HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT # 4301
PERIOD COVERED: UT February 15, 2007 (DOY 046)
OBSERVATIONS SCHEDULED
WFPC2 10520
Resolving the Complex Star Formation History of the Leo I
Dwarf
Spheroidal Galaxy
Determining the star formation histories {SFHs} and
chemical evolution
of nearby galaxies gives us powerful constrains on the
physical
processes that regulate galaxy evolution. The SFHs can be
measured most
accurately by comparing the observed densities of stars in
color-magnitude diagrams {CMDs} to predictions from
stellar evolutionary
models. WFPC2 imaging of the Leo I dSph shows it is unique
because its
stellar population is relatively young. Approximately 68%
of its stars
formed between 1 and 7 Gyr ago and only 12% of its stars
formed >~ 10
Gyr ago. We propose to vastly improve the derived SFH of
Leo I by
exploiting ACS/WFC's higher quantum efficiency at bluer
wavelengths,
higher spatial resolution, and larger field-of-view. The
figure of merit
for our proposed observations, defined as the age
resolution times the
number of stars detected, will be a factor of 12 higher
than existing
WFPC2 observations. To surmount the degeneracy of age and
metallicity in
the CMD, we have independently measured the metallicity
distribution of
its stars using spectroscopy. Simultaneously modeling the
metallicity
distribution and CMD, we will firmly constrain the
evolution of the Leo
I dSph, a unique example of an isolated dwarf galaxy that
has not been
influenced by interactions with the Milky Way or M31.
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 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.
NIC3 11082
NICMOS Imaging of GOODS: Probing the Evolution of the
Earliest Massive
Galaxies, Galaxies Beyond
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 10871
Observations of the Galilean Satellites in Support of the
New Horizons
Flyby
On February 28 2007 the New Horizons {NH} spacecraft will
fly by Jupiter
on its way to Pluto, and will conduct an extensive series
of
observations of the Jupiter system, including the Galilean
satellites.
We propose HST observations to support and complement the
New Horizons
observations in four ways: 1} Determine the distribution
and variability
of Io's plumes in the two weeks before NH closest
approach, to look for
correlations with Io- derived dust streams that may be
detected by New
Horizons, to understand the origin of the dust streams; 2}
Imaging of
SO2 and S2 gas absorption in Io's plumes in Jupiter
transit, which
cannot be done by NH; 3} Color imaging of Io's surface to
determine the
effects of the plumes and volcanos seen by New Horizons on
the surface-
New Horizons cannot image the sunlit surface in color due
to saturation;
4} Imaging of far-UV auroral emissions from the
atmospheres of Io,
Europa, and Ganymede in Jupiter eclipse, near-
simultaneously with
disk-integrated NH UV spectra, to locate the source of the
UV emissions
seen by NH and use the response of the satellite
atmospheres to the
eclipse to constrain production mechanisms.
WFPC2 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 11089
WFPC2 UV Throughput Check after 27-Jan-2007 Safemode
Check UV throughput of standard star GRW+70D5824 in all
four chips
following safemode caused by ACS Side 2 failure.
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 10 10
FGS REacq 05 05
OBAD with Maneuver 30 30
SIGNIFICANT EVENTS:
Flash Report: ACS Side-1 Switch and SBC-Only Operations
The Flight Readiness Review for the switch to ACS Side-1
and subsequent
SBC-Only Operations was held on 15 February 2007 (DOY
046). Authority
was given to proceed with the first two steps of switching
to Side-1,
which consist of establishing ACS in its Side-1 Safing
configuration and
updating the SMAC20. Ops Requests #18018 and #18017 will
be executed
between 047/15:54 and 047/16:39.
Further ACS Side-1 reconfigurations will stand down until
the ST ScI
reports their analysis of WFPC2 UV Images. A telephone
tag-up is planned
for noon, February 16, for the ST ScI to report their
findings. The
remaining ACS transitions are planned to be executed
between 047/18:00
and 048/02:25, pending HST Project approval at the tag-up
telecon.