NASA Hubble Space Telescope Daily Report # 4483
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 # 4483
– Continuing to collect World Class Science
PERIOD COVERED: UT November 05, 2007 (DOY 309)
OBSERVATIONS SCHEDULED
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.
WFPC2 11024
WFPC2 CYCLE 15 INTERNAL MONITOR
This calibration proposal is the Cycle 15 routine internal monitor for WFPC2, to be run weekly to monitor the health of the cameras. A variety of internal exposures are obtained in order to provide a monitor of the integrity of the CCD camera electronics in both bays {both gain 7 and gain 15 — to test stability of gains and bias levels}, a test for quantum efficiency in the CCDs, and a monitor for possible buildup of contaminants on the CCD windows. These also provide raw data for generating annual super-bias reference files for the calibration pipeline.
FGS 11212
Filling the Period Gap for Massive Binaries
The current census of binaries among the massive O-type stars is seriously incomplete for systems in the period range from years to millennia because the radial velocity variations are too small and the angular separations too close for easy detection. Here we propose to discover binaries in this observational gap through a Faint Guidance Sensor SNAP survey of relatively bright targets listed in the Galactic O Star Catalog. Our primary goal is to determine the binary frequency among those in the cluster/association, field, and runaway groups. The results will help us assess the role of binaries in massive star formation and in the processes that lead to the ejection of massive stars from their natal clusters. The program will also lead to the identification of new, close binaries that will be targets of long term spectroscopic and high angular resolution observations to determine their masses and distances. The results will also be important for the interpretation of the spectra of suspected and newly identified binary and multiple systems.
NIC1/NIC2/NIC3 11060
NICMOS Photometric Stability Monitoring
This NICMOS calibration proposal carries out photometric monitoring observations during Cycle 15. The format is the same as the Cycle 14 version of the program {10725}, but a few modifications were made with respect to the Cycle 12 program 9995 and Cycle 13 program 10381. Provisions had to be made to adopt to 2-gyro mode {G191B2B was added as extra target to provide target visibility through most of the year}. Where before 4 or 7 dithers were made in a filter before we moved to the next filter, now we observe all filters at one position before moving to the next dither position. While the previous method was chosen to minimize the effect of persistence, we now realize that persistence may be connected to charge trapping and by moving through the filter such that the count rate increases, we reach equilibrium more quickly between charge being trapped and released. We have also increased exposure times where possible to reduce the charge trapping non- linearity effects.
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 11341
Lower Luminosity AGNs at Cosmologically Interesting Redshifts: SEDs and Accretion Rates of z~0.36 Seyferts
We propose a multiwavelength campaign to constrain the SEDs of Seyferts at z~0.36. This epoch, corresponding to a look back time of 4 Gyrs, is cosmologically interesting for studies of the coeval development of black holes and their host galaxy bulges. Our sample, comprising 24 Seyferts, has unprecedented high quality Keck spectroscopy and HST imaging already invested to extract host galaxy bulge properties, estimate black hole masses, and separate nuclear and host optical luminosities. To supplement and extend this successful program, we request 93 ks of Chandra time (to measure the shape and power of the AGN-only X-ray continuum), 11 hrs each of Spitzer and Gemini (to constrain the dust temperature), and 7 orbits of HST (to determine the nuclear luminosity for the final 7 objects).
NIC3/WFPC2 10921
Tangential Velocities of Objects in the Orion Nebula and Locating the Embedded Outflow Sources.
The Orion Nebula is arguably the Rosetta Stone for studying a very young star cluster and how the radiation and outflowing plasma from its stars interact with ambient material. It has been the subject of numerous HST imaging studies, which means that there is good opportunity for determining tangential velocities by obtaining second epoch images during Cycle 15, which may be the last cycle for which the WFPC2 is available. These velocities in the plane-of-the-sky will allow us to determine the patterns of outflow from micro-jets smaller than the Solar System to jet driven shocks more than a parsec from their sources. Combined with radial velocities, we’ll obtain spatial velocities, which are critical to determining where the embedded sources are located that produce the numerous HH objects coming from the Orion-S and BN-KL regions. We’ll also be able to determine the physics that is operating in the LL Ori type of outflows {where a bipolar jet is being distorted by a slow wind coming from the nebula}. We will also be able to search for runaway stars caused by the disintegration of young multiple-star systems. All of this is possible because the long-time base of the WFPC2 and ACS observations allow a new level of astrometric precision to be obtained and to be done efficiently by making coordinated parallel observations with all images.
WFPC2 10900
Optical polarimetry of PSR B0540-69 and its synchrotron nebula.
