NASA Hubble Space Telescope Daily Report # 4632
HUBBLE SPACE TELESCOPE DAILY REPORT #4632
Continuing to collect World Class Science
PERIOD COVERED: 5am June 13 – 5am June 16, 2008 (DOY 165/0900z-168/0900z)
OBSERVATIONS SCHEDULED
NIC1/NIC2/NIC3 8795
NICMOS Post-SAA Calibration – CR Persistence Part 6
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.
NIC3 11512
Molecules in Exoplanet Atmospheres
We propose to characterize the conditions, composition, and chemistry in two transiting exoplanet atmospheres using molecules as probes. This will be accomplished through high precision, near-IR spectroscopy during an interval that spans the primary and/or secondary eclipse events. We have selected the hot-Jovian HD 209458b and the warm-Neptune GJ 436b for spectroscopy from 1.4 to 2.5 microns and we expect to detect the molecules H2O, CH4, CO, CO2, and NH3. We will infer the atmospheric temperature-pressure profiles and determine the abundance of detected molecules; this will be done by comparing detailed radiative transfer models with emission and transmission spectra of the exoplanet atmospheres. Taken together with the existing observations of HD 189733b, the proposed measurements will probe the diversity of exoplanet atmospheres and the effects of radiation from the stellar primary.
NIC3 11332
NICMOS Cycle 16 Time Dependent Flat Fields
This proposal obtains sequences of NICMOS narrow, medium and broad band filter flat fields for camera 1. In cameras 2 and 3, parallel observations will allow us to obtain high S/N flats for all spectral elements.
WFPC2 11316
HST Cycle 16 & Pre-SM4 Optical Monitor
This is a continuation of the Cycle 15 & pre-SM4 Optical Monitor, 11020. Please see that proposal for a more complete description of the observing strategy. The 6 visits comprising this proposal observe two single standard stars with WFPC2/PC in order to establish overall OTA focal length for the purposes of focus maintenance. The goal of this monitoring before SM4 is to establish a best estimate of the OTA focus entering SMOV.
WFPC2 11218
Snapshot Survey for Planetary Nebulae in Globular Clusters of the Local Group
Planetary nebulae {PNe} in globular clusters {GCs} raise a number of interesting issues related to stellar and galactic evolution. The number of PNe known in Milky Way GCs, 4, is surprisingly low if one assumes that all stars pass through a PN stage. However, it is likely that the remnants of stars now evolving in Galactic GCs leave the AGB so slowly that any ejected nebula dissipates long before the star becomes hot enough to ionize it. Thus there should not be ANY PNe in Milky Way GCs–but there are four! It has been suggested that these PNe are the result of mergers of binary stars within GCs, i.e., that they are descendants of blue stragglers. The frequency of occurrence of PNe in external galaxies poses more questions, because it shows a range of almost an order of magnitude. I propose a Snapshot survey aimed at discovering PNe in the GC systems of Local Group galaxies more distant than the Magellanic Clouds. These clusters, some of which may be much younger than their counterparts in the Milky Way, might contain many more PNe than those of our own galaxy. I will use the standard technique of emission-line and continuum imaging, which easily discloses PNe.
FGS 11213
Distances to Eclipsing M Dwarf Binaries
We propose HST FGS observations to measure accurate distances of 5 nearby M dwarf eclipsing binary systems, from which model-independent luminosities can be calculated. These objects have either poor or no existing parallax measurements. FGS parallax determinations for these systems, with their existing dynamic masses determined to better than 0.5%, would serve as model-independent anchor points for the low-mass end of the mass-luminosity diagram.
WFPC2/NIC2 11173
Completing an Accurate Map of M31 Microlensing
The halo microlensing masses detected in the MACHO survey (claimed to compose about 20% of the Galaxy’s mass) represent a major enigma in astrophysics, one that must be effectively cross-examined by an independent test. We have completed a large, densely-sampled survey of M31 that can reveal in another galaxy such a halo microlensing signal if it exists. In a previous HST/ACS+WFPC2 program (GO 10273, Cycle 13, 16 orbits) we were able to learn considerably more about a subsample of these M31 microlensing events. We were pleased to find that in most cases we could isolate the source star for each event, find its baseline flux and colors (essential for ruling out classes of confusing variable stars), test for misidentification of background supernovae, and measure the Einstein parameters, which constrain the range of most likely lens mass. (These Cycle 13 results are published in The Astrophysical Journal Letters.) We propose to finish the job, taking a similar series of exposures to more than double the sample of well-constrained microlensing events, which together with the larger ground-based sample for which we are completing our analyses will provide 20-30 M31 bona fide microlensing events observed by HST. This will be done via a series of targeted PC exposures, meant to maximize the number of candidates studied, one (or two) at a time. A sample of this size and quality should be sufficient to settle the issue of a significant contribution to the halos of galaxies by stellar-mass lenses. Furthermore, if there is a surplus of such microlensing events above what might be expected from stars alone, the higher quality of information will allow us to more accurately describe the spatial distribution of these lenses. We will also complete several unique studies of M31 stellar populations, both in support of the microlensing measurement and in their own right.
