Status Report

NASA Hubble Space Telescope Daily Report # 3883

By SpaceRef Editor
June 17, 2005
Filed under , ,

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT      # 3883

PERIOD COVERED: UT June 16, 2005 (DOY 167)


ACS/HRC 10182

Towards a Comprehensive Understanding of Type Ia Supernovae: The
Necessity of UV Observations

Type Ia supernovae {SNe Ia} are very important to many diverse areas
of astrophysics, from the chemical evolution of galaxies to
observational cosmology which led to the discovery of dark energy and
the accelerating Universe. However, the utility of SNe Ia as
cosmological probes depends on the degree of our understanding of SN
Ia physics, and various systematic effects such as cosmic chemical
evolution. At present, the progenitors of SNe Ia and the exact
explosion mechanisms are still poorly understood, as are evolutionary
effects on SN Ia peak luminosities. Since early-time UV spectra and
light curves of nearby SNe Ia can directly address these questions, we
propose an approach consisting of two observational components: {1}
Detailed studies of two very bright, young, nearby SNe Ia with HST UV
spectroscopy at 13 epochs within the first 1.5 months after discovery;
and {2} studies of correlations with luminosity for five somewhat more
distant Hubble-flow SNe Ia, for which relative luminosities can be
determined with precision, using 8 epochs of HST UV spectroscopy
and/or broad-band imaging. The HST data, along with extensive
ground-based optical to near-IR observations, will be analyzed with
state-of-the-art models to probe SN Ia explosion physics and constrain
the nature of the progenitors. The results will form the basis for the
next phase of precision cosmology measurements using SNe Ia, allowing
us to more fully capitalize on the substantial past {and future}
investments of time made with HST in observations of high-redshift SNe

ACS/HRC 10330

Coronagraphic search for disks around nearby stars

We will use the coronagraphic and imaging modes of the High Resolution
camera to study of the role of circumstellar disks in planetary system
formation over timescales of ~1-1000 Myr. Our targets comprise pre
Main-Sequence {MS} and MS stars, selected by infrared excess, and
targets selected from SIRTF surveys. Some targets, like Beta Pictoris
have debris disks that have been detected at optical or near-IR
wavelengths, while others have disks inferred from mid-IR or ISO
observations. We will obtain multicolor images of each target’s
circumstellar environment for the purpose of {1} detecting and
characterizing disk morphologies over all scales {including warps and
regions of enhanced or depleted density}, and {2} seeking evidence of
embedded planets. Direct and occulted images will be recorded for
studying the disks within 2 arcseconds of these targets; the
coronagraph will be used to image the outer regions of the disks.
Together with existing infrared observations, we will provide
constraints on the sizes, distribution, and composition of dust
grains. Unconfirmed disks will first be imaged in F606W, and if they
exist we may later observe them in F435W and F814W.

ACS/HRC 10422

Resolving Changes on Triton’s Surface: Imaging over Triton’s full
longitudinal range.

We have found, from ground-based photometry, evidence of possible
seasonal surface changes on Triton which may be brought about by
geophysical activity and which have transpired since as recently as
1995. We propose to confirm and characterize these changes using the
HST ACS instrument to image Triton at UV, B, V, I and Methane-band
wavelengths over as much of its surface as visible from near Earth. By
so doing, we will determine the resurfacing rates and set model
constraints on activity and surface temperature as well as
composition. Such constraints have profound implications for our
understanding of Triton’s evolution as well as the history of other
outer solar system bodies, including outer solar system satellites
which may undergo similar geophysical processes or have similar


Accurate and Robust Calibration of the Extragalactic Distance Scale
with the Maser Galaxy NGC4258 II

The extragalactic distance scale {EDS} is defined by a comparison of
Cepheid Period-Luminosity {PL} relations for nearby galaxies and the
LMC, whose uncertain distance is thereby the SOLE anchor. Studies of
masers orbiting the central black hole in NGC4258 have provided the
most accurate extragalactic distance ever {7.2+/-0.5 Mpc}, and new
radio data and analysis techniques will reduce the uncertainty to < 3.5% {0.07 mag} by 2005. Since this distance is well determined and based on geometric arguments, NGC4258 can provide a much needed new anchor for the EDS. Ultimately, the combination of an independent measurement of H0 and measurements of CMB fluctuations {e.g., WMAP} can be used to directly constrain cosmological parameters including the equation of state of dark energy. In our Cycle 12 proposal, we defined a program spanning two cycles. The Cycle 12 portion was accepted. We have acquired WFC images and are constructing well sampled PL relations in 3 colors {BVI}. The purpose of the Cycle 13 observations is to address systematic sources of error and is crucial for the success of the entire program. To disentangle the effects of reddening and metallicity, and to characterize the effects of blending, we require 50 orbits to obtain H-band photometry {NICMOS/NIC2} and high resolution images {ACS/HRC}.

