Status Report

NASA Hubble Space Telescope Daily Report # 3775

By SpaceRef Editor
January 13, 2005
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HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT        # 3775




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 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.


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 over
dense 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.


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 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 2.7 < z < 3.5 demonstrates the great potential of such probes of the IGM, but the current critically-small sample limits confidence in resulting cosmological inferences. The requisite unobscured quasar sightlines to high-redshift are extremely rare, especially due to severe absorption in random intervening Lyman-limit systems, but SDSS provides hundreds of bright, new quasars at such redshifts potentially suitable for HeII studies. Our cycle 13 SNAP program proposes to verify the UV detectability of 40 new, bright, z>2.9 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.


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

HSTAR 9656: FHST U1,3FM Update @ 012/18:55:52Z failed due to large
update errors of 67.705, -1286.431, and 603.701 arcsec. The first
update succeeded with small errors and the GS Acquisition that
followed also passed with no problems. Under investigation.



  • 1297-0 Bay 6 Aft ES Bulkhead Temperature Increase @ 012/1033z
  • 1298-0 OTA Fitting Temperature Limit Change @ 012/1533z
  • 1299-0 Main Ring and Bay 6 Upper Limit Change @ 012/2159z
  • 1300-0 Tan Link-1 Temperture Limit change @ 013/0004z
  • 1301-0 B7 Hnycmb Dr INT Temp1 and Tunnl Structure Temp Limit Change @ 013/0128z
  • 1302-0 Raise TB5TNSTR Upper Temperature Limit @ 013/0713z

                             SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS Gsacq                  07                       07
FGS Reacq                  09                       09
Update               10                        09 


SpaceRef staff editor.