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Daily Report #4299

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Old February 14th 07, 09:53 PM posted to sci.astro.hubble
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Default Daily Report #4299

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science


PERIOD COVERED: UT February 13, 2007 (DOY 044)


WFPC2 10918

Reducing Systematic Errors on the Hubble Constant: Metallicity
Calibration of the Cepheid PL Relation

Reducing the systematic errors on the Hubble constant is still of
significance and of immediate importance to modern cosmology. One of
the largest remaining uncertainties in the Cepheid-based distance
scale {which itself is at the foundation of the HST Key Project
determination of H_o} which can now be addressed directly by HST, is
the effect of metallicity on the Cepheid Period-Luminosity relation.
Three chemically distinct regions in M101 will be used to directly
measure and thereby calibrate the change in zero point of the Cepheid
PL relation over a range of metallicities that run from SMC-like,
through Solar, to metallicities as high as the most metal-enriched
galaxies in the pure Hubble flow. ACS for the first time offers the
opportunity to make a precise calibration of this effect which
currently accounts for at least a third of the total systematic
uncertainty on Ho. The calibration will be made in the V and I
bandpasses so as to be immediately and directly applicable to the
entire HST Cepheid-based distance scale sample, and most especially to
the highest-metallicity galaxies that were hosts to the Type Ia
supernovae, which were then used to extend the the distance scale
calibration out to cosmologically significant distances.

NIC1/NIC2/NIC3 8793

NICMOS Post-SAA calibration - CR Persistence Part 4

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=3Ddate/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.

NIC3 11064


Now that the spectrophotometric capabilities of the NICMOS grism have
been established, cycle 15 observations are needed to refine the
sensitivity estimates, to check for sensitivity loss with time, to
improve the accuracy of the linearity correction, to improve the
secondary flux standards by re-observation, and to expand the G206
data set now that the sky subtraction technique has been shown to
produce useful fluxes for some of the fainter secondary standards.
These faint secondary IR standards will be a significant step towards
establishing flux standards for JWST, as well as for SNAP, Spitzer,
and SOFIA. 1.Re- observe the 3 primary WDs GD71, G191B2b, & GD153
twice each, once at the beginning and once near the end of the 18
month cycle. To date, we have only 2 observation of each star, while
the corresponding STIS data set for these primary standards ranges
from 6 to 23 obs. No observations exist for GD71 or GD153 with G206,
so that the current G206 sensitivity is defined solely by G191B2B.
Purposes: Refine sensitivities, measure sens losses. Orbits: 2 for
each of 6 visits =3D 12 2. Re-observe WD1057 = & WD1657 plus another
P041C lamp-on visit to improve the scatter in the non-lin measurements
per Fig. 8 of NIC ISR 2006-02. The WD stars require 2 orbits each,
while the lamp-on test is done in one. The very faintest and most
crucial standard WD1657 has 2 good visits already, so to substantially
improve the S/N, two visits of two orbits are needed. Include G206 for
P041C in the lamp-off baseline part of that orbit. Orbits: WD1057-2,
WD1657-4, P041C-1 -- 7 3. Re-observe 9 secondary standards to improve
S/N of the faint ones and to include G206 for all 9. BD+17 {3 obs} is
not repeated in this cycle. Four are bright enough to do in one orbit:
VB8, 2M0036+18, P330E, and P177D. Orbits:2*5+4=3D14 Grand Total orbits
over 18 month cycle 15 is 12+6+14=3D32 {Roelof will submit the P041C
lamp-on visit in a separate program.}

NIC3 11080

Exploring the Scaling Laws of Star Formation

As a variety of surveys of the local and distant Universe are
approaching a full census of galaxy populations, our attention needs
to turn towards understanding and quantifying the physical mechanisms
that trigger and regulate the large-scale star formation rates {SFRs}
in galaxies.

WFPC2 10890

Morphologies of the Most Extreme High-Redshift Mid-IR-Luminous

The formative phase of the most massive galaxies may be extremely
luminous, characterized by intense star- and AGN-formation. Till now,
few such galaxies have been unambiguously identified at high redshift,
restricting us to the study of low-redshift ultraluminous infrared
galaxies as possible analogs. We have recently discovered a sample of
objects which may indeed represent this early phase in galaxy
formation, and are undertaking an extensive multiwavelength study of
this population. These objects are bright at mid-IR wavelengths
{F[24um]0.8mJy}, but deep ground based imaging suggests extremely
faint {and in some cases extended} optical counterparts {R~24-27}.
Deep K-band images show barely resolved galaxies. Mid-infrared
spectroscopy with Spitzer/IRS reveals that they have redshifts z ~
2-2.5, suggesting bolometric luminosities ~10^{13-14}Lsun! We propose
to obtain deep ACS F814W and NIC2 F160W images of these sources and
their environs in order to determine kpc-scale morphologies and
surface photometry for these galaxies. The proposed observations will
help us determine whether these extreme objects are merging systems,
massive obscured starbursts {with obscuration on kpc scales!} or very
reddened {locally obscured} AGN hosted by intrinsically low-luminosity

WFPC2 10913

The Light Echoes around V838 Monocerotis

V838 Monocerotis, which burst upon the astronomical scene in early
2002, is a completely unanticipated new object. It underwent a
large-amplitude and very luminous outburst, during which its spectrum
remained that of an extremely cool supergiant. A rapidly evolving set
of light echoes around V838 Mon was discovered soon after the
outburst, and quickly became the most spectacular display of the
phenomenon ever seen. These light echoes provide the means to
accomplish four unique types of measurements based on continued HST
imaging during the event: {1} Study effects of MHD turbulence at high
resolution and in 3 dimensions; {2} Construct the first unambiguous
and fully 3-D map of a circumstellar dust envelope in the Milky Way;
{3} Study dust physics in a unique setting where the spectrum and
light curve of the illumination, and the scattering angle, are
unambiguously known; and {4} Determine the distance to V838 Mon
through direct geometric techniques. Because of the extreme rarity of
light echoes, this is almost certainly the only opportunity to achieve
such results during the lifetime of HST. We propose two visits during
Cycle 15, in order to continue the mapping of the circumstellar dust
and to achieve the other goals listed above.

WFPC2 11095

Hubble Heritage Observations of NGC 6050

The Hubble Heritage team will use a single pointing of WFPC2 to obtain
F450W, F555W, F656N, and F814W images of NGC 6050 as part of a public
release image.


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


10689 - GSacq(2,3,3) failed to RGA control

GSacq(2,3,3) scheduled at 044/17:25:14 failed at 17:29:07 due to Scan
Step Limit exceeded on FGS 2. The OBAD at 17:19:58 showed errors of
V1=3D2.32, V2=3D-7.92, V3=3D24.45, and RSS=3D 25.80.

10692 - GSACQ(1,2,1) failed, Search Radius Limit Exceeded on FGS 1

Upon acquisition of signal at 045:08:50:59 vehicle was in gyro control
with FGS 1 search radius limit flag set. GSACQ(1,2,1) at 045:08:35:24
failed with search radius limit exceeded. OBAD map after GSACQ failure
showed RSS error of 6.87 arcseconds.



FGS GSacq 06 04
FGS REacq 08 08
OBAD with Maneuver 27 27



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