#1
|
|||
|
|||
Daily 3678
HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science
DAILY REPORT # 3678 PERIOD COVERED: DOY 232 OBSERVATIONS SCHEDULED ACS/HRC 10255 A Never Before Explored Phase Space: Resolving Close White Dwarf / Red Dwarf Binaries We propose an ACS Snapshot imaging survey to resolve a well-defined sample of highly probable white dwarf plus red dwarf close binaries. These candidates were selected from a search for white dwarfs with infrared excess from the 2MASS database. They represent unresolved systems {separations less than approximately 2" in the 2MASS images} and are distributed over the whole sky. Our HST+ACS observations will be sensitive to a separation range {1-20 AU} never before probed by any means. The proposed study will be the first empirical test of binary star parameters in the post-AGB phase, and cannot be accomplished from the ground. By resolving as few as 20 of our ~100 targets with HST, we will be able to characterize the distribution of orbital semi-major axes and secondary star masses. ACS/HRC 10262 The 3D Morphology of the Extreme Red Supergiant VY Cma The extreme RSG and powerful OH/IR source VY CMa is surrounded by an asymmetric reflection nebula dominated by a prominent nebulous arc, bright filamentary arcs, and several clumps of dusty knots that are evidence for multiple and asymmetric mass loss events. Our groundbased velocities show that these structures are kinematically distinct from the general flow of the diffuse gas and may be directional. We have speculated that these arcs and knots may be caused by localized activity on the star involving convection and possibly magnetic fields analogous to lower mass stars. If correct this would have important implications for the causes of high mass loss events in evolved massive stars. Fortunately, VY CMa provides us with an opportunity to learn more about its possible mass loss mechanisms and history from the morphology of its ejecta. We propose to use polarimetry and second epoch images combined with our radial velocities to map the morphology of the nebula and the discrete structures embedded in it. ACS/HRC/WFC 10061 CCD Daily Monitor This program consists of basic tests to monitor, the read noise, the development of hot pixels and test for any source of noise in ACS CCD detectors. This programme will be executed once a day for the entire lifetime of ACS. ACS/WFC 10325 Low Redshift Cluster Gravitational Lensing Survey This proposal has two main scientific goals: to determine the dark matter distribution of massive galaxy clusters, and to observe the high redshift universe using these clusters as powerful cosmic telescopes. Deep, g, r, i, z imaging of a sample of low-z {0.2-0.4} clusters will yield a large sample of lensed background galaxies with reliable photometric redshifts. By combining strong and weak lensing constraints with the photometric redshift information it will be possible to precisely measure the cluster dark matter distribution with an unprecedented combination of high spatial resolution and area coverage, avoiding many of the uncertainties which plague ground-based studies and yielding definitive answers about the structure of massive dark matter haloes. In addition, the cosmological parameters can be constrained in a largely model independent way using the multiply lensed objects due to the dependence of the Einsteinng radius on the distance to the source. We can also expect to detect several highly magnified dropout galaxies behind the clusters in the redshift ranges 4-5 5-6 and 7-8, corresponding to a drop in the flux in the g, r, and i bands relative to longer wavelength. We will obtain the best information to date on the giant arcs already known in these clusters, making possible detailed, pixel-by-pixel studies of their star formation rate, dust distribution and structural components, including spiral arms, out to a redshift of around z~2.5 in several passbands. ACS/WFC/WFC2 9857 A tailored survey of proplyds with the ACS While our specific understanding of the proto-planetary disks in Orion is increasing, our general knowledge of what promotes and hinders their birth and longevity is hampered by having good observations in only this one region. Observations of proplyds in other regions with different conditions of ultraviolet irradiation and age can provide more stringent tests of our present models. We have therefore designed an ACS/WFC and parallel WFC2 survey of open clusters embedded in H II regions that, with a small number of orbits, maximizes the probability of successfully finding proplyds there. Our observing strategy will additionally afford a quantitative study of the detected proplyds, as well as the derivation of a correlation between those characteristics and the clusters' stellar population. ACS gives us an unprecedented opportunity to kick start the mass discovery of proplyds in many environments, an obvious way in which progress can be made in this field. This small tailored survey, gives us an excellent chance to obtain a huge return at low cost. ACS/WFC/WFPC2 9837 Stellar Populations in the Outskirts of M33: A Unique Probe of Disk Galaxy Formation The fossil record of galaxy formation and evolution is imprinted on the structure and composition of galactic stellar populations. We have recently completed an extensive ground-based imaging survey of the low mass Local Group spiral, M33. Our analysis of the global structure of M33 suggests it is a 'pure disk' galaxy, with no discernible stellar halo. Furthermore, the disk surface brightness declines very abruptly beyond ~5 scalelengths. We propose here to obtain deep ACS imagery of two fields in the far outer disk of M33, located at 4.5 and 6 exponential scalelengths. Deep colour-magnitude diagrams reaching main sequence