Status Report

NASA Hubble Space Telescope Daily Report # 4637

By SpaceRef Editor
June 23, 2008
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NASA Hubble Space Telescope Daily Report # 4637


Continuing to collect World Class Science

PERIOD COVERED: 5am June 20 – 5am June 23, 2008 (DOY 172/0900z-175/0900z)


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 images. Each observation will need its own CRMAP, as different SAA passages leave different imprints on the NICMOS detectors.

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.

WFPC2 11233

Multiple Generations of Stars in Massive Galactic Globular Clusters

This is a follow-up to recent HST imaging of NGC 2808, which discovered that its main sequence is triple, with three well-separated parallel branches {Fig.~1}. Along with the double MS of Omega Centauri, this challenges the long-held paradigm that globular clusters are simple, single stellar populations. The cause of this main sequence multiplicity in both clusters is likely to be differences in helium abundance, which could play a fundamental role in the understanding of stellar populations. We propose to image seven more of the most massive globular clusters, to examine their main sequences for indications of splitting.

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.

WFPC2 11206

At the Cradle of the Milky Way: Formation of the Most Massive Field Disk Galaxies at z>1

We propose to obtain 2 orbit WFPC2 F814W images of a sample of the 15 most massive galaxies found at $1 < z < 1.3$. These were culled from over 20,000 Keck spectra collected as part of DEEP and are unique among high redshift massive galaxy samples in being kinematically selected. Through a recent HST NICMOS-2 imaging program {GO-10532}, we have confirmed that these galaxies have regular stellar disks, and their emission line kinematics are not due to gradients from merging components. These potentially very young galaxies are likely precursors to massive local disks, assuming no further merging. The proposed WFPC2 and existing NIC-2 data provide colors, stellar masses, and ages of bulge and disk subcomponents, to assess whether old stellar bulges and disks are in place at that time or still being built, and constrain their formation epochs. Finally, this sample will yield the first statistically significant results on the $z > 1$ evolution of the size-velocity-luminosity scaling relations, for massive galaxies at different wavelengths, and constrain whether this evolution reflects stellar mass growth, or passive evolution, of either bulge or disk components.

WFPC2 11202

The Structure of Early-type Galaxies: 0.1-100 Effective Radii

The structure, formation and evolution of early-type galaxies is still largely an open problem in cosmology: how does the Universe evolve from large linear scales dominated by dark matter to the highly non-linear scales of galaxies, where baryons and dark matter both play important, interacting, roles? To understand the complex physical processes involved in their formation scenario, and why they have the tight scaling relations that we observe today {e.g. the Fundamental Plane}, it is critically important not only to understand their stellar structure, but also their dark-matter distribution from the smallest to the largest scales. Over the last three years the SLACS collaboration has developed a toolbox to tackle these issues in a unique and encompassing way by combining new non-parametric strong lensing techniques, stellar dynamics, and most recently weak gravitational lensing, with high-quality Hubble Space Telescope imaging and VLT/Keck spectroscopic data of early-type lens systems. This allows us to break degeneracies that are inherent to each of these techniques separately and probe the mass structure of early-type galaxies from 0.1 to 100 effective radii. The large dynamic range to which lensing is sensitive allows us both to probe the clumpy substructure of these galaxies, as well as their low-density outer haloes. These methods have convincingly been demonstrated, by our team, using smaller pilot-samples of SLACS lens systems with HST data. In this proposal, we request observing time with WFPC2 and NICMOS to observe 53 strong lens systems from SLACS, to obtain complete multi-color imaging for each system. This would bring the total number of SLACS lens systems to 87 with completed HST imaging and effectively doubles the known number of galaxy-scale strong lenses. The deep HST images enable us to fully exploit our new techniques, beat down low-number statistics, and probe the structure and evolution of early-type galaxies, not only with a uniform data-set an order of magnitude larger than what is available now, but also with a fully coherent and self-consistent methodological approach!

WEPC2 11196

An Ultraviolet Survey 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 starbursts and creating/fueling central AGN. We propose far {ACS/SBC/F140LP} and near {WFPC2/PC/F218W} UV imaging of a sample of 27 galaxies drawn from the complete IRAS Revised Bright Galaxy Sample {RBGS} LIRGs sample and known, from our Cycle 14 B and I-band ACS imaging observations, to have significant numbers of bright {23 < B < 21 mag} star clusters in the central 30 arcsec. The HST UV data will be combined with previously obtained HST, Spitzer, and GALEX images to {i} calculate the ages of the clusters as function of merger stage, {ii} measure the amount of UV light in massive star clusters relative to diffuse regions of star formation, {iii} assess the feasibility of using the UV slope to predict the far-IR luminosity {and thus the star formation rate} both among and within IR-luminous galaxies, and {iv} provide a much needed catalog of rest- frame UV morphologies for comparison with rest-frame UV images of high-z LIRGs and Lyman Break Galaxies. These observations will achieve the resolution required to perform both detailed photometry of compact structures and spatial correlations between UV and redder wavelengths for a physical interpretation our IRX-Beta results. The HST UV data, combined with the HST ACS, Spitzer, Chandra, and GALEX observations of this sample, will result in the most comprehensive study of luminous starburst galaxies to date.