NIC1/NIC2 11172
Defining Classes of Long Period Variable Stars in M31
We propose a thrifty but information-packed investigation {1440 exposures total} with NICMOS F205W, F160W and F110W providing crucial information about Long Period Variables in M31, at a level of detail that has recently allowed the discovery of new variable star classes in the Magellanic Clouds, a very different stellar population. These observations are buttressed by an extensive map of the same fields with ACS and WFPC2 exposures in F555W and F814W, and a massive ground-based imaging patrol producing well-sampled light curves for more than 400,000 variable stars. Our primary goal is to collect sufficient NIR data in order to analyze and classify the huge number of long-period variables in our catalog {see below} through Period- Luminosity {P/L} diagrams. We will produce accurate P/L diagrams for both the bulge and a progression of locations throughout the disk of M31. These diagrams will be similar in quality to those currently in the Magellanic Clouds, with their lower metallicity, radically different star formation history, and larger spread in distance to the variables. M31 offers an excellent chance to study more typical disk populations, in a manner which might be extended to more distant galaxies where such variables are still visible, probing a much more evenly spread progenitor age distribution than cepheids {and perhaps useful as a distance scale alternative or cross- check}. Our data will also provide a massive and unique color-magnitude dataset, and allow us to confirm the microlensing nature of a large sample of candidate lensed sources in M31. We expect that this study will produce several important results, among them a better understanding of P/L and P/L-color relations for pulsating variables which are essential to the extragalactic distance ladder, will view these variables at a common distance over a range of metallicities {eliminating the distance-error vs. metallicity ambiguity between the LMC and SMC}, allow further insight into possible faint-variable mass-loss for higher metallicities, and in general produce a sample more typical of giant disk galaxies predominant in many studies.
NIC2/WFPC2 11142
Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3
We aim to determine physical properties of IR luminous galaxies at 0.3
targets with spectroscopic redshifts {0.3
WFPC2 11129
The Star Formation History of the Fornax Dwarf Spheroidal Galaxy
The Fornax dwarf spheroidal galaxy is one of the most luminous dwarf satellites of the Milky Way. It is unusual in many ways: it hosts 5 globular clusters, shows some relatively young stars, and has faint sub-structures which have been interpreted as signs of recent interactions. It is thus of great interest to learn the complete star formation history {SFH} of Fornax to establish a link between its evolutionary path and the predictions from numerical simulations, as a test of our understanding of dwarf galaxy evolution. Yet many questions remain open. Is the old stellar population made up of stars formed in a very early burst, perhaps before the epoch of re-ionization, or the result of a more continuous star formation between 13 and 9 Gyr ago ? How quickly did Fornax increase its metallicity during its initial assembly and during subsequent episodes of star formation ? Are accretion episodes required to explain the age-metallicity history of Fornax ? However, there has never been a comprehensive study of the global SFH of the Fornax field based on data of sufficient depth to unambiguously measure the age mixture of the stellar populations and their spatial variation. We propose to use the WFPC2 to obtain very deep images in several fields across the central region of Fornax in order to reach the oldest main-sequence turnoffs. The number of fields is determined by the need to measure the SFH over different regions with distinct kinematics and metallicity. The resolution achievable with HST is crucial to answer these questions because, to derive the age distribution of the oldest stars, we are interested in I magnitude differences of the order 0.2 mag in crowded fields at V=24.5. We will directly measure the time variation in star-formation rate over the entire galaxy history, from first stars coeval with the Milky Way halo to the youngest populations 200 Myr ago. The combination of detailed CMD analysis with WFPC2 with our existing metallicity and kinematic information will allow us to trace out the early phases of its evolution.
