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Daily Report #4625
HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science
DAILY REPORT***** # 4625 PERIOD COVERED: 5am June 04 - 5am June 05, 2008 (DOY 156/0900z-157/0900z) OBSERVATIONS SCHEDULED ACS/SBC 11230 HST FUV Observations of Brightest Cluster Galaxies: The Role of Star Formation in Cooling Flows and BCG Evolution The intracluster medium (ICM) now appears to be a very dynamic place where heating and cooling processes vie for dominance and an uneasy equilibrium is maintained. Since these same processes may operate during the process of galaxy formation, the centers of clusters of galaxies provide low redshift laboratories for studying the critical processes involved in galaxy formation and black hole growth. At the present time, the main questions are (1) How much gas is cooling out of the ICM? (2) How much star formation is ongoing? (3) What is the impact of the gas and star formation on the central BCG? In order to measure the current star formation in BCGs we have undertaken a program of Spitzer IRAC and MIPS observations. We are in process of obtaining observations of a sample of Brightest Cluster Galaxies in 70 clusters selected from the ROSAT all sky survey. In about 25% of the sources observed so far, we detect a mid-IR excess which we attribute to dust heated by star formation. We propose to obtain ACS/SBC observations of the Lyman Alpha emission line and the adjacent FUV continuum in 7 BCGs which are in cooling core clusters of galaxies and have a large mid-IR excess. We also propose WFPC2 F606W observations of the two clusters without high resolution imaging to allow us to image the dust on the same scale as the Far UV continuum. The FUV will allow us to confirm the presence of ongoing star formation in these BCGs and will allow us to rule out an AGN as the dominant contributor to the mid-IR. The morphology and spatial extent of the young stars and the heated dust and CO will constrain the spatial scale over which star formation occurs and thus where the cooling gas is deposited. The combination of our FUV and IR observations will allow us to estimate the star formation rates which must balance the rate at which cold gas is deposited in the BCG. Our proposed FUV observations will produce unique information about the cooling gas, the true mass accretion rates, and the star formation rates in BCGs and its effect on the galaxy. 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 11123 A NICMOS Survey for Proplyds in the RCW 38 Massive Embedded Cluster We propose a search for line emission from photoevaporating protoplanetary disks in the Massive Embedded Cluster RCW 38. These disks would be analogous to the "proplyds" discovered in the Orion Nebula: disks around young low mass stars which are being photoionized by a nearby O star. We will search for these disks in RCW 38 using narrowband imaging in the lines of Paschen alpha and molecular hydrogen (1-0) S(1) with NICMOS. The RCW 38 region is an excellent target for determining whether proplyds are observable in large numbers outside of Orion. It is a young embedded cluster hosting a few hundred low mass young stars with a large percentage showing infrared excess indicating the presence of disks. About 100 of these stars are found within 0.1 pc of the central O5 star, and the cluster is located within a cleared cavity 0.2 pc in size, embedded within a molecular cloud, exposing the cluster members directly to the UV radiation from the O star. Unlike Orion, but like many other young clusters, RCW 38 is not seen in visible light, and infrared imaging is needed. The best line in the infrared for revealing proplyds is the Paschen alpha line, which is not detectable from the ground. Only HST is able to perform these observations. From these observations we will estimate the lifetime of the evaporating disks, and ascertain whether these disks will survive long enough to form planets. NIC2 11148 High Contrast Imaging of Dusty White Dwarfs For the past 18 years, only one white dwarf with a circumstellar dust disk was known to exist. In the last two years, six new disks have been discovered. Since all material inwards of a few AU should be scoured clean during post main sequence evolution, the primary explanation is the presence of a planetary system that is perturbing relic planetesimals into the tidal disruption radius of the white dwarf. Dusty disks around white dwarfs should be markers for planets and we propose to use high contrast imaging to search for faint companions down to 6 M_$J$ that may be feeding the disks. White dwarfs are uniquely suited for planet searches, where the planet/white dwarf contrast is less than for main sequence stars. NIC2 11157 NICMOS Imaging Survey of Dusty Debris Around Nearby Stars Across the Stellar Mass Spectrum Association of planetary systems with dusty debris disks is now quite secure, and advances in our understanding of planet formation and evolution can be achieved by the identification and characterization of an ensemble of debris disks orbiting a range of central stars with different masses and ages. Imaging debris disks in starlight scattered by dust grains remains technically challenging so that only about a dozen systems have thus far been imaged. A further advance in this field needs an increased number of imaged debris disks. However, the technical challenge of such observations, even with the superb combination of HST and NICMOS, requires the best targets. Recent HST imaging investigations of debris disks were sample-limited not limited by the technology used. We performed a search for debris disks from a IRAS/Hipparcos cross correlation which involved an exhaustive background contamination check to weed out false excess stars. Out of ~140 identified debris disks, we selected 22 best targets in terms of dust optical depth and disk angular size. Our target sample represents