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HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5198

PERIOD COVERED: 8pm October 6 - 7:59pm October 7, 2010 (DOY 280/00:00z-280/23:59z)

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               11             11       

FGS REAcq               07             07       

OBAD with Maneuver 08             08       

SIGNIFICANT EVENTS: (None)

OBSERVATIONS SCHEDULED:

ACS/WFC 12209

A Strong Lensing Measurement of the Evolution of Mass Structure in Giant

Elliptical Galaxies

The structure and evolution of giant elliptical galaxies provide key

quantitative tests for the theory of hierarchical galaxy formation in a

cold dark matter dominated universe. Strong gravitational lensing

provides the only direct means for the measurement of individual

elliptical galaxy masses beyond the local universe, but there are

currently no large and homogeneous samples of strong lens galaxies at

significant cosmological look-back time. Hence, an accurate and

unambiguous measurement of the evolution of the mass-density structure

of elliptical galaxies has until now been impossible. Using

spectroscopic data from the recently initiated Baryon Oscillation

Spectroscopic Survey (BOSS) of luminous elliptical galaxies at redshifts

from approximately 0.4 to 0.7, we have identified a large sample of

high-probability strong gravitational lens candidates at significant

cosmological look-back time, based on the detection of emission-line

features from more distant galaxies along the same lines of sight as the

target ellipticals. We propose to observe 45 of these systems with the

ACS-WFC in order to confirm the incidence of lensing and to measure the

masses of the lens galaxies. We will complement these lensing mass

measurements with stellar velocity dispersions from ground-based

follow-up spectroscopy. In combination with similar data from the Sloan

Lens ACS (SLACS) Survey at lower redshifts, we will directly measure the

cosmic evolution of the ratio between lensing mass and dynamical mass,

to reveal the structural explanation for the observed size evolution of

elliptical galaxies (at high mass). We will also measure the evolution

of the logarithmic mass-density profile of massive ellipticals, which is

sensitive to the details of the merging histories through which they are

assembled. Finally, we will use our lensing mass-to-light measurements

to translate the BOSS galaxy luminosity function into a mass function,

and determine its evolution in combination with data from the original

Sloan Digital Sky Survey.

ACS/WFC 12210

SLACS for the Masses: Extending Strong Lensing to Lower Masses and

Smaller Radii

Strong gravitational lensing provides the most accurate possible

measurement of mass in the central regions of early-type galaxies

(ETGs). We propose to continue the highly productive Sloan Lens ACS

(SLACS) Survey for strong gravitational lens galaxies by observing a

substantial fraction of 135 new ETG gravitational-lens candidates with

HST-ACS WFC F814W Snapshot imaging. The proposed target sample has been

selected from the seventh and final data release of the Sloan Digital

Sky Survey, and is designed to complement the distribution of previously

confirmed SLACS lenses in lens-galaxy mass and in the ratio of Einstein

radius to optical half-light radius. The observations we propose will

lead to a combined SLACS sample covering nearly two decades in mass,

with dense mapping of enclosed mass as a function of radius out to the

half-light radius and beyond. With this longer mass baseline, we will

extend our lensing and dynamical analysis of the mass structure and

scaling relations of ETGs to galaxies of significantly lower mass, and

directly test for a transition in structural and dark-matter content

trends at intermediate galaxy mass. The broader mass coverage will also

enable us to make a direct connection to the structure of well-studied

nearby ETGs as deduced from dynamical modeling of their line-of-sight

velocity distribution fields. Finally, the combined sample will allow a

more conclusive test of the current SLACS result that the intrinsic

scatter in ETG

mass-density structure is not significantly correlated with any other

galaxy observables. The final SLACS sample at the conclusion of this

program will comprise approximately 130 lenses with known foreground and

background redshifts, and is likely to be the largest confirmed sample

of strong-lens galaxies for many years to come.

COS/NUV/FUV 12178

Spanning the Reionization History of IGM Helium: a Highly Efficient

Spectral Survey of the Far-UV-Brightest Quasars

The reionization of IGM helium likely occurred at redshifts of z=3 to 4.

Detailed studies of HeII Ly-alpha absorption toward a handful of quasars

at 2.7<z<3.3 confirm the potential of such IGM probes, but the small

sample and redshift range limited confidence in cosmological inferences.

