NASA Hubble Space Telescope Daily Report #5090

HUBBLE SPACE TELESCOPE DAILY REPORT #5090

Continuing To Collect World Class Science

PERIOD COVERED: 05:00 am May 5, 2010 – 05:00 am May 6, 2010 (DOY 125/0900z – 126/0900z)

OBSERVATIONS SCHEDULED: COS/FUV 11687

SNAPing Coronal Iron

This is a Snapshot Survey to explore two forbidden lines of highly ionized iron in late-type coronal sources. Fe XII 1349 (T~ 2 MK) and Fe XXI 1354 (T~ 10 MK) — well known to Solar Physics — have been detected in about a dozen cool stars, mainly with HST/STIS. The UV coronal forbidden lines are important because they can be observed with velocity resolution of better than 15 km/s, whereas even the state-of-the-art X-ray spectrometers on Chandra can manage only 300 km/s in the kilovolt band where lines of highly ionized iron more commonly are found. The kinematic properties of hot coronal plasmas, which are of great interest to theorists and modelers, thus only are accessible in the UV at present. The bad news is that the UV coronal forbidden lines are faint, and were captured only in very deep observations with STIS. The good news is that 3rd-generation Cosmic Origins Spectrograph, slated for installation in HST by SM4, in a mere 25 minute exposure with its G130M mode can duplicate the sensitivity of a landmark 25-orbit STIS E140M observation of AD Leo, easily the deepest such exposure of a late-type star so far. Our goal is to build up understanding of the properties of Fe XII and Fe XXI in additional objects beyond the current limited sample: how the lineshapes depend on activity, whether large scale velocity shifts can be detected, and whether the dynamical content of the lines can be inverted to map the spatial morphology of the stellar corona (as in “Doppler Imaging”). In other words, we want to bring to bear in the coronal venue all the powerful tricks of spectroscopic remote sensing, well in advance of the time that this will be possible exploiting the corona’s native X-ray radiation. The 1290-1430 band captured by side A of G130M also contains a wide range of key plasma diagnostics that form at temperatures from below 10, 000 K (neutral lines of CNO), to above 200, 000 K (semi-permitted O V 1371), including the important bright multiplets of C II at 1335 and Si IV at 1400; yielding a diagnostic gold mine for the subcoronal atmosphere. Because of the broad value of the SNAP spectra, beyond the coronal iron project, we waive the normal proprietary rights.

COS/FUV/COS/NUV 11645

HST COS Observations of the Atmosphere and Airglow/Aurora of Enceladus

Recent observations from several instruments on the Cassini spacecraft have revealed plumes of dust and water from the southern polar region, and clearly shown that Enceladus contributes large amounts of plasma to Saturn?s magnetosphere. This implies a global thin atmosphere containing water and likely other species, and a local region with orders of magnitude higher density near the plumes. While water and dust have been identified from the plumes, the presence of many other species in the atmosphere is possible and not yet ruled out. The identification of all significant species in the atmosphere of Enceladus is of key importance to speculation about the source of the water plumes, and the implications for any form of life at or below the surface. In addition, modeling suggests that Enceladus? mass loading region may be comparable in extent to Io?s, and interacts strongly with Saturn?s corotating magnetic field and plasma. We have recently concluded a search for an auroral footprint of Enceladus in HST images, which set a low upper limit implying that the magnetospheric interaction is concentrated near Enceladus, rather than being communicated along field lines to Saturn?s ionosphere. The next step will be to observe the interaction at the satellite, and to learn whatever we can about the physics of the release of the atmospheric gas. We propose here an exploratory set of spectral observations with HST COS to measure the solar reflection spectrum over a broad range of UV wavelengths for atmospheric absorption signatures. This will at the same time measure the emission spectrum of the atmosphere from both the leading and trailing hemispheres ? Enceladus orbit apart, as was done in HST STIS observations of Io to study its interaction at Jupiter. The higher sensitivity of COS will be needed to study the much smaller and relatively weakly-interacting Enceladus, and the outcome of these observations will determine the nature of future studies of the atmosphere of Enceladus and its plasma interaction with the Saturnian magnetosphere.

COS/FUV/COS/NUV 11698

The Structure and Dynamics of Virgo’s Multi-Phase Intracluster Medium

The dynamical flows of the intracluster medium (ICM) are largely unknown. We propose to map the spatial and kinematic distribution of the warm ICM of the nearby Virgo cluster using the Cosmic Origins Spectrograph. 15 sightlines at a range of impact parameters within the virial radius of the cluster (0.2 – 1.7 Mpc) will be probed for Lyman-alpha absorption and the data compared to blind HI, dust and x-ray surveys to create a multi-phase map of the cluster’s ICM. Absorption line sightlines are commonly 40-100 kpc from a galaxy, allowing the flow of baryons between galaxies and the ICM to be assessed. The velocity distribution of the absorbers will be directly compared to simulations and used to constrain the turbulent motions of the ICM. This proposal will result in the first map of a cluster’s warm ICM and provide important tests for our theoretical understanding of cluster formation and the treatment of gas cooling in cosmological simulations.

