HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT       # 4553

PERIOD COVERED: UT February 22,23,24, 2008 (DOY 053,054,055)

OBSERVATIONS SCHEDULED

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 i

mages. Each observation will need its own CRMAP, as different SAA

passages leave different imprints on the NICMOS detectors.

WFPC2 11289

SL2S: The Strong Lensing Legacy Survey

Recent systematic surveys of strong galaxy-galaxy lenses {CLASS, SLACS,

GOODS, etc.} are producing spectacular results for galaxy masses roughly

below a transition mass M~10^13 Mo. The observed lens properties and

their evolution up to z~0.2, consistent with numerical simulations, can

be described by isothermal elliptical potentials. In contrast, modeling

of giant arcs in X-ray luminous clusters {halo masses M >~10^13 Mo}

favors NFW mass profiles, suggesting that dark matter halos are not

significantly affected by baryon cooling. Until recently, lensing

surveys were neither deep nor extended enough to probe the intermediate

mass density regime, which is fundamental for understanding the assembly

of structures. The CFHT Legacy Survey now covers 125 square degrees, and

thus offers a large reservoir of strong lenses probing a large range of

mass densities up to z~1. We have extracted a list of 150 strong lenses

using the most recent CFHTLS data release via automated procedures.

Following our first SNAPSHOT proposal in cycle 15, we propose to

continue the Hubble follow-up targeting a larger list of 130 lensing

candidates. These are intermediate mass range candidates {between

galaxies and clusters} that are selected in the redshift range of 0.2-1

with no a priori X-ray selection. The HST resolution is necessary for

confirming the lensing candidates, accurate modeling of the lenses, and

probing the total mass concentration in galaxy groups up to z~1 with the

largest unbiased sample available to date.

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.

FGS 11213

Distances to Eclipsing M Dwarf Binaries

We propose HST FGS observations to measure accurate distances of 5

nearby M dwarf eclipsing binary systems, from which model-independent

luminosities can be calculated. These objects have either poor or no

existing parallax measurements. FGS parallax determinations for these

systems, with their existing dynamic masses determined to better than

0.5%, would serve as model-independent anchor points for the low-mass

end of the mass-luminosity diagram.

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 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.

WFPC2 11202

The Structure of Early-type Galaxies: 0.1-100 Effective Radii

The structure, formation and evolution of early-type galaxies is still

largely an open problem in cosmology: how does the Universe evolve from

large linear scales dominated by dark matter to the highly non-linear

scales of galaxies, where baryons and dark matter both play important,

interacting, roles? To understand the complex physical processes

involved in their formation scenario, and why they have the tight

scaling relations that we observe today {e.g. the Fundamental Plane}, it

is critically important not only to understand their stellar structure,

but also their dark-matter distribution from the smallest to the largest

scales. Over the last three years the SLACS collaboration has developed

a toolbox to tackle these issues in a unique and encompassing way by

combining new non-parametric strong lensing techniques, stellar

dynamics, and most recently weak gravitational lensing, with

high-quality Hubble Space Telescope imaging and VLT/Keck spectroscopic

data of early-type lens systems. This allows us to break degeneracies

that are inherent to each of these techniques separately and probe the

mass structure of early-type galaxies from 0.1 to 100 effective radii.

The large dynamic range to which lensing is sensitive allows us both to

probe the clumpy substructure of these galaxies, as well as their

low-density outer haloes. These methods have convincingly been

demonstrated, by our team, using smaller pilot-samples of SLACS lens

systems with HST data. In this proposal, we request observing time with

WFPC2 and NICMOS to observe 53 strong lens systems from SLACS, to obtain

complete multi-color imaging for each system. This would bring the total

number of SLACS lens systems to 87 with completed HST imaging and

effectively doubles the known number of galaxy-scale strong lenses. The

deep HST images enable us to fully exploit our new techniques, beat down

low-number statistics, and probe the structure and evolution of

early-type galaxies, not only with a uniform data-set an order of

magnitude larger than what is available now, but also with a fully

coherent and self-consistent methodological approach!