turn-offs of ~8 Gyr {corresponding to star formation episodes since z 1} will be constructed and used for quantitative modelling of the star formation history. State-of-the-art cosmological simulations of galaxy formation predict stars in the outer regions of galactic disks should be predominantly young-to-intermediate age. The data we propose to obtain will directly test this idea, and provide a much-needed observational constraint on the epoch at which disk galaxies were assembled. The proposed observations will provide an excellent complement to an ongoing Cycle 11 program to study the outer disk of the more massive system, M31. FGS 10108 Dynamical Masses and Radii of Four White Dwarf Stars The cool white dwarf stars WD1639+153 and WD1818+126 were recently resolved by HST FGS1r to be double degenerate binary systems with projected separations of 112 mas and 174 mas respectively. At a distance of less than 50 pc they may both have periods shorter than about 20 years, making them ideal candidates for follow up studies for dynamical mass determinations. This will increase the number of white dwarfs with dynamical mass measurements from the current 4 up to 8. Continued observations of these white dwarfs along with nearby field stars with the FGS will accurately determine the orbital elements and parallax of each system. The mass and radius of all four white dwarfs can be determined to an unprecedented 1%, making it possible to test and calibrate the theoretical white dwarf mass radius relation at the cool end of the cooling curve for the DA and DC subclasses. Since the components of the binary are coeval, once the mass and radius, and hence the cooling age of each star is known, it will be possible to estimate the relation between the initial mass and final mass for all four white dwarfs. We are requesting a total of 4 HST orbits per year for the next three cycles to initiate the process that will result in a determination of the mass and radius of the four white dwarfs. NIC/NIC3 10226 The NICMOS Grism Parallel Survey We propose to continue managing the NICMOS pure parallel program. Based on our experience, we are well prepared to make optimal use of the parallel opportunities. The improved sensitivity and efficiency of our observations will substantially increase the number of line-emitting galaxies detected. As our previous work has demonstrated, the most frequently detected line is Halpha at 0.7z1.9, which provides an excellent measure of current star formation rate. We will also detect star-forming and active galaxies in other redshift ranges using other emission lines. The grism observations will produce by far the best available Halpha luminosity functions over the crucial--but poorly observed--redshift range where galaxies appear to have assembled most of their stellar mass. This key process of galaxy evolution needs to be studied with IR data; we found that observations at shorter wavelengths appear to have missed a large fraction of the star-formation in galaxies, due to dust reddening. We will also obtain deep F110W and F160W images, to examine the space densities and morphologies of faint red galaxies. In addition to carrying out the public parallels, we will make the fully reduced and calibrated images and spectra available on-line, with some ground-based data for the deepest parallel fields included. NIC1/NIC2/NIC3 8793 NICMOS Post-SAA calibration - CR Persistence Part 4 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. NIC2 10176 Coronagraphic Survey for Giant Planets Around Nearby Young Stars A systematic imaging search for extra-solar Jovian planets is now possible thanks to recent progress in identifying "young stars near Earth". For most of the proposed young {~ 30 Myrs} and nearby {~ 60 pc} targets, we can detect a few Jupiter-mass planets as close as a few tens of AUs from the primary stars. This represents the first time that potential analogs of our solar system - that is planetary systems with giant planets having semi-major axes comparable to those of the four giant planets of the Solar System - come within the grasp of existing instrumentation. Our proposed targets have not been observed for planets with the Hubble Space Telescope previously. Considering the very successful earlier NICMOS observations of low mass brown dwarfs and planetary disks among members of the TW Hydrae Association, a fair fraction of our targets should also turn out to posses low mass brown dwarfs, giant planets, or dusty planetary disks because our targets are similar to {or even better than} the TW Hydrae stars in terms of youth and proximity to Earth. Should HST time be awarded and planetary mass candidates be found, proper motion follow-up of candidate planets will be done with ground-based AOs. WFPC2 10071 WFPC2 CYCLE 12 Supplemental Darks Part 3/3 This dark calibration program obtains 3 dark frames every day to provide data for monitoring and characterizing the evolution of hot pixels. FLIGHT OPERATIONS SUMMARY: Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.) HSTAR 9520: GS Acquisition (2,1,1) @ 232/09:28:19Z resulted in FL backup (2,0,2) using FGS 2 due to SSLE on FGS 1. There were no FHST FM Updates scheduled prior to the primary GS acquisition. Subsequent FHST Map @ 232/09:36:35Z showed 3-axis (RSS) value ~ 12.00 arcsec. Under investigation. COMPLETED OPS REQs: 17256-0 Genslew for proposal 9862 - slot 4 @ 232/15:22:30z OPS NOTES EXECUTED: None SCHEDULED SUCCESSFUL FAILURE TIMES FGS GSacq 08 08 FGS REacq 10 10 FHST Update 12 12 LOSS of LOCK SIGNIFICANT EVENTS: None |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
EVOLUTION DEAD AT AGE 126 -- R.I.P. | Ed Conrad | Astronomy Misc | 4 | August 21st 04 12:01 AM |
Monitoring NASA Daily ISS Report | JimO | Space Station | 2 | June 1st 04 10:33 PM |