NIC3 11147

The Origin of Diffuse UV Light from Spiral Disks

The ultraviolet light from galaxies has been used as a beacon for tracing the cosmic star formation history of the Universe, yet we have an incomplete understanding of many characteristics of this light. Most of the UV emission from nearby, normal star–forming galaxies is unresolved and “diffuse”, and GALEX has shown that in spiral disks it permeates the inter-arm regions. The nature of this diffuse inter- arm component is under debate. Recent results suggest that it may arise from non- ionizing UV photons which originate in star forming regions in the spiral arms, travel in the plane of the galaxy, and then scatter off of diffusely distributed cold dust grains. Alternatively, an in-situ, unresolved stellar population could produce the observed inter-arm UV emission. This project seeks to establish which of the two competing scenarios is responsible for the bulk of this diffuse emission. We propose to use HST’s UV imaging capability (ACS/SBC) to obtain deep observations of selected fields in the nearby spiral galaxy M101, for which available (low angular resolution) data favor the ‘scattered light’ scenario. Our observations are designed to detect any faint, UV-luminous stellar population down to main sequence B5 stars. With these data, we will establish the nature of the bulk of the diffuse UV light in this spiral galaxy by: (i) quantifying the contribution from dust-scattered light; (ii) measuring the contribution to the ubiquitous diffuse ionized medium from in- situ ionizing stars; and (iii) providing constraints on the observed stellar mass function in the field. Only HST has the UV sensitivity and angular resolution to discriminate in-situ stellar populations from scattered light. The ultimate goal of this project is to re-‘calibrate’ the UV emission as a star formation rate indicator, which will need to account for any scattered component.

NIC2 11143

NICMOS Imaging of Submillimeter Galaxies With CO and PAH Redshifts

We propose to obtain F110W and F160W imaging of 10 z~2.4 submillimeter galaxies {SMGs} whose optical redshifts have been confirmed by the detection of millimeter CO and/or mid- infrared PAH emission. With the 4000A break falling within/between the two imaging filters, we will be able to study these sources’ spatially resolved stellar populations {modulo extinction} in the rest-frame optical. SMGs’ large luminosities appear to be due largely to merger-triggered starbursts; high-resolution NICMOS imaging will help us understand the stellar masses, mass ratios, and other properties of the merger progenitors, valuable information in the effort to model the mass assembly history of the universe.

WFPC2 11137

First Accurate Geometric Distance to a Galactic Wolf-Rayet Star: Knots in the Ejecta M1-67

M 1-67 is the youngest known ejection nebula surrounding a Population I Wolf-Rayet star, in this case the WN8 star WR 124. Our deep H-alpha HST/WFPC2 image of this object in March 1997 revealed, for the first time in such a nebula, numerous bright, mostly unresolved knots (typical diameters 0.1-0.2″) often surrounded by what appear to be their own local spherical diffuse ‘wind’ bubbles. We propose to obtain a second epoch H-alpha image of M 1-67, essentially repeating the Epoch1 instrumental set-up. By measuring the proper motions of the knots, we will derive a relatively precise and assumption-free geometric distance (thus also a luminosity) to a Galactic Wolf-Rayet star, the first of its kind. This will help to confirm the suspected runaway status of WR 124 and shed new light on the nature of progenitors of gamma-ray bursts. Moreover, we intend to document and measure the anticipated morphology/brightness changes in the fine-stucture features of the nebula over the 11-year interval, as they relate to wind-embedded shocks. This will provide important input for interaction models of a stellar wind with circumstellar matter.

ACS/SBC 11110

Searching for Lyman Apha Emission from FUSE Lyman Continuum Candidates

We have recently been granted time on FUSE to characterize the escape fraction of hydrogen Lyman continuum (Lyc) photons from a morphologically diverse set of star forming galaxies. The FUSE program is designed to provide ~ 5 sigma detections of Lyc photons emitted from star forming galaxies with escape fractions ~5%. With this proposal we seek hydrogen Lyman alpha (Lya) observations of a representative subset of the FUSE program targets to constrain the observational relationship between Lyc, Lya, and hydrogen Balmer line emission in these systems. Such observations explore the detailed balance between the simple optically thin (Case A) and optically thick (Case B) limits in recombination theory. The ultimate goal of this program is to quantify the relationship between escaping Lya and Lyc emission and the first structures that form in the early universe.

