HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science
DAILY REPORT # 3776
PERIOD COVERED: DOY 013 Next Daily Report will be issued on 1/18/05 due to
MLK Holiday.
OBSERVATIONS SCHEDULED
ACS/WFC 10452
HST/ACS Mosaic of M51
A six-pointing ACS WFC mosaic of the galaxy pair M51 will be obtained
in four filters, B, V, I and H-alpha. Four orbits per pointing will
allow high-quality S/N images of the entire galaxy.
ACS/WFC/NIC2/WFPC2 9873
Main Sequence Turnoff Ages For Second Parameter Clusters in M33
In cycle 5, we were granted 40 orbits to study the early formation
history of M33 by investigating the nature of the "second parameter"
phenomenon among its globular star clusters. Discovered among the
globular clusters of the Milky Way more than 30 years ago, the "second
parameter" effect describes the degeneracy in the behavior of
horizontal branch {HB} morphology with metal abundance. This
degeneracy implies the existence of a second parameter, which, in
addition to metal abundance, influences the morphology of the HB. We
constructed {V, V-I} color-magnitude diagrams for 10 M33 halo globular
clusters. From these diagrams, we measured the cluster metallicities
and HB morphologies. Surprisingly, 8 of the 10 clusters display
extremely red horizontal branches, with most of the HB stars lying
near or on top of the red giant branch, yet their metal abundances are
in the range -1.6 <= [Fe/H] <= -1.0. A likely explanation is that the
halo clusters in M33 are several Gyr younger than those in the Milky
Way. To test this hypothesis, we propose to obtain main sequence
turnoff photometry for two of our M33 clusters with similar
metallicities but vastly differing HBs - a so-called `second parameter
pair.' This will help to answer the question of whether age is the
second parameter among the M33 halo clusters and provide an important
clue to the overall nature of the second parameter effect.
ACS/WFC/NIC3 10127
Imaging a protocluster at z=3.1: Effects of environment and evolution
on galaxy populations in the early universe
We propose imaging a rich protocluster, 0316-26 at z = 3.13, with 31
confirmed Lya cluster members. The bright radio galaxy host is
identified with the progenitor of the dominant cluster galaxy. Because
its redshift places Lya into an ACS narrow-band filter, the
protocluster provides a unique laboratory for studying galaxies at a
crucial epoch in the evolution of the Universe. We shall {i} measure
and compare sizes, morphologies and colors of galaxies from
populations detected using 4 different selection techniques {Lyman and
4000A breaks, Lya and [OIII] excesses}, {ii} study effects of an
overdense environment by comparing the properties of protocluster
galaxies with z~3 field galaxies from GOODS, {iii} study effects of
evolution by relating our data to observations of similar
protocluster/cluster targets at redshifts z = 4.1, 2.2, and 1.2, and
{iv} constrain the formation of the most massive cluster galaxies by
investigating the spatial distribution, Lya equivalent widths and
other properties within the 5" radio galaxy host. The ultimate aim is
to disentangle the history of structure development and stellar
evolution for rich clusters of galaxies.
ACS/WFC/WFPC2 10242
Pre-History of a Starburst: Deep Imaging of IC 10
The peculiar Local Group dwarf galaxy IC 10 is the nearest case of a
starburst in progress. Starburst galaxies are a prime laboratory for
studying the physical processes which regulate star formation in
galaxies; as the closest example, IC 10 is potentially the key galaxy
for understanding the starburst phenomenon. We propose to obtain deep
optical images of IC 10 with the ACS/WFC to achieve three main goals:
1} To make the first estimates of the pre-burst history of IC 10 based
on morphological and statistical analysis of its {V, I}
color-magnitude diagram; 2} to search for evidence of a past history
of burst-dormancy cycles; and 3} to explore the connection between the
ages and locations of bright stars and the large-scale structure of
the interstellar medium. The distance {0.8 Mpc}, extinction {2.5 mag},
and high surface brightness of IC 10 make these goals unobtainable
except with HST. The observations proposed here will yield far and
away the deepest images, in absolute magnitudes, ever obtained for any
starburst galaxy. Our photometry will reach to magnitudes {V, I} =
{28.5, 27.5}, which is below the level of the red clump/horizontal
branch and the location of the main-sequence turnoff of stars as old
as a billion years. For the first time, it will be possible to measure
the detailed history of a starburst host for the Gigayear time period
leading up to the burst. The horizontal branch morphology and colors
will provide new information on the metallicity and age distribution
of stars spanning the entire age of IC 10. Because of its close
distance, IC 10 is the ONLY starburst galaxy for which this type of
information is obtainable now or in the next decade. We propose to use
WFPC2 in parallel to search for a low-surface brightness population
associated with the neutral gas filaments surrounding IC 10.
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.
WFPC2 10132
UV Confirmation of New Quasar Sightlines Suitable for the Study of
Intergalactic Helium
The reionization of intergalactic helium is thought to have occurred
between redshifts of about 3 and 4. The study of HeII Lyman-alpha
absorption towards a half-dozen quasars at 2.72.9 SDSS quasars, but with special
emphasis on extending helium studies to the highest redshift
sightlines. Our proposed approach has already proven successful, and
additional sightlines will enable follow-up spectal observations to
measure the spectrum and evolution of the ionizing background
radiation, the density of intergalactic baryons, and the epoch of
reionization of the IGM.
WFPC2 10357
Saturn's Inner Satellites at True Opposition
We request one HST orbit to observe Janus, Epimetheus, Mimas, and
Enceladus with WFPC2 exactly at opposition, when the Earth transits
the center of the solar disk seen from Saturn on UT 13/14 January
2005. Data obtained at this unique viewing geometry are essential to
determining physical properties of the moon's surface, related to its
emplacement and evolution, and critical for the interpretation of
photometric data obtained by Cassini at higher phase angles. This
single observation will be the capstone of 9 years of legacy HST WFPC2
observations of the Saturnian system {Cycles 6-12, R. French, PI} from
which we have constructed precise, multiwavelength phase curves which
demonstrate how the reflectance of these satellites varies with solar
phase angle from 0.07 to 6.4 degrees. Each satellite exhibits a
dramatic increase in brightness, or "opposition effect", as phase
angles decrease below 1 degree. Since 1998 {Cycle 7} the minimum
observable phase angle at opposition has decreased each year to 0.07
degrees in Cycle 12; however, the absolute minimum observable phase
angle, about 0.02 degrees {limited by the angular size of the Sun
viewed from Saturn}, has not been accessible until Cycle 13. Using the
same set of broadband filters for continuity with our previous
programs, we will place observations made during the Earth transit on
the existing UVBRI phase curves and establish the amplitude of each
satellite's opposition surge. From these observations we will
determine surface properties such as porosity, grain size distribution
and particle opacity using radiative transfer models. While the
Cassini spacecraft will obtain images at larger phase angles, it will
miss entirely the narrow brightness surge near opposition due to
orbital constraints. Because these inner satellites will be either
lost in or contaminated by the glare of the fully open rings, they are
not accessible to ground-based telescopes. The 2005 opposition
presents the only opportunity for HST to observe the Saturnian system
during this rare planetary alignment. The next transit of Earth across
the solar disk seen from Saturn occurs in 2020; the next central
transit occurs in 2049.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.) None
COMPLETED OPS REQs: None
OPS NOTES EXECUTED: None
SCHEDULED SUCCESSFUL FAILURE TIMES
FGS Gsacq 06 06
FGS Reacq 10 10
FHST Update 09 09
LOSS of LOCK
SIGNIFICANT EVENTS: None
