Daily Report #4595
Cooper, Joe
DAILY REPORT # 4595
PERIOD COVERED: UT April 22, 2008 (DOY 113)
OBSERVATIONS SCHEDULED
ACS/SBC 11131
Star formation at large radii in cooling flow brightest cluster
galaxies
We propose to take deep ACS FUV images of the bright central galaxies
in two powerful cooling flow clusters for which we have VLT UBR
images, with the object of determining whether the UV excesses we
observe at large radii (>15kpc) are caused by young stars, ultrahot
(WR) stars, or an as yet unknown source. Current models of excess UV
light at the AGN-dominated centers of these galaxies cannot easily be
extended to large radii. New understanding of star formation in these
clusters will be directly applicable to scenarios of galaxy formation
in the early universe.
ACS/SBC 11151
Evaluating the Role of Photoevaporation of Protoplanetary Disk
Dispersal
Emission produced by accretion onto the central star leads to
photoevaporation, which may play a fundamental role in disk dispersal.
Models of disk photoevaporation by the central star are challenged by
two potential problems: the emission produced by accretion will be
substantially weaker for low-mass stars, and photoevaporation must
continue as accretion slows. Existing FUV spectra of CTTSs are biased
to solar-mass stars with high accretion rates, and are therefore
insufficient to address these problems. We propose use HST/ACS SBC
PR130L to obtain FUV spectra of WTTSs and of CTTSs at low masses and
mass accretion rates to provide crucial data to evaluate
photoevaporation models. We will estimate the FUV and EUV luminosities
of low-mass CTTSs with small mass accretion rates, CTTSs with
transition disks and slowed accretion, and of magnetically-active
WTTSs.
FGS 11210
The Architecture of Exoplanetary Systems
Are all planetary systems coplanar? Concordance cosmogony makes that
prediction. It is, however, a prediction of extrasolar planetary
system architecture as yet untested by direct observation for main
sequence stars other than the Sun. To provide such a test, we propose
to carry out FGS astrometric studies on four stars hosting seven
companions. Our understanding of the planet formation process will
grow as we match not only system architecture, but formed planet mass
and true distance from the primary with host star characteristics for
a wide variety of host stars and exoplanet masses. We propose that a
series of FGS astrometric observations with demonstrated 1 millisecond
of arc per-observation precision can establish the degree of
coplanarity and component true masses for four extrasolar systems: HD
202206 {brown dwarf+planet}; HD 128311 {planet+planet}, HD 160691 = mu
Arae {planet+planet}, and HD 222404AB = gamma Cephei {planet+star}. In
each case the companion is identified as such by assuming that the
minimum mass is the actual mass. For the last target, a known stellar
binary system, the companion orbit is stable only if coplanar with the
AB binary orbit.
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.
NIC1/NIC2/NIC3 8795
NICMOS Post-SAA calibration - CR Persistence Part 6
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.
NIC2 11219
Active Galactic Nuclei in nearby galaxies: a new view of the origin of
the radio-loud radio-quiet dichotomy?
Using archival HST and Chandra observations of 34 nearby early-type
galaxies {drawn from a complete radio selected sample} we have found
evidence that the radio-loud/radio-quiet dichotomy is directly
connected to the structure of the inner regions of their host galaxies
in the following sense: [1] Radio-loud AGN are associated with
galaxies with shallow cores in their light profiles [2] Radio-quiet
AGN are only hosted by galaxies with steep cusps. Since the brightness
profile is determined by the galaxy's evolution, through its merger
history, our results suggest that the same process sets the AGN
flavour. This provides us with a novel tool to explore the
co-evolution of galaxies and supermassive black holes, and it opens a
new path to understand the origin of the radio-loud/radio-quiet AGN
dichotomy. Currently our analysis is statistically incomplete as the
brightness profile is not available for 82 of the 116 targets. Most
galaxies were not observed with HST, while in some cases the study is
obstructed by the presence of dust features. We here propose to
perform an infrared NICMOS snapshot survey of these 82 galaxies. This
will enable us to i} test the reality of the dichotomic behaviour in a
substantially larger sample; ii} extend the comparison between
radio-loud and radio-quiet AGN to a larger range of luminosities.
