NASA Hubble Space Telescope Daily Report #5065
HUBBLE SPACE TELESCOPE DAILY REPORT #5065
Continuing to Collect World Class Science
PERIOD COVERED: 5am March 31 – 5am April 1, 2010 (DOY 090/09:00z-091/09:00z)
OBSERVATIONS SCHEDULED
ACS/WFC 11715
The Luminous Galactic Cepheid RS Puppis: A Geometric Distance from its Nested Light Echoes
RS Puppis is one of the most luminous Cepheids in the Milky Way (P = 41.4 days) and an analog of the bright Cepheids used to measure extragalactic distances. An accurate distance would help anchor the zero-point of the bright end of the period-luminosity relation, but at a distance of about 2 kpc it is too far away for a trigonometric parallax with existing instrumentation.
RS Pup is unique in being surrounded by a reflection nebula, whose brightness varies as pulses of light from the Cepheid propagate outwards. Members of our team have used ground-based imaging of the nebula to derive phase lags in the light variations of individual features in the nebula, and have inferred a seemingly very precise geometric distance to the star. However, there is an unavoidable ambiguity involving the cycle counts, which was resolved by assuming that the features lie in the plane of the sky. If this assumption is incorrect, a large systematic error would be introduced into the distance measurement.
We show that polarimetric imaging using the high spatial resolution of ACS/WFC and its ability to image close to the star can resolve this ambiguity and yield a reliable geometric distance to RS Pup. We will also obtain a wide-field multicolor image of the nebula, in order to study its morphology and the mass-loss history of the Cepheid.
ACS/WFC 11995
CCD Daily Monitor (Part 2)
This program comprises basic tests for measuring the read noise and dark current of the ACS WFC and for tracking the growth of hot pixels. The recorded frames are used to create bias and dark reference images for science data reduction and calibration. This program will be executed four days per week (Mon, Wed, Fri, Sun) for the duration of Cycle 17. To facilitate scheduling, this program is split into three proposals. This proposal covers 320 orbits (20 weeks) from 1 February 2010 to 20 June 2010.
ACS/WFC3 11599
Distances of Planetary Nebulae from SNAPshots of Resolved Companions
Reliable distances to individual planetary nebulae (PNe) in the Milky Way are needed to advance our understanding of their spatial distribution, birthrates, influence on galactic chemistry, and the luminosities and evolutionary states of their central stars (CSPN). Few PNe have good distances, however. One of the best ways to remedy this problem is to find resolved physical companions to the CSPN and measure their distances by photometric main-sequence fitting. We have previously used HST to identify and measure probable companions to 10 CSPN, based on angular separations and statistical arguments only. We now propose to use HST to re-observe 48 PNe from that program for which additional companions are possibly present. We then can use the added criterion of common proper motion to confirm our original candidate companions and identify new ones in cases that could not confidently be studied before. We will image the region around each CSPN in the V and I bands, and in some cases in the B band. Field stars that appear close to the CSPN by chance will be revealed by their relative proper motion during the 13+ years since our original survey, leaving only genuine physical companions in our improved and enlarged sample. This study will increase the number of Galactic PNe with reliable distances by 50 percent and improve the distances to PNe with previously known companions.
COS/FUV 11897
FUV Spectroscopic Sensitivity Monitoring
The purpose of this proposal is to monitor sensitivity in each FUV grating mode to detect any changes due to contamination or other causes.
