HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT      # 4587

PERIOD COVERED: UT April 10, 2008 (DOY 101)

OBSERVATIONS SCHEDULED

NIC1/NIC2/NIC3 11318

NICMOS Cycle 16 Multiaccum Darks

The purpose of this proposal is to monitor the dark current, read noise,

and shading profile for all three NICMOS detectors throughout the

duration of Cycle 16. This proposal is a slightly modified version of

proposal 10380 of cycle 13 and 9993 of cycle12 and is the same as Cycle

15. Covers the period from April 08 to November 08 (inclusive)

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.

NIC2 11155

Dust Grain Evolution in Herbig Ae Stars: NICMOS Coronagraphic Imaging

and Polarimetry

We propose to take advantage of the sensitive coronagraphic capabilities

of NICMOS to obtain multiwavelength coronagraphic imaging and

polarimetry of primordial dust disks around young intermediate-mass

stars {Herbig Ae stars}, in order to advance our understanding of how

dust grains are assembled into larger bodies. Because the polarization

of scattered light is strongly dependent on scattering particle size and

composition, coronagraphic imaging polarimetry with NICMOS provides a

uniquely powerful tool for measuring grain properties in spatially

resolved circumstellar disks. It is widely believed that planets form

via the gradual accretion of planetesimals in gas-rich, dusty

circumstellar disks, but the connection between this suspected process

and the circumstellar disks that we can now observe around other stars

remains very uncertain. Our proposed observations, together with

powerful 3-D radiative transfer codes, will enable us to quantitatively

determine dust grain properties as a function of location within disks,

and thus to test whether dust grains around young stars are in fact

growing in size during the putative planet-formation epoch. HST imaging

polarimetry of Herbig Ae stars will complement and extend existing

polarimetric studies of disks around lower-mass T Tauri stars and debris

disks around older main-sequence stars. When combined with these

previous studies, the proposed research will help us establish the

influence of stellar mass on the growth of dust grains into larger

planetesimals, and ultimately to planets. Our results will also let us

calibrate models of the thermal emission from these disks, a critical

need for validating the properties of more distant disks inferred on the

basis of spectral information alone.

NIC2 11208

The co-evolution of spheroids and black holes in the last six billion

years

The masses of giant black holes are correlated with the luminosities,

masses, and velocity dispersions of the bulges of their host galaxies.

This empirical correlation of phenomena on widely different scales {from

pcs to kpcs} suggests that the formation and evolution of galaxies and

central black holes are closely linked. In Cycle 13, we have started a

campaign to map directly the co-evolution of spheroids and black-holes

by measuring in observationally favorable redshift windows the empirical

correlations connecting their properties. By focusing on Seyfert 1s,

where the nucleus and the stars contribute comparable fractions of total

light, black hole mass and bulge dispersion are obtained from Keck

spectroscopy. HST is required for accurate measurement of the non

stellar AGN continuum, the morphology of the galaxy, and the structural

parameters of the bulge. The results at z=0.36 indicate a surprisingly

fast evolution of bulges in the past 4 Gyrs {significant at the 95%CL},

in the sense that bulges were significantly smaller for a given black

hole mass. Also, the large fraction of mergers and disturbed galaxies

{4+2 out of 20} identifies gas-rich mergers as the mechanisms

responsible for bulge-growth. Going to higher redshift -- where

evolutionary trends should be stronger -- is needed to confirm these

tantalizing results. We propose therefore to push our investigation to

the next suitable redshift window z=0.57 {lookback-time 6 Gyrs}. Fifteen

objects are the minimum number required to map the evolution of the

empirical correlations between bulge properties and black- hole mass,

and to achieve a conclusive detection of evolution {>99%CL}.

NIC2/NIC1/NIC3 11159

The True Galactic Bulge Luminosity Function

We propose to obtain second epoch imaging of the deep Galactic bulge

field observed using NICMOS by Zoccali et al. (2000). The bulge

luminosity and mass function suffered from 30-50% contamination by

foreground disk stars, which was impossible to correct for in the

original study. Revisiting the field after 9 years, we propose to

segregate the foreground disk stars because they have large transverse

velocities, thus revealing the luminosity function of Galactic bulge low

mass stars to near the hydrogen burning limit. The slope of the mass

function has implications for galaxy formation and for understanding the

nature of microlensing in the Galactic bulge.

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.