WFPC2 11040
Geometric Distortion / Astrometry Closeout
These observations will serve as a final characterization of the
geometric distortion and astrometric calibration. The Omega-Cen inner
calibration field is used. Filters F300W, F555W, and F814W are
observed at 5 roll angles spanning 180 degrees; F218W is observed at a
single roll angle.
WFPC2 11160
Escape fraction and stellar populations in a highly magnified
Lyman-Break Galaxy
Understanding how star-forming galaxies contribute to cosmic
reionization is one of the frontiers of observational cosmology. A key
ingredient in this issue is measuring the escape fraction of
Lyman-continuum photons in high redshift galaxies (z>3).
Gravitationally lensed Lyman-break galaxies (LBGs) act as important
laboratories for studying the resolved physical properties at sub-kpc
scales with high signal-to-noise. Correlating the local escape
fraction with physical parameters derived from stellar population
modeling (such as the star formation rate, age and reddening) will
offer new insights into understanding the physical processes involved
with the production of ionizing photons. We propose here follow-up
observations of the "Cosmic Eye", a remarkable, highly magnified (x
30), Lyman-break galaxy at z~3.07 using WFPC2 and NICMOS. Deep
ultraviolet WFPC2 imaging will provide a detailed study of variations
in the escape fraction, while WFPC2 and NICMOS/NIC2 imaging will
complement the current broad-band detections to allow a precise
modeling of the spatially-dependent spectral energy distribution. This
will allow the first comprehensive analysis between the escape
fraction, the local SED and the dynamics of a distant galaxy.
WFPC2 11232
Determination of Angular Expansion Velocities in the Ring Nebula
The Ring Nebula (NGC 6720) represents an important stage in the
evolution of planetary nebulae, being large enough that it has entered
the post fast-wind stage yet has not reached the late ballistic phase
of objects like the Helix Nebula. Understanding this nebula well
presents the opportunity to determine how nebulae transition from
their creation phase into the form they have as their material enters
the interstellar medium. A recent study based on ground-based
spectroscopy has derived a new and accurate model for the Ring Nebula.
A well defined characteristic of this model is that it predicts a
tangential velocity of 20 km/s whereas the application of its quite
uncertain trigonometric parallax distance of 700 (+450/-200) pc with
the angular expansion velocity determined from HST observations with a
2 year time base indicates a tangential velocity of 69 (+45/-20) km/s.
This disagreement indicates that either the distance is even more
uncertain than thought or that the earlier angular velocity is
incorrect. We propose to make a new set of observations of the Ring
Nebula in the diagnostic emission line filters F469N (HeII), F502N
([OIII]), and F658N ([NII]) that will produce much more accurate
angular velocities than the previous study by having a time base of
8.8 years and imaging the nebula entirely within a single CCD of the
WFPC2. The primary result from this study will be an accurate distance
to this important nebula and from this to be able to use this object
to refine our picture of how planetary nebulae evolve during
middle-age.
WFPC2 11233
Multiple Generations of Stars in Massive Galactic Globular Clusters
This is a follow-up to recent HST imaging of NGC 2808, which
discovered that its main sequence is triple, with three well-separated
parallel branches {Fig.~1}. Along with the double MS of Omega
Centauri, this challenges the long-held paradigm that globular
clusters are simple, single stellar populations. The cause of this
main sequence multiplicity in both clusters is likely to be
differences in helium abundance, which could play a fundamental role
in the understanding of stellar populations. We propose to image seven
more of the most massive globular clusters, to examine their main
sequences for indications of splitting.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.)
HSTARS:
11267 - GSAcq(1,2,1) failed to RGA Control while LOS
Upon acquisition of signal at 113/22:09:19 vehicle was in RGA control,
GSAcq(1,2,1) scheduled for 113/21:46:03 failed to RGA control with
QF2STOPF and QSTOP flags set. No other flags were seen.
Post-acquisition OBAD map at 21:54:07 had RSS error of 20.16
arcseconds.
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL
FGS GSacq 09 08
FGS REacq 06 06
OBAD with Maneuver 30 30
SIGNIFICANT EVENTS: (None)