Status Report

NASA Hubble Space Telescope Daily Report # 3892

By SpaceRef Editor
June 30, 2005
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HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT       #3892

PERIOD COVERED: UT June 29, 2005 (DOY 180)


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 CCDs daily monitor – Cycle 13 – Part 2

This program consists of a set of basic tests to monitor, the read
noise, the development of hot pixels and test for any source of noise
in ACS CCD detectors. The files, biases and dark will be used to
create reference files for science calibration. This program will be
for the entire lifetime of ACS.


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}.


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< z <1.0 will be of enormous scientific benefit for additional studies of weak lensing, AGN host galaxies, the morphology-density relation, and the merger rate as a function of redshift.

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.


The Ghosts of Galaxies: Tidal Debris and the Formation of Clusters

Intergalactic stellar populations and tidal debris are now recognized
as important components of galaxy clusters. This project examines the
interrelated processes of galaxy destruction, recycling of tidal
debris, and creation of dwarf galaxies and intergalactic star
clusters, all of which are part of the grand scheme of cluster
formation. We propose deep multicolor imaging of two examples of newly
created tidal debris, the spectacular plumes in the Centaurus and Coma
clusters. The Centaurus observations will extend our earlier work,
which demonstrated the existence of tidal debris dwarf galaxies and
star cluster in the body of the Centaurus plume. Deep ACS/WFC
observations can determine rough ages and cluster membership, better
characterizing the new debris. The Coma observations will reproduce
this work for a second plume feature, in the quintessential rich
cluster of galaxies. Parallel WFPC2 observations will investigate the
central intracluster spaces at the bottom of the each cluster’s
potential, where older debris is thickest.


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

HSTARS: (None)



                           SCHEDULED     SUCCESSFUL    FAILURE TIMES 
 FGS Gsacq                05                      05 
 FGS Reacq                10                      10 
 FHST Update              09                      09 


SpaceRef staff editor.