The requisite unobscured sightlines to high redshift are extremely rare;

but we've cross-correlated 10, 000 z>2.8 SDSS DR7 (and other) quasars

with GALEX GR4/5, to identify 630 candidates potentially useful for HST

HeII studies. Our cycle 15-16 HST trials confirm our approach, verifying

twenty new HeII quasars at unprecedented 40% efficiency. We propose to

complete the first efficient (80% with refinements) survey for HeII

quasars, via reconnaissance (~1 orbit) COS spectra of a highly select

subset of 17 SDSS/GALEX quasars at 2.7<z<3.8. Along with past work, this

program will yield 3-4 of the brightest far-UV HeII sightlines within

each of 10-12 redshift bins spanning 2.7<z<3.8, enabling a community

sample suitable for detailed spectral follow-up with HST. Herein, we

will also directly obtain quality UV spectral stacks within each

redshift bin to trace the reionization history of IGM helium; such

spectral stacks average over cosmic variance and individual object

pathology. Our high-yield HeII sightline sample and spectral stacks will

enable confident conclusions about the IGM baryon density, the spectrum

and evolution of the ionizing background, the evolution of HeII opacity,

and the epoch of helium reionization.

COS/NUV/FUV 12299

Spectroscopic Signatures of Binary and Recoiling Black Holes

We propose to obtain UV the spectra of the Ly-alpha and Mg II lines of

13 SDSS quasars whose H-beta lines are offset by 1000-4000 km/s from

their systemic redshifts. Such lines have been suggested to originate in

recoiling or close binary black holes. However these interpretations are

not unique and UV spectroscopy, possible only with the HST, can

discriminate between competing possibilities. Identifying such systems

is extremely important in the context of scenarios for galaxy formation

and evolution and in view of recent predictions from numerical

relativity. Close binary black holes represent an apparently inevitable

stage in the merger of two massive galaxies. The subsequent merger of

the members of the binary is expected to produce a recoiling black hole

in some fraction of cases. Thus, the census of such systems, their

environments, and hosts can constrain some of the more uncertain

parameters in evolutionary models. But before we can find them in any

numbers, we need to evaluate the candidates known so far. This is the

goal of our proposal.

COS/NUV/FUV/WFC3/UV 12248

How Dwarf Galaxies Got That Way: Mapping Multiphase Gaseous Halos and

Galactic Winds Below L*

One of the most vexing problems in galaxy formation concerns how gas

accretion and feedback influence the evolution of galaxies. In high mass

galaxies, numerical simulations predict the initial fuel is accreted

through 'cold' streams, after which AGN suppress star formation to leave

galaxies red and gas-poor. In the shallow potential wells that host

dwarf galaxies, gas accretion can be very efficient, and "superwinds"

driven either by hot gas expelled by SNe or momentum imparted by SNe and

hot-star radiation are regarded as the likely source(s) of feedback.

However, major doubts persist about the physics of gas accretion, and

particularly about SN-driven feedback, including their scalings with

halo mass and their influence on the evolution of the galaxies. While

"superwinds" are visible in X-rays near the point of their departure,

they generally drop below detectable surface-brightness limits at ~ 10

kpc. Cold clumps in winds can be detected as blue-shifted absorption

against the galaxy's own starlight, but the radial extent of these winds

are difficult to constrain, leaving their energy, momentum, and ultimate

fate uncertain. Wind prescriptions in hydrodynamical simulations are

uncertain and at present are constrained only by indirect observations,

e.g. by their influence on the stellar masses of galaxies and IGM

metallicity. All these doubts lead to one conclusion: we do not

understand gas accretion and feedback because we generally do not

observe the infall and winds directly, in the extended gaseous halos of

galaxies, when it is happening. To do this effectively, we must harness

the power of absorption-line spectroscopy to measure the density,

temperature, metallicity, and kinematics of small quantities of diffuse

gas in galaxy halos. The most important physical diagnostics lie in the

FUV, so this is uniquely a problem for HST and COS. We propose new COS

G130M and G160M observations of 41 QSOs that probe the gaseous halos of

44 SDSS dwarf galaxies well inside their virial radii. Using sensitive

absorption-line measurements of the multiphase gas diagnostics Lya,

CII/IV, Si II/III/IV, and other species, supplemented by optical data

from SDSS and Keck, we will map the halos of galaxies with L = 0.02 -

0.3 L*, stellar masses M* = 10^(8-10) Msun, over impact parameter from

15 - 150 kpc. These observations will directly constrain the content and

kinematics of accreting and outflowing material, provide a concrete

target for simulations to hit, and statistically test proposed galactic

superwind models. These observations will also inform the study of

galaxies at high z, where the shallow halo potentials that host dwarf

galaxies today were the norm. These observations are low-risk and

routine for COS, easily schedulable, and promise a major advance in our

understanding of how dwarf galaxies came to be.

STIS/CCD 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

STIS/CCD 11847

CCD Bias Monitor-Part 2

Monitor the bias in the 1x1, 1x2, 2x1, and 2x2 bin settings at gain=1,

and 1x1 at gain = 4, to build up high-S/N superbiases and track the

evolution of hot columns.

