Daily #4014

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT #4014

PERIOD COVERED: UT December 22, 2005 (DOY 356)

OBSERVATIONS SCHEDULED

ACS/HRC 10476

Accurate Mass Determination of the Ancient White Dwarf ER 8 Through
Astrometric Microlensing

We propose to determine the mass of the very cool white dwarf ER 8
through astrometric microlensing. We have predicted that ER 8 will
pass very close to a 15th-mag background star in January 2006, with an
impact parameter of less than 0.05 arcsec. As it passes in front, it
will cause a deflection of the background star's image by 8
milliarcsec, an amount easily detectable with HST/FGS. The
gravitational deflection angle depends only on the distances and
relative positions of the stars, and on the mass of the white dwarf.
Since the distances and positions can be determined precisely before
the event, the astrometric measurement offers a unique and direct
method to measure the mass of the white dwarf to high accuracy {5%}.
Unlike all other stellar mass determinations, this technique works for
single stars {but only if they are nearby and of sufficient mass}. The
mass of ER 8 is of special interest because it is a member of the
Galactic halo, and appears to be the oldest known field white dwarf.
This object can thus set a lower limit on the age of the Galactic
halo, but since white-dwarf cooling rates depend on their masses, the
mass is a necessary ingredient in the age determination. As a
byproduct, we will obtain an accurate parallax for ER 8, and thus its
luminosity and {from its effective temperature} its radius. Such
quantities are at present rather poorly known for the coolest white
dwarfs, and will provide strong constraints on white-dwarf physics.

ACS/HRC 10547

A SNAP Program to Obtain Complete Wavelength Coverage of Interstellar
Extinction

We propose a SNAP program to obtain ACS/HRC spectra in the near-UV
{PR200L} and near-IR {G800L} for a set of main sequence B stars with
available IUE UV spectrophotometry, optical photometry, and 2MASS IR
photometry. Together with these existing data, the new observations
will provide complete photometric and spectrophotometric coverage from
1150 to 11000 A and enable us to produce complete extinction curves
from the far-UV to the near-IR, with well- determined values of R{V}.
The proposed set of 50 program sight lines includes the full range of
interstellar extinction curve types and a wide range of color
excesses. The new data will allow us to examine variability in the
near-UV through near-IR spectral regions, including the UV-optical
"knee" and the "Very Broad Structure." We will examine the response of
these features to different interstellar environments and their
relationship to other curve features. These are largely unexplored
aspects of extinction curves which will provide additional constraints
on the properties of interstellar grains. The curves will be derived
using stellar atmosphere models to represent the intrinsic spectral
energy distributions of the program stars, eliminating the need to
observe unreddened "standard stars." This approach virtually
eliminates "mismatch error", allowing us to derive extinction curves
with much higher precision than previously possible. In addition, the
new spectra will provide higher S/N data for the peak of the 2175 A
bump than previously available.

ACS/WFC 10497

Cepheid Calibrations of the Luminosity of Two Reliable Type Ia
Supernovae and a Re- determination of the Hubble Constant

We propose to determine the luminosity of two type Ia supernovae {SNe
Ia}, 1995al in NGC 3021 and SN 2002fk in NGC 1309, by observing
Cepheids in their spiral hosts. Modern CCD photometry yields an
extremely tight Hubble diagram for SNe Ia with a precisely determined
intercept {i.e., Delta H_0/H_0}. Yet, the measurement of the true
Hubble constant via SNe Ia is limited by the calibration derived from
problematic and unreliable SN data. Most of the SNe Ia calibrated by
HST to date are significantly compromised by the systematics of
photographic photometry, high reddening and SN peculiarity, and by the
photometric anomolies associated with WFPC2. The extended reach of ACS
now provides opportunities to more reliably calibrate SNe Ia and H_0.
Our Cepheid calibration of a reliable SN Ia dataset, SN 1994ae, using
ACS in Cycle 11 resulted in a 15% increase in H_0 from the value
derived by the HST SN Ia Calibration Program. Yet, there remains a
terribly small sample of reliable SN Ia data sets on which to base
such a crucial cosmological result. SN 1995al and SN 2002fk are two of
the best observed SNe Ia both with little reddening. They provide two
opportunities to use ACS for placing the calibration of H_0 via SN Ia
on firmer footing and potentially improve its precision.

