NASA Hubble Space Telescope Daily Report: # 4491
Notice: Due to the conversion of some ACS WFC or HRC observations into WFPC2, or NICMOS observations after the loss of ACS CCD science capability in January, there may be an occasional discrepancy between a proposal’s listed (and correct) instrument usage and the abstract that follows it.
HUBBLE SPACE TELESCOPE DAILY REPORT # 4491
– Continuing to collect World Class Science
PERIOD COVERED: UT November 16, 17 & 18, 2007 (DOY 320,321,322)
OBSERVATIONS SCHEDULED
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.
S/C 11320
NICMOS Focus Monitoring Cycle 16
This program is a version of the standard focus sweep used since cycle 7. It has been modified to go deeper and uses more narrow filters for improved focus determination. A new source was added in Cycle 14 in order to accommodate 2-gyro mode: the open cluster NGC1850. This source is part of the current proposal. The old target, the open cluster NGC3603, will be used whenever available and the new target used to fill the periods when NGC3603 is not visible. Steps: a) Use refined target field positions as determined from cycle 7 calibrations b) Use MULTIACCUM sequences of sufficient dynamic range to account for defocus c) Do a 17-point focus sweep, +/- 8mm about the PAM mechanical zeropoint for each cameras 1 and 2, in 1.0mm steps. For NIC3 we step from -0.5mm to -9.5mm relative to mechanical zero, in steps of 1.0mm. d) Use PAM X/Y tilt and OTA offset slew compensations refined from previous focus monitoring/optical alignment activities.
WFPC2 11312
The Local Cluster Substructure Survey {LoCuSS}: Deep Strong Lensing Observations with WFPC2
LoCuSS is a systematic and detailed investigation of the mass, substructure, and thermodynamics of 100 X-ray luminous galaxy clusters at 0.15< z<0.3. The primary goal is to test our recent suggestion that this population is dominated by dynamically immature disturbed clusters, and that the observed mass-temperature relation suffers strong structural segregation. If confirmed, this would represent a paradigm shift in our observational understanding of clusters, that were hitherto believed to be dominated by mature, undisturbed systems. We propose to complete our successful Cycle 15 program {SNAP:10881} which prior to premature termination had delivered robust weak-lensing detections in 17 clusters, and candidate strongly-lensed arcs in 11 of these 17. These strong and weak lensing signals will give an accurate measure of the total mass and structure of the dark matter distribution that we will subsequently compare with X-ray and Sunyaev Zeldovich Effect observables. The broader applications of our project include 1} the calibration of mass-temperature and mass-SZE scaling relations which will be critical for the calibration of proposed dark energy experiments, and 2} the low redshift baseline study of the demographics of massive clusters to aid interpretation of future high redshift {z>1} cluster samples. To complete the all-important high resolution imaging component of our survey, we request deep WFPC2 observations of 20 clusters through the F606W filter, for which wide-field weak-lensing data are already available from our Subaru imaging program. The combination of deep WFPC2 and Subaru data for these 20 clusters will enable us to achieve the science program approved by the Cycle 15 TAC.
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.
ACS/SBC 11215
New Sightlines for the Study of Intergalactic Helium: Dozens of High-Confidence, UV-Bright Quasars from SDSS/GALEX
The reionization of IGM helium is thought to have occurred at redshifts of z=3 to 4. Detailed study of HeII Lyman-alpha absorption toward a handful of QSOs at 2.7< z<3.3 demonstrated the high potential of such IGM probes, but the critically small sample size limits confidence in cosmological inferences. The requisite unobscured sightlines to high-z are extremely rare, but SDSS provides 5800, z>3.1 QSOs potentially suitable for HeII studies. We’ve cross-correlated SDSS quasars with GALEX UV sources to obtain dozens of new, high confidence, candidate sightlines {z=3.1-4.9} potentially useful for detailed HeII studies with HST. We propose brief, 2-orbit reconnaissance ACS SBC prism exposures toward each of the best dozen new quasars, to definitively verify UV flux down to HeII. Our combined SDSS/GALEX selection insures a high confirmation rate, as the quasars are already known to be UV bright in GALEX. Our program will provide a statistical sample of HeII sightlines extending to high redshift, enabling future long exposure follow-up spectra with the SBC prism, or superb quality COS or STIS spectra after SM4. Stacks of our prism spectra will also directly yield ensemble information. Ultimately, the new sightlines will enable confident measures of the spectrum and evolution of the ionizing background, the evolution of HeII opacity, the epoch of helium reionization, and the density of IGM baryons.