COS/NUV 11561
An Intensive COS Spectroscopic Study of the Planetary Debris Disks Around two Warm White Dwarfs
It is very likely that the gas giants in our Solar system will survive the evolution of the Sun into a white dwarf, and the same is thought to be generally true for Jovian planets around solar-like stars if their initial orbits are wider than ~3AU. Despite this prediction, no unambiguous detection of a planet around a white dwarf has been announced so far. However, over the past few years, about a dozen white dwarfs have been identified which host metal-rich debris disks that are thought to stem from the tidal disruption of asteroids. In most cases the debris disks are observed in the form of an infrared flux excess, and offer relatively little diagnostic potential for the study of their structure. We have discovered three warm (T~20000K) white dwarfs with metal-rich debris disks in a gaseous phase which display strong double-peaked CaII emission lines in the I-band and weak Fe 5169A emission. The line profiles can be modeled in terms of Keplerian disks with an extension of ~1Rsun around the white dwarfs. Photospheric MgII 4481A absorption demonstrates that the white dwarfs are accreting from the debris disks. Besides these spectral features, the optical wavelength range is devoid of other useful metal transitions. Here, we propose an intensive spectroscopic ultraviolet study of these systems, which will provide (a) ~1000 photospheric absorption lines of 15 chemical elements, allowing an accurate abundance study of the material accreted from the debris disks, and (b) ~2 dozen additional emission lines of Mg, Cr, Ti, and Fe that will provide detailed insight into the dynamical, thermal, and density structure of these exo-planetary debris disks.
COS/NUV 11894
NUV Detector Dark Monitor
The purpose of this proposal is to measure the NUV detector dark rate by taking long science exposures with no light on the detector. The detector dark rate and spatial distribution of counts will be compared to pre-launch and SMOV data in order to verify the nominal operation of the detector. Variations of count rate as a function of orbital position will be analyzed to find dependence of dark rate on proximity to the SAA. Dependence of dark rate as function of time will also be tracked.
COS/NUV/FUV/WFC3/UVIS/IR 11520
COS-GTO: QSO Absorbers, Galaxies and Large-Scale Structures in the Local Universe
This is a program to probe the large scale structure of baryons in the universe, including addressing questions of baryon fraction, physical conditions and relationships between absorbers and large-scale structures of galaxies. Besides these specific goals, this proposed GTO program also probes a large enough total path length in Ly alpha and OVI to add significantly to what STIS/FUSE has already observed. Several Galactic High Velocity Cloud Complexes also are probed by these sightlines, particularly the M Complex. The total path length of this proposed program for Ly alpha large-scale structure surveys is delta_z~5.5.
We have selected a variety of targets to address these questions, under the following subcategories:
1. Target 8 bright BL Lac objects to search for low contrast Ly alpha absorbers from the warm- hot interstellar medium (WHIM).
2. Ly alpha cloud sizes: The targets are a bright AGN pair which yield tangential distance separations of 100–500 kpc at z=0.01–0.05, where galaxy surveys are excellent. This pair has two filaments and two voids in this distance range.
3. Probes of starburst outflows: The targets are bright AGN, <= 100 kpc in projection out of the minor axis of nearby starburst galaxies. 4. A large galaxy’s gaseous halo: Three probes of the kinematics and metallicity of a single L* galaxy halo. These observations includes G130M, G160M exposures at SNR~20 and G285M at 2850A and SNR~10 for MgII. The 2L* galaxy, ESO 157-G049 (cz=1678 km/s), being probed by these sightlines has an available H I 21cm map from ATCA, H alpha imaging from CTIO and long- slit spectra from MSSSO. 5. Dwarf galaxy winds: These targets probe the kinematics and metallicities of outflows from active and inactive (in terms of star formation) dwarfs. STIS/CC 11845 CCD Dark Monitor Part 2 Monitor the darks for the STIS CCD. STIS/CC 11847 CCD Bias Monitor-Part 2 Monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1, and 1×1 at gain = 4, to build up high-S/N superbiases and track the evolution of hot columns. STIS/CC/MA 11516 COS-GTO: Cold ISM With the COS, we will be able to observe interstellar spectra in a new regime, translucent clouds, for atomic, ionic, and molecular lines and bands, and extinction curves. The COS will allow us to observe stars with total visual extinctions up to 10 magnitudes, and the grain size indicator Rv up to 4.5. In