HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

 

DAILY REPORT #5154

 

PERIOD COVERED: 5am August 5 - 5am August 6, 2010 (DOY 217/09:00z-218/09:00z)

 

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               8                 8     

FGS REAcq               6                 6     

OBAD with Maneuver 6                 6     

 

SIGNIFICANT EVENTS: (None)

 

 

 

OBSERVATIONS SCHEDULED:

 

ACS/WFC3 11670

 

The Host Environments of Type Ia Supernovae in the SDSS Survey

 

The Sloan Digital Sky Survey Supernova Survey has discovered nearly 500

type Ia supernovae and created a large, unique, and uniform sample of

these cosmological tools. As part of a comprehensive study of the

supernova hosts, we propose to obtain Hubble ACS images of a large

fraction of these galaxies. Integrated colors and spectra will be

measured from the ground, but we require high-resolution HST imaging to

provide accurate morphologies and color information at the site of the

explosion. This information is essential in determining the systematic

effects of population age on type Ia supernova luminosities and

improving their reliability in measuring dark energy. Recent studies

suggest two populations of type Ia supernovae: a class that explodes

promptly after star-formation and one that is delayed by billions of

years. Measuring the star-formation rate at the site of the supernova

from colors in the HST images may be the best way to differentiate

between these classes.

 

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/ACS/IR 11563

 

Galaxies at z~7-10 in the Reionization Epoch: Luminosity Functions to

<0.2L* from Deep IR Imaging of the HUDF and HUDF05 Fields

 

The first generations of galaxies were assembled around redshifts

z~7-10+, just 500-800 Myr after recombination, in the heart of the

reionization of the universe. We know very little about galaxies in this

period. Despite great effort with HST and other telescopes, less than

~15 galaxies have been reliably detected so far at z>7, contrasting with

the ~1000 galaxies detected to date at z~6, just 200-400 Myr later, near

the end of the reionization epoch. WFC3 IR can dramatically change this

situation, enabling derivation of the galaxy luminosity function and its

shape at z~7-8 to well below L*, measurement of the UV luminosity

density at z~7-8 and z~8-9, and estimates of the contribution of

galaxies to reionization at these epochs, as well as characterization of

their properties (sizes, structure, colors). A quantitative leap in our

understanding of early galaxies, and the timescales of their buildup,

requires a total sample of ~100 galaxies at z~7-8 to ~29 AB mag. We can

achieve this with 192 WFC3 IR orbits on three disjoint fields

(minimizing cosmic variance): the HUDF and the two nearby deep fields of

the HUDF05. Our program uses three WFC3 IR filters, and leverages over

600 orbits of existing ACS data, to identify, with low contamination, a

large sample of over 100 objects at z~7-8, a very useful sample of ~23

at z~8-9, and limits at z~10. By careful placement of the WFC3 IR and

parallel ACS pointings, we also enhance the optical ACS imaging on the

HUDF and a HUDF05 field. We stress (1) the need to go deep, which is

paramount to define L*, the shape, and the slope alpha of the luminosity

function (LF) at these high redshifts; and (2) the far superior

performance of our strategy, compared with the use of strong lensing

clusters, in detecting significant samples of faint z~7-8 galaxies to

derive their luminosity function and UV ionizing flux. Our recent z~7.4

NICMOS results show that wide-area IR surveys, even of GOODS-like depth,

simply do not reach faint enough at z~7-9 to meet the LF and UV flux

objectives. In the spirit of the HDF and the HUDF, we will waive any

proprietary period, and will also deliver the reduced data to STScI. The

proposed data will provide a Legacy resource of great value for a wide

range of archival science investigations of galaxies at redshifts z~2-9.

The data are likely to remain the deepest IR/optical images until JWST

is launched, and will provide sources for spectroscopic follow up by

JWST, ALMA and EVLA.

 

WFC3/ACS/IR 11677

 

Is 47 Tuc Young? Measuring its White Dwarf Cooling Age and Completing a

Hubble Legacy

 

With this proposal we will firmly establish the age of 47 Tuc from its

cooling white dwarfs. 47 Tuc is the nearest and least reddened of the

metal-rich disk globular clusters. It is also the template used for

studying the giant branches of nearby resolved galaxies. In addition,

the age sensitive magnitude spread between the main sequence turnoff and

horizontal branch is identical for 47 Tuc, two bulge globular clusters

and the bulge field population. A precise relative age constraint for 47

Tuc, compared to the halo clusters M4 and NGC 6397, both of which we

recently dated via white dwarf cooling, would therefore constrain when

the bulge formed relative to the old halo globular clusters. Of

particular interest is that with the higher quality ACS data on NGC

6397, we are now capable with the technique of white dwarf cooling of

determining ages to an accuracy of +/-0.4 Gyrs at the 95% confidence

level. Ages derived from the cluster turnoff are not currently capable

of reaching this precision. The important role that 47 Tuc plays in

galaxy formation studies, and as the metal-rich template for the

globular clusters, makes the case for a white dwarf cooling age for this

metal-rich cluster compelling.

