HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5189

PERIOD COVERED: 5am September 24 - 5am September 27, 2010 (DOY 267/09:00z-270/09:00z)

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               24             24      

FGS REAcq               23             23      

OBAD with Maneuver 22             22      

SIGNIFICANT EVENTS: (None)

OBSERVATIONS SCHEDULED:

COS/NUV/FUV/STIS/CCD 12312

Hubble Investigation of 103P/Hartley 2 in Support of NASA's DIXI Mission

Comet 103P/Hartley 2 is a small but highly active comet that will pass

unusually close to the Earth (0.12 AU) during the fall of 2010, when it

will also be visited by NASA's DIXI spacecraft. We propose a 15-orbit

spectroscopic observing campaign with Hubble, comprised of three 5-orbit

visits spanning a 2-month period, to measure the abundances of several

key volatiles (CO, CO2, S2) and their possible seasonal variations. CO

has not yet been detected in 103P, and Hubble may be the only facility

capable of doing it. Hubble is also uniquely capable of providing

confirmation of DIXI's measurements of the CO2 abundance. The DIXI flyby

is an exceptional opportunity to study the nature of comets, and Hubble

will contribute important and unique data to the international campaign

supporting this mission.

ACS/WFC 12292

SWELLS: Doubling the Number of Disk-dominated Edge-on Spiral Lens

Galaxies

The formation of realistic disk galaxies within the LCDM cosmology is

still largely an unsolved problem. Theory is now beginning to make

predictions for how dark matter halos respond to galaxy formation, and

for the properties of disk galaxies. Measuring the density profiles of

dark matter halos on galaxy scales is therefore a strong test for the

standard paradigm of galaxy formation, offering great potential for

discovery. However, the degeneracy between the stellar and dark matter

contributions to galaxy rotation curves remains a major obstacle. Strong

gravitational lensing, when combined with spatially resolved kinematics

and stellar population models, can solve this long-standing problem.

Unfortunately, this joint methodology could not be exploited until

recently due to the paucity of known edge-on spiral lenses. We have

developed and demonstrated an efficient technique to find exactly these

systems. During supplemental cycle-16 we discovered five new spiral lens

galaxies, suitable for rotation curve measurements. We propose

multi-color HST imaging of 16 candidates and 2 partially-imaged

confirmed systems, to measure a sample of eight new edge-on spiral

lenses. This program will at least double the number of known

disk-dominated systems. This is crucial for constraining the relative

contribution of the disk, bulge and dark halo to the total density

profile.

WFC3/IR 12217

Spectroscopy of Faint T Dwarf Calibrators: Understanding the Substellar

Mass Function and the Coolest Brown Dwarfs

More than 100 methane brown dwarfs, or T dwarfs, have now been

discovered in the local field with 2MASS, SLOAN and UKIDSS, opening up a

new area of physics describing objects at 450-1400 K. However, very few

calibrator objects exist with well established ages and metallicities. A

very surprising result from the UKIDSS sample (supported by 2MASS and

SLOAN) is that the substellar mass function in the local field appears

to decline to lower masses, in marked contrast to the rising initial

mass function (IMF) observed in young clusters. Given that such a

difference between the present day IMF and the Galactic time-averaged

IMF is unlikely, it is very possible that the apparently falling IMF is

an artifact of serious errors in either T model atmospheres or the

evolutionary isochrones. We propose WFC3 spectroscopy of 4 faint T dwarf

calibrators with well established ages and metallicities in the Pleiades

and Sigma Ori clusters, and 2 faint field T dwarfs from UKIDSS for

comparison. These spectra will constitute vital calibration data for T

dwarf atmospheres with a wide range of surface gravities, which will be

used to test and improve the model atmospheres. They will also aid

preparation for future spectroscopy of the much larger numbers of field

T dwarfs to soon be found by VISTA and WISE. These new surveys will

permit a more precise measurement of the mass function and detection of

even cooler objects.

COS/NUV 12042

COS-GTO: Pluto

We seek to measure Pluto's albedo below 2100, to better constrain

surface composition. COS observations will provide a substantial

improvement in the S/N of Pluto spectra from <1800 to 2100. Accumulation

of past HST/FOS spectra yields extremely low S/N below 2000 (S/N of only

1-3 in 100 bins; Krasnopolsky 2001). We expect to achieve S/N=5 at 1950

with 10 binning. In addition to spectrally broad albedo measurements,

these observations could reveal line or molecular band emission, such as

C I 1931 or CO 1993.

