Status Report

NASA Hubble Space Telescope Daily Report # 3794

By SpaceRef Editor
February 10, 2005
Filed under , ,

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT       # 3794



ACS/HRC 10133

HST / Chandra Monitoring of a Dramatic Flare in the M87 Jet

As the nearest galaxy with an optical jet, M87 affords an unparalleled
opportunity to study extragalactic jet phenomena at the highest
resolution. During 2002, HST and Chandra monitoring of the M87 jet
detected a dramatic flare in knot HST-1 located ~1″ from the nucleus.
As of late 2003 its brightness has increased twenty-fold in the
optical band, and continues to increase sharply; the X-rays show a
similarly dramatic outburst. In both bands HST-1 now greatly exceeds
the nucleus in brightness. To our knowledge this is the first
incidence of an optical or X-ray outburst from a jet region which is
spatially distinct from the core source; this presents an
unprecedented opportunity to study the processes responsible for
non-thermal variability and the X-ray emission. We propose seven
epochs of monitoring during Cycle 13, as well as seven epochs of
Chandra/ACIS observation {5ksec each}. We also include a brief HRC/ACS
observations that will be used to gather spectral information and map
the magnetic field structure. This monitoring is continued into Cycles
14 and 15. The results of this investigation are of key importance not
only for understanding the nature of the X-ray emission of the M87
jet, but also for understanding flares in blazar jets, which are
highly variable, but where we have never before been able to resolve
the flaring region in the optical or X-rays. These observations will
allow us to test synchrotron emission models for the X-ray outburst,
constrain particle acceleration and loss timescales, and study the jet
dynamics associated with this flaring component. Revisions 6 Oct 2004:
We are replacing STIS visits 1-7 with ACS/HRC observations in new
visits 31- 37.

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 1

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 programme will be
for the entire lifetime of ACS.

ACS/WFC 10407

When did M31’s disk form?

The recent discovery of THIN disk globular clusters in M31 provides a
unique opportunity to determine the age of M31’s disk. The globular
cluster kinematics imply that the disk has not been significantly
heated or destroyed by a merger since they were formed. Thus the
cluster ages provide a lower limit to the disk age. This limit will
complement the high-redshift data, where few disk galaxies are
currently known because of their relatively low surface brightness. We
propose to obtain BV ACS imaging of seven disk clusters to below the
level of the horizontal branch {HB} to determine the distribution of
evolved stars in the color-magnitude diagram. The contribution of
evolved stars, particularly blue HB stars, is crucial to estimating
the age of the globular cluster from both color-magnitude diagrams and
the high S/N integrated spectra which we will obtain from the ground.

ACS/WFC 10420

The assembly of a massive galaxy cluster: The 4/h Mpc filament feeding

We propose a deep ACS/WFC F606W+F814W mosaic of the massive cluster
MACSJ0717.5+3745 at z=0.55 in order to obtain the first direct
detection of cluster evolution through infall of matter along
large-scale filaments. Existing optical, X-ray, and ground based
weak-lensing data show strong evidence of galaxy groups and dark
matter in a coherent structure spanning at least 10 arcmin {4/h Mpc,
LCDM} in the plane of the sky. The size of this object rules out prior
interaction between the groups and the cluster, thus making it a prime
candidate for a genuine filament as opposed to a merger remnant. The
proposed observation will 1} allow the first direct measurement of the
dark matter content and mass distribution along a large-scale filament
via weak lensing, and 2} provide, through galaxy morphology and
resolved colour information, unprecedented insights into the physical
processes and environmental effects governing the transition from
field to cluster galaxies.


Resolving the Red Giant Population in Early Type Galaxies

This project addresses the fundamental issue of the age and abundance
of the stellar populations in early type galaxies. We propose deep
imaging observations with ACS/WFC in F606W, F814W, and NICMOS/NIC2 in
F110W, F160W to create optical/IR color-magnitude diagrams of the
upper red giant branch in the nearest example of a bona fide
elliptical galaxy, NGC3379, and simultaneously in the disk and halo of
its companion, the S0 galaxy NGC3384. These observations will build
upon the results from our NICMOS study of NGC3379, which produced the
first deep IR color-magnitude data for a normal, luminous elliptical
galaxy. This is the most direct way to establish the metallicity,
metallicity spread, and presence of intermediate age populations in
these representative Hubble types, exploring their star formation
histories and evolution. The data will enable comparison with M32, the
M31 halo, NGC5128, and other nearby galaxies similarly observed with

ACS/WFC/NIC3 10196

Morphologies of a new class of rest-frame optical selected high
redshift galaxies

We have obtained deep very Js, H, Ks imaging with the VLT of two
fields with excellent optical imaging, in order to study high redshift
galaxies. Using these Near-IR images, we identified a class of
galaxies with Js – Ks color larger than 2.3. Photometric redshifts and
spectroscopic follow-up showed that their mean redshift is 2.5 +- 0.7.
These galaxies are complementary to Lyman break selected galaxies: the
overlap is minimal, and the rest-frame optical colors of the Js-Ks
selected galaxies are much redder. Their contribution to the stellar
mass density is comparable to that of Lyman breaks in our fields. SED
fits and Near-IR spectroscopy of the Js-Ks selected galaxies indicate
median ages between 1 and 2 Gyr, a factor of 3-5 older than the ages
of Lyman break galaxies estimated by similar methods. They are likely
the oldest galaxies at z=2.5, and may be evolving into the most
massive galaxies at z=0. We propose to obtain images of the
spectroscopically confirmed Js-Ks galaxies with the NICMOS/NIC3 camera
in the H band. These galaxies lie the field of MS1054-03, for which we
have excellent groundbased and HST optical imaging. The increased
depth and spatial resolution of the NICMOS imaging will allow us to
determine the restframe optical morphologies of the Js – Ks galaxies,
in order to study their intensity profiles and regularity, to
decompose the largest galaxies in bulges and disks, to measure scale
lengths, and to look for evidence of merging and recent star
formation. This study would provide us unique insight into the nature
of these red galaxies, their evolutionary history and their likely
descendants at low redshift.


NICMOS Post-SAA calibration – CR Persistence Part 2

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
investigated.) None



                            SCHEDULED     SUCCESSFUL    FAILURE TIMES 
 FGS Gsacq                 08                       08 
 FGS Reacq                 07                        07 
 FHST Update               15                        15 


SpaceRef staff editor.