WFC3/IR 12283

WFC3 Infrared Spectroscopic Parallel Survey (WISP): A Survey of Star

Formation Across Cosmic Time

We will use the unique power of WFC3 slitless spectroscopy to measure

cosmic star formation across its peak epoch. The broad, continuous,

spectral coverage of the G102 and G141 grisms provides the best

currently feasible measurement of the star formation rate continuously

from 0.5<z<2.5, over which ground-based searches are severely limited.

Our Cycle 17 pure-parallel grism program has proven efficient for

identifying line emission from galaxies across this large fraction of

cosmic time. With less than two months of WFC3 observing completed, our

new measurements have more than doubled the sample of emission-line

galaxies that we found over the entire NICMOS Parallel Grism program. We

propose to extend this cost-effective WFC3 Survey by using 280 orbits of

pure parallel grism spectroscopy in 50 deep (4-5 orbit) fields with both

G102 and G141, and 40 shallow (2-3 orbit) fields with G141 alone. This

will complete a sample of 2000-3000 emission line galaxies in the

"redshift desert" and search for serendipitous Lya emitters at z>5.5.

Our primary science goals are: (1) Measure ratios of bright emission

lines ([OII], [OIII], Ha, and Hb) in a substantial fraction of these

galaxies, thereby estimating dust and metallicity evolution in a sample

of galaxies that is not biased by photometric selection. (2) Derive an

extinction-corrected Ha luminosity function, with a 20 times larger

sample than our previous NICMOS results. (3) Measure the

mass-metallicity relation at crucial intermediate redshifts, with the

support of our ongoing ground-based, follow-up, observing program (4)

Determine the spectroscopic close pair fraction in this sample, in order

to constrain hierarchal merging models (5) Uncover a new sample of

obscured AGN at these redshifts and, (6) Use the Balmer break diagnostic

to constrain the ages of continuum detected sources down to H = 25.

As a bonus, these observations will be sensitive to Lya emission at

z>5.5, taking advantage of continuous spectral coverage to observe large

volumes for luminous galaxies at the highest redshifts. Over Cycles 17

and 18, we expect to detect 5-20 LAEs over redshifts spanning 5.5 < z <

7.5. These observations will likely place the most stringent constraint

on the numbers of z>6.5 Lya emitters until JWST. We are waiving all

proprietary rights to our data and will make high-level data products

available through the ST/ECF.

WFC3/IR/S/C 11929

IR Dark Current Monitor

Analyses of ground test data showed that dark current signals are more

reliably removed from science data using darks taken with the same

exposure sequences as the science data, than with a single dark current

image scaled by desired exposure time. Therefore, dark current images

must be collected using all sample sequences that will be used in

science observations. These observations will be used to monitor changes

in the dark current of the WFC3-IR channel on a day-to-day basis, and to

build calibration dark current ramps for each of the sample sequences to

be used by Gos in Cycle 17. For each sample sequence/array size

combination, a median ramp will be created and delivered to the

calibration database system (CDBS).

WFC3/IR/UV 12163

Structure and Stellar Content of the Nearest Nuclear Clusters in

Late-Type Spiral Galaxies

HST surveys have shown that nuclear star clusters are nearly ubiquitous

in late-type, bulgeless disk galaxies. In early-type galaxies, the

central black hole mass correlates with the bulge mass and velocity

dispersion, but the relationship between black hole mass and host galaxy

properties in bulgeless galaxies is not yet understood. Some nuclear

clusters (such as the one in M33) do not contain a central massive black

hole at all, while other late-type galaxies (such as NGC 4395) are known

to contain accretion-powered active nuclei within their nuclear

clusters, indicating that a central black hole is present. But, the

overall "occupation fraction" of black holes within nuclear clusters is

largely unconstrained. Measurement of the structure, dynamics, and

stellar content of nuclear star clusters is an important pathway toward

understanding the demographics of low-mass black holes in late-type

galaxies.

We propose to obtain multi-filter WFC3 UV, optical, and near-IR images

of 10 of the nearest and brightest nuclear clusters in late-type spiral

galaxies. We will use the new WFC3 data to measure the cluster radial

profiles, to search for color gradients, and in combination with

ground-based spectroscopy and stellar population modeling, to determine

the stellar masses of the clusters. Since nuclear clusters are known to

contain stellar populations with a wide range of ages, the broad

wavelength coverage of our data will provide new leverage to constrain

the star formation history of the clusters. We will carry out dynamical

modeling for the clusters, using the cluster structural parameters and

stellar M/L ratios measured from the WFC3 data and kinematics measured

from ground-based, adaptive-optics assisted integral-field spectroscopy

(already obtained or approved for 8 of the 10 targets). This will yield

tight new constraints on the masses of intermediate-mass black holes

(IMBH) within the clusters, and may result in the first dynamical

detections of IMBHs in the nuclei of late-type spirals.