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 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!
NIC3 11191
NICMOS Imaging of a z>4 High-Redshift Ultraluminous Submillimeter Source
We propose 16 orbits of deep NICMOS 1.6 um imaging of GOODS850-5, a unique z>4 candidate SCUBA source that is bright in the submillimeter {submm} but extremely faint at all other wavelengths. GOODS850-5 is a 11 mJy 850 um source discovered in our GOODS- N SCUBA survey. It does not have a radio counterpart and its accurate location was recently determined with the SMA interferometer. It is not detected by the GOODS-N HST ACS imaging and is just above the detection limit of the ultradeep Spitzer imaging at 3.6-24 um. Its faint radio flux and its Spitzer color suggest a redshift of z>4, and potentially even z>6. It has an incredible star formation rate of ~1000 solar mass per year, and it can quickly grow into a >10^11 solar mass massive galaxy. Radio faint submm sources like GOODS850-5 may be a new population of high-redshift massive galaxies that are not picked up by any of the previous optical, near-IR, and radio surveys, and therefore it is crucial to obtain the redshift of GOODS850-5. However, because of its extreme optical faintness, the only way to constrain its redshift is photometric redshift with the existing Spitzer photometry and the proposed NICMOS 1.6 um photometry. NICMOS is the only instrument that can provide information about its redshift and morphology among all space- based and ground-based instruments at all wavelengths. The proposed observation will provide unique insight on galaxy evolution and mass assembly at high redshift.
WFPC2 11178
Probing Solar System History with Orbits, Masses, and Colors of Transneptunian Binaries
The recent discovery of numerous transneptunian binaries {TNBs} opens a window into dynamical conditions in the protoplanetary disk where they formed as well as the history of subsequent events which sculpted the outer Solar System and emplaced them onto their present day heliocentric orbits. To date, at least 47 TNBs have been discovered, but only about a dozen have had their mutual orbits and separate colors determined, frustrating their use to investigate numerous important scientific questions. The current shortage of data especially cripples scientific investigations requiring statistical comparisons among the ensemble characteristics. We propose to obtain sufficient astrometry and photometry of 23 TNBs to compute their mutual orbits and system masses and to determine separate primary and secondary colors, roughly tripling the sample for which this information is known, as well as extending it to include systems of two near-equal size bodies. To make the most efficient possible use of HST, we will use a Monte Carlo technique to optimally schedule our observations.
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 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 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.
ACS/SBC 11116
Exploring the Early FUV History of Cool Stars: Transition Regions at 30 Myr
Stellar magnetic activity derives from the so-called “dynamo,” a hydromagnetic interplay between overturning plasma motions and differential rotation in stars cool enough to support significant surface convection zones. The magnetic fields resulting from dynamo action are in turn are responsible for a wide range of high-energy emissions, including the spectacular outbursts called flares. Dynamo powered magnetic activity is not confined solely to stars, but also must occur, for example, in accretion disks of all descriptions, and in some planets. A great deal is known about magnetic activity in middle-aged G dwarfs like our Sun, thanks to its proximity. Less is known, however, about the much younger stars, newly emerged from the T-Tauri stage. Yet, it is during this phase that they reach the peak of their magnetic activity, and subsidiary influences, such as the impact of ionizing radiation and strong coronal winds on developing solar systems, also are maximum. One of the key missing ingredients in our current understanding are measurements of FUV emissions of such stars, to complement the extensive collections of coronal {1-10 MK} X-ray measurements, particularly from recent ROSAT, Chandra and XMM-Newton surveys. We propose to conduct sensitive ACS/SBC prism ultraviolet spectroscopy of selected fields in two young {30 Myr} Galactic clusters–IC 2391 and IC 2602–to inventory the key C IV emission index {~0.1 MK} over a much larger and more diverse sample of coeval objects than has been possible hitherto. A key question is whether the FUV emissions also suffer the “saturation” and “super-saturation” at short rotation periods seen in coronal X-rays, or whether they continue to rise in the fastest rotating stars. The saturation behavior of the different temperature regimes holds important clues to the organization of the surface active regions on these very young stars, and should allow us to distinguish among several competing models.
