Status Report

NASA Hubble Space Telescope Daily Report # 3893

By SpaceRef Editor
July 1, 2005
Filed under , ,

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science


PERIOD COVERED: UT June 30, 2005 (DOY 181)


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 10198

Probing the Dynamics of the Galactic Bar through the Kinematics of
Microlensed Stars

The observed optical depths to microlensing of stars in the Galactic
bulge are difficult to reconcile with our present understanding of
Galactic dynamics. The main source of uncertainty in those comparisons
is now shifting from microlensing measurements to the dynamical models
of the Galactic bar. We propose to constrain the Galactic bar models
with proper motion observations of Bulge stars that underwent
microlensing by determining both the kinematic identity of the
microlensed sources and the importance of streaming motions. The
lensed stars are typically farther than randomly selected stars.
Therefore, our proper motion determinations for 36 targeted MACHO
events will provide valuable constraints on the dynamics of bulge
stars as a function of distance. The first epoch data for our proposed
events is already available in the HST archive so the project can be
completed within a single HST cycle. The exceptional spatial
resolution of HST is essential for completion of the project.
Constraints on the total mass in the bulge will ultimately lead to the
determination of the amount of dark matter in inner Galaxy.

ACS/S/C/SBC 10233

Determining the Instability Strip for Accreting White Dwarfs

Using UV observations with SBC and PR110L, we will obtain spectra of 3
newly discovered pulsating white dwarfs found among recent cataclysmic
variables identified in the SDSS. Our Cycle 8 observations of the only
previously known accreting, pulsating, white dwarf in GW Lib revealed
large amplitude UV pulsations, a spectrum that showed metals and
required a dual temperature fit with a high white dwarf mass. Since
accretion likely causes abundance, rotation, and atmospheric
temperature differences in accreting white dwarfs versus single white
dwarfs, we will use these systems to explore the location of the
instability strip for accreting white dwarfs and determine whether
they are all massive and spotted objects. Light curves can be
constructed at different wavelengths to aid in mode identification.
Having knowledge of the atmospheres and interior structure of 4 sytems
will provide great insight into the interaction of accretion, stellar
pulsation and long term evolution. Due to optical contamination by the
disk, stream, and/or secondary, the UV is the optimum regime to study
pulsating, accreting white dwarfs.

ACS/WFC 10095

Hubble Heritage Observations of Deep Impact Target Comet Tempel-1

This proposal observes Comet Tempel-1 near the time of Deep Impact,
using the ACS- WFC, in filters F435W {3×345 sec} and F606W {3×345

ACS/WFC 10235

Dark vs. luminous matter in the CenA/M83 galaxy complex

The distribution of dark vs. luminous matter on scales of 0.1-1.0 Mpc
remains poorly understood. For a nearby group, the total mass can be
determined from the radius of “the zero-velocity surface”, which
separates the group from the general Hubble flow. This new method
requires the measurement of accurate distances and radial velocities
of galaxies around the group, but gives total mass estimates
independent of assumptions about the state of relaxation or orbital
characteristics. The mass pertains to the group at the full scale to
which it is bound. Upon application in several nearest groups, the
method yields mass estimates in agreement with the sum of the virial
masses of subcomponents. However, the typical total M/L ratio for the
nearby groups of ~30 Mo/Lo implies a local mean density of matter
which is only 1/7 the canonical global density . The nearby complex of
galaxies around Cen A and M83 resembles our Local Group by the
dumb-bell concentration of objects around a pair of dominant galaxies.
Accurate distances have been acquired recently for ~20 group members
by the TRGB method using HST. We will measure TRGB distances to the 17
remaining galaxies in the region. These observations will constrain
the dynamical state of the halo surrounding the nearest giant E-galaxy
Cen A, providing a comparison with the halos of the nearest spirals.


Environmental drivers of galaxy evolution: an HST survey of dwarf
galaxy morphologies in the Abell Galaxies in dense environments are
subject to numerous physical processes that leave a lasting impact,
yet studies of galaxy evolution to date have been limited to the most
luminous galaxies — those least sensitive to environmental influence.
We propose to explore the environmental drivers of DWARF galaxy
evolution: with a mosaic of 9×9 ACS pointings in F606W we will
determine morphologies for ~1200 galaxies down to M_V=-14 in the
A901/902 supercluster, spanning 3×3 Mpc at z=0.16. The deep ACS data
will allow us to probe their surface brightness profiles, shapes,
sizes, asymmetry and fine structure such as tidal features. With the
addition of extensive existing multi- wavelength data, we will probe
the dependence of these important parameters on dark matter content
{from weak lensing maps}, the hot intercluster medium {from deep XMM-
Newton imaging}, and local galaxy density {from hyper-accurate
COMBO-17 photometric redshifts with delta z=0.02 to m_R=24}, thus
disentangling the various environmental processes shaping dwarf galaxy
evolution. Furthermore, the 8000+ background galaxies at 0.2

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.


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

HSTARS: (None)

COMPLETED OPS REQUEST: #17459-1: Clear ACS Event Flag #2 @ 181/1901z

COMPLETED OPS NOTES: #0915-3: HSTAR Requirements for FHST Map/Update
Failures @ 181/21:56:46z

                               SCHEDULED                    SUCCESSFUL 
 FGS Gsacq                  06                                         06 
 FGS Reacq                 10                                          10 
 FHST Update              10                                          09 


SpaceRef staff editor.