WFC3/UV 12215

Searching for the Missing Low-Mass Companions of Massive Stars

Recent results on binary companions of massive O stars appear to

indicate that the distribution of secondary masses is truncated at low

masses. It thus mimics the distribution of companions of G dwarfs and

also the Initial Mass Function (IMF), except that it is shifted upward

by a factor of 20 in mass. These results, if correct, provide a

distribution of mass ratios that hints at a strong constraint on the

star-formation process. However, this intriguing result is derived from

a complex simulation of data which suffer from observational

incompleteness at the low-mass end.

We propose a snapshot survey to test this result in a very direct way.

HST WFC3 images of a sample of the nearest Cepheids (which were formerly

B stars of ~5 Msun) will search for low-mass companions down to M

dwarfs. We will confirm any companions as young stars, and thus true

physical companions, through follow-up Chandra X-ray images. Our survey

will show clearly whether the companion mass distribution is truncated

at low masses, but at a mass much higher than that of the IMF or G

dwarfs.

WFC3/UV 12245

Orbital Evolution and Stability of the Inner Uranian Moons

Nine densely-packed inner moons of Uranus show signs of chaos and

orbital instability over a variety of time scales. Many moons show

measureable orbital changes within a decade or less. Long-term

integrations predict that some moons could collide in less than one

million years. One faint ring embedded in the system may, in fact, be

the debris left behind from an earlier such collision. Meanwhile, the

nearby moon Mab falls well outside the influence of the others but

nevertheless shows rapid, as yet unexplained, changes in its orbit. It

is embedded within a dust ring that also shows surprising variability. A

highly optimized series of observations with WFC3 over the next three

cycles will address some of the fundamental open questions about this

dynamically active system: Do the orbits truly show evidence of chaos?

If so, over what time scales? What can we say about the masses of the

moons involved? What is the nature of the variations in Mab's orbit? Is

Mab's motion predictable or random? Astrometry will enable us to derive

the orbital elements of these moons with 10-km precision. This will be

sufficient to study the year-by-year changes and, combined with other

data from 2003-2007, the decadal evolution of the orbits. The pairing of

precise astrometry with numerical integrations will enable us to derive

new dynamical constraints on the masses of these moons. Mass is the

fundamental unknown quantity currently limiting our ability to reproduce

the interactions within this system. This program will also capitalize

upon our best opportunity for nearly 40 years to study the unexplained

variations in Uranus's faint outer rings.

WFC3/UV 12324

The Temperature Profiles of Quasar Accretion Disks

We can now routinely measure the size of quasar accretion disks using

gravitational microlensing of lensed quasars. At optical wavelengths we

observe a size and scaling with black hole mass roughly consistent with

thin disk theory but the sizes are larger than expected from the

observed optical fluxes. One solution would be to use a flatter

temperature profile, which we can study by measuring the wavelength

dependence of the disk size over the largest possible wavelength

baseline. Thus, to understand the size discrepancy and to probe closer

to the inner edge of the disk we need to extend our measurements to UV

wavelengths, and this can only be done with HST. For example, in the UV

we should see significant changes in the optical/UV size ratio with

black hole mass. We propose monitoring 5 lenses spanning a broad range

of black hole masses with well-sampled ground based light curves,

optical disk size measurements and known GALEX UV fluxes during Cycles

17 and 18 to expand from our current sample of two lenses. We would

obtain 5 observations of each target in each Cycle, similar to our

successful strategy for the first two targets.

WFC3/UV 12345

UVIS Long Darks Test

Darks during SMOV showed a systematically lower global dark rate as well

as lower scatter when compared to the Cycle 17 darks. Those two sets of

exposures differ in exposure time - 1800 sec during SMOV and 900 sec

during Cycle 17. Hypothetically, the effect could be caused by

short-duration stray light, say ~500-sec in duration. During the latter

part of Cycle 17, operation of WFC3 was changed to additionally block

the light path to the detector with the CSM. This program acquires a

small number of darks at the longer SMOV exposure times (1800 sec) in

order to check whether the effect repeats in the new operating mode.

WFC3/UVIS 11905

WFC3 UVIS CCD Daily Monitor

The behavior of the WFC3 UVIS CCD will be monitored daily with a set of

full-frame, four-amp bias and dark frames. A smaller set of 2Kx4K

subarray biases are acquired at less frequent intervals throughout the

cycle to support subarray science observations. The internals from this

proposal, along with those from the anneal procedure (Proposal 11909),

will be used to generate the necessary superbias and superdark reference

files for the calibration pipeline (CDBS).