HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT      # 4535

PERIOD COVERED: UT January 28, 2008 (DOY 028)

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.

NIC3 11153

The Physical Nature and Age of Lyman Alpha Galaxies

In the simplest scenario, strong Lyman alpha emission from high redshift

galaxies would indicate that stellar populations younger than 10 Myrs

dominate the UV. This does not, however, constrain the stellar

populations older than 100 Myrs, which do not contribute to UV light.

Also, the Lyman alpha line can be boosted if the interstellar medium is

both clumpy and dusty. Different studies with small samples have reached

different conclusions about the presence of dust and old stellar

populations in Lyman alpha emitters. We propose HST- NICMOS and

Spitzer-IRAC photometry of 35 Lyman-alpha galaxies at redshift

4.5<z<6.5, in order to determine their spectral energy distribution

{SED} extending through rest-frame optical. This will allow us to

measure accurately {1} The total stellar mass in these objects,

including old stars which may have formed at redshifts {z > 8} not

easily probed by any other means. {2} The dust extinction in the

rest-frame UV, and therefore a correction to their present

star-formation rates. Taken together, these two quantities will yield

the star-formation histories of Lyman alpha galaxies, which form fully

half of the known galaxies at z=4-6. They will tell us whether these are

young or old galaxies by straddling the 4000A break. Data from NICMOS is

essential for these compact and faint {i=25-26th magnitude AB} high

redshift galaxies, which are too faint for good near-IR photometry from

the ground.

NIC3 11195

Morphologies of the Most Extreme High-Redshift Mid-IR-luminous Galaxies

II: The `Bump' Sources

The formative phase of some of the most massive galaxies may be

extremely luminous, characterized by intense star- and AGN-formation.

Till now, few such galaxies have been unambiguously identified at high

redshift, and thus far we have been restricted to studying the

low-redshift ultraluminous infrared galaxies as possible analogs. We

have recently discovered a sample of objects which may indeed represent

this early phase in galaxy formation, and are undertaking an extensive

multiwavelength study of this population. These objects are optically

extremely faint {R>26} but nevertheless bright at mid-infrared

wavelengths {F[24um] > 0.5 mJy}. Mid-infrared spectroscopy with

Spitzer/IRS reveals that they have redshifts z~2, implying luminosities

~1E13 Lsun. Their mid-IR SEDs fall into two broad, perhaps overlapping,

categories. Sources with brighter F[24um] exhibit power-law SEDs and SiO

absorption features in their mid-IR spectra characteristic of AGN,

whereas those with fainter F[24um] show a "bump" characteristic of the

redshifted 1.6um peak from a stellar population, and PAH emission

characteristic of starformation. We have begun obtaining HST images of

the brighter sources in Cycle 15 to obtain identifications and determine

kpc-scale morphologies for these galaxies. Here, we aim to target the

second class {the "bump" sources} with the goal of determining if these

constitute morphologically different objects, or simply a "low-AGN"

state of the brighter class. The proposed observations will help us

determine whether these objects are merging systems, massive obscured

starbursts {with obscuration on kpc scales!} or very reddened {locally

obscured} AGN hosted by intrinsically low-luminosity galaxies.

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.

WFPC2 11198

Pure Parallel Imaging in the NDWFS Bootes Field

The NOAO Deep-Wide Field Survey {NDWFS} Bootes field is the target of

one of the most extensive multiwavelength campaigns in astronomy. In

addition to ground-based optical and near-infrared imaging, deep radio

mapping, and extensive spectroscopy, this entire region has been imaged

by the Chandra, Spitzer {IRAC and MIPS}, and GALEX missions. Robust

photometric redshifts {calibrated using over 20,000 spectroscopic

redshifts} exist for all sources brighter than R=24.5 or than 13 uJy at

4.5 microns. To enhance the value of this data set, we propose pure

parallel observations for all approved Cycle 16 programs in this region

that lack coordinated parallel observations. The primary aim of this

program will be to provide a database useful for the broad range of

science programs underway in this region.

WFPC2 11339

A deep observation of NGC4261: understanding its unique X-ray source

population, gas morphology, and jet properties

The nearby early-type galaxy NGC4261 reveals strikingly asymmetric

distributions of X-ray sources as seen with Chandra, and globular

clusters (GC) as seen in the optical band. To address the link between

these populations based on their spatial correlation, luminosity

function and spectral properties, and to investigate the possibility

that this effect is due to the galaxy's merger history, we propose a

100ksec Chandra ACIS-S3 exposure, which will detect X-ray sources down

to typical LMXB luminosities (Lx~5E37 erg/s), and HST-WFPC2 observations

to obtain a deep census of the GC population over the whole galaxy.

These data will also allow a detailed study of its complex gaseous

component, and provide information on the unique two-sided X-ray jet.

WFPC2 11020

Cycle 15 Focus Monitor

The focus of HST is measured primarily with ACS/HRC over full CVZ orbits

to obtain accurate mean focus values via a well sampled breathing curve.

Coma and astigmatism are also determined from the same data in order to

further understand orbital effects on image quality and optical

alignments. To monitor the stability of ACS to WFPC2 relative focii,

we've carried over from previous focus monitor programs parallel

observations taken with the two cameras at suitable orientations of

previously observed targets, and interspersed them with the HRC CVZ

visits.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary reports

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

HSTARS:

11163 - GSacq(2,0,2) failed to RGA control

           GSacq(2,0,2) scheduled at 028/10:32:17 failed during LOS. At AOS

           (10:52:55) stop flags QF2STOPF and QSTOP were set. The map at 10:37:58

           showed errors of V1=-1.48, V2=-5.49, V3=8.53, and RSS=10:25.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

                        SCHEDULED      SUCCESSFUL  

FGS GSacq                11                 10          

FGS REacq               03                  03                   

OBAD with Maneuver 28                  28

SIGNIFICANT EVENTS: (None)