Status Report

NASA Hubble Space Telescope Daily Report #5197

By SpaceRef Editor
October 7, 2010
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HUBBLE SPACE TELESCOPE – Continuing to Collect World Class Science


PERIOD COVERED: 8:00pm October 5 – 7:59pm October 6, 2010 (DOY 279/00:00z-279/23:59z)


Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)


12457 – GSAcq(2,3,3) at 279/15:10:26z resulted in fine lock back-up on FGS2.

Observations possibly affected WFC3 39-40, Proposal ID#11905



Scheduled Successful
FGS GSAcq 7 7
FGS REAcq 8 8
OBAD with Maneuver 4 4



ACS/WFC 11996

CCD Daily Monitor (Part 3)

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 308 orbits (19.25 weeks) from 21 June 2010 to 1 November 2010.

ACS/WFC3 11734

The Hosts of High Redshift Gamma-Ray Bursts

Gamma-ray bursts are the most luminous explosive events known, acting as beacons to the high redshift universe. Long duration GRBs have their origin in the collapse of massive stars and thus select star forming galaxies across a wide range of redshift. Due to their bright afterglows we can study the details of GRB host galaxies via absorption spectroscopy, providing redshifts, column densities and metallicities for galaxies far too faint to be accessible directly with current technology. We have already obtained deep ground based observations for many hosts and here propose ACS/WFC3 and WFC3 observations of the fields of bursts at z>3 which are undetected in deep ground based images. These observations will study the hosts in emission, providing luminosities and morphologies and will enable the construction of a sample of high-z galaxies with more detailed physical properties than has ever been possible before.


Spanning the Reionization History of IGM Helium: a Highly Efficient Spectral Survey of the Far-UV-Brightest Quasars

The reionization of IGM helium likely occurred at redshifts of z=3 to 4. Detailed studies of HeII Ly-alpha absorption toward a handful of quasars at 2.7< z<3.3 confirm the potential of such IGM probes, but the small sample and redshift range limited confidence in cosmological inferences. The requisite unobscured sightlines to high redshift are extremely rare; but we've cross-correlated 10, 000 z>2.8 SDSS DR7 (and other) quasars with GALEX GR4/5, to identify 630 candidates potentially useful for HST HeII studies. Our cycle 15-16 HST trials confirm our approach, verifying twenty new HeII quasars at unprecedented 40% efficiency. We propose to complete the first efficient (80% with refinements) survey for HeII quasars, via reconnaissance (~1 orbit) COS spectra of a highly select subset of 17 SDSS/GALEX quasars at 2.7< z<3.8. Along with past work, this program will yield 3-4 of the brightest far-UV HeII sightlines within each of 10-12 redshift bins spanning 2.7< z<3.8, enabling a community sample suitable for detailed spectral follow-up with HST. Herein, we will also directly obtain quality UV spectral stacks within each redshift bin to trace the reionization history of IGM helium; such spectral stacks average over cosmic variance and individual object pathology. Our high-yield HeII sightline sample and spectral stacks will enable confident conclusions about the IGM baryon density, the spectrum and evolution of the ionizing background, the evolution of HeII opacity, and the epoch of helium reionization. COS/NUV/FUV/WFC3/UV 12248 How Dwarf Galaxies Got That Way: Mapping Multiphase Gaseous Halos and Galactic Winds Below L* One of the most vexing problems in galaxy formation concerns how gas accretion and feedback influence the evolution of galaxies. In high mass galaxies, numerical simulations predict the initial fuel is accreted through ‘cold’ streams, after which AGN suppress star formation to leave galaxies red and gas-poor. In the shallow potential wells that host dwarf galaxies, gas accretion can be very efficient, and “superwinds” driven either by hot gas expelled by SNe or momentum imparted by SNe and hot-star radiation are regarded as the likely source(s) of feedback. However, major doubts persist about the physics of gas accretion, and particularly about SN-driven feedback, including their scalings with halo mass and their influence on the evolution of the galaxies. While “superwinds” are visible in X-rays near the point of their departure, they generally drop below detectable surface-brightness limits at ~ 10 kpc. Cold clumps in winds can be detected as blue-shifted absorption against the galaxy’s own starlight, but the radial extent of these winds are difficult to constrain, leaving their energy, momentum, and ultimate fate uncertain. Wind prescriptions in hydrodynamical simulations are uncertain and at present are constrained only by indirect observations, e.g. by their influence on the stellar masses of galaxies and IGM metallicity. All these doubts lead to one conclusion: we do not understand gas accretion and feedback because we generally do not observe the infall and winds directly, in the extended gaseous halos of galaxies, when it is happening. To do this effectively, we must harness the power of absorption-line spectroscopy to measure the density, temperature, metallicity, and kinematics of small quantities of diffuse gas in galaxy halos. The most important physical diagnostics lie in the FUV, so this is uniquely a problem for HST and COS. We propose new COS G130M and G160M observations of 41 QSOs that probe the gaseous halos of 44 SDSS dwarf galaxies well inside their virial radii. Using sensitive absorption-line measurements of the multiphase gas diagnostics Lya, CII/IV, Si II/III/IV, and other species, supplemented by optical data from SDSS and Keck, we will map the halos of galaxies with L = 0.02 – 0.3 L*, stellar masses M* = 10^(8-10) Msun, over impact parameter from 15 – 150 kpc. These observations will directly constrain the content and kinematics of accreting and outflowing material, provide a concrete target for simulations to hit, and statistically test proposed galactic superwind models. These observations will also inform the study of galaxies at high z, where the shallow halo potentials that host dwarf galaxies today were the norm. These observations are low-risk and routine for COS, easily schedulable, and promise a major advance in our understanding of how dwarf galaxies came to be. FGS 11298 Calibrating Cosmological Chronometers: White Dwarf Masses We propose to use HST/FGS1R to determine White Dwarf {WD} masses. The unmatched resolving power of HST/FGS1R will be utilized to follow up four selected WD binary pairs. This high precision obtained with HST/FGS1R simply cannot be equaled by any ground based technique. This proposed effort complements that done by CoI Nelan in which a sample of WDs is being observed with HST/FGS1R. This proposal will dramatically increase the number of WDs for which dynamical mass measurements are possible, enabling a better calibration of the WD mass-radius relation, cooling curves, initial to final mass relations, and ultimately giving important clues to the star formation history of our Galaxy and the age of its disk as well as in other galaxies. {This project is part of Subasavage’s PhD thesis work at Georgia State University.} 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. WFC3/IR 12184 A SNAP Survey for Gravitational Lenses Among z~6 Quasars We propose a SNAP imaging survey of a complete sample of 54 quasars at 5.7 < z < 6.4 using HST/WFC3-IR to quantify the prevalence of strongly lensed quasars at z~6. Gravitational lensing magnification bias, boosted by the observed steep luminosity function of high-redshift quasars, strongly suggest that lenses should be common amongst the highest-redshift quasars known. However, the highest redshift strongly lensed quasar known is only at z=4.8; but among the 59 quasars known at z>5.9, only five have been imaged with HST. Our HST images will be sensitive to the multiple images of lensed quasar, even at small separations and large flux ratios. Based on the current best estimate of the quasar luminosity function, we expect to discover 2-9 strongly lensed quasars in our entire sample, or 1-4 for the nominal SNAP completion rate of 40%. This program will likely discover the first quasar lenses at z~6, enabling detailed follow-up observations to constrain lensing models, to study quasar host galaxy properties and to probe the small-scale structure of the IGM. The measurement of or upper limit on the lensing fraction will strongly constrain the bright end of the quasar luminosity function, leading to important constraints on models of quasar evolution and allowing us to better quantify the quasar contribution to the reionization photon budget.

