Daily Report #4626

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT***** # 4626

PERIOD COVERED: 5am June 05 - 5am June 06, 2008 (DOY
157/0900z-158/0900z)

OBSERVATIONS SCHEDULED

WFPC2 10583

Resolving the LMC Microlensing Puzzle: Where Are the Lensing Objects ?

We are requesting 32 HST orbits to help ascertain the nature of the
population that gives rise to the observed set of microlensing events
towards the LMC. The SuperMACHO project is an ongoing ground-based
survey on the CTIO 4m that has demonstrated the ability to detect LMC
microlensing events in real-time via frame subtraction. The
improvement in angular resolution and photometric accuracy available
from HST will allow us to 1} confirm that the detected flux excursions
arise from LMC source stars rather than extended objects {such as for
background supernovae or AGN}, and 2} obtain reliable baseline flux
measurements for the objects in their unlensed state. The latter
measurement is important to resolve degeneracies between the event
timescale and baseline flux, which will yield a tighter constraint on
the microlensing optical depth.

FGS 11211

An Astrometric Calibration of Population II Distance Indicators

In 2002 HST produced a highly precise parallax for RR Lyrae. That
measurement resulted in an absolute magnitude, M{V}= 0.61+/-0.11, a
useful result, judged by the over ten refereed citations each year
since. It is, however, unsatisfactory to have the direct,
parallax-based, distance scale of Population II variables based on a
single star. We propose, therefore, to obtain the parallaxes of four
additional RR Lyrae stars and two Population II Cepheids, or W Vir
stars. The Population II Cepheids lie with the RR Lyrae stars on a
common K-band Period-Luminosity relation. Using these parallaxes to
inform that relationship, we anticipate a zero-point error of 0.04
magnitude. This result should greatly strengthen confidence in the
Population II distance scale and increase our understanding of RR
Lyrae star and Pop II Cepheid astrophysics.

FGS 11214

HST/FGS Astrometric Search for Young Planets Around Beta Pic and AU
Mic

Beta Pic and AU Mic are two nearby Vega-type debris disk stars. Both
of these disk systems have been spatially resolved in exquisite
detail, predominantly via the ACS coronagraph and WFPC-2 cameras
onboard HST. These images exhibit a wealth of morphological features
which provide compelling indirect evidence that these systems likely
harbor short-period planetary body{ies}. We propose to use the
superlative astrometric capabilities of HST/FGS to directly detect
these planets, hence provide the first direct planet detection in a
Vega-type system whose disk has been imaged at high spatial
resolution.

NIC1/NIC2/NIC3 11330

NICMOS Cycle 16 Extended Dark

This takes a series of Darks in parallel to other instruments.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA Calibration - CR Persistence Part 5

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 DARKs. 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.

NIC2 11166

The Mass-dependent Evolution of the Black Hole-Bulge Relations

In the local universe, the masses of giant black holes are correlated
with the luminosities, masses and velocity dispersions of their host
galaxy bulges. This indicates a surprisingly close connection between
the evolution of galactic nuclei (on parsec scales) and of stars on
kpc scales. A key observational test of proposed explanations for
these correlations is to measure how they have evolved over cosmic
time. Our ACS imaging of 20 Seyfert 1 galaxies at z=0.37 showed them
to have smaller bulges (by a factor of 3) for a given central black
hole mass than is found in galaxies in the present-day universe.
However, since all our sample galaxies had black hole masses in the
range 10^8.0--8.5 Msun, we could only measure the OFFSET in black hole
mass to bulge luminosity ratios from the present epoch. By extending
this study to black hole masses another factor of 10 lower, we propose
to determine the full CORRELATION of black hole mass with host galaxy
properties at a lookback time of 4 Gyrs and to test mass-dependency of
the evolution. We have selected 14 Seyfert galaxies from SDSS DR5
whose narrow Hbeta emission lines (and estimated nuclear luminosities)
imply that they have black hole masses around 10^7 Msuns. We will soon
complete our Keck spectroscopic measures of their bulge velocity
dispersions. We need a 1-orbit NICMOS image of each galaxy to separate
its nonstellar luminosity from its bulge and disk. This will allow us
to make the first determination of the full black hole/bulge relations
at z=0.37 (e.g. M-L and M-sigma), as well as a test of whether active
galaxies obey the Fundamental Plane relation at that epoch.