ACS/WFC 10596

AGNs with Intermediate-mass Black Holes: A Test of the Black
Hole-Bulge Paradigm

The recent progress in the study of central black holes in galactic
nuclei has led to a general consensus that supermassive {10^6-10^9
solar mass} black holes are closely connected with the formation and
evolutionary history of large galaxies, especially their bulge
component. Two outstanding issues, however, remain unresolved. Can
central black holes form in the absence of a bulge? And does the mass
function of central black holes extend below 10^6 solar masses?
Intermediate-mass black holes {10^4-10^6 solar masses}, if they exist,
may offer important clues to the nature of the seeds of supermassive
black holes. In a first systematic search using the Sloan Digital Sky
Survey, we have recently discovered 19 Type 1 AGNs with candidate
intermediate-mass black holes that reside in low-luminosity,
presumably late-type host galaxies. Follow-up observations with Keck
indicate that these objects obey the low-mass extension of the
well-known correlation between black hole mass and bulge stellar
velocity dispersion. However, very little is known about the host
galaxies themselves, including the crucial question of whether they
have bulges or not. We propose to obtain ACS/WFC images of this unique
sample of AGNs in order to investigate the detailed structural
properties of the host galaxies. We are particularly keen to determine
whether the hosts contain bulges, and if so, where they lie on the
fundamental plane of spheroids compared to the bulges of supermassive
black holes. We will also be able to measure an accurate optical
luminosity for the AGN, which is an essential ingredient to improve
the current mass estimates.

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.

NIC1/NIC3 10726

NICMOS non-linearity tests

This program incorporates a number of tests to analyse the count rate
dependent non-linearity seen in NICMOS spectro-photometric
observations. In visit 1 we will observe a few fields with stars of a
range in luminosity in NGC1850 with NICMOS in NIC1 in F090M, F110W and
F160W and NIC2 F110W, F160W, and F180W. We will repeat the
observations with flatfield lamp on, creating artificially high
count-rates, allowing tests of NICMOS linearity as function of count
rate. To access the effect of charge trapping and persistence, we
first take darks {so there is not too much charge already trapped},
than take exposures with the lamp off, exposures with the lamp on, and
repeat at the end with lamp off. Finally, we continue with taking
darks during occultation. In visit 2 we will observe
spectro-photometric standard P041C using the G096 and G141 grisms in
NIC3, and repeat the lamp off/on/off test to artificially create a
high background. In visits 3&4 we repeat photometry measurements of
faint standard stars SNAP-2 and WD1657+343, on which the NICMOS
non-linearity was originally discovered using grism observations.
These measurements are repeated, because previous photometry was
obtained with too short exposure times, hence substantially affected
by charge trapping non-linearity. Measurements will be made with NIC1:
Visit 5 forms the persistence test of the program. The bright star
GL-390 {used in a previous persistence test} will iluminate the 3
NICMOS detectors in turn for a fixed time, saturating the center many
times, after which a series of darks will be taken to measure the
persistence {i.e. trapped electrons and the decay time of the traps}.
To determine the wavelength dependence of the trap chance, exposures
of the bright star in different filters will be taken, as well as one
in the G096 grism with NIC3. Most exposures will be 128s long, but two
exposures in the 3rd orbit will be 3x longer, to seperate the effects
of count rate versus total counts of the trap probability {in one
exposure, we get the full PSF worth of count rates, but we need a
longer exposure to separate the effect of rate versus total couts}.
Filters used: NIC1 F090M, F110W, F170M and F160W; NIC2 F110W, F160W,
F205W, F187W; NIC3 G096, F110W, F160W; 3x longer exposures: NIC1 and
NIC2 F110W.

NIC2 10603

Multiwavelength Imaging of Edge-on Protoplanetary Disks: Quantifying
the Growth of Circumstellar Dust

Young, edge-on circumstellar disks are uniquely valuable laboratories
for the study of planet formation. In these objects, the central star
is occulted from direct view, significant PSF artifacts are absent,
and the disk is clearly seen as a central dust lane flanked by faint
disk reflected light. The detailed morphology of these nebulae and its
variation with wavelength provide crucial information on the disk
internal structure and the properties of its constituent dust grains.
A key observable is the slope defining the wavelength dependence of
the dust scattering opacity, which becomes shallower when grain growth
has taken place; multiwavelength resolved disk images are the key
dataset enabling such measurements. Recent analyses of three different
edge-on disks have revealed a diversity in their dust properties that
is indicative of different degrees of dust grain evolution having
taken place in each system. This characterization of disk grain
growth, when applied comparatively to a larger sample of these
objects, would enable the construction of an evolutionary sequence of
young disks at successive stages on the road to planet formation. In
pursuit of this goal, we have identified a sample of 15 edge-on disks
previously discovered by HST or groundbased telescopes, but for which
high fidelity, high spatial resolution images do not yet exist in both
the optical and near-infrared. We propose broad-band multicolor
imaging with NICMOS of all these targets, and ACS imaging of nine of
these targets In combination with existing data, the proposed images
will form a complete database of high resolution optical/near-IR
images for these 15 disk systems. Scattered light modeling will be
used to derive the disk structure and dust properties, yielding
results that will be of fundamental importance for our understanding
of grain properties during protoplanetary disk evolution.

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 05 05
FGS REacq 09 09
OBAD with Maneuver 28 28

SIGNIFICANT EVENTS: (None)