#1
|
|||
|
|||
Daily 3679
HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science
DAILY REPORT # 3679 PERIOD COVERED: DOYs 233-235 OBSERVATIONS SCHEDULED ACS/HRC 9862 ACS detection of sub-stellar companions around Vega, Fomalhaut and beta Pic via parallax & proper motion The first visible light coronagraph on HST provides contrast ratios near very bright stars that are unparalleled by ground-based observations. Vega, Fomalhaut and Beta Pictoris have dusty debris disks with structure thought to originate from the presence of yet-undetected, substellar companions. The detection of substellar companions is possible with the ACS HRC coronagraph if observations are made in two epochs. Here we propose to image Vega in two epochs within Cycle 12. We argue that in a few months interval, the sky plane motion of any companions due to parallax and proper motion is large relative to the HRC astrometric uncertainties. Likewise, we propose to obtain a second epoch image of Beta Pic and Fomalhaut within Cycle 12 to complement the single epoch imaging of the GTO program. Because Vega, Fomalhaut and Beta Pictoris are young and nearby, this imaging campaign will be sensitive to brown dwarfs and massive extrasolar giant planets at their predicted locations 40-60 AU projected radius from each star. Either positive or negative results for each system will be used to constrain the physical characteristics of massive objects hypothesized to cause the observed disk asymmetries. NIC1/NIC2 9844 Brown dwarf atmospheric variability observations We propose to use NIC1 and NIC2 to study brown dwarfs for atmospheric variability. We will observe a sequence of early Ts, a detected variable T2, a T3 and a T4.5. Atmospheric variability, that is expected by some models for these objects, would constrain the physical parameters of cloud vertical distribution, horizontal homogeneity and the dynamics of the very cool atmospheres. The existence and amplitude of the variations would reveal the size and distribution of the cloud cover over the surface of the brown dwarf and test a model explaining the rapidity of the L to T type transition. The relative color changes would constrain the vertical extent of dynamical process and the depth in the atmosphere at which they take place. If a periodicity is measured, the rotational period of the dwarf could be estimated. HST provides the unique and crucial opportunity to observe beyond Earth atmospheric variable absorption, particularly in the important water bands NIC3 9735 ACS, NICMOS Observations of Three Ongoing Mergers We propose to make ACS {U, B, V, I, H_alpha}, and NICMOS {J, H, K} observations of NGC 520, NGC 2623, and NGC 3256, three merging galaxies in the middle of the Toomre Sequence and currently in the throes of violent relaxation. Two of these {NGC 2623 and NGC 3256} are the most IR luminous galaxies in the sequence. Hence, these ongoing mergers are ideal candidates for studying the triggering mechanism responsible for the formation of stars and star clusters. The ACS observations will allow us to age date the star clusters, and reliably distinguish clusters from stars based on their apparent sizes. They will also be used in conjunction with ground-based measurements of the stellar velocity dispersion to determine dynamical masses of the clusters and hence address the question of whether the IMF is truncated. The NICMOS observations will allow us to penetrate the dust and answer several fundamental questions such as: What fraction of the young clusters are hidden by dust? How do these clusters form and evolve? 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. 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 Einsteining 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/WFPC2 10273 Accurately Mapping M31's Microlensing Population We propose to augment an existing microlensing survey of M31 with source identifications provided by a modest amount of ACS {and WFPC2 parallel} observations to yield an accurate measurement of the masses responsible for microlensing in M31, and presumably much of its dark matter. The main benefit of these data is the determination of the physical {or "Einstein"} timescale of each microlensing event, rather than an effective {"FWHM"} timescale, allowing masses to be determined more than twice as accurately as without HST data. The Einstein timescale is the ratio of the lensing cross-sectional radius and relative velocities. Velocities are known from kinematics, and the cross-section is directly proportional to the {unknown} lensing mass. We cannot easily measure these quantities without knowing the amplification, hence the baseline magnitude, which requires the resolution of HST to find the source star. This makes a crucial difference