WFC3/IR 12217

Spectroscopy of Faint T Dwarf Calibrators: Understanding the Substellar Mass Function and the Coolest Brown Dwarfs

More than 100 methane brown dwarfs, or T dwarfs, have now been discovered in the local field with 2MASS, SLOAN and UKIDSS, opening up a new area of physics describing objects at 450-1400 K. However, very few calibrator objects exist with well established ages and metallicities. A very surprising result from the UKIDSS sample (supported by 2MASS and SLOAN) is that the substellar mass function in the local field appears to decline to lower masses, in marked contrast to the rising initial mass function (IMF) observed in young clusters. Given that such a difference between the present day IMF and the Galactic time-averaged IMF is unlikely, it is very possible that the apparently falling IMF is an artifact of serious errors in either T model atmospheres or the evolutionary isochrones. We propose WFC3 spectroscopy of 4 faint T dwarf calibrators with well established ages and metallicities in the Pleiades and Sigma Ori clusters, and 2 faint field T dwarfs from UKIDSS for comparison. These spectra will constitute vital calibration data for T dwarf atmospheres with a wide range of surface gravities, which will be used to test and improve the model atmospheres. They will also aid preparation for future spectroscopy of the much larger numbers of field T dwarfs to soon be found by VISTA and WISE. These new surveys will permit a more precise measurement of the mass function and detection of even cooler objects.

WFC3/IR 12283

WFC3 Infrared Spectroscopic Parallel Survey (WISP): A Survey of Star Formation Across Cosmic Time

We will use the unique power of WFC3 slitless spectroscopy to measure cosmic star formation across its peak epoch. The broad, continuous, spectral coverage of the G102 and G141 grisms provides the best currently feasible measurement of the star formation rate continously from 0.5< z<2.5, over which ground-based searches are severely limited. Our Cycle 17 pure-parallel grism program has proven efficient for identifying line emission from galaxies across this large fraction of cosmic time. With less than two months of WFC3 observing completed, our new measurments have more than doubled the sample of emission-line galaxies that we found over the entire NICMOS Parallel Grism program. We propose to extend this cost-effective WFC3 Survey by using 280 orbits of pure parallel grism spectroscopy in 50 deep (4-5 orbit) fields with both G102 and G141, and 40 shallow (2-3 orbit) fields with G141 alone. This will complete a sample of 2000-3000 emission line galaxies in the "redshift desert" and search for serendipitous Lya emitters at z>5.5.

