HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT      # 4626

PERIOD COVERED: 5am June 05 - 5am June 06, 2008 (DOY 157/0900z-158/0900z)

OBSERVATIONS SCHEDULED

WFPC2 10583

Resolving the LMC Microlensing Puzzle: Where Are the Lensing Objects ?

We are requesting 32 HST orbits to help ascertain the nature of the

population that gives rise to the observed set of microlensing events

towards the LMC. The SuperMACHO project is an ongoing ground-based

survey on the CTIO 4m that has demonstrated the ability to detect LMC

microlensing events in real-time via frame subtraction. The improvement

in angular resolution and photometric accuracy available from HST will

allow us to 1} confirm that the detected flux excursions arise from LMC

source stars rather than extended objects {such as for background

supernovae or AGN}, and 2} obtain reliable baseline flux measurements

for the objects in their unlensed state. The latter measurement is

important to resolve degeneracies between the event timescale and

baseline flux, which will yield a tighter constraint on the microlensing

optical depth.

FGS 11211

An Astrometric Calibration of Population II Distance Indicators

In 2002 HST produced a highly precise parallax for RR Lyrae. That

measurement resulted in an absolute magnitude, M{V}= 0.61+/-0.11, a

useful result, judged by the over ten refereed citations each year

since. It is, however, unsatisfactory to have the direct,

parallax-based, distance scale of Population II variables based on a

single star. We propose, therefore, to obtain the parallaxes of four

additional RR Lyrae stars and two Population II Cepheids, or W Vir

stars. The Population II Cepheids lie with the RR Lyrae stars on a

common K-band Period-Luminosity relation. Using these parallaxes to

inform that relationship, we anticipate a zero-point error of 0.04

magnitude. This result should greatly strengthen confidence in the

Population II distance scale and increase our understanding of RR Lyrae

star and Pop II Cepheid astrophysics.

FGS 11214

HST/FGS Astrometric Search for Young Planets Around Beta Pic and AU Mic

Beta Pic and AU Mic are two nearby Vega-type debris disk stars. Both of

these disk systems have been spatially resolved in exquisite detail,

predominantly via the ACS coronagraph and WFPC-2 cameras onboard HST.

These images exhibit a wealth of morphological features which provide

compelling indirect evidence that these systems likely harbor

short-period planetary body{ies}. We propose to use the superlative

astrometric capabilities of HST/FGS to directly detect these planets,

hence provide the first direct planet detection in a Vega-type system

whose disk has been imaged at high spatial resolution.

NIC1/NIC2/NIC3 11330

NICMOS Cycle 16 Extended Dark

This takes a series of Darks in parallel to other instruments.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA Calibration - CR Persistence Part 5

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 DARKs. 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

images. Each observation will need its own CRMAP, as different SAA

passages leave different imprints on the NICMOS detectors.

NIC2 11166

The Mass-dependent Evolution of the Black Hole-Bulge Relations

In the local universe, the masses of giant black holes are correlated

with the luminosities, masses and velocity dispersions of their host

galaxy bulges. This indicates a surprisingly close connection between

the evolution of galactic nuclei (on parsec scales) and of stars on kpc

scales. A key observational test of proposed explanations for these

correlations is to measure how they have evolved over cosmic time. Our

ACS imaging of 20 Seyfert 1 galaxies at z=0.37 showed them to have

smaller bulges (by a factor of 3) for a given central black hole mass

than is found in galaxies in the present-day universe. However, since

all our sample galaxies had black hole masses in the range 10^8.0--8.5

Msun, we could only measure the OFFSET in black hole mass to bulge

luminosity ratios from the present epoch. By extending this study to

black hole masses another factor of 10 lower, we propose to determine

the full CORRELATION of black hole mass with host galaxy properties at a

lookback time of 4 Gyrs and to test mass-dependency of the evolution. We

have selected 14 Seyfert galaxies from SDSS DR5 whose narrow Hbeta

emission lines (and estimated nuclear luminosities) imply that they have

black hole masses around 10^7 Msuns. We will soon complete our Keck

spectroscopic measures of their bulge velocity dispersions. We need a

1-orbit NICMOS image of each galaxy to separate its nonstellar

luminosity from its bulge and disk. This will allow us to make the first

determination of the full black hole/bulge relations at z=0.37 (e.g. M-L

and M-sigma), as well as a test of whether active galaxies obey the

Fundamental Plane relation at that epoch.