NIC3 11149

Characterizing the Stellar Populations in Lyman-Alpha Emitters and Lyman

Break Galaxies at 5.7<z<7 in the Subaru Deep Field

The epoch of reionization marks a major phase transition of the

Universe, during which the intergalactic space became transparent to UV

photons. Determining when this occurred and the physical processes

involved represents the latest frontier in observational cosmology. Over

the last few years, searches have intensified to identify the population

of high-redshift (z>6) galaxies that might be responsible for this

process, but the progress is hampered partly by the difficulty of

obtaining physical information (stellar mass, age, star formation

rate/history) for individual sources. This is because the number of z>6

galaxies that have both secure spectroscopic redshifts and high-quality

infrared photometry (especially with Spitzer/IRAC) is still fairly

small. Considering that only several photometric points are available

per source, and that many model SEDs are highly degenerate, it is

crucial to obtain as many observational constraints as possible for each

source to ensure the validity of SED modeling. To better understand the

physical properties of high-redshift galaxies, we propose here to

conduct HST/NICMOS (72 orbits) and Spitzer/IRAC (102 hours) imaging of

spectroscopically confirmed, bright (z<26 mag (AB)) Ly-alpha emitters

(LAEs) and Lyman-break galaxies (LBGs) at 5.7<z<7 selected from the

Subaru Deep Field. Spectroscopic redshifts remove one critical free

parameter from SED modeling while bright source magnitudes ensure

high-quality photometric data. By making accurate determinations of

stellar masses, ages, and star-formation histories, we will specifically

address the following major questions: (1) Do LAEs and LBGs represent

physically different galaxy populations at z>6 as suggested recently?

(2) Is Ly-alpha emission systematically suppressed at z>6 with respect

to continuum emission? (i.e., are we reaching the epoch of incomplete

reionization?), and (3) Do we see any sign of abnormally young stellar

population in any of the z>6 galaxies?

WFPC2 10841

A Proper Motion Search for Intermediate Mass Black Holes in Globular

Clusters {2nd Epoch Observations}

Establishing the presence or absence of intermediate-mass black holes

{IMBH} in globular clusters is crucial for understanding the evolution

of dense stellar systems. Observationally, this search has been hampered

by the low number of stars with known velocities in the central few

arcseconds. This limits our knowledge of the velocity dispersion in the

region where the gravitational influence of any IMBH would be felt. In

Cycle 13, we successfully obtained ACS/HRC images of the centers of five

carefully chosen Galactic globular clusters {GO-10401} for a new proper

motion study. Although the science case was approved and the first epoch

images obtained, the requested future cycle observations were not

granted {due to a general policy decision based on the strong

uncertainties at the time concerning the immediate future of HST}. We

have now assessed the quality of the first epoch observations. The HRC

resolution reveals many isolated stars in to the very center of each

cluster that remained blended or unresolved in previous WFPC2 data.

Given a two year baseline, we are confident that we can achieve the

proper motion precision required to place strict limits on the presence

of an IMBH. Therefore, we request the second-epoch, follow-up

observations to GO-10401 in order to measure the proper motions of stars

in our target clusters. These velocity measurements will allow us to:

{i} place constraints on the mass of a central black hole in each

cluster; {ii} derive the internal velocity dispersion as a function of

cluster radius; {iii} verify or reject previous reports of cluster

rotation; and {iv} directly measure velocity anisotropy as a function of

radius. If no second epoch data are obtained then the observing time

already invested in the first epoch will have been wasted.

WFPC2 11201

Systemic and Internal motions of the Magellanic Clouds: Third Epoch

Images

In Cycles 11 and 13 we obtained two epochs of ACS/HRC data for fields in

the Magellanic Clouds centered on background quasars. We used these data

to determine the proper motions of the LMC and SMC to better than 5% and

15% respectively. These are by far the best determinations of the proper

motions of these two galaxies. The results have a number of unexpected

implications for the Milky Way-LMC-SMC system. The implied

three-dimensional velocities are larger than previously believed, and

are not much less than the escape velocity in a standard 10^12 solar

mass Milky Way dark halo. Orbit calculations suggest the Clouds may not

be bound to the Milky Way or may just be on their first passage, both of

which would be unexpected in view of traditional interpretations of the

Magellanic Stream. Alternatively, the Milky Way dark halo may be a

factor of two more massive than previously believed, which would be

surprising in view of other observational constraints. Also, the

relative velocity between the LMC and SMC is larger than expected,

leaving open the possibility that the Clouds may not be bound to each

other. To further verify and refine our results we now request an epoch

of WFPC2/PC data for the fields centered on 40 quasars that have at

least one epoch of ACS imaging. We request execution in snapshot mode,

as in our previous programs, to ensure the most efficient use of HST

resources. A third epoch of data of these fields will provide crucial

information to verify that there are no residual systematic effects in

our previous measurements. More importantly, it will increase the time

baseline from 2 to 5 yrs and will increase the number of fields with at

least two epochs of data. This will reduce our uncertainties

correspondingly, so that we can better address whether the Clouds are

indeed bound to each other and to the Milky Way. It will also allow us

to constrain the internal motions of various populations within the

Clouds, and will allow us to determine a distance to the LMC using

rotational parallax.

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                 06                06                   

FGS REacq                 08                08                  

OBAD with Maneuver  28                28                

SIGNIFICANT EVENTS: (None)