COS/NUV 11720

Detailed analysis of carbon atmosphere white dwarfs

We propose to obtain UV spectra for the newly discovered white dwarf stars with a carbon-dominated atmosphere. Model calculations show that these stars emit most of their light in the UV part of the electromagnetic spectrum and that an accurate determination of the flux in this region is crucial for an accurate determination of the atmospheric parameters. It will also provide a unique opportunity to test the atomic data and broadening theory in stellar conditions never met before. This will play a primordial role in our path to understand the origin of these objects as well to obtain a better understanding of the evolution of stars in general. The principal objective we hope to achieve with these observations are 1) obtain accurate surface gravity/mass for these stars, 2) constrain/determine the abundance of other elements (O, He, Mg, Ne etc.), especially oxygen, 3) verify the accuracy of the various theoretical atomic data used in the model calculations, 4) understand the origin and evolution of carbon atmosphere white dwarfs, in particular whether progenitor stars as massive as 10.5 solar masses can produce white dwarfs, rather than supernovae. We propose to observe 5 objects chosen carefully to cover the range of observed properties among carbon atmosphere white dwarfs (effective temperature, surface gravity, abundance of hydrogen/helium and magnetic field).

S/C/WFC3/IR 11929

IR Dark Current Monitor

Analyses of ground test data showed that dark current signals are more reliably removed from science data using darks taken with the same exposure sequences as the science data, than with a single dark current image scaled by desired exposure time. Therefore, dark current images must be collected using all sample sequences that will be used in science observations. These observations will be used to monitor changes in the dark current of the WFC3-IR channel on a day-to-day basis, and to build calibration dark current ramps for each of the sample sequences to be used by GOs in Cycle 17. For each sample sequence/array size combination, a median ramp will be created and delivered to the calibration database system (CDBS).

STIS/CCD 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

STIS/CCD 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/MA1 11861

MAMA FUV Flats

This program will obtain FUV-MAMA observations of the STIS internal Krypton lamp to construct an FUV flat applicable to all FUV modes.

WFC3/IR 11235

HST NICMOS Survey of the Nuclear Regions of Luminous Infrared Galaxies in the Local Universe

At luminosities above 1011.4 L_sun, the space density of far-infrared selected galaxies exceeds that of optically selected galaxies. These `luminous infrared galaxies’ (LIRGs) are primarily interacting or merging disk galaxies undergoing enhanced star formation and Active Galactic Nuclei (AGN) activity, possibly triggered as the objects transform into massive S0 and elliptical merger remnants. We propose NICMOS NIC2 imaging of the nuclear regions of a complete sample of 88 L_IR > 1011.4 L_sun luminous infrared galaxies in the IRAS Revised Bright Galaxy Sample (RBGS: i.e., 60 micron flux density > 5.24 Jy). This sample is ideal not only in its completeness and sample size, but also in the proximity and brightness of the galaxies. The superb sensitivity and resolution of NICMOS NIC2 on HST enables a unique opportunity to study the detailed structure of the nuclear regions, where dust obscuration may mask star clusters, AGN and additional nuclei from optical view, with a resolution significantly higher than possible with Spitzer IRAC. This survey thus provides a crucial component to our study of the dynamics and evolution of IR galaxies presently underway with Wide-Field, HST ACS/WFC and Spitzer IRAC observations of these 88 galaxies. Imaging will be done with the F160W filter (H-band) to examine as a function of both luminosity and merger stage (i) the luminosity and distribution of embedded star clusters, (ii) the presence of optically obscured AGN and nuclei, (iii) the correlation between the distribution of 1.6 micron emission and the mid-IR emission as detected by Spitzer IRAC, (iv) the evidence of bars or bridges that may funnel fuel into the nuclear region, and (v) the ages of star clusters for which photometry is available via ACS/WFC observations. The NICMOS data, combined with the HST ACS, Spitzer, and GALEX observations of this sample, will result in the most comprehensive study of merging and interacting galaxies to date.