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 11334

NICMOS Cycle 16 Spectrophotometry

Observation of the three primary WD flux standards must be repeated to

refine the NICMOS absolute calibration and monitor for sensitivity

degradation. So far, NICMOS grism spectrophotometry is available for

only ~16 stars with good STIS spectra at shorter wavelengths. There are

more in the HST CALSPEC standard star data base with good STIS spectra

that would also become precise IR standards with NICMOS absolute SED

measurements. Monitoring the crucial three very red stars (M, L, T) for

variability and better S/N in the IR. Apparent variability was

discovered at shorter wavelengths during the ACS cross-calibration work

that revealed a ~2% discrepancy of the cool star fluxes with respect to

the hot primary WD standards. About a third of these stars are bright

enough to do in one orbit, the rest require 2 orbits.

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.

WFPC2 11227

The Orbital Period for an Ultraluminous X-ray Source in NGC1313

The ultraluminous X-ray sources {ULXs} are extragalactic point sources

with luminosities that exceed the Eddington luminosity for conventional

stellar-mass black holes by factors of 10 - 100. It has been hotly

debated whether the ULXs are just common stellar-mass black hole sources

with beamed emission or whether they are sub-Eddington sources that are

powered by the long-sought intermediate mass black holes {IMBH}. To

firmly decide this question, one must obtain dynamical mass measurements

through photometric and spectroscopic monitoring of the secondaries of

these system. The crucial first step is to establish the orbital period

of a ULX, and arguably the best way to achieve this goal is by

monitoring its ellipsoidal light curve. The extreme ULX NGC1313 X-2

provides an outstanding target for an orbital period determination

because its relatively bright optical counterpart {V = 23.5} showed a

15% variation between two HST observations separated by three months.

This level of variability is consistent with that expected for a tidally

distorted secondary star. Here we propose a set of 20 imaging

observations with HST/WFPC2 to define the orbital period. This would be

the first photometric measurement of the orbital period of a ULX binary.

Subsequently, we will propose to obtain spectroscopic observations to

obtain its radial velocity amplitude and thereby a dynamical estimate of

its mass.

WFPC2 11235

HST NICMOS Survey of the Nuclear Regions of Luminous Infrared Galaxies

in the Local Universe

At luminosities above 10^11.4 L_sun, the space density of far-infrared

selected galaxies exceeds that of optically selected galaxies. These

`luminous infrared galaxies' {LIRGs} are primarily interacting or

merging disk galaxies undergoing enhanced star formation and Active

Galactic Nuclei {AGN} activity, possibly triggered as the objects

transform into massive S0 and elliptical merger remnants. We propose

NICMOS NIC2 imaging of the nuclear regions of a complete sample of 88

L_IR > 10^11.4 L_sun luminous infrared galaxies in the IRAS Revised

Bright Galaxy Sample {RBGS: i.e., 60 micron flux density > 5.24 Jy}.

This sample is ideal not only in its completeness and sample size, but

also in the proximity and brightness of the galaxies. The superb

sensitivity and resolution of NICMOS NIC2 on HST enables a unique

opportunity to study the detailed structure of the nuclear regions,

where dust obscuration may mask star clusters, AGN and additional nuclei

from optical view, with a resolution significantly higher than possible

with Spitzer IRAC. This survey thus provides a crucial component to our

study of the dynamics and evolution of IR galaxies presently underway

with Wide-Field, HST ACS/WFC and Spitzer IRAC observations of these 88

galaxies. Imaging will be done with the F160W filter {H-band} to examine

as a function of both luminosity and merger stage {i} the luminosity and

distribution of embedded star clusters, {ii} the presence of optically

obscured AGN and nuclei, {iii} the correlation between the distribution

of 1.6 micron emission and the mid- IR emission as detected by Spitzer

IRAC, {iv} the evidence of bars or bridges that may funnel fuel into the

nuclear region, and {v} the ages of star clusters for which photometry

is available via ACS/WFC observations. The NICMOS data, combined with

the HST ACS, Spitzer, and GALEX observations of this sample, will result

in the most comprehensive study of merging and interacting galaxies to

date.

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                10                 10

FGS REacq                03                 03                      

OBAD with Maneuver  26                 26                                 

SIGNIFICANT EVENTS: (None)