WFPC2 11103
A Snapshot Survey of The Most Massive Clusters of Galaxies
We propose the continuation of our highly successful SNAPshot survey of a sample of 125 very X-ray luminous clusters in the redshift range 0.3-0.7. As demonstrated by the 25 snapshots obtained so far in Cycle14 and Cycle15 these systems frequently exhibit strong gravitational lensing as well as spectacular examples of violent galaxy interactions. The proposed observations will provide important constraints on the cluster mass distributions, the physical nature of galaxy-galaxy and galaxy-gas interactions in cluster cores, and a set of optically bright, lensed galaxies for further 8-10m spectroscopy. All of our primary science goals require only the detection and characterization of high-surface-brightness features and are thus achievable even at the reduced sensitivity of WFPC2. Because of their high redshift and thus compact angular scale our target clusters are less adversely affected by the smaller field of view of WFPC2 than more nearby systems. Acknowledging the broad community interest in this sample we waive our data rights for these observations. Due to a clerical error at STScI our approved Cycle15 SNAP program was barred from execution for 3 months and only 6 observations have been performed to date – reinstating this SNAP at Cycle16 priority is of paramount importance to reach meaningful statistics.
ACS/SBC 10872
Lyman Continuum Emission in Galaxies at z=1.2
Lyman continuum photons produced in massive starbursts may have played a dominant role in the reionization of the Universe. Starbursts are important contributors to the ionizing metagalactic background at lower redshifts as well. However, their contribution to the background depends upon the fraction of ionizing radiation that escapes from the intrinsic opacity of galaxies below the Lyman limit. Current surveys suggest escape fractions of a few percent, up to 10%, with very few detections {as opposed to upper limits} having been reported. No detections have been reported in the epochs between z=0.1 and z=2. We propose to measure the fraction of escaping Lyman continuum radiation from 15 luminous z~1.2 galaxies in the GOODS fields. Using the tremendous sensitivity of the ACS Solar- blind Channel, we will reach AB=30 mag., allowing us to detect an escape fraction of 1%. We will correlate the amount of escaping radiation with the photometric and morphological properties of the galaxies. A non-detection in all sources would imply that QSOs provide the overwhelming majority of ionizing radiation at z=1.3, and it would strongly indicate that the properties of galaxies at higher redshift have to be significantly different for galaxies to dominate reionization. The deep FUV images will also be useful for extending the FUV study of other galaxies in the GOODS fields.
WFPC2 10766
A Deep X-ray Survey of the Small Magellanic Cloud
We request deep observations of 2 representative fields in the Small Magellanic Cloud with Chandra and HST, with the primary goal of measuring the luminosity function and space density of X-ray binaries and other sources down to an unprecedented faint luminosity limit of 2x10E32 erg/s. This will be the faintest XLF ever obtained for any galaxy, including our own. HST photometry to 24th magnitude in V and I filters will identify the sources and provide Fx/Fopt, which will be vital in quantifying the LMXB population and in measuring the properties of the first coronally active stars ever detected in an external galaxy.
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 21 21 FGS REacq 18 18 OBAD with Maneuver 78 78
SIGNIFICANT EVENTS: (None)