Polarization measurements of pulsars and of their synchrotron nebulae are uniquely able to provide deep insights into the highly magnetized relativistic environment of young rotating neutron stars. Apart from the radio band, pulsar polarization is best measured in the optical, for the rare cases of detectable optical emission. One of the brightest pulsars together with Crab {PSR B0531+21} and Vela {PSR B0833-45}, for which optical polarization measurements support the newly developed two-pole caustic model {TPC}, is PSR B0540-69 in the Large Magellanic Clouds, often referred as the Crab Twin for their overall similarities in both age and energetics. Together with the Crab, PSR B0540-69 is also the only pulsar embedded in a synchrotron nebula visible at optical wavelengths. We plan to observe PSR B0540-69 and its compact nebula {4 arcsec diameter} with the Advanced Camera for Surveys {ACS} and the Wide Field Channel {WFC} detector using UV and visual polarization filters. Thanks to the superb angular resolution of ACS, these observations will allow us to spectacularly resolve the pulsar from its nebular background, providing the first firm measure of the pulsar polarization which will be crucial to assess, on a broader sample, the validity of the TPC model with respect to other pulsars magnetosphere models. These observations will also provide the first detailed polarization map of the nebula, including the jet and the torus seen in our previous WFPC2 images.
WFPC2 10919
Eclipsing Binaries in the Local Group: II – Calibration of the Zeropoint of the Cosmic Distance Scale and Fundamental Properties of Stars in M33 (uses NIC3)
The Great Spiral Galaxy in Triangulum {M33} is potentially a crucial calibrator for the Cosmic Distance Scale, and thus for determining the age and evolution of the Universe. M33 is viewed face-on, has a simple geometry, large and diverse stellar populations, and morphologies similar to our Galaxy and other more distant galaxies used for distance determinations. Yet currently the M33 distance {d ~ 830 +/- 110 kpc} still has measurement dispersions of 10-15%. We have demonstrated, in our work on the LMC and M31 distances, that double-line eclipsing binaries can serve as excellent “standard candles.” Distances derived from eclipsing binaries are basically geometric and essentially free from many assumptions and uncertainties that plague other less direct methods, such as metallicity differences and calibration zeropoints. The absolute radii of the component stars of eclipsing binaries can be determined to better than a few percent from the time- tested analyses of their light and radial velocity curves. With accurate determinations of radii, temperatures, and ISM absorption it is possible to determine reliable distances. We are extending our program of using eclipsing binaries as standard candles to determine an accurate distance to M33. As a first step, we are proposing to carry out HST/ACS spectrophotometry of a well suited ~19th mag ~O7 + ~O7 eclipsing binary system in M33 that has been previously observed from the ground. HST/ACS prism/grism low-resolution spectrophotometry {118-850 nm} is the only missing key element of this program and is used to determine more reliable values for T_eff, [Fe/H], and ISM extinction. These quantities, when combined with the results from existing light and radial velocity curves for the target, yield the stellar masses, radii, luminosities and, importantly, the distance. The proposed HST/ACS program can be carried out effectively with only 1 HST orbit. Based on our previous experience, we expect to reduce the uncertainty of the M33 distance to better than 5-7%, thereby leading to a firmer calibration of the Cosmic Distance Scale and the zeropoint of the Hubble Constant {Ho}.
WFPC2 11028
WFPC2 Cycle 15 UV Earth Flats
Monitor flat field stability. This proposal obtains sequences of earth streak flats to improve the quality of pipeline flat fields for the WFPC2 UV filter set. These Earth flats will complement the UV earth flat data obtained during cycles 8-14.
WFPC2 11070
WFPC2 CYCLE 15 Standard Darks – part II
This dark calibration program obtains dark frames every week in order to provide data for the ongoing calibration of the CCD dark current rate, and to monitor and characterize the evolution of hot pixels. Over an extended period these data will also provide a monitor of radiation damage to the CCDs.
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.
WFPC2 11169
Collisions in the Kuiper belt
For most of the 15 year history of observations of Kuiper belt objects, it has been speculated that impacts must have played a major role in shaping the physical and chemical characteristics of these objects, yet little direct evidence of the effects of such impacts has been seen. The past 18 months, however, have seen an explosion of major new discoveries giving some of the first insights into the influence of this critical process. From a diversity of observations we have been led to the hypotheses that: {1} satellite- forming impacts must have been common in the Kuiper belt; {2} such impacts led to significant chemical modification; and {3} the outcomes of these impacts are sufficiently predictable that we can now find and study these impact-derived systems by the chemical and physical attributes of both the satellites and the primaries. If our picture is correct, we now have in hand for the first time a set of incredibly powerful tools to study the frequency and outcome of collisions in the outer solar system. Here we propose three linked projects that would answer questions critical to the multiple prongs of our hypothesis. In these projects we will study the chemical effects of collisions through spectrophotometric observations of collisionally formed satellites and through the search for additional satellites around primaries with potential impact signatures, and we will study the physical effects of impacts through the examination of tidal evolution in proposed impact systems. The intensive HST program that we propose here will allow us to fully test our new hypotheses and will provide the ability to obtain the first extensive insights into outer solar system impact processes.
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!
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)
