiwavelength study of this
population.
These objects are bright at mid-IR wavelengths
{F[24um]>0.8mJy},
but deep ground based imaging suggests extremely faint
{and
in some cases extended} optical counterparts {R~24-27}. Deep K-band
images
show barely resolved galaxies. Mid-infrared spectroscopy with
Spitzer/IRS
reveals that they have redshifts z ~ 2-2.5, suggesting
bolometric
luminosities ~10^{13-14}Lsun! We propose to obtain deep ACS
F814W
and NIC2 F160W images of these sources and their environs in order
to
determine kpc-scale morphologies and surface photometry for these
galaxies.
The proposed observations will help us determine whether these
extreme
objects are merging systems, massive obscured starbursts {with
obscuration
on kpc scales!} or very reddened {locally obscured} AGN
hosted
by intrinsically low-luminosity galaxies.
WFPC2
11038
Narrow
Band and Ramp Filter Closeout
These
observations are to improve calibration of narrow band and ramp
filters.
We also test for changes in the filter properties during
WFPC2's
14 years on-board HST.
WFPC2
11128
Time
Scales Of Bulge Formation In Nearby Galaxies
Traditionally,
bulges are thought to fit well into galaxy formation
models
of hierarchical merging. However, it is now becoming well
established
that many bulges formed through internal, secular evolution
of
the disk rather than through mergers. We call these objects
pseudobulges.
Much is still unknown about pseudobulges, the most
pressing
questions being: How, exactly, do they build up their mass? How
long
does it take? And, how many exist? We are after an answer to these
questions.
If pseudobulges form and evolve over longer periods than the
time
between mergers, then a significant population of pseudobulges is
hard
to explain within current galaxy formation theories. A pseudobulge
indicates
that a galaxy has most likely not undergone a major merger
since
the formation of the disk. The ages of pseudobulges give us an
estimate
for the time scale of this quiescent evolution. We propose to
use
24 orbits of HST time to complete UBVIH imaging on a sample of 33
nearby
galaxies that we have observed with Spitzer in the mid-IR. These
data
will be used to measure spatially resolved stellar population
parameters
{mean stellar age, metallicity, and star formation history};
comparing
ages to star formation rates allows us to accurately constrain
the
time scale of pseudobulge formation. Our sample of bulges includes
both
pseudo- and classical bulges, and evenly samples barred and
unbarred
galaxies. Most of our sample is imaged, 13 have complete UBVIH
coverage;
we merely ask to complete missing observations so that we may
construct
a uniform sample for studying bulge formation. We also wish to
compare
the stellar population parameters to a variety of bulge and
global
galaxy properties including star formation rates, dynamics,
internal
bulge morphology, structure from bulge-disk decompositions, and
gas
content. Much of this data set is already or is being assembled.
This
will allow us to derive methods of pseudobulge identification that
can
be used to accurately count pseudobulges in large surveys. Aside
from
our own science goals, we will present this broad set of data to
the
community. Thus, we waive proprietary periods for all observations.
WFPC2
11289
SL2S:
The Strong Lensing Legacy Survey
Recent
systematic surveys of strong galaxy-galaxy lenses {CLASS, SLACS,
GOODS,
etc.} are producing spectacular results for galaxy masses roughly
below
a transition mass M~10^13 Mo. The observed lens properties and
their
evolution up to z~0.2, consistent with numerical simulations, can
be
described by isothermal elliptical potentials. In contrast, modeling
of
giant arcs in X-ray luminous clusters {halo masses M >~10^13 Mo}
favors
NFW mass profiles, suggesting that dark matter halos are not
significantly
affected by baryon cooling. Until recently, lensing
surveys
were neither deep nor extended enough to probe the intermediate
mass
density regime, which is fundamental for understanding the assembly
of
structures. The CFHT Legacy Survey now covers 125 square degrees, and
thus
offers a large reservoir of strong lenses probing a large range of
mass
densities up to z~1. We have extracted a list of 150 strong lenses
using
the most recent CFHTLS data release via automated procedures.
Following
our first SNAPSHOT proposal in cycle 15, we propose to
continue
the Hubble follow-up targeting a larger list of 130 lensing
candidates.
These are intermediate mass range candidates {between
galaxies
and clusters} that are selected in the redshift range of 0.2-1
with
no a priori X-ray selection. The HST resolution is necessary for
confirming
the lensing candidates, accurate modeling of the lenses, and
probing
the total mass concentration in galaxy groups up to z~1 with the
largest
unbiased sample available to date.
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
07
07
OBAD
with Maneuver 26
26
SIGNIFICANT
EVENTS: (None)