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Daily #4032
HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science
DAILY REPORT #4032 PERIOD COVERED: UT January 19, 2006 (DOY 019) OBSERVATIONS SCHEDULED ACS/HRC 10542 Charting the Sparkling Star Formation in NGC346 New, stunning V, I images of the youngest and most massive star forming region NGC 346, in the Small Magellanic Cloud, have been recently obtained with the HST/ACS. They reveal a myriad of small compact clusters: some are still embedded in dust, possibly connected by gas and dust filaments. We also discover a rich population of pre-main sequence low mass stars {~3 -0.6 Mo} mainly distributed in the body of NGC 346 and in these compact clusters, which formed with the central cluster {~5My ago}, but have not reached the main sequence yet. The immediate question that emerges is: how did star formation occur in this region? Is there evidence for an age spread among these clusters, that could be indicative of sequential star formation? We are, therefore, requesting an immediate follow up investigation with the ACS/HRC to perform a comprehensive UV/U study of the ten largest clusters identified in the NGC 346 region, with the objective of determining, in combination with the already available deep V, I data, their mass function, their upper mass cut-off, whether mass segregation is present, whether there are age variations, and what is the impact of the stellar feedback, with the final aim to establish how star formation has occured and progressed in this low metallicity environment. ACS/HRC 10559 Astrometric monitoring of binary L and T dwarfs We propose to obtain high angular resolution ACS images of five binary L and T dwarfs in order to determine their orbital parameters and dynamical masses, and directly constrain the evolutionary models of ultracool and substellar objects. The binaries have estimated periods ranging between 5 and 14 years. All of them have already been resolved at least twice {sometimes more} using HST, providing first and second epochs measurements. We propose to obtain two more ACS imaging observations separated by 9 to 12 months during cycle 14. The expected period coverage should therefore range between 35% and 117%, allowing us to compute precise orbital parameters and masses. Our sample is large enough and covers a sufficiently wide range of spectral types {from L3 to T5.5} to allow us to obtain strong constraints the evolutionnary models. ACS/HRC 10564 Resolving Ultracool White Dwarf Binaries We propose an ACS/HRC imaging survey of the coolest white dwarfs known in order to search for binarity. Current models fail to match observed spectral energy distributions of these sub- 4000K stellar remnants, consistently predicting much lower luminosities than observed. A possible explanation is that they are binary in nature. Because these cool degenerates have no spectral features, the only way to investigate their apparent overluminosity is with very high resolution imaging, which can only be done with HST {these stars are far too faint to be observed with adaptive optics on the ground}. Optical wavelengths are ideal because the spectral energy distributions of these old degenerates peak near 600 nm. With the F435W filter we will be able to partially resolve equally luminous binaries as close as 0.02", which corresponds to within 0.6 AU for over half of the 12 proposed target stars. The collected data will be critical in determining whether these stars represent the oldest white dwarfs in the solar neighborhood. ACS/HRC/WFC 10514 Kuiper Belt Binaries: Probes of Early Solar System Evolution Binaries in the Kuiper Belt are a scientific windfall: in them we have relatively fragile test particles which can be used as tracers of the early dynamical evolution of the outer Solar System. We propose a Snapshot program using the ACS/HRC that has a potential discovery efficiency an order of magnitude higher than the HST observations that have already discovered the majority of known transneptunian binaries. By more than doubling the number of observed objects in dynamically hot and cold subpopulations we will be able to answer, with statistical significance, the question of whether these groups differ in the abundance of binaries as a result of their particular dynamical paths into the Kuiper Belt. Today's Kuiper Belt bears the imprints of the final stages of giant-planet building and migration; binaries may offer some of the best preserved evidence of that long-ago era. ACS/WFC 10543 Microlensing in M87 and the Virgo Cluster Resolving the nature of dark matter is an urgent problem. The results of the MACHO survey of the Milky Way dark halo toward the LMC indicate that a significant fraction of the halo consists of stellar mass objects. The VATT/Columbia survey of M31 finds a similar lens fraction in the M31 dark halo. We propose a series of observations with ACS that will provide the most thorough search for microlensing toward M87, the central elliptical galaxy of the Virgo cluster. This program is optimized for lenses in the mass range from 0.01 to 1.0 solar masses. By comparing with archival data, we can detect lenses as massive as 100 solar masses, such as the remnants of the first stars. These observations will have at least 15 times more sensitivity to microlensing than any previous survey, e.g. using WFPC2. This is due to the factor of 2 larger area, factor of more than 4 more sensitivity in the I-band, superior pixel scale and longer baseline of observations. Based on the halo microlensing results in the Milky Way and M31, we might expect that galaxy collisions and stripping would populate the overall cluster halo with a large number of stellar mass objects. This program would determine definitively if such objects compose the cluster dark matter at the level seen in the Milky Way. A negative result would indicate that such objects do not populate the intracluster medium, and may indicate that galaxy harassment is not as vigorous as expected. We can measure the level of events due to the M87 halo: this would be the best exploration to date of such a lens population in an elliptical galaxy. Star-star lensing should also be detectable. About 20 erupting classical novae will be seen, allowing to determine the definitive nova rate for this giant elliptical galaxy. We will determine if our recent HST detection of an M87 globular cluster nova was a fluke, or indicative of a 100x higher rate of incidence of cataclysmic variables and nova eruptions in globulars than previously believed. We will examine the populations of variable stars, and will be able to cleanly separate them from microlensing. WFPC2 10777 WFPC2 WF4 Bay 1 Temperature Reduction Test #1 This proposal tests methods to improve WF4 bias level stability by adjusting some temperatures inside WFPC2. 1 external and 24 internal orbits. FLIGHT OPERATIONS SUMMARY: Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.) HSTARS: 10091 - GSAcq (1,2,2) failed to RGA control (T2G) due to Search Radius Limit Exceeded on FGS 1 @ 019/0959z GSAcq (1,2,2) scheduled at 019/09:59:53 falied due to search radius limit exceeded on FGS 1. ESB 1902 (OBAD Failed Identification) was received. ESB a05 (FGS Coarse Trac Failed-Search Radius Limit Exceeded) was received, also 3 ESB 1805's were received. OBAD 1 = V1 716.06, V2 -505.87, V3 - 203.06, RSS 899.93 OBAD 2 = V1 11760.04, V2 -492.93, V3 50827.72, RSS 52172.78 OBAD Map showed the following errors: V1 -4.62, V2 -244.50, V3 -1.22, RSS 244.55 COMPLETED OPS REQUEST: (None) COMPLETED OPS NOTES: (None) SCHEDULED SUCCESSFUL FAILURE TIMES FGS GSacq 07 06 019/0959z (HSTAR 10091) FGS REacq 08 08 OBAD with Maneuver 29 28 019/0957z (HSTAR 10091) SIGNIFICANT EVENTS: (None) |
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