NIC3 11120

A Paschen-Alpha Study of Massive Stars and the ISM in the Galactic
Center

The Galactic center (GC) is a unique site for a detailed study of a
multitude of complex astrophysical phenomena, which may be common to
nuclear regions of many galaxies. Observable at resolutions
unapproachable in other galaxies, the GC provides an unparalleled
opportunity to improve our understanding of the interrelationships of
massive stars, young stellar clusters, warm and hot ionized gases,
molecular clouds, large scale magnetic fields, and black holes. We
propose the first large-scale hydrogen Paschen alpha line survey of
the GC using NICMOS on the Hubble Space Telescope. This survey will
lead to a high resolution and high sensitivity map of the Paschen
alpha line emission in addition to a map of foreground extinction,
made by comparing Paschen alpha to radio emission. This survey of the
inner 75 pc of the Galaxy will provide an unprecedented and complete
search for sites of massive star formation. In particular, we will be
able to (1) uncover the distribution of young massive stars in this
region, (2) locate the surfaces of adjacent molecular clouds, (3)
determine important physical parameters of the ionized gas, (4)
identify compact and ultra-compact HII regions throughout the GC. When
combined with existing Chandra and Spitzer surveys as well as a wealth
of other multi-wavelength observations, the results will allow us to
address such questions as where and how massive stars form, how
stellar clusters are disrupted, how massive stars shape and heat the
surrounding medium, and how various phases of this medium are
interspersed.

NIC3 11334

NICMOS Cycle 16 Spectrophotometry

Observation of the three primary WD flux standards must be repeated to
refine the NICMOS absolute calibration and monitor for sensitivity
degradation. So far, NICMOS grism spectrophotometry is available for
only ~16 stars with good STIS spectra at shorter wavelengths. There
are more in the HST CALSPEC standard star data base with good STIS
spectra that would also become precise IR standards with NICMOS
absolute SED measurements. Monitoring the crucial three very red stars
(M, L, T) for variability and better S/N in the IR. Apparent
variability was discovered at shorter wavelengths during the ACS
cross-calibration work that revealed a ~2% discrepancy of the cool
star fluxes with respect to the hot primary WD standards. About a
third of these stars are bright enough to do in one orbit, the rest
require 2 orbits.

WFPC2 11201

Systemic and Internal motions of the Magellanic Clouds: Third Epoch
Images

In Cycles 11 and 13 we obtained two epochs of ACS/HRC data for fields
in the Magellanic Clouds centered on background quasars. We used these
data to determine the proper motions of the LMC and SMC to better than
5% and 15% respectively. These are by far the best determinations of
the proper motions of these two galaxies. The results have a number of
unexpected implications for the Milky Way-LMC-SMC system. The implied
three-dimensional velocities are larger than previously believed, and
are not much less than the escape velocity in a standard 10^12 solar
mass Milky Way dark halo. Orbit calculations suggest the Clouds may
not be bound to the Milky Way or may just be on their first passage,
both of which would be unexpected in view of traditional
interpretations of the Magellanic Stream. Alternatively, the Milky Way
dark halo may be a factor of two more massive than previously
believed, which would be surprising in view of other observational
constraints. Also, the relative velocity between the LMC and SMC is
larger than expected, leaving open the possibility that the Clouds may
not be bound to each other. To further verify and refine our results
we now request an epoch of WFPC2/PC data for the fields centered on 40
quasars that have at least one epoch of ACS imaging. We request
execution in snapshot mode, as in our previous programs, to ensure the
most efficient use of HST resources. A third epoch of data of these
fields will provide crucial information to verify that there are no
residual systematic effects in our previous measurements. More
importantly, it will increase the time baseline from 2 to 5 yrs and
will increase the number of fields with at least two epochs of data.
This will reduce our uncertainties correspondingly, so that we can
better address whether the Clouds are indeed bound to each other and
to the Milky Way. It will also allow us to constrain the internal
motions of various populations within the Clouds, and will allow us to
determine a distance to the LMC using rotational parallax.