the best currently available target set in terms of both disk brightness and resolvability. For example, our targets have higher dust optical depth, in general, than newly identified Spitzer disks. Also, our targets cover a wider range of central star ages and masses than previous debris disk surveys. This will help us to investigate planetary system formation and evolution across the stellar mass spectrum. The technical feasibility of this program in two-gyro mode guiding has been proven with on-orbit calibration and science observations during HST cycles 13, 14, and 15. NIC2 11164 Molecular Hydrogen Disks Around T Tauri Stars We propose to measure the properties of planetary system-sized disks around Sun- like, pre-main sequence stars by imaging the inner parts of these disks for the first time in gaseous emission from their most dominant constituent, molecular hydrogen gas. Specifically, we will use the F212N filter and NICMOS to determine the spatial distribution of ro-vibrational H2 emission from protoplanetary disks around selected classical and weak-lined T Tauri stars. The target stars are among those detected by members of this team through high resolution, ground-based infrared spectroscopy. The spectra reveal H2 emission at the rest velocities of the stars and at positions spatially coincident with the stars at the spatial resolution of the spectroscopic data. This imaging experiment, which is impossible to do using ground- based facilities, is possible using the NICMOS camera aboard the HST because the point spread function of this system is extremely stable and can be measured to a very high accuracy. This experiment is an important test of the interpretation that the 2.122 micron H2 line emission seen toward T Tauri stars is produced at distances of 10 to 30 AU from the stars, the region in which giant planets are expected to form around these stars. These observations will contribute toward developing a better understanding of the process, likelihood, and timescale for the formation of planets around Sun-like stars. WFPC2 11201 Systemic and Internal motions of the Magellanic Clouds: Third Epoch Images In Cycles 11 and 13 we obtained two epochs of ACS/HRC data for fields in the Magellanic Clouds centered on background quasars. We used these data to determine the proper motions of the LMC and SMC to better than 5% and 15% respectively. These are by far the best determinations of the proper motions of these two galaxies. The results have a number of unexpected implications for the Milky Way-LMC-SMC system. The implied three-dimensional velocities are larger than previously believed, and are not much less than the escape velocity in a standard 10^12 solar mass Milky Way dark halo. Orbit calculations suggest the Clouds may not be bound to the Milky Way or may just be on their first passage, both of which would be unexpected in view of traditional interpretations of the Magellanic Stream. Alternatively, the Milky Way dark halo may be a factor of two more massive than previously believed, which would be surprising in view of other observational constraints. Also, the relative velocity between the LMC and SMC is larger than expected, leaving open the possibility that the Clouds may not be bound to each other. To further verify and refine our results we now request an epoch of WFPC2/PC data for the fields centered on 40 quasars that have at least one epoch of ACS imaging. We request execution in snapshot mode, as in our previous programs, to ensure the most efficient use of HST resources. A third epoch of data of these fields will provide crucial information to verify that there are no residual systematic effects in our previous measurements. More importantly, it will increase the time baseline from 2 to 5 yrs and will increase the number of fields with at least two epochs of data. This will reduce our uncertainties correspondingly, so that we can better address whether the Clouds are indeed bound to each other and to the Milky Way. It will also allow us to constrain the internal motions of various populations within the Clouds, and will allow us to determine a distance to the LMC using rotational parallax. WFPC2 11227 The Orbital Period for an Ultraluminous X-ray Source in NGC1313 The ultraluminous X-ray sources {ULXs} are extragalactic point sources with luminosities that exceed the Eddington luminosity for conventional stellar-mass black holes by factors of 10 - 100. It has been hotly debated whether the ULXs are just common stellar-mass black hole sources with beamed emission or whether they are sub-Eddington sources that are powered by the long-sought intermediate mass black holes {IMBH}. To firmly decide this question, one must obtain dynamical mass measurements through photometric and spectroscopic monitoring of the secondaries of these system. The crucial first step is to establish the orbital period of a ULX, and arguably the best way to achieve this goal is by monitoring its ellipsoidal light curve. The extreme ULX NGC1313 X-2 provides an outstanding target for an orbital period determination because its relatively bright optical counterpart {V = 23.5} showed a 15% variation between two HST observations separated by three months. This level of variability is consistent with that expected for a tidally distorted secondary star. Here we propose a set of 20 imaging observations with HST/WFPC2 to define the orbital period. This would be the first photometric measurement of the orbital period of a ULX binary. Subsequently, we will propose to obtain spectroscopic observations to obtain its radial velocity amplitude and thereby a dynamical estimate of its mass. 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*************** 12***************** 12 FGS REacq*************** 02***************** 02 OBAD with Maneuver* **** 28***************** 28 SIGNIFICANT EVENTS: (None) |
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