WFC3/UVIS 12018

Ultra-Luminous X-Ray Sources in the Most Metal-Poor Galaxies

There is growing observational and theoretical evidence to suggest that

Ultra-Luminous X-ray sources (ULX) form preferentially in low

metallicity environments. Here we propose a survey of 27 nearby (<

30Mpc) star-forming Extremely Metal Poor Galaxies (Z<5% solar). There

are almost no X-ray observations of such low abundance galaxies (3 in

the Chandra archive). These are the most metal-deficient galaxies known,

and a logical place to find ULX if they favor metal-poor systems. We

plan to test recent population synthesis models which predict that ULX

should be very numerous in metal-poor galaxies. We will also test the

hypothesis that ULX form in massive young star clusters, and ask for HST

time to obtain the necessary imaging data.

ACS/WFC 11996

CCD Daily Monitor (Part 3)

This program comprises basic tests for measuring the read noise and dark

current of the ACS WFC and for tracking the growth of hot pixels. The

recorded frames are used to create bias and dark reference images for

science data reduction and calibration. This program will be executed

four days per week (Mon, Wed, Fri, Sun) for the duration of Cycle 17. To

facilitate scheduling, this program is split into three proposals. This

proposal covers 308 orbits (19.25 weeks) from 21 June 2010 to 1 November

2010.

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/UVIS 11914

UVIS Earth Flats

This program is an experimental path finder for Cycle 18 calibration.

Visible-wavelength flat fields will be obtained by observing the dark

side of the Earth during periods of full moon illumination. The

observations will consist of full-frame streaked WFC3 UVIS imagery: per

22- min total exposure time in a single "dark-sky" orbit, we anticipate

collecting 7000 e/pix in F606W or 4500 e/pix in F814W. To achieve

Poisson S/N > 100 per pixel, we require at least 2 orbits of F606W and 3

orbits of F814W.

For UVIS narrowband filters, exposures of 1 sec typically do not

saturate on the sunlit Earth, so we will take sunlit Earth flats for

three of the more-commonly used narrowband filters in Cycle 17 plus the

also-popular long-wavelength quad filters, for which we get four filters

at once.

Why not use the Sunlit Earth for the wideband visible-light filters? It

is too bright in the visible for WFC3 UVIS minimum exposure time of 0.5

sec. Similarly, for NICMOS the sunlit-Earth is too bright which

saturates the detector too quickly and/or induces abnormal behaviors

such as super-shading (Gilmore 1998, NIC 098-011). In the narrowband

visible and broadband near- UV its not too bright (predictions in Cox et

al. 1987 "Standard Astronomical Sources for HST: 6. Spatially Flat

Fields." and observations in ACS Program 10050).

Other possibilities? Cox et al.'s Section II.D addresses many other

possible sources for flat fields, rejecting them for a variety of

reasons. A remaining possibility would be the totally eclipsed moon.

Such eclipses provide approximately 2 hours (1 HST orbit) of opportunity

per year, so they are too rare to be generically useful. An advantage of

the moon over the Earth is that the moon subtends less than 0.25 square

degree, whereas the Earth subtends a steradian or more, so scattered

light and light potentially leaking around the shutter presents

additional problems for the Earth. Also, we're unsure if HST can point

180 deg from the Sun.

WFC3/UVIS 11908

Cycle 17: UVIS Bowtie Monitor

Ground testing revealed an intermittent hysteresis type effect in the

UVIS detector (both CCDs) at the level of ~1%, lasting hours to days.

Initially found via an unexpected bowtie- shaped feature in flatfield

ratios, subsequent lab tests on similar e2v devices have since shown

that it is also present as simply an overall offset across the entire

CCD, i.e., a QE offset without any discernable pattern. These lab tests

have further revealed that overexposing the detector to count levels

several times full well fills the traps and effectively neutralizes the

bowtie. Each visit in this proposal acquires a set of three 3x3 binned

internal flatfields: the first unsaturated image will be used to detect

any bowtie, the second, highly exposed image will neutralize the bowtie

if it is present, and the final image will allow for verification that

the bowtie is gone.

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).

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.

STIS/CCD 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

FGS 11787

Dynamical Masses and Radii of Four White Dwarf Stars

This proposal uses the FGS1R in Trans mode to resolve a pair of double

degenerate binary systems (WD1639+153 and WD 1818+26) in order to

determine their orbital elements. In addition, the binaries and several

nearby field stars are observed by FGS1R in Pos mode to establish the

local inertial reference frame of each binary, as well as its parallax

and proper motion. This will allow for a direct measurement of the

distance, which yields the intrinsic luminosity, and when combined with

the spectroscopic estimates of the T_eff, the radius of each of the four

WD stars. When combined with the orbital elements, this leads to a

dynamical mass measurement for each WD, and a four calibration points of

the WD mass-radius relation.

