#1
|
|||
|
|||
Daily 3774
HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science
DAILY REPORT # 3774 PERIOD COVERED: DOY 011 OBSERVATIONS SCHEDULED ACS/HRC 10204 Evolution of Light Echoes of SN 1993J SN 1993J is the nearest SN in the last decade, and only one of seven objects to produce confirmed light echoes. Our analyses of archival HST/WFPC2 data revealed that the SN has illuminated at least two light-echo structures in the galaxy M81. Those echoes appear to define two sheets of dust, located roughly 260 ly and 770 ly in front of the SN, which are the first, and most efficient, 3-D probes of the ISM in M81. The echoes not only reveal the ISM's structure, but also constrain the density, composition and grain-size of its dust. Echoes are transient events, and as they change on timescales shorter than a year, continued monitoring will reveal new illuminated material, tracing interstellar and circumstellar structure. We propose a modest and highly efficient campaign by HST to image these and yet undiscovered echoes toward SN 1993J. Such observations will build the first direct 3-D map of the ISM within a million cubic parsecs of M81's spiral arm, and may glimpse the circumstellar environment affected by the projenitor's mass loss. Such results probe the nature of extragalactic dust, reveal spatio-kinematic information about the M81's disk, tightly constrain its internal extinction, and under the proper circumstances, provide an independent distance measurement to the host galaxy. ACS/WFC 10152 A Snapshot Survey of a Complete Sample of X-ray Luminous Galaxy Clusters from Redshift 0.3 to 0.7 We propose a public, uniform imaging survey of a well-studied, complete, and homogeneous sample of X-ray clusters. The sample of 73 clusters spans the redshift range between 0.3-0.7. The samples spans almost 2 orders of magnitude of X-ray luminosity, where half of the sample has X-ray luminosities greater than 10^44 erg/s {0.5-2.0 keV}. These snapshots will be used to obtain a fair census of the morphology of cluster galaxies in the cores of clusters, to detect radial and tangential arc candidates, to detect optical jet candidates, and to provide an approximate estimate of the shear signal of the clusters themselves, and potentially an assessment of the contribution of large scale structure to lensing shear. ACS/WFC 10181 ACS/NICMOS Imaging of Bright Lyman Break Galaxy Candidates from SDSS The recent surprising discovery of six unusually bright {r~20 mag} Lyman break galaxy {LBG} candidates with z=2.45-2.80 in the Sloan Digital Sky Survey {SDSS} raises a number of questions that only HST can address. Specifically, what is the true nature of these objects, and what role if any is played by gravitational lensing? We propose to use the superior resolution and sensitivity of ACS and NICMOS to obtain deep images of these objects and their environments. Compared to SDSS images, HST will allow us to determine their morphologies {extended, point-source, or lensed}, the appearance of their environments {rich or poor}, and to detect any faint foreground groups or clusters that might be responsible for lensing these objects. All outcomes would be intriguing. If the objects are lensed, it increases from 1 {MS1512-cB58} to 7 the number of normal LBGs bright enough to study individually. If they are instead unlensed point sources, they will represent a new class of previously unidentified absorption-line quasars. Finally, if they are unlensed and extended star-forming galaxies, they are at least 4mag brighter than L_* LBGs, thus making them the most luminous star-forming objects yet seen, representing a heretofore unknown extreme population of objects. 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/NIC3 10195 Probing the Surroundings of a Highly Luminous Redshift 6.5 Galaxy We propose deep images of a recently discovered galaxy at z=6.535, which is among the most luminous Lyman-alpha emitting galaxies known at high redshift. The brightness and rarity of this source imply that it is associated with a high peak in the matter density distribution. {It is the brightest Lyman alpha source in 2e5 comoving Mpc3, with a luminosity of 6 L*.} Further objects in this peak are expected to be visible with HST's sensitivity. The Lyman alpha line has a large rest frame equivalent width, with a lower bound 100 Angstroms. Such a large equivalent width would be impossible for objects embedded in neutral gas, and instead requires either that {a} the universe was reionized before z=6.5 or {b} the galaxy resides in a local ionized bubble, in which case an additional contribution to the ionizing photon budget from presently undetected neighbors is required. With 19 orbits of ACS and NICMOS imaging, we will measure this object's morphology and spectral energy distribution, thus searching for either active nuclei or old stellar populations. We will also search for possible neighbors, which could establish the first known galaxy group at z6, and may provide sufficient ionizing flux to allow the escape of the observed Lyman alpha photons in a neutral universe. If