 

Several recent analyses have suggested that 47 Tuc is more than 2 Gyrs

younger than the Galactic halo. Others have suggested an age similar to

that of the most metal poor globular clusters. The current situation is

clearly uncertain and obviously a new approach to age dating this

important cluster is required.

 

With the observations of 47 Tuc, this project will complete a legacy for

HST. It will be the third globular cluster observed for white dwarf

cooling; the three covering almost the full metallicity range of the

cluster system. Unless JWST has its proposed bluer filters (700 and 900

nm) this science will not be possible perhaps for decades until a large

optical telescope is again in space. Ages for globular clusters from the

main sequence turnoff are less precise than those from white dwarf

cooling making the science with the current proposal truly urgent.

 

WFC3/ACS/IR 11731

 

Studying Cepheid Systematics in M81: H-Band Observations

 

The local value of the Hubble Constant remains one of the most important

constraints in cosmology, but improving on the 10% accuracy of the HST

Key Project is challenging. No improvements will be convincing until the

metallicity dependence is well constrained and blending effects are

fully understood. M81 and its dwarf companion Holmberg IX are superb

laboratories for studying Cepheid systematics because they contain large

numbers of bright Cepheids with a good spread in metallicity lying at a

common, relatively close distance. We have identified 180 12<P< 70 day

Cepheids in these two galaxies using the Large Binocular Telescope

(compared to 30 in total by the KP), and will expand the sample further

in 2008-2009. We will use 10 orbits with WFC3/IR to obtain H-band images

of 100 Cepheids in M81 to add to the ACS/BVI calibrations we will obtain

from archival data and 1 orbit with WFC3/UVIS to add B-band data for

Holmberg IX. Four band BVIH photometry will allow us to flux calibrate,

estimate extinction, measure metallicity effects and then check the

results in detail. We can also examine blending effects on WFC3/IR data

in a relatively nearby galaxy before it is applied to more distant

galaxies. Our M81 sample is three times larger than the next best

sample, that of NGC4258, and suffers less from blending because M81 is

at half the distance, so it is an excellent laboratory for studying

Cepheid systematics even if it lacks as precise a geometric distance as

NGC4258.

 

WFC3/ACS/UVIS 11613

 

GHOSTS: Stellar Outskirts of Massive Spiral Galaxies

 

We propose to continue our highly successful GHOSTS HST survey of the

resolved stellar populations of nearby, massive disk galaxies using

SNAPs. These observations provide star counts and color-magnitude

diagrams 2-3 magnitudes below the tip of the Red Giant Branch of the

outer disk and halo of each galaxy. We will measure the metallicity

distribution functions and stellar density profiles from star counts

down to very low average surface brightnesses, equivalent to ~32 V-mag

per square arcsec.

 

This proposal will substantially improve our unique sampling of galaxy

outskirts. Our targets cover a range in galaxy mass, luminosity,

inclination, and morphology. As a function of these galaxy properties,

this survey provides: - the most extensive, systematic measurement of

radial light profiles and axial ratios of the diffuse stellar halos and

outer disks of spiral galaxies; - a comprehensive analysis of halo

metallicity distributions as function of galaxy type and position within

the galaxy; - an unprecedented study of the stellar metallicity and age

distribution in the outer disk regions where the disk truncations occur;

- the first comparative study of globular clusters and their field

stellar populations.

 

We will use these fossil records of the galaxy assembly process to test

halo formation models within the hierarchical galaxy formation scheme.

 

WFC3/UVIS 11630

 

Monitoring Active Atmospheres on Uranus and Neptune

 

We propose Snapshot observations of Uranus and Neptune to monitor

changes in their atmospheres on time scales of weeks and months, as we

have been doing for the past seven years. Previous Hubble Space

Telescope observations (including previous Snapshot programs 8634,

10170, 10534, and 11156), together with near-IR images obtained using

adaptive optics on the Keck Telescope, reveal both planets to be dynamic

worlds which change on time scales ranging from hours to (terrestrial)

years. Uranus equinox occurred in December 2007, and the northern

hemisphere is becoming fully visible for the first time since the early

1960s. HST observations during the past several years (Hammel et al.

2005, Icarus 175, 284 and references therein) have revealed strongly

wavelength-dependent latitudinal structure, the presence of numerous

visible-wavelength cloud features in the northern hemisphere, at least

one very long- lived discrete cloud in the southern hemisphere, and in

2006 the first clearly defined dark spot seen on Uranus. Long term

ground-based observations (Lockwood and Jerzekiewicz, 2006, Icarus 180,

442; Hammel and Lockwood 2007, Icarus 186, 291) reveal seasonal

brightness changes that seem to demand the appearance of a bright

northern polar cap within the next few years. Recent HST and Keck

observations of Neptune (Sromovsky et al. 2003, Icarus 163, 256 and

references therein) show a general increase in activity at south

temperate latitudes until 2004, when Neptune returned to a rather

Voyager-like appearance with discrete bright spots rather than active

latitude bands. Further Snapshot observations of these two dynamic

planets will elucidate the nature of long-term changes in their zonal

atmospheric bands and clarify the processes of formation, evolution, and

dissipation of discrete albedo features.

 

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).