HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT      # 4591

PERIOD COVERED: UT April 16, 2008 (DOY 107)

OBSERVATIONS SCHEDULED

ACS/SBC/WFPC2 11230

HST FUV Observations of Brightest Cluster Galaxies: The Role of Star

Formation in Cooling Flows and BCG Evolution

The intracluster medium (ICM) now appears to be a very dynamic place

where heating and cooling processes vie for dominance and an uneasy

equilibrium is maintained. Since these same processes may operate during

the process of galaxy formation, the centers of clusters of galaxies

provide low redshift laboratories for studying the critical processes

involved in galaxy formation and black hole growth. At the present time,

the main questions are (1) How much gas is cooling out of the ICM? (2)

How much star formation is ongoing? (3) What is the impact of the gas

and star formation on the central BCG? In order to measure the current

star formation in BCGs we have undertaken a program of Spitzer IRAC and

MIPS observations. We are in process of obtaining observations of a

sample of Brightest Cluster Galaxies in 70 clusters selected from the

ROSAT all sky survey. In about 25% of the sources observed so far, we

detect a mid-IR excess which we attribute to dust heated by star

formation. We propose to obtain ACS/SBC observations of the Lyman Alpha

emission line and the adjacent FUV continuum in 7 BCGs which are in

cooling core clusters of galaxies and have a large mid-IR excess. We

also propose WFPC2 F606W observations of the two clusters without high

resolution imaging to allow us to image the dust on the same scale as

the Far UV continuum. The FUV will allow us to confirm the presense of

ongoing starformation in these BCGs and will allow us to rule out an AGN

as the dominant contributer to the mid-IR. The morphology and spatial

extent of the young stars and the heated dust and CO will constrain the

spatial scale over which star formation occurs and thus where the

cooling gas is deposited. The combination of our FUV and IR observations

will allow us to estimate the star formation rates which must balance

the rate at which cold gas is deposited in the BCG. Our proposed FUV

observations will produce unique information about the cooling gas, the

true mass accretion rates, and the star formation rates in BCGs and its

effect on the galaxy.

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 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.

WFPC2 11125

The Dynamical Evolution of Globular Clusters

Globular clusters evolve through dynamical interactions, with primordial

binaries extending the time until core collapse by up to an order of

magnitude, depending on the initial binary fraction. These dynamical

interactions plus mass segregation causes the binary fraction to rise in

the core but fall at larger radii. We hope to eventually test these

broad predictions by comparing them to the binary properties for

globular clusters at different states of evolution, defined by the ratio

of their age to the dynamical relaxation time at the half-light radius.

The most important unknown aspects in the modeling process are the

initial conditions of binaries in the cluster. Here we propose to

determine the initial binary fraction as a function of radius by

studying three of the dynamically youngest globular clusters {NGC 5053,

NGC 5466, and NGC 5897}. The presence of binaries thickens the Main

Sequence in a color-magnitude diagram, which can be detected with deep

multicolor images.

WFPC2 11130

AGNs with Intermediate-mass Black Holes: Testing the Black Hole-Bulge

Paradigm, Part II

The recent progress in the study of central black holes in galactic

nuclei has led to a general consensus that supermassive {10^6-10^9 solar

mass} black holes are closely connected with the formation and

evolutionary history of large galaxies, especially their bulge

component. Two outstanding issues, however, remain unresolved. Can

central black holes form in the absence of a bulge? And does the mass

function of central black holes extend below 10^6 solar masses?

Intermediate-mass black holes {<10^6 solar masses}, if they exist, may

offer important clues to the nature of the seeds of supermassive black

holes. Using the SDSS, our group has successfully uncovered a new

population of AGNs with intermediate-mass black holes that reside in

low-luminosity galaxies. However, very little is known about the

detailed morphologies or structural parameters of the host galaxies

themselves, including the crucial question of whether they have bulges

or not. Surprisingly, the majority of the targets of our Cycle 14 pilot

program have structural properties similar to dwarf elliptical galaxies.

The statistics from this initial study, however, are really too sparse

to reach definitive conclusions on this important new class of black

holes. We wish to extend this study to a larger sample, by using the

Snapshot mode to obtain WFPC2 F814W images from a parent sample of 175

AGNs with intermediate- mass black holes selected from our final SDSS

search. We are particularly keen to determine whether the hosts contain

bulges, and if so, how the fundamental plane properties of the host

depend on the mass of their central black holes. We will also

investigate the environment of this unique class of AGNs.

WFPC2 11132

Constraining the age of the AB Dor system

The zero-age main sequence K-type star AB Dor, with an age of 25 to 125

Myr, is the most active young star in the solar neighbourhood. It is

part of a quadruple system of young stars. The mass of AB Dor C, the

closest and lowest mass companion, has been derived from astrometric

observations (with the VLA and adaptive optics at the VLT) to 94+-3

times the mass of Jupiter. The low mass (close to the hydrogen burning

limit) combined with the young age makes AB Dor C a unique calibration

source for evolutionary tracks for very low-mass stars and brown dwarfs,

provided that a precise age estimate can be derived for the system. We

propose to use the HST planetary camera to obtain resolved component

photometry of the M-type pre-main sequence star AB Dor Ba and Bb in

order to derive individual spectral types and luminosities, which will

enable us to age-date the AB Dor system to better than +-20 Myr. In

addition, the observations will help to constrain the Ba/Bb orbit, and

hence to derive dynamical mass estimates as well.

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:

11255 - GSAcq(2,1,2) failed to RGA Hold (Gyro Control)

           Upon acquisition of siganl at 107/16:22:31, the GSAcq(2,1,2) scheduled

           at 107/15:08:24 - 15:16:29 failed to RGA Hold due to (QF1STOPF) stop

           flag indication on FGS-1. Pre-acquisition OBADs (RSS) attitude

           correction values are not available due to LOS. Post-acq OBAD/MAP had

           (RSS) value of 1373.29 arcseconds.

COMPLETED OPS REQUEST:

18225-0 - Modify RWA Spin Down Estimate Parameters @107/1314z

18054-0 - Preview KF Sun Vector Data via Telemetry Diags @107/1321z

COMPLETED OPS NOTES: (None)

                        SCHEDULED      SUCCESSFUL  

FGS GSacq                08                 07          

FGS REacq                04                 04                 

OBAD with Maneuver  24                 24               

SIGNIFICANT EVENTS: (None)