WFPC2 11227

The Orbital Period for an Ultraluminous X-ray Source in NGC1313

The ultraluminous X-ray sources {ULXs} are extragalactic point sources
with luminosities that exceed the Eddington luminosity for
conventional stellar-mass black holes by factors of 10 - 100. It has
been hotly debated whether the ULXs are just common stellar-mass black
hole sources with beamed emission or whether they are sub-Eddington
sources that are powered by the long-sought intermediate mass black
holes {IMBH}. To firmly decide this question, one must obtain
dynamical mass measurements through photometric and spectroscopic
monitoring of the secondaries of these system. The crucial first step
is to establish the orbital period of a ULX, and arguably the best way
to achieve this goal is by monitoring its ellipsoidal light curve. The
extreme ULX NGC1313 X-2 provides an outstanding target for an orbital
period determination because its relatively bright optical counterpart
{V = 23.5} showed a 15% variation between two HST observations
separated by three months. This level of variability is consistent
with that expected for a tidally distorted secondary star. Here we
propose a set of 20 imaging observations with HST/WFPC2 to define the
orbital period. This would be the first photometric measurement of the
orbital period of a ULX binary. Subsequently, we will propose to
obtain spectroscopic observations to obtain its radial velocity
amplitude and thereby a dynamical estimate of its mass.

WFPC2 11235

HST NICMOS Survey of the Nuclear Regions of Luminous Infrared Galaxies
in the Local Universe

At luminosities above 10^11.4 L_sun, the space density of far-infrared
selected galaxies exceeds that of optically selected galaxies. These
`luminous infrared galaxies' {LIRGs} are primarily interacting or
merging disk galaxies undergoing enhanced star formation and Active
Galactic Nuclei {AGN} activity, possibly triggered as the objects
transform into massive S0 and elliptical merger remnants. We propose
NICMOS NIC2 imaging of the nuclear regions of a complete sample of 88
L_IR 10^11.4 L_sun luminous infrared galaxies in the IRAS Revised
Bright Galaxy Sample {RBGS: i.e., 60 micron flux density 5.24 Jy}.
This sample is ideal not only in its completeness and sample size, but
also in the proximity and brightness of the galaxies. The superb
sensitivity and resolution of NICMOS NIC2 on HST enables a unique
opportunity to study the detailed structure of the nuclear regions,
where dust obscuration may mask star clusters, AGN and additional
nuclei from optical view, with a resolution significantly higher than
possible with Spitzer IRAC. This survey thus provides a crucial
component to our study of the dynamics and evolution of IR galaxies
presently underway with Wide-Field, HST ACS/WFC and Spitzer IRAC
observations of these 88 galaxies. Imaging will be done with the F160W
filter {H-band} to examine as a function of both luminosity and merger
stage {i} the luminosity and distribution of embedded star clusters,
{ii} the presence of optically obscured AGN and nuclei, {iii} the
correlation between the distribution of 1.6 micron emission and the
mid- IR emission as detected by Spitzer IRAC, {iv} the evidence of
bars or bridges that may funnel fuel into the nuclear region, and {v}
the ages of star clusters for which photometry is available via
ACS/WFC observations. The NICMOS data, combined with the HST ACS,
Spitzer, and GALEX observations of this sample, will result in the
most comprehensive study of merging and interacting galaxies to date.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS: (None)

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

*********************** SCHEDULED***** SUCCESSFUL

FGS GSacq*************** 10**************** 10
FGS REacq*************** 03**************** 03
OBAD with Maneuver* **** 26**************** 26

SIGNIFICANT EVENTS: (None)