NIC3 11107
Imaging of Local Lyman Break Galaxy Analogs: New Clues to Galaxy Formation in the Early Universe
We have used the ultraviolet all-sky imaging survey currently being conducted by the Galaxy Evolution Explorer {GALEX} to identify for the first time a rare population of low-redshift starbursts with properties remarkably similar to high-redshift Lyman Break Galaxies {LBGs}. These “compact UV luminous galaxies” {UVLGs} resemble LBGs in terms of size, SFR, surface brightness, mass, metallicity, kinematics, dust, and color. The UVLG sample offers the unique opportunity of investigating some very important properties of LBGs that have remained virtually inaccessible at high redshift: their morphology and the mechanism that drives their star formation. Therefore, in Cycle 15 we have imaged 7 UVLGs using ACS in order to 1} characterize their morphology and look for signs of interactions and mergers, and 2} probe their star formation histories over a variety of timescales. The images show a striking trend of small- scale mergers turning large amounts of gas into vigorous starbursts {a process referred to as dissipational or “wet” merging}. Here, we propose to complete our sample of 31 LBG analogs using the ACS/SBC F150LP {FUV} and WFPC2 F606W {R} filters in order to create a statistical sample to study the mechanism that triggers star formation in UVLGs and its implications for the nature of LBGs. Specifically, we will 1} study the trend between galaxy merging and SFR in UVLGs, 2} artificially redshift the FUV images to z=1-4 and compare morphologies with those in similarly sized samples of LBGs at the same rest-frame wavelengths in e.g. GOODS, UDF, and COSMOS, 3} determine the presence and morphology of significant stellar mass in “pre- burst” stars, and 4} study their immediate environment. Together with our Spitzer {IRAC+MIPS}, GALEX, SDSS and radio data, the HST observations will form a unique union of data that may for the first time shed light on how the earliest major episodes of star formation in high redshift galaxies came about. This proposal was adapted from an ACS HRC+WFC proposal to meet the new Cycle 16 observing constraints, and can be carried out using the ACS/SBC and WFPC2 without compromising our original science goals.
WFPC2 11079
Treasury Imaging of Star Forming Regions in the Local Group: Complementing the GALEX and NOAO Surveys
We propose to use WFPC2 to image the most interesting star-forming regions in the Local Group galaxies, to resolve their young stellar populations. We will use a set of filters including F170W, which is critical to detect and characterize the most massive stars, to whose hot temperatures colors at longer wavelengths are not sensitive. WFPC2’s field of view ideally matches the typical size of the star-forming regions, and its spatial resolution allows us to measure individual stars, given the proximity of these galaxies. The resulting H-R diagrams will enable studies of star-formation properties in these regions, which cover largely differing metallicities {a factor of 17, compared to the factor of 4 explored so far} and characteristics. The results will further our understanding of the star-formation process, of the interplay between massive stars and environment, the properties of dust, and will provide the key to interpret integrated measurements of star-formation indicators {UV, IR, Halpha} available for several hundreds more distant galaxies. Our recent deep surveys of these galaxies with GALEX {FUV, NUV} and ground-based imaging {UBVRI, Halpha, [OIII] and [SII]} provided the identification of the most relevant SF sites. In addition to our scientific analysis, we will provide catalogs of HST photometry in 6 bands, matched corollary ground-based data, and UV, Halpha and IR integrated measurements of the associations, for comparison of integrated star-formation indices to the resolved populations. We envisage an EPO component.
WFPC2 10583
Resolving the LMC Microlensing Puzzle: Where Are the Lensing Objects?
We are requesting 32 HST orbits to help ascertain the nature of the population that gives rise to the observed set of microlensing events towards the LMC. The SuperMACHO project is an ongoing ground-based survey on the CTIO 4m that has demonstrated the ability to detect LMC microlensing events in real-time via frame subtraction. The improvement in angular resolution and photometric accuracy available from HST will allow us to 1} confirm that the detected flux excursions arise from LMC source stars rather than extended objects {such as for background supernovae or AGN}, and 2} obtain reliable baseline flux measurements for the objects in their unlensed state. The latter measurement is important to resolve degeneracies between the event timescale and baseline flux, which will yield a tighter constraint on the microlensing optical depth.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
HSTARS:
11342 – Reacq(2,0,2) failed to RGA control
The Reacq(2,0,2)scheduled at 166/03:38:49 failed to RGA hold. There were no flags. OBAD1 showed errors of V1=-521.21, V2=-807.25, V3=278.46, and RSS=1000.42. OBAD2 showed errors of V1=-7.40, V2=-7.41, V3=14.43, and RSS=17.83.
Observations affected: NIC 75 -80 Proposal# (11172)A1F-C3-JT and (11172)A1F-C3-K6
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SIGNIFICANT EVENTS: (None)
SCHEDULED SUCCESSFUL
FGS GSacq 20 20
FGS REacq 24 23
OBAD with Maneuver 88 88