translucent clouds we expect to see the transition from neutral and ionized carbon to mostly C I, and then from there, we should expect to see carbon increasingly locked up in molecular form, as CO. Other species are expected to make similar transitions, so we should find detectable abundances of molecules such as H2O, OH, CS, CH2, SiO, and others; also, lower ionization fractions of the metallic elements – and higher depletions of those elements as well. Given that we expect to find higher depletions, we should see an altered grain size distribution, which may show up in the extinction curves, probably as lower far-UV extinction than in diffuse clouds. Finally, we will search for neutral PAHs in absorption, as diffuse bands in the UV, paralleling the optical DIBs (which are thought by some scientists to be formed by singly-ionized PAHs). In translucent clouds, models show that the PAHs will be neutral, not in cationic form. STIS/CCD/MA2 11568 A SNAPSHOT Survey of the Local Interstellar Medium: New NUV Observations of Stars with Archived FUV Observations We propose to obtain high-resolution STIS E230H SNAP observations of MgII and FeII interstellar absorption lines toward stars within 100 parsecs that already have moderate or high-resolution far-UV (FUV), 900-1700 A, observations available in the MAST Archive. Fundamental properties, such as temperature, turbulence, ionization, abundances, and depletions of gas in the local interstellar medium (LISM) can be measured by coupling such observations. Due to the wide spectral range of STIS, observations to study nearby stars also contain important data about the LISM embedded within their spectra. However, unlocking this information from the intrinsically broad and often saturated FUV absorption lines of low-mass ions, (DI, CII, NI, OI), requires first understanding the kinematic structure of the gas along the line of sight. This can be achieved with high resolution spectra of high-mass ions, (FeII, MgII), which have narrow absorption lines, and can resolve each individual velocity component (interstellar cloud). By obtaining short (~10 minute) E230H observations of FeII and MgII, for stars that already have moderate or high- resolution FUV spectra, we can increase the sample of LISM measurements, and thereby expand our knowledge of the physical properties of the gas in our galactic neighborhood. STIS is the only instrument capable of obtaining the required high resolution data now or in the foreseeable future. STIS/MA1/MA2 11857 STIS Cycle 17 MAMA Dark Monitor This proposal monitors the behavior of the dark current in each of the MAMA detectors. The basic monitor takes two 1380s ACCUM darks each week with each detector. However, starting Oct 5, pairs are only included for weeks that the LRP has external MAMA observations planned. The weekly pairs of exposures for each detector are linked so that they are taken at opposite ends of the same SAA free interval. This pairing of exposures will make it easier to separate long and short term temporal variability from temperature dependent changes. For both detectors, additional blocks of exposures are taken once every six months. These are groups of five 1314s FUV-MAMA Time-Tag darks or five 3x315s NUV ACCUM darks distributed over a single SAA-free interval. This will give more information on the brightness of the FUV MAMA dark current as a function of the amount of time that the HV has been on, and for the NUV MAMA will give a better measure of the short term temperature dependence. WFC3/UVIS/IR 11909 UVIS Hot Pixel Anneal The on-orbit radiation environment of WFC3 will continually generate new hot pixels. This proposal performs the procedure required for repairing those hot pixels in the UVIS CCDs. During an anneal, the two-stage thermo-electric cooler (TEC) is turned off and the four-stage TEC is used as a heater to bring the UVIS CCDs up to ~20 deg. C. As a result of the CCD warmup, a majority of the hot pixels will be fixed; previous instruments such as WFPC2 and ACS have seen repair rates of about 80%. Internal UVIS exposures are taken before and after each anneal, to allow an assessment of the procedure’s effectiveness in WFC3, provide a check of bias, global dark current, and hot pixel levels, as well as support hysteresis (bowtie) monitoring and CDBS reference file generation. One IR dark is taken after each anneal, to provide a check of the IR detector. FLIGHT OPERATIONS SUMMARY: Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.) HSTARS: 12234 ? OBAD(1,3) at 091/07:56:38z failed due to too few stars on FHST#1. GSAcq(1,2,1) at 091/08:02:11z was successful. COMPLETED OPS REQUEST: (None) COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL
FGS GSAcq 9 9
FGS REAcq 7 7
OBAD with Maneuver 5 4
SIGNIFICANT EVENTS: (None)