WFPC2 11134

WFPC2 Tidal Tail Survey: Probing Star Cluster Formation on the Edge

The spectacular HST images of the interiors of merging galaxies such as

the Antennae and NGC 7252 have revealed rich and diverse populations of

star clusters created over the course of the interaction. Intriguingly,

our WFPC2 study of tidal tails in these and other interacting pairs has

shown that star cluster birth in the tails does not follow a similarly

straightforward evolution. In fact, cluster formation in these

relatively sparse environments is not guaranteed -- only one of six

tails in our initial study showed evidence for a significant population

of young star clusters. The tail environment thus offers the opportunity

to probe star cluster formation on the edge of the physical parameter

space {e.g., of stellar and gas mass, density, and pressure} that

permits it to occur. We propose to significantly extend our pilot sample

of optically bright, gas-rich tidal tails by a factor of 4 in number to

include a more diverse population of tails, encompassing major and minor

mergers, gas-rich and gas-poor tails, as well as early, late, and merged

interaction stages. With 21 orbits of HST WFPC2 imaging in the F606W and

F814W filters, we can identify, roughly age-date, and measure sizes of

star clusters to determine what physical parameters affect star cluster

formation. WFPC2 imaging has been used effectively in our initial study

of four mergers, and it will be possible in this program to reach

similar limits of Mv=-8.5 for each of 16 more tails. With the much

larger sample we expect to isolate which factors, such as merger stage,

HI content, and merger mass ratio, drive the formation of star clusters.

WFPC2 11128

Time Scales Of Bulge Formation In Nearby Galaxies

Traditionally, bulges are thought to fit well into galaxy formation

models of hierarchical merging. However, it is now becoming well

established that many bulges formed through internal, secular evolution

of the disk rather than through mergers. We call these objects

pseudobulges. Much is still unknown about pseudobulges, the most

pressing questions being: How, exactly, do they build up their mass? How

long does it take? And, how many exist? We are after an answer to these

questions. If pseudobulges form and evolve over longer periods than the

time between mergers, then a significant population of pseudobulges is

hard to explain within current galaxy formation theories. A pseudobulge

indicates that a galaxy has most likely not undergone a major merger

since the formation of the disk. The ages of pseudobulges give us an

estimate for the time scale of this quiescent evolution. We propose to

use 24 orbits of HST time to complete UBVIH imaging on a sample of 33

nearby galaxies that we have observed with Spitzer in the mid-IR. These

data will be used to measure spatially resolved stellar population

parameters {mean stellar age, metallicity, and star formation history};

comparing ages to star formation rates allows us to accurately constrain

the time scale of pseudobulge formation. Our sample of bulges includes

both pseudo- and classical bulges, and evenly samples barred and

unbarred galaxies. Most of our sample is imaged, 13 have complete UBVIH

coverage; we merely ask to complete missing observations so that we may

construct a uniform sample for studying bulge formation. We also wish to

compare the stellar population parameters to a variety of bulge and

global galaxy properties including star formation rates, dynamics,

internal bulge morphology, structure from bulge-disk decompositions, and

gas content. Much of this data set is already or is being assembled.

This will allow us to derive methods of pseudobulge identification that

can be used to accurately count pseudobulges in large surveys. Aside

from our own science goals, we will present this broad set of data to

the community. Thus, we waive proprietary periods for all observations.

WFPC2 11122

Expanding PNe: Distances and Hydro Models

We propose to obtain repeat narrowband images of a sample of eighteen

planetary nebulae {PNe} which have HST/WFPC2 archival data spanning time

baselines of a decade. All of these targets have previous high

signal-to-noise WFPC2/PC observations and are sufficiently nearby to

have readily detectable expansion signatures after a few years. Our main

scientific objectives are {a} to determine precise distances to these

PNe based on their angular expansions, {b} to test detailed and highly

successful hydrodynamic models that predict nebular morphologies and

expansions for subsamples of round/elliptical and axisymmetric PNe, and

{c} to monitor the proper motions of nebular microstructures in an

effort to learn more about their physical nature and formation

mechanisms. The proposed observations will result in high-precision

distances to a healthy subsample of PNe, and from this their expansion

ages, luminosities, CSPN properties, and masses of their ionized cores.

With good distances and our hydro models, we will be able to determine

fundamental parameters {such as nebular and central star masses,

luminosity, age}. The same images allow us to monitor the changing

overall ionization state and to search for the surprisingly

non-homologous growth patterns to bright elliptical PNe of the same sort

seen by Balick & Hajian {2004} in NGC 6543. Non-uniform growth is a sure

sign of active pressure imbalances within the nebula that require

careful hydro models to understand.

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.

WFPC2 11083

The Structure, Formation and Evolution of Galactic Cores and Nuclei

A surprising result has emerged from the ACS Virgo Cluster Survey

{ACSVCS}, a program to obtain ACS/WFC gz imaging for a large, unbiased

sample of 100 early-type galaxies in the Virgo Cluster. On subarcsecond

scales {i.e., <0.1"-1"}, the HST brightness profiles vary systematically

from the brightest giants {which have nearly constant surface brightness

cores} to the faintest dwarfs {which have compact stellar nuclei}.