ACS/WFC3 11735

The LSD Project: Dynamics, Merging and Stellar Populations of a Sample

of Well-Studied LBGs at z~3

A large observational effort with the ground-based ESO/VLT telescopes

allowed us to obtain deep, spatially-resolved, near-IR spectra of

complete sample of 11 Lyman-Break Galaxies at z~3.1. These observations

were used to obtain, for the first time, the metallicity and the

dynamical properties of a sample of objects that, albeit small, is

representative of the total population of the LBGs. We propose to use

HST to obtain high-resolution optical and near-IR images of this sample

of LBGs in order to study the broad-band morphology and the stellar

light distribution of these galaxies. These images, exploiting the

superior spatial resolution of HST images and the low-background : 1-

will allow a precise measure of the dynamical mass from the velocity

field derived with spectroscopy; 2- will permit a comparison of the

distribution of star formation (from the line emission) with the

underlying stellar population, and, 3- will be used to check if the

complex velocity field and the multiple line-emitting regions detected

in most targets can be ascribed to on-going mergers. This accurate study

will shed light on a number of unsolved problems still affecting the

knowledge of the LBGs.

ACS/WFC3 11734

The Hosts of High Redshift Gamma-Ray Bursts

Gamma-ray bursts are the most luminous explosive events known, acting as

beacons to the high redshift universe. Long duration GRBs have their

origin in the collapse of massive stars and thus select star forming

galaxies across a wide range of redshift. Due to their bright afterglows

we can study the details of GRB host galaxies via absorption

spectroscopy, providing redshifts, column densities and metallicities

for galaxies far too faint to be accessible directly with current

technology. We have already obtained deep ground based observations for

many hosts and here propose ACS/WFC3 and WFC3 observations of the fields

of bursts at z>3 which are undetected in deep ground based images. These

observations will study the hosts in emission, providing luminosities

and morphologies and will enable the construction of a sample of high-z

galaxies with more detailed physical properties than has ever been

possible before.

COS/FUV 11619

Definitive ISM Abundances through Low-mass X-ray Binaries as Lighthouses

We propose observations of the UV spectra of two low-mass X-ray binaries

(Sco X-1 and Cyg X-2) with existing Chandra X-Ray Observatory (CXO)

data. From the X-ray data we will measure total (phase-independent)

column densities of O, Ne, and Fe. From the UV data we will determine

gas-phase column densities of H and O. The data in conjunction will

allow us to make unique measurements of the total interstellar

abundances of oxygen, neon, and iron, and direct measurements of the

dust-phase abundances of O and Fe.

WFC3/UV 11605

Obtaining the Missing Links in the Test of Very Low Mass Evolutionary

Models with HST

We are proposing for spatially resolved ACS+HRC observations of 11 very

low mass binaries spanning late-M, L and T spectral types in order to

obtain precise effective temperature measurements for each component.

All of our targets are part of a program in which we are measuring

dynamical masses of very low-mass binaries to an unprecedented precision

of 10% (or better). However, without precise temperature measurements,

the full scientific value of these mass measurements cannot be realized.

Together, mass and temperature measurements will allow us to distinguish

between brown dwarf evolutionary models that make different assumptions

about the interior and atmospheric structure of these ultra-cool

objects. While dynamical masses can be obtained from the ground in the

near-IR, obtaining precise temperatures require access to optical data

which, for these sub-arcsecond binaries, can only be obtained from space

with Hubble.

WFC3/ACS/IR 11600

Star Formation, Extinction, and Metallicity at 0.7<z<1.5: H-Alpha Fluxes

and Sizes from a Grism Survey of GOODS-N

The global star formation rate (SFR) is ~10x higher at z=1 than today.

This could be due to drastically elevated SFR in some fraction of

galaxies, such as mergers with central bursts, or a higher SFR across

the board. Either means that the conditions in z=1 star forming galaxies

could be quite different from local objects. The next step beyond

measuring the global SFR is to determine the dependence of SFR,

obscuration, metallicity, and size of the star-forming region on galaxy

mass and redshift. However, SFR indicators at z=1 typically apply local

calibrations for UV, [O II] and far-IR, and do not agree with each other

on a galaxy-by-galaxy basis. Extinction, metallicity, and dust

properties cause uncontrolled offsets in SFR calibrations. The great

missing link is Balmer H-alpha, the most sensitive probe of SFR. We

propose a slitless WFC3/G141 IR grism survey of GOODS-N, at 2

orbits/pointing. It will detect Ha+[N II] emission from 0.7<z<1.5, to

L(Ha) = 1.7 x 10^41 erg/sec at z=1, measuring H-alpha fluxes and sizes

for > 600 galaxies, and a small number of higher-redshift emitters. This

will produce: an emission-line redshift survey unbiased by magnitude and

color selection; star formation rates as a function of galaxy

properties, e.g. stellar mass and morphology/mergers measured by ACS;