because M31 lens mass determinations can be more accurate than those towards the Magellanic Clouds through our Galaxy's halo {for the same number of microlensing events} due to the better constrained geometry in the M31 microlensing situation. Furthermore, our larger survey, just completed, should yield at least 100 M31 microlensing events, more than any Magellanic survey. A small amount of ACS+WFPC2 imaging will deliver the potential of this large database {about 350 nights}. For the whole survey {and a delta-function mass distribution} the mass error should approach only about 15%, or about 6% error in slope for a power-law distribution. These results will better allow us to pinpoint the lens halo fraction, and the shape of the halo lens spatial distribution, and allow generalization/comparison of the nature of halo dark matter in spiral galaxies. In addition, we will be able to establish the baseline magnitude for about 50, 000 variable stars, as well as measure an unprecedentedly detailed color-magnitude diagram and luminosity function over much of M31. 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. 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. ACS/WFC 10216 Co-evolution of spheroids and black holes The masses of the giant black holes in galaxies are correlated with the luminosities, masses, and velocity dispersions of their host spheroids. This empirical connection of phenomena on widely different scales {from sub-parsec to kiloparsec} suggests that the evolution of a galaxy and its central black hole are closely linked. We propose to test various unified formation models, by measuring the cosmic evolution of the black hole/spheroid relations, back to z=0.37 {a lookback time of 4 Gyrs}. We will obtain 1-orbit ACS images of a sample of 20 Seyfert 1 galaxies, for which we already have extensive new ground-based measures of the black hole masses and the stellar velocity dispersions. HST resolution is required for accurate measurement of the nonstellar AGN continuum, and the luminosity and effective radius of the bulge of each host galaxy. This will complete the set of observables needed to map the co-evolution of spheroids and black-holes. The proposed sample is the minimum required to make the first measure of the black hole mass/bulge correlation and of the fundamental plane for active galaxies outside the local Universe. ACS/WFC 10210 Groups of Dwarf Galaxies: Pools of Mostly Dark Matter? Within 5 Mpc, there are 6 groups with well-known luminous galaxies but there also appears to be a comparable number of groups containing only dwarfs. If these dwarf entities are truly bound then M/L values are an order of magnitude higher than values found for groups with luminous spiral galaxies. There are theoretical reasons to anticipate that low mass halos may frequently be mostly dark. The dynamical influence of low mass halos is negligible in familiar groups with luminous members. By contrast, a study of the dynamics of `groups of dwarfs' may provide direct evidence of the existence of dark matter potential wells with few baryons. The goal of the present study is to gather detailed information on the 3-D distribution of dwarf galaxies suspected to lie within 7 groups of dwarfs within 5 Mpc. Distances with 7% relative accuracy can be measured with the Tip of the Giant Branch method with ACS and integrations within 1 orbit per target. ACS/WFC 10207 Star Formation in Damped Lya Galaxies: Testing the Connection with the Lyman Break Population The principal challenge of damped Lya {DLA} research is to identify and study the stellar components of these galaxies. Although two decades of absorption-line research has yielded the HI gas content, metallicity, velocity fields, molecular and dust content of these galaxies only a handful have been studied in emission. Therefore, it has been very difficult to compare the DLA galaxies with the successful surveys of high z galaxies discovered in emission {e.g. Lyman break galaxies; LBG}. This is particularly important given that DLA systems are the probable precursors to galaxies like the Milky Way. Because the DLA systems are identified toward bright background quasars, deep observations at high spatial resolution with astable PSF are essential. Recently, two major advances have greatly enhanced the prospects for measuring emission from DLA host galaxies: {1} we have developed a new spectroscopic technique for inferring the star formation rates {SFR} of the DLA which enables one to pre-select the brightest candidates; {2} the high spatial resolution and sensitivity of the ACS represents a major improvement over previous capabilities. We will obtain deep V-band images with the ACS of 5 high z DLA with the highest inferred apparent optical magnitudes. The