NASA Hubble Space Telescope Daily Report #5008

HUBBLE SPACE TELESCOPE DAILY REPORT #5008

Continuing to Collect World Class Science

PERIOD COVERED: 5am January 7 – 5am January 8, 2010 (DOY 007/10:00z-008/10:00z)

OBSERVATIONS SCHEDULED

COS/FUV 11526

COS-GTO: Sampling the Local ISM with Hot White Dwarfs

We shall use hot white dwarf stars located within 150pc of the Sun to probe the absorption properties of the interstellar gas associated with the local cavity. There is still much debate concerning the ionization state of the local gas, since previously detected highly ionized lines (such as CIV and SiIV) could be associated with the circumstellar environments of hot white dwarfs. By using a priori knowledge of the velocity structure of the interstellar sight-lines to these targets (gained from high spectral resolution ground- based observations) in conjunction with the UV absorption data gained with HST-COS, we shall be able to better determine both the physical and chemical state of the numerous diffuse interstellar clouds present within the local cavity.

COS/FUV/WFC3/UVIS/IR 11519

COS-GTO: Great Wall Tomography

This is a program to observe several targets behind the Great Wall (GW), a typical galaxy filament in the Universe. The approach is to observe a series of targets in one area of sky to perform a “cosmic tomography” in a 10 Mpc^2 region which includes sightlines through regions of varying galaxy density from no galaxies within 3 Mpc of the sight line to a dozen or more galaxies within 3 Mpc of the sight line. The Sloan Digital Sky Survey (SDSS) plus various CfA redshift surveys are nearly complete at Great Wall distances to 0.1-0.25L*, making the available galaxy survey material sufficient for this study. This program will address several science drivers, including probing the typical covering factor of warm, photoionized gas in galaxy filaments and the metallicity of such gas and how far it is spread from large and small galaxies. Preliminary studies suggest such material extends ~800 kpc from the nearest L* galaxy (even if that galaxy is not the source of the gas) and ~250 kpc from the nearest 0.1L* galaxy. (H0 assumed to be 70 km/s/Mpc)

COS/NUV/FUV 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).

STIS/CCD 11844

CCD Dark Monitor Part 1

The purpose of this proposal is to monitor the darks for the STIS CCD.

STIS/CCD 11846

CCD Bias Monitor-Part 1

The purpose of this proposal is to 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.

WFC3/ACS/UVIS 11360

Star Formation in Nearby Galaxies

Star formation is a fundamental astrophysical process; it controls phenomena ranging from the evolution of galaxies and nucleosynthesis to the origins of planetary systems and abodes for life. The WFC3, optimized at both UV and IR wavelengths and equipped with an extensive array of narrow-band filters, brings unique capabilities to this area of study. The WFC3 Scientific Oversight Committee (SOC) proposes an integrated program on star formation in the nearby universe which will fully exploit these new abilities. Our targets range from the well-resolved R136 in 30 Dor in the LMC (the nearest super star cluster) and M82 (the nearest starbursting galaxy) to about half a dozen other nearby galaxies that sample a wide range of star-formation rates and environments. Our program consists of broad band multiwavelength imaging over the entire range from the UV to the near-IR, aimed at studying the ages and metallicities of stellar populations, revealing young stars that are still hidden by dust at optical wavelengths, and showing the integrated properties of star clusters. Narrow-band imaging of the same environments will allow us to measure star-formation rates, gas pressure, chemical abundances, extinction, and shock morphologies. The primary scientific issues to be addressed are: (1) What triggers star formation? (2) How do the properties of star-forming regions vary among different types of galaxies and environments of different gas densities and compositions? (3) How do these different environments affect the history of star formation? (4) Is the stellar initial mass function universal or determined by local conditions?

WFC3/IR 11696

Infrared Survey of Star Formation Across Cosmic Time

We propose to use the unique power of WFC3 slitless spectroscopy to measure the evolution of cosmic star formation from the end of the reionization epoch at z>6 to the close of the galaxy-building era at z~0.3.Pure parallel observations with the grisms have proven to be efficient for identifying line emission from galaxies across a broad range of redshifts. The G102 grism on WFC3 was designed to extend this capability to search for Ly-alpha emission from the first galaxies. Using up to 250 orbits of pure parallel WFC3 spectroscopy, we will observe about 40 deep (4-5 orbit) fields with the combination of G102 and G141, and about 20 shallow (2-3 orbit) fields with G141 alone.