comparisons of SFRs from H-alpha to UV and far-IR indicators;

calibrations of line ratios of H-alpha to important nebular lines such

as [O II] and H-beta, measuring variations in metallicity and extinction

and their effect on SFR estimates; and the first measurement of scale

lengths of the H-alpha emitting, star-forming region in a large sample

of z~1 sources.

ACS/WFC3 11593

Dynamical Masses of the Coolest Brown Dwarfs

T dwarfs are excellent laboratories to study the evolution and the

atmospheric physics of both brown dwarfs and extrasolar planets. To

date, only a single T dwarf binary has a dynamical mass determination,

and more are sorely needed. The prospects of measuring more dynamical

masses over the next decade are limited to 6 known short-period T dwarf

binaries. We propose here to obtain Long-Term HST/ACS monitoring for the

3 of the 6 binaries which cannot be resolved with AO from the ground.

Upon completion, our program will substantially increase the number of T

dwarf dynamical mass measurements and thereby provide key benchmarks for

testing theoretical models of ultracool objects.

WFC3/IR 11591

Are Low-Luminosity Galaxies Responsible for Cosmic Reionization?

Our group has demonstrated that massive clusters, acting as powerful

cosmic lenses, can constrain the abundance and properties of

low-luminosity star-forming sources beyond z~6; such sources are thought

to be responsible for ending cosmic reionization. The large

magnification possible in the critical regions of well-constrained

clusters brings sources into view that lie at or beyond the limits of

conventional exposures such as the UDF. We have shown that the

combination of HST and Spitzer is particularly effective in delivering

the physical properties of these distant sources, constraining their

mass, age and past star formation history. Indirectly, we therefore gain

a valuable glimpse to yet earlier epochs. Recognizing the result (and

limitations) of blank field surveys, we propose a systematic search

through 10 lensing clusters with ACS/F814W and WFC3/[F110W+F160W] (in

conjunction with existing deep IRAC data). Our goal is to measure with

great accuracy the luminosity function at z~7 over a range of at least 3

magnitude, based on the identification of about 50 lensed galaxies at

6.5<z<8. Our survey will mitigate cosmic variance and extend the search

both to lower luminosities and, by virtue of the WFC3/IRAC combination,

to higher redshift. Thanks to the lensing amplification spectroscopic

follow-up will be possible and make our findings the most robust prior

to the era of JWST and the ELTs.

ACS/SBC/COS/NUV/FUV 11579

The Difference Between Neutral- and Ionized-Gas Metal Abundances in

Local Star-Forming Galaxies with COS

The metallicity of galaxies and its evolution with redshift is of

paramount importance for understanding galaxy formation. Abundances in

the interstellar medium (ISM) are typically determined using

emission-line spectroscopy of HII regions. However, since HII regions

are associated with recent SF they may not have abundances typical for

the galaxy as a whole. This is true in particular for star-forming

galaxies (SFGs), in which the bulk of the metals may be contained in the

neutral gas. It is therefore important to directly probe the metal

abundances in the neutral gas. This can be done using absorption lines

in the Far UV. We have developed techniques to do this in SFGs, where

the absorption is measured for sightlines toward bright SF regions

within the galaxy itself. We have successfully applied this technique to

a sample of galaxies observed with FUSE. The results have been very

promising, suggesting in I Zw 18 that abundances in the neutral gas may

be up to 0.5 dex lower than in the ionized gas. However, the

interpretation of the FUSE data is complicated by the very large FUSE

aperture (30 arcsec), the modest S/N, and the limited selection of

species available in the FUSE bandpass. The advent of COS on HST now

allows a significant advance in all of these areas. We will therefore

obtain absorption line spectroscopy with G130M in the same sample for

which we already have crude constraints from FUSE. We will obtain

ACS/SBC images to select the few optimal sightlines to target in each

galaxy. The results will be interpreted through line-profile fitting to

determine the metal abundances constrained by the available lines. The

results will provide important new insights into the metallicities of

galaxies, and into outstanding problems at high redshift such as the

observed offset between the metallicities of Lyman Break Galaxies and

Damped Lyman Alpha systems.