complete survey will offer a robust statistical analysis of: {a} the extent and morphology of the DLA star forming regions; {b} the likelihood that the DLA and LBG correspond to the same population of protogalaxies; {c} a test of the protogalactic clump models favored by CDM cosmology. We emphasize this program will offer a major advance over all previous studies. Finally, we will complement these HST observations with an extensive observing campaign {IFU spectroscopy and deep IR imaging} on the Keck, VLT, and Magellan telescopes to provide the most extensive dataset yet on the physical properties of high z DLA. FGS 10202 Resolving OB Binaries in the Carina Nebula, Resuming the Survey In March 2002 we carried out a small, high-angular resolution survey of some of the brightest OB stars in the Carina Nebula with FGS1r in an attempt to resolve binary systems which had thus far evaded detection by other techniques. Of 23 stars observed, 5 new OB binaries were discovered with component separations ranging from 0.015" to0.325". This yield over the spatial domain of FGS1r's angular resolution, coupled with published statistics of the incidence of OB stars in short-period spectroscopic, and long-period visual binaries suggests that the fraction of binarity or multiplicity among OB stars is near unity. Our unexpected resolution of the prototype O2 If* star HD 93129A as a 55 milli-arcsecond double is a case in point that great care must be exercised when one attempts to establish the IMF and upper-mass cuttoff at the high-mass end of the HR diagram. We propose to resume the survey to observe a larger, statistically meaningful sample of OB stars to establish a firm assessment of multiplicity at the high-mass end of the IMF in these clusters. We will also investigate the single-star/binary-star status of several astrophysically important, individual stars in order to enable a better understanding of the evolution of high-mass stars. ACS/HRC 10182 Towards a Comprehensive Understanding of Type Ia Supernovae: The Necessity of UV Observations Type Ia supernovae {SNe Ia} are very important to many diverse areas of astrophysics, from the chemical evolution of galaxies to observational cosmology which led to the discovery of dark energy and the accelerating Universe. However, the utility of SNe Ia as cosmological probes depends on the degree of our understanding of SN Ia physics, and various systematic effects such as cosmic chemical evolution. At present, the progenitors of SNe Ia and the exact explosion mechanisms are still poorly understood, as are evolutionary effects on SN Ia peak luminosities. Since early-time UV spectra and light curves of nearby SNe Ia can directly address these questions, we propose an approach consisting of two observational components: {1} Detailed studies of two very bright, young, nearby SNe Ia with HST UV spectroscopy at 13 epochs within the first 1.5 months after discovery; and {2} studies of correlations with luminosity for five somewhat more distant Hubble-flow SNe Ia, for which relative luminosities can be determined with precision, using 8 epochs of HST UV spectroscopy and/or broad-band imaging. The HST data, along with extensive ground-based optical to near-IR observations, will be analyzed with state-of-the-art models to probe SN Ia explosion physics and constrain the nature of the progenitors. The results will form the basis for the next phase of precision cosmology measurements using SNe Ia, allowing us to more fully capitalize on the substantial past {and future} investments of time made with HST in observations of high-redshift SNe Ia. ACS/WFC 10178 Imaging Polarimetry of Young Stellar Objects with ACS and NICMOS: A study in dust grain evolution The formation of planetary systems is intimately linked to the dust population in circumstellar disks, thus understanding dust grain evolution is essential to advancing our understanding of how planets form. By combining {1} the high resolution polarimetric capabilities of ACS and NICMOS, {2} powerful 3-D radiative transfer codes, and {3} observations of objects known to span the earliest stellar evolutionary phases, we will gain crucial insight into the initial phases of dust grain growth: evolution away from an ISM distribution. Fractional polarization is a strong function of wavelength, therefore by comparing polarimetric images in the optical and infrared, we can sensitively constrain not only the geometry and optical depth of the scattering medium, but also the grain size distribution. By observing objects representative of the earliest evolutionary sequence of YSOs, we will be able to investigate how the dust population evolves in size and distribution during the crucial transition from a disk+envelope system to a disk+star