WFPC2 11079

Treasury Imaging of Star Forming Regions in the Local Group: Complementing the GALEX and NOAO Surveys

We propose to use WFPC2 to image the most interesting star-forming regions in the Local Group galaxies, to resolve their young stellar populations. We will use a set of filters including F170W, which is critical to detect and characterize the most massive stars, to whose hot temperatures colors at longer wavelengths are not sensitive. WFPC2’s field of view ideally matches the typical size of the star-forming regions, and its spatial resolution allows us to measure individual stars, given the proximity of these galaxies. The resulting H-R diagrams will enable studies of star-formation properties in these regions, which cover largely differing metallicities {a factor of 17, compared to the factor of 4 explored so far} and characteristics. The results will further our understanding of the star-formation process, of the interplay between massive stars and environment, the properties of dust, and will provide the key to interpret integrated measurements of star-formation indicators {UV, IR, Halpha} available for several hundreds more distant galaxies. Our recent deep surveys of these galaxies with GALEX {FUV, NUV} and ground-based imaging {UBVRI, Halpha, [OIII] and [SII]} provided the identification of the most relevant SF sites. In addition to our scientific analysis, we will provide catalogs of HST photometry in 6 bands, matched corollary ground-based data, and UV, Halpha and IR integrated measurements of the associations, for comparison of integrated star-formation indices to the resolved populations. We envisage an EPO component.

WFPC2 11032

CTE Extended Targets Closeout

Measuring the charge transfer efficiency {CTE} of an astronomical CCD camera is crucial to determining the CCD’s photometric fidelity across the field of view. WFPC2’s CTE has degraded steadily over the last 13 years because of continuous exposure to trapped particles in HST’s radiation environment. The fraction of photometric signal lost from WFPC2’s CTI {change transfer inefficiency} is a function of WFPC2’s time in orbit, the integrated signal in the image, the location of the image on the CCD, and the background signal. Routine monitoring of WFPC2’s degrading CTE over the last 13 years has primarily concerned the effects of CTI on point-source photometry. However, most of the sources imaged by WFPC2 are extended rather than point- like. This program aims to characterize the effects of CTI on the photometry and morphology of extended sources near the end of WFPC2’s functional life. Images of a standard field within the rich galaxy cluster Abell 1689 are recorded with each WFPC2 camera using the F606W and F814W filters. These images will be compared with contemporaneous images of Abell 1689 recorded with the field rotated by approximately 180 degrees to assess differences between extended sources imaged near and far from the serial register. The images will also be compared with similar images recorded in Cycle 8 {Program 8456} to characterize the rate of CTE degradation over the lifetime of WFPC2.

WFPC2 11022

WFPC2 Cycle 15 Decontaminations and Associated Observations

This proposal is for the WFPC2 decons. Also included are instrument monitors tied to decons: photometric stability check, focus monitor, pre- and post-decon internals {bias, intflats, kspots, & darks}, UV throughput check, VISFLAT sweep, and internal UV flat check.


Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)


11350 – REacq(1,2,1) failed to RGA hold.

REacq(1,2,1) scheduled at 172/17:16:56 – 17:24:18 failed to RGA hold during LOS. At AOS there were no flags. During LOS we received an ESB a0a “FL Timeout”. OBAD1 showed errors of V1=435.74, V2=633.13, V3=-307.65, and RSS=827.87. OBAD2 showed errors of V1=-0.75, V2=-2.32, V3=11.46, and RSS=11.71.

Observations affected: WFPC 152-155 Proposal ID# 11233

The REacq(1,2,1) scheduled at 172/18:52:49 – 19:00:00 also failed during LOS. There were no flags. OBAD1:V1=-365.74, V2=-546.47,V3=148.45, RSS=674.11 OBAD2: V1=0.25, V2=0.89, V3=2.09, RSS=2.28

Observations affected: WFPC 156-159 Proposal ID# 11233

Reacq(1,2,1) scheduled at 172/20:28:42 also failed to RGA hold. ESB message a0a “FL Timeout” was received.

OBAD1: V1=-435.55, V2=-648.68, V3=189.11, RSS=803.90 OBAD2: V1=1.45, V2=4.26, V3=8.64, RSS=9.73

Observations affected: WFPC 160-162 Proposal ID#11233

Upon acquisition of signal at 172/22:39:30, the REacq(1,2,1) scheduled at 172/22:09:38 had failed to RGA Hold with (QF1SRLEX), (QF1STOPF) indication flags set on FGS-1. One 486 ESB message “a07” (FGS Coarse Track failed – Timed out waiting for data valid FGS-1) was received. Pre-acq OBADs attitude corrections (RSS) values are not available due to LOS. Post-acq OBAD/MAP had not been scheduled.

Observations affected: WFPC 164, 165 Proposal ID#11233



                       SCHEDULED      SUCCESSFUL

FGS GSacq               17                 17
FGS REacq               10                 06
OBAD with Maneuver      54                 54


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