Remarkably, the fraction of galaxy mass contributed by the nuclei in the

faint galaxies is identical to that contributed by supermassive black

holes in the bright galaxies {0.2%}. These findings strongly suggest

that a single mechanism is responsible for both types of Central Massive

Object: most likely internally or externally modulated gas inflows that

feed central black holes or lead to the formation of "nuclear star

clusters". Understanding the history of gas accretion, star formation

and chemical enrichment on subarcsecond scales has thus emerged as the

single most pressing question in the study of nearby galactic nuclei,

either active or quiescent. We propose an ambitious HST program {199

orbits} that constitutes the next, obvious step forward:

high-resolution, ultraviolet {WFPC2/F255W} and infrared {NIC1/F160W}

imaging for the complete ACSVCS sample. By capitalizing on HST's unique

ability to provide high-resolution images with a sharp and stable PSF at

UV and IR wavelengths, we will leverage the existing optical HST data to

obtain the most complete picture currently possible for the history of

star formation and chemical enrichment on these small scales. Equally

important, this program will lead to a significant improvement in the

measured structural parameters and density distributions for the stellar

nuclei and the underlying galaxies, and provide a sensitive measure of

"frosting" by young stars in the galaxy cores. By virtue of its superb

image quality and stable PSF, NICMOS is the sole instrument capable of

the IR observations proposed here. In the case of the WFPC2

observations, high-resolution UV imaging {< 0.1"} is a capability unique

to HST, yet one that could be lost at any time.

NIC1/NIC2/NIC3 11060

NICMOS Photometric Stability Monitoring

This NICMOS calibration proposal carries out photometric monitoring

observations during Cycle 15. The format is the same as the Cycle 14

version of the program {10725}, but a few modifications were made with

respect to the Cycle 12 program 9995 and Cycle 13 program 10381.

Provisions had to be made to adapt to 2-gyro mode {G191B2B was added as

extra target to provide target visibility through most of the year}.

Where before 4 or 7 dithers were made in a filter before we moved to the

next filter, now we observe all filters at one position before moving to

the next dither position. While the previous method was chosen to

minimize the effect of persistence, we now realize that persistence may

be connected to charge trapping and by moving through the filter such

that the count rate increases, we reach equilibrium more quickly between

charge being trapped and released. We have also increased exposure times

where possible to reduce the charge trapping non-linearity effects.

WFPC2 11030

WFPC2 WF4 Temperature Reduction #3

In the fall of 2005, a serious anomaly was found in images from the WF4

CCD in WFPC2. The WF4 CCD bias level appeared to have become unstable,

resulting in sporadic images with either low or zero bias level. The

severity and frequency of the problem was rapidly increasing, making it

possible that WF4 would soon become unusable if no work-around were

found. Examination of bias levels during periods with frequent WFPC2

images showed low and zero bias episodes every 4 to 6 hours. This

periodicity is driven by cycling of the WFPC2 Replacement Heater, with

the bias anomalies occurring at the temperature peaks. The other three

CCDs {PC1, WF2, and WF3} appear to be unaffected and continue to operate

properly. Lowering the Replacement Heater temperature set points by a

few degrees C effectively eliminates the WF4 anomaly. On 9 January 2006,

the upper set point of the WFPC2 Replacement Heater was reduced from

14.9C to 12.2C. On 20 February 2006, the upper set point was reduced

from 12.2C to 11.3C, and the lower set point was reduced from 10.9C to

10.0C. These changes restored the WF4 CCD bias level; however, the bias

level has begun to trend downwards again, mimicking its behavior in late

2004 and early 2005. A third temperature reduction is planned for March

2007. We will reduce the upper set point of the heater from 11.3C to

10.4C and the lower set point from 10.0C to 9.1C. The observations

described in this proposal will test the performance of WFPC2 before and

after this temperature reduction. Additional temperature reductions may

be needed in the future, depending on the performance of WF4. Orbits:

internal 26, external 1

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.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary reports

of potential non-nominal performance that will be investigated.)

HSTARS:

11199 - Gsacq(1,3,1) results in fine lock backup

           During LOS GSacq(1,3,1) scheduled at 055/08:15:54 resulted in fine lock

           backup (1,0,1). Stop flags QF3STOPF and QSTOP was received on FGS 3. The

           Map at 08:23:09 showed errors of V1= -8.65, V2= -10.21, V3= -4.41, and

           RSS= 14.10.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

                        SCHEDULED      SUCCESSFUL

FGS GSacq               28                  28                  

FGS REacq               13                  13                 

OBAD with Maneuver 82                 82               

SIGNIFICANT EVENTS: (None)