ACS/WFC 10135

Unveiling the Progenitors and Physics of Cosmic Explosions

GRBs and XRFs are clearly highly asymmetric explosions and require a
long-lived power source {central engine}. In contrast, nearby
core-collapse events are essentially spherical explosions. However,
the failure of spherical neutrino driven collapses has led to the idea
that asymmetric energy release is essential for the explosion. The
recent finding of a Type Ic SN in GRB 030329, the association of the
low energy event GRB 980425 with SN 1998bw, the theoretical
development discussed above and the rise of collapsar models make it
timely to consider whether all these explosions contain engines. Given
the uncertainties in theoretical modeling it is clear that
observations are needed to guide models. A priori there is little
reason to expect connection between the ultra-relativistic jet that
powers the GRB and the explosive nucleosynthesis of the ~0.5 solar
masses of Nickel-56 that powers the accompanying supernova. We propose
a comprehensive program of ACS photometric searches {and measurements}
for SNe associated with GRBs and XRFs. In concert, we will undertake
ground- based spectroscopy to determine velocity widths, and measure
engine parameters from pan- chromatic afterglow observations. Our goal
is to produce a comprehensive database of engine and SN physical
parameters against which theoretical modeling will be guided.


The Formation and Evolution of Spirals: An ACS and WFPC2 Imaging
Survey of Nearby Galaxies

Over 50% of galaxies in the local universe are spirals. Yet the star
formation histories and evolution of this crucial population remain
poorly understood. We propose to combine archival data with new
ACS/WFC and WFPC2 observations of 11 galaxies, to tackle a
comprehensive investigation of nearby spirals covering the entire
spiral sequence. The new observations will fill a serious deficiency
in HST’s legacy, and maximize the scientific return of existing HST
data. The filter combination of UBVI, and Halpha is ideal for studying
stellar populations, dust properties, and the ISM. Our immediate
scientific objectives are: {i} to use the resolved cluster
populations, both young massive clusters and ancient globular clusters
as a chronometer, to understand how spirals assembled as a function of
time; {ii} study the rapid disruption properties of young clusters;
and {iii} understand dust distributions in spirals from pc to kpc
scales. Each of these goals provides an important step towards
charting the evolution of galaxies, and an essential baseline for
interpreting the galaxy populations being surveyed in both the early
and present universe. The resolution of our survey, which exploits the
excellent imaging capabilities of HST’s two optical cameras, will
enable us to understand the record of star cluster, and galaxy
formation in a level of detail which is not possible for more distant
systems. Finally, the proposed observations will provide a key to
interpret an extensive, multiwavelength archive of space- and ground-
based data at lower spatial resolution {SPITZER, CHANDRA, GALEX,
NICMOS P alpha and H band imaging} for local spirals.

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 8792

NICMOS Post-SAA calibration – CR Persistence Part 3

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.

NIC2/NIC1 10419

An in-depth analysis of a prototypical giant H II region: NGC 604

NGC 604 is, together with 30 Doradus, the extragalactic prototype
giant H II region. Its stellar content and mass {~200 O+WR stars,
~10**5 M_Sun}, age {~3.5 Myr}, proximity {840 kpc}, and low foreground
extinction {E{B-V} <= 0.1} make it an ideal object to study the massive stellar population of a scaled OB association, its interaction with the surrounding medium, and the effects caused by the strong differential extinction. We propose new HST observations which, combined with existent ones, will provide the most thorough multi-wavelength study of NGC 604 from the FUV to the NIR. We will obtain spectral classifications for ~200 stars, measure their spectral energy distributions from 1300 A to 2.2 microns, identify embedded very-young stellar populations hidden inside dust clouds, measure the extinction law and its possible variations as a function of environmental conditions, and analyze the relationship between the hot stars and the surrounding gas. The new data we are proposing is divided into three parts: {a} slitless objective-prism FUV spectroscopy using ACS/SBC, {b} multi-filter {6 broad-band and 2 narrow- band} NUV-optical imaging using ACS/HRC, and {c} HST/NICMOS broadband imaging. Our final goal is to analyze in detail a well-resolved giant H II region in order to understand the properties of similar but unresolved objects located at cosmological distances.


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


9852 – GSacq(3,2,2) results in finelock backup (3,0,3) @168/0504z
During ZOE the GSacq(3,2,2) scheduled at 168/05:04:23 resulted in
finelock backup (3,0,3). At AOS (05:57:15) there were no flags.



                           SCHEDULED     SUCCESSFUL    FAILURE TIMES FGS Gsacq                11                       11 FGS Reacq                 3                         3 FHST Update              19                       19 LOSS of LOCK


SpaceRef staff editor.