system. The proposed study will help to establish the fundamental time scales for the initial depletion of ISM-like grains: the first step in understanding the transformation from small submicron sized dust grains, to large millimeter sized grains, and untimely to planetary bodies. ACS/WFC/WFPC2 10138 Searching for the Bottom of the Initial Mass Function The minimum mass of the Initial Mass Function {IMF} should be a direct reflection of the physical processes that dominate in the formation of stars and brown dwarfs. To date, the IMF has been measured down to 10 M_Jup in a few young clusters; there is no sign of a low-mass cutoff in the data for these clusters. We propose to obtain deep images in the SDSS i and z filters {i=26, z=25} with the ACS/WFC on HST for a 800"x1000" field in the Chamaeleon I star-forming region {2 Myr, 160 pc}. By combining these HST data {0.8, 0.9 um} with comparably deep broad-band photometry from ground-based telescopes {1.2, 1.6, 2.2 um} and SIRTF {3.6, 4.5, 5.8, 8.0 um}, we will measure the mass function of brown dwarfs down to the mass of Jupiter and thus determine the lowest mass at which objects can form in isolation in a typical star forming cluster. ACS/HRC 10102 Rings of Uranus: Dynamics, Particle Properties and Shepherding Moons Last year, our Uranian ring and moon observing program {GO-9823} resulted in the discovery of two moons, S/2003 U 1 and S/2003 U 2. We imaged two additional small moons, Ophelia and S/1986 U 10, that had not been seen since the Voyager encounter of 1986. Furthermore, our data show faint arcs and clumps orbiting within the rings, which were not seen by Voyager and are completely unexpected. We employed several "tricks" of the HRC to achieve this remarkable sensitivity; specifically, we used the CLEAR filter and oriented the images so that the planet, though vastly overexposed, did not interfere with the ring/moon region of interest to us. This allowed us to detect 25th-magnitude moons circling a 5th-magnitude planet. Now we propose to complete the task by carrying out a comprehensive survey of the system using the same techniques. Our goals are to recover the moons, better discern their orbital elements, and learn more about the dynamics of the ring clumps. In particular, we need to {1} understand the long-term stability of S/2003 U 2, which orbits perilously close to the larger moon Belinda; {2} complete our search for moons, which was only ~ 50% complete last year, and {3} better understand how the clumps and arcs within the ring system might relate to nearby "shepherding" moons, seen or unseen. This program is now a merger of two programs 10275 and 10102. The former is our new program, whereas the latter is the second year of our three-year program to study the light scattering properties of Uranus's rings as they approach their edge-on presentation in 2007. WFPC2 10080 Wavelength Stability of Narrow Band and Linear Ramp Filters Verify the mapping of wavelength as a function of CCD position on LRFs; check for changes in central wavelengths of narrow band filters. 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. 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/HRC 10050 ACS Earth Flats High signal sky flats will be obtained by observing the bright Earth with the HRC and WFC. These observations will be used to verify the accuracy of the flats currently used by the pipeline and will provide a comparison with flats derived via other techniques: L-flats from stellar observations, sky flats from stacked GO observations, and internal flats using the calibration lamps. Weekly coronographic monitoring is required to assess the changing position of the spots. WFPC2/ACS/HRC/WFC 10013 Focus Monitor The focus of HST is measured from WFPC2/PC and ACS/HRC images of stars. Multiple exposures are taken in parallel over an orbit to determine the influence of breathing on the derived mean focus. Observations are taken of clusters with suitable orientations to ensure stars appear in all fields. FLIGHT OPERATIONS SUMMARY: Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.) HSTAR 9521: GS Acquisition (2,3,2) @ 234/14:38:53Z resulted in FL backup (2,0,2) due to SSLE on FGS 3. Under investigation. COMPLETED OPS REQs: None OPS NOTES EXECUTED: 1115-0 CCC IPCONFIG Connections @ 233/10:52z SCHEDULED SUCCESSFUL FAILURE TIMES FGS GSacq 28 28 FGS REacq 22 22 FHST Update 44 44 LOSS of LOCK SIGNIFICANT EVENTS: Battery 3 Capacity Test is scheduled to start on entry into shadow @ 236/12:34Z (OR 17259 with attached script). Solar Arrays are being managed to be near normal during the period 236/11:40Z - 239/07:00Z. Continuous Engineering Recording (CER) is scheduled to occur 236/12:34Z - 20:34Z. |
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 |