Status Report

NASA Hubble Space Telescope Daily Report #3869

By SpaceRef Editor
May 28, 2005
Filed under , ,

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT       # 3869



ACS/HRC 10145

Physical parameters of the upper atmosphere of the extrasolar planet

Every 3.5 days, the transits of the gaseous planet orbiting HD209458
offer the unique opportunity to investigate the spectral features of
an extra-solar planetary atmosphere. Using HST, we first discovered
the extended upper atmosphere of HD209458b through the detection of a
15% HI Lyman alpha absorption. We concluded that the hydrogen must be
escaping the planet with a lower limit rate of 10^10 g/s {Vidal-Madjar
et al. 2003}. Additional observations, subsequently allowed to detect
OI and CII in the upper atmosphere implying that this atmosphere is
hydrodynamically escaping {in “blow off”, Vidal-Madjar et al. 2004}.
Here we propose to further study this upper atmosphere to better
constrain the “blow off” state by directly estimating the physical
conditions and the flow characteristics. In particular we will
determine the temperature and density at the base of the upper
atmosphere {the thermosphere}, and the density distribution and
ionization state just below that level. Comparison between the optical
and ultraviolet occultation light curves will provide useful
information on the molecular/haze content of the lower atmosphere. The
observation of six HD209458b transits with HRC and SBC settings will
allow the detection of many lines adressing these issues. The proposed
observations will give us for the first time a detailed probe of the
atmosphere of an “evaporating” extra-solar planet.With species as
abundant as FeII or MgII, the damping wings in the strongest lines
will start to form at levels around 1.9% absorption. Due to either the
strength of the MgII doublet lines around 280 nm or the packing of
FeII lines, strong absorptions arising from the accumulated damping
wings should show up clearly in FeII and MgII. All these signatures
should be easily detected even with the 40 to 100 Angstrom resolution
of the PR200L prism in these spectral regions. In addition to these
goals, any signature of molecules {e.g CO below 154 nm}, dust or haze
should also show up as broad band absorption in both PR110L and PR200L
settings. The estimate of the planet radius at different wavelengths
in the UV would become possible for all efficient absorbers in this
spectral range. The achievement of 0.1% precision in the occultation
curves thus provides sensitivity high enough to potentially lead to
important discoveries.

ACS/WFC 10412

The host galaxies of dust-reddened quasars

We have used the 2MASS near-infrared and FIRST radio surveys, together
with the Palomar Observatory Sky Survey plates to select a sample of
dust-reddened, radio- intermediate quasars. We wish to use ACS to
study the host galaxies of these quasars. The dust reddening of the
quasars makes it possible to study the hosts at rest-frame optical-UV
wavelengths much more easily than the hosts of normal quasars of
similar bolometric luminosity. Our study will compare the hosts of our
dust-reddened quasars to those of normal quasars from the HST archive
to test the hypothesis that dust-reddened quasars are young objects,
whose hosts still show morphological evidence of recent merger events
which triggered the quasar.

ACS/WFC/NIC3 10195

Probing the Surroundings of a Highly Luminous Redshift 6.5 Galaxy

We propose deep images of a recently discovered galaxy at z=6.535,
which is among the most luminous Lyman-alpha emitting galaxies known
at high redshift. The brightness and rarity of this source imply that
it is associated with a high peak in the matter density distribution.
{It is the brightest Lyman alpha source in 2e5 comoving Mpc3, with a
luminosity of 6 L*.} Further objects in this peak are expected to be
visible with HST’s sensitivity. The Lyman alpha line has a large rest
frame equivalent width, with a lower bound >100 Angstroms. Such a
large equivalent width would be impossible for objects embedded in
neutral gas, and instead requires either that {a} the universe was
reionized before z=6.5 or {b} the galaxy resides in a local ionized
bubble, in which case an additional contribution to the ionizing
photon budget from presently undetected neighbors is required. With 19
orbits of ACS and NICMOS imaging, we will measure this object’s
morphology and spectral energy distribution, thus searching for either
active nuclei or old stellar populations. We will also search for
possible neighbors, which could establish the first known galaxy group
at z>6, and may provide sufficient ionizing flux to allow the escape
of the observed Lyman alpha photons in a neutral universe. If
neighbors are not found, it will lead to an upper bound on the neutral
fraction in the general IGM at z=6.5.

FGS 10432

Precise Distances to Nearby Planetary Nebulae

We propose to carry out astrometry with the FGS to obtain accurate and
precise distances to four nearby planetary nebulae. In 1992, Cahn et
al. noted that “The distances to Galactic planetary nebulae remain a
serious, if not THE most serious, problem in the field, despite
decades of study.” Twelve years later, the same statement still
applies. Because the distances to planetary nebulae are so uncertain,
our understanding of their masses, luminosities, scale height, birth
rate, and evolutionary state is severely limited. To help remedy this
problem, HST astrometry can guarantee parallaxes with half the error
of any other available approach. These data, when combined with
parallax measurements from the USNO, will improve distance
measurements by more than a factor of two, producing more accurate
distances with uncertainties that are of the order of ~6%. Lastly,
most planetary nebula distance scales in the literature are
statistical. They require several anchor points of known distance in
order to calibrate their zero point. Our program will provide “gold
standard” anchor points by the end of 2006, a decade before any
anticipated results from future space astrometry missions.

NIC2 10169

Star Formation in Luminous Infrared Galaxies: giant HII Regions and
Super Star Clusters

Luminous Infrared Galaxies {LIRGs, LIR = 10^11-10^12Lsol} and
Ultraluminous Infrared Galaxies {LIR>10^12Lsol} account for
approximately 75% of all the galaxies detected in the mid-infrared in
the redshift range z=0-1.5. In the local universe it is found that
LIRGs are predominantly powered by intense star formation {SF}.
However, the physical conditions and processes governing such dramatic
activity over scales of tens to a few hundred parsecs are poorly
known. In the last decade HST has been playing a significant role,
mainly with the discovery of super star clusters {SSCs}, and more
recently, giant HII regions. Based on observations of a few LIRGs, we
found that these giant HII regions and associated SSCs appear to be
more common in LIRGs than in normal galaxies, and may dominate the
star formation activity in LIRGs. A larger sample is required to
address fundamental questions. We propose an HST/NICMOS targeted
campaign of a volume limited sample {v<5200km/s} of 24 LIRGs. This proposal will probe the role of giant HII regions in the overall energetics of the current star formation, their relation to SSCs, and the dependence of star formation properties on other parameters of LIRGs. Such detailed knowledge of the SF properties of LIRGs in the local universe is essential for understanding galaxies at high redshift.


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.

S/C 10700

Guide Star Test for the Deep Impact Encounter

This proposal is to perform guide star tests on the critical HST
science visits circum- encounter of the Deep Impact mission with comet
9P/Tempel 1.


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


9834 – The GSacq(2,1,2) scheduled during ZOE at 146/08:51:31 -08:59:33
failed to RGA control at AOS 146/09:00:27 (TDW). Three 486 ESB
messages A0E(hex) were also observed at AOS when telemetry was
reacquired, indicating FGS Sequential Attitude update failed because
roll error was too large to correct. Prior FM Updates at 146/08:35:03,
146/08:37:48 showed good attitude error vector.



                            SCHEDULED     SUCCESSFUL    FAILURE TIMES 
 FGS Gsacq                 05                     04               Hstar # 9834 
 FGS Reacq                 10                      07              Hstar # 9834 
 FHST Update               09                     09 


SpaceRef staff editor.