neighbors are not found, it will lead to an upper bound on the neutral fraction in the general IGM at z=6.5. ACS/WFC/WFPC2 10402 The Formation and Evolution of Spirals: An ACS and WFPC2 Imaging Survey of Nearby Galaxies Over 50% of galaxies in the local universe are spirals. Yet the star formation histories and evolution of this crucial population remain poorly understood. We propose to combine archival data with new ACS/WFC and WFPC2 observations of 11 galaxies, to tackle a comprehensive investigation of nearby spirals covering the entire spiral sequence. The new observations will fill a serious deficiency in HST's legacy, and maximize the scientific return of existing HST data. The filter combination of UBVI, and Halpha is ideal for studying stellar populations, dust properties, and the ISM. Our immediate scientific objectives a {i} to use the resolved cluster populations, both young massive clusters and ancient globular clusters as a chronometer, to understand how spirals assembled as a function of time; {ii} study the rapid disruption properties of young clusters; and {iii} understand dust distributions in spirals from pc to kpc scales. Each of these goals provides an important step towards charting the evolution of galaxies, and an essential baseline for interpreting the galaxy populations being surveyed in both the early and present universe. The resolution of our survey, which exploits the excellent imaging capabilities of HST's two optical cameras, will enable us to understand the record of star cluster, and galaxy formation in a level of detail which is not possible for more distant systems. Finally, the proposed observations will provide a key to interpret an extensive, multiwavelength archive of space- and ground- based data at lower spatial resolution {SPITZER, CHANDRA, GALEX, NICMOS P alpha and H band imaging} for local spirals. NIC1 10143 Ultracool companions to the nearest L dwarfs We propose to conduct the most sensitive survey to date for low mass companions to nearby L dwarfs. We will use NICMOS to image targets drawn from a volume-complete sample of 70 L dwarfs within 20 parsecs. The combination of infrared imaging and proximity will allow us to search for T dwarf companions at separations as small as 1.6 AU. This is crucial, since no ultracool binaries are currently known with separations exceeding 15 AU. Only 10 dwarfs in this sample have previous HST observations primarily at optical wavelengths. With the increased sensitivity of our survey, we will provide the most stringent test to date of brown dwarf models which envisage formation as ejected stellar embryos. In addition, our observations will be capable of detecting binaries with mass ratios as low as 0.3, and will therefore also test the apparent preference for equal-mass ultracool binaries. Finally, our observations offer the best prospect to date of detecting companions significantly cooler than the coolest t dwarf currently known. NICMOS 8790 NICMOS Post-SAA calibration - CR Persistence Part 1. 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. WFPC2 10132 UV Confirmation of New Quasar Sightlines Suitable for the Study of Intergalactic Helium The reionization of intergalactic helium is thought to have occurred between redshifts of about 3 and 4. The study of HeII Lyman-alpha absorption towards a half-dozen quasars at 2.7z3.5 demonstrates the great potential of such probes of the IGM, but the current critically-small sample limits confidence in resulting cosmological inferences. The requisite unobscured quasar sightlines to high-redshift are extremely rare, especially due to severe absorption in random intervening Lyman-limit systems, but SDSS provides hundreds of bright, new quasars at such redshifts potentially suitable for HeII studies. Our cycle 13 SNAP program proposes to verify the UV detectability of 40 new, bright, z2.9 SDSS quasars, but with special emphasis on extending helium studies to the highest redshift sightlines. Our proposed approach has already proven successful, and additional sightlines will enable follow-up spectal observations to measure the spectrum and evolution of the ionizing background radiation, the density of intergalactic baryons, and the epoch of reionization of the IGM. WFPC2 10360 WFPC2 CYCLE 13 INTERNAL MONITOR This calibration proposal is the Cycle 13 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 {gain 7 and gain 15}, a test for quantum efficiency in the CCDs, and a monitor for possible buildup of contaminants on the CCD windows. FLIGHT OPERATIONS SUMMARY: Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.) None COMPLETED OPS REQs: None OPS NOTES EXECUTED: None SCHEDULED SUCCESSFUL FAILURE TIMES FGS Gsacq 10 10 FGS Reacq 06 06 FHST Update 14 14 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 |
Great customizable site for daily astro phenomena | Victor | Amateur Astronomy | 2 | April 8th 04 12:01 AM |
JimO Speaks on 'Daily Planet' re Hubble | JimO | Policy | 0 | February 11th 04 10:53 PM |
Spirit's daily activities schedule? | Matti Anttila | Policy | 0 | January 15th 04 08:39 AM |