Our primary science goals at the highest redshifts are: (1) Detect Lya in ~100 galaxies with z>5.6 and measure the evolution of the Lya luminosity function, independent of of cosmic variance; 2) Determine the connection between emission line selected and continuum-break selected galaxies at these high redshifts, and 3) Search for the proposed signature of neutral hydrogen absorption at re-ionization. At intermediate redshifts we will (4) Detect more than 1000 galaxies in Halpha at 0.5< z<1.8 to measure the evolution of the extinction-corrected star formation density across the peak epoch of star formation. This is over an order-of-magnitude improvement in the current statistics, from the NICMOS Parallel grism survey. (5) Trace ``cosmic downsizing" from 0.5 < z<2.2; and (6) Estimate the evolution in reddening and metallicty in star-forming galaxies and measure the evolution of the Seyfert population. For hundreds of spectra we will be able to measure one or even two line pair ratios -- in particular, the Balmer decrement and [OII]/[OIII] are sensitive to gas reddening and metallicity. As a bonus, the G102 grism offers the possibility of detecting Lya emission at z=7-8.8. To identify single-line Lya emitters, we will exploit the wide 0.8–1.9um wavelength coverage of the combined G102+G141 spectra. All [OII] and [OIII] interlopers detected in G102 will be reliably separated from true LAEs by the detection of at least one strong line in the G141 spectrum, without the need for any ancillary data. We waive all proprietary rights to our data and will make high-level data products available through the ST/ECF. WFC3/IR/S/C 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). WFC3/UVIS 11594 A WFC3 Grism Survey for Lyman Limit Absorption at z=2 We propose to conduct a spectroscopic survey of Lyman limit absorbers at redshifts 1.8 < z < 2.5, using WFC3 and the G280 grism. This proposal intends to complete an approved Cycle 15 SNAP program (10878), which was cut short due to the ACS failure. We have selected 64 quasars at 2.3 < z < 2.6 from the Sloan Digital Sky Survey Spectroscopic Quasar Sample, for which no BAL signature is found at the QSO redshift and no strong metal absorption lines are present at z > 2.3 along the lines of sight. The survey has three main

observational goals. First, we will determine the redshift frequency dn/dz of the LLS over the column density range 16.0 < log(NHI) < 20.3 cm^-2. Second, we will measure the column density frequency distribution f(N) for the partial Lyman limit systems (PLLS) over the column density range 16.0 < log(NHI) < 17.5 cm^-2. Third, we will identify those sightlines which could provide a measurement of the primordial D/H ratio. By carrying out this survey, we can also help place meaningful constraints on two key quantities of cosmological relevance. First, we will estimate the amount of metals in the LLS using the f(N), and ground based observations of metal line transitions. Second, by determining f(N) of the PLLS, we can constrain the amplitude of the ionizing UV background at z~2 to a greater precision. This survey is ideal for a snapshot observing program, because the on-object integration times are all well below 30 minutes, and follow-up observations from the ground require minimal telescope time due to the QSO sample being bright. WFC3/UVIS 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 (Proposal 11909), will be used to generate the necessary superbias and superdark reference files for the calibration pipeline (CDBS). WFC3/UVIS 11908 Cycle 17: UVIS Bowtie Monitor Ground testing revealed an intermittent hysteresis type effect in the UVIS detector (both CCDs) at the level of ~1%, lasting hours to days. Initially found via an unexpected bowtie-shaped feature in flatfield ratios, subsequent lab tests on similar e2v devices have since shown that it is also present as simply an overall offset across the entire CCD, i.e., a QE offset without any discernable pattern. These lab tests have further revealed that overexposing the detector to count levels several times full well fills the traps and effectively neutralizes the bowtie. Each visit in this proposal acquires a set of three 3×3 binned internal flatfields: the first unsaturated image will be used to detect any bowtie, the second, highly exposed image will neutralize the bowtie if it is present, and the final image will allow for verification that the bowtie is gone. 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: (None) COMPLETED OPS REQUEST: (None) COMPLETED OPS NOTES: (None)

                        SCHEDULED      SUCCESSFUL
FGS GSAcq                 05              05
FGS REAcq                 09              09
OBAD with Maneuver        05              05

SIGNIFICANT EVENTS: (None)