WFC3/IR 11700

Bright Galaxies at z>7.5 with a WFC3 Pure Parallel Survey

The epoch of reionization represents a special moment in the history of the Universe as it is during this era that the first galaxies and star clusters are formed. Reionization also profoundly affects the environment where subsequent generations of galaxies evolve. Our overarching goal is to test the hypothesis that galaxies are responsible for reionizing neutral hydrogen. To do so we propose to carry out a pure parallel WFC3 survey to constrain the bright end of the redshift z>7.5 galaxy luminosity function on a total area of 176 arcmin^2 of sky. Extrapolating the evolution of the luminosity function from z~6, we expect to detect about 20 Lyman Break Galaxies brighter than M_* at z~8 significantly improving the current sample of only a few galaxies known at these redshifts. Finding significantly fewer objects than predicted on the basis of extrapolation from z=6 would set strong limits to the brightness of M_*, highlighting a fast evolution of the luminosity function with the possible implication that galaxies alone cannot reionize the Universe. Our observations will find the best candidates for spectroscopic confirmation, that is bright z>7.5 objects, which would be missed by small area deeper surveys. The random pointing nature of the program is ideal to beat cosmic variance, especially severe for luminous massive galaxies, which are strongly clustered. In fact our survey geometry of 38 independent fields will constrain the luminosity function like a contiguous single field survey with two times more area at the same depth. Lyman Break Galaxies at z>7.5 down to m_AB=26.85 (5 sigma) in F125W will be selected as F098M dropouts, using three to five orbits visits that include a total of four filters (F606W, F098M, F125W, F160W) optimized to remove low-redshift interlopers and cool stars. Our data will be highly complementary to a deep field search for high-z galaxies aimed at probing the faint end of the luminosity function, allowing us to disentangle the degeneracy between faint end slope and M_* in a Schechter function fit of the luminosity function. We waive proprietary rights for the data. In addition, we commit to release the coordinates and properties of our z>7.5 candidates within one month from the acquisition of each field.

WFC3/IR 11926

IR Zero Points

We will measure and monitor the zeropoints through the IR filters using observations of the white dwarf standard stars, GD153, GD71 and GD191B2B and the solar analog standard star, P330E. Data will be taken monthly during Cycle 17. Observations of the star cluster, NGC 104, are made twice to check color transformations. We expect an accuracy of 2% in the wide filter zeropoints relative to the HST photometric system, and 5% in the medium- and narrow-band filters.

WFC3/UVI 11602

High-resolution imaging of three new UV-bright lensed arcs

We have identified and spectroscopically confirmed three new strongly lensed, UV-bright star-forming galaxies at z ~ 2 that are similar to the well-studied gravitationally lensed Lyman Break Galaxy (LBG) MS1512-cB58, and are of comparable brightness to the ”8 O’Clock Arc” (Allam et al. 2007) and ”Clone” systems (Lin et al. 2008). The 8 O’Clock Arc and Clone have already been awarded 20 orbits for deep WFPC2 and NICMOS imaging in five bands (HST cycle 16, Program 11167, PI: Allam). Adding these three recently discovered objects thus completes a unique set of the brightest known strongly lensed galaxies at z ~ 2, with magnitudes of r~20-21, and they provide a new window into the detailed study of the properties of high redshift galaxies. We propose 21 orbits for deep WFC3 imaging in five bands (F475W, F606W, F814W, F110W, and F160W) in order to construct detailed lensing models, to probe the mass and light profiles of the lensing galaxies and their environments, and to constrain the spectral energy distributions, star formation histories, and morphologies of the lensed galaxies.

WFC3/UVI 11650

Mutual Orbits, Colors, Masses, and Bulk Densities of 3 Cold Classical Transneptunian Binaries

Many transneptunian objects (TNOs) have been found to be binary or multiple systems. As in other astrophysical settings, trans?neptunian binaries (TNBs) offer uniquely valuable information. Their mutual orbits allow the direct determination of their system masses, perhaps the most fundamental physical quantity of any astronomical object. Their frequency of occurrence and dynamical characteristics provide clues to formation conditions and evolution scenarios affecting both the binaries and their single neighbors. Combining masses with sizes, bulk densities can be measured. Densities constrain bulk composition and internal structure, key clues to TNO origins and evolution over time. Several TNB bulk densities have been determined, hinting at interesting trends. But none of them belongs to the Cold Classical sub-population, the one group of TNOs with demonstrably distinct physical characteristics. Two top-priority Spitzer programs will soon observe and measure the sizes of 3 Cold Classical TNBs. This proposal seeks to determine the mutual orbits and thus masses of these systems, enabling computation of their densities.

WFC3/UVI 11729

Photometric Metallicity Calibration with WFC3 Specialty Filters

The community has chosen to include several filters in the WFC3 filter complement that have been designed to allow fairly precise estimates of stellar metallicities, and many science programs are enabled by this capability. Since these filters do not exactly match those used for this purpose on the ground, however, the mapping of stellar colors to stellar metallicities needs to be calibrated. We propose to achieve this calibration through observations of five stellar clusters with well known metallicities. We will calibrate several different filter calibrations which will allow future users to determine what filter combination best meets their science needs.

WFC3/UVI 11905

WFC3 UVIS CCD Daily Monitor

The behavior of the WFC3 UVIS CCD will be monitored daily with a set of full-frame, four-amp bias
and dark frames. A smaller set of 2Kx4K subarray biases are acquired at less frequent intervals
throughout the cycle to support subarray science observations. The internals from this proposal,
along with those from the anneal procedure (11909), will be used to generate the necessary superbias
and superdark reference files for the calibration pipeline (CDBS).

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               9                    9

FGS REAcq               6                    6

OBAD with Maneuver      4                    4

SIGNIFICANT EVENTS: none