Our primary science goals are: (1) Measure ratios of bright emission lines ([OII], [OIII], Ha, and Hb) in a substantial fraction of these galaxies, thereby estimating dust and metallicity evolution in a sample of galaxies that is not biased by photometric selection. (2) Derive an extinction-corrected Ha luminosity function, with a 20 times larger sample than our previous NICMOS results. (3) Measure the mass-metallicity relation at crucial intermediate redshifts, with the support of our ongoing ground-based, follow-up, observing program (4) Determine the spectroscopic close pair fraction in this sample, in order to constrain hierarchal merging models (5) Uncover a new sample of obscured AGN at these redshifts and, (6) Use the Balmer break diagnostic to constrain the ages of continuum detected sources down to H = 25.

As a bonus, these observations will be sensitive to Lya emission at z>5.5, taking advantage of continuous spectral coverage to observe large volumes for luminous galaxies at the highest redshifts. Over Cycles 17 and 18, we expect to detect 5-20 LAEs over redshifts spanning 5.5 < z < 7.5. These observations will likely place the most stringent constraint on the numbers of z>6.5 Lya emitters until JWST. We are waiving all proprietary rights to our data and will make high-level data products available through the ST/ECF.

WFC3/IR 12286

Hubble Infrared Pure Parallel Imaging Extragalactic Survey (HIPPIES)

WFC3 has demonstrated its unprecedented power in probing the early universe. Here we propose to continue our pure parallel program with this instrument to search for LBGs at z~6–8. Our program, dubbed as the Hubble Infrared Pure Parallel Imaging Extragalactic Survey (“HIPPIES”), will carry on the HST pure parallel legacy in the new decade. We request 205 orbits in Cycle-18, which will spread over ~ 50 high Galactic latitude visits (|b|>20deg) that last for 3 orbits and longer, resulting a total survey area of ~230 square arcmin. Combining the WFC3 pure parallel observations in Cycle-17, HIPPIES will complement other existing and forthcoming WFC3 surveys, and will make unique contributions to the study in the new redshift frontier because of the randomness of the survey fields. To make full use of the parallel opportunities, HIPPIES will also take ACS parallels to study LBGs at z~5–6. Being a pure parallel program, HIPPIES will only make very limited demand on the scarce HST resources, but will have potentially large scientific returns. As in previous cycle, we waive all proprietary data rights, and will make the enhanced data products public in a timely manner.

(1) The WFC3 part of HIPPIES aims at the most luminous LBG population at z~8 and z~7. As its survey fields are random and completely uncorrelated, the number counts of the bright LBGs from HIPPIES will be least affected by the “cosmic variance”, and hence we will be able to obtain the best constraint on the bright-end of the LBG luminosity function at z~8 and 7. Comparing the result from HIPPIES to the hydrodynamic simulations will test the input physics and provide insight into the nature of the early galaxies. (2) The z~7–8 candidates from HIPPIES, most of which will be the brightest ones that any surveys would be able to find, will have the best chance to be spectroscopically confirmed at the current 8–10m telescopes. (3) The ACS part of HIPPIES will produce a significant number of candidate LBGs at z~5 and z~6 per ACS field. Combining with the existing, suitable ACS fields in the HST archive, we will be able to utilize the random nature of the survey to quantify the cosmic variance and to measure the galaxy bias at z~5–6, and therefore the galaxy halo masses at these redshifts. (4) We will also find a large number of extremely red, old galaxies at intermediate redshifts, and the fine spatial resolution offered by the WFC3 will enable us constrain their formation history based on the study of their morphology, and hence shed light on their connection to the very early galaxies in the universe.

WFC3/UV 12019

After the Fall: Fading AGN in Post-starburst Galaxies

We propose joint Chandra and HST observations of an extraordinary sample of 12 massive post-starburst galaxies at z=0.4-0.8 that are in the short-lived evolution phase a few 100 Myr after the peak of merger-driven star formation and AGN activity. We will use the data to measure X-ray luminosities, black hole masses, and accretion rates; and with the accurate “clocks” provided by post-starburst stellar populations, we will directly test theoretical models that predict a power-law decay in the AGN light curve. We will also test whether star formation and black hole accretion shut down in lock-step, quantify whether the black holes transition to radiatively inefficient accretion states, and constrain the observational signatures of black hole mergers.

WFC3/UV 12345

UVIS Long Darks Test

Darks during SMOV showed a systematically lower global dark rate as well as lower scatter when compared to the Cycle 17 darks. Those two sets of exposures differ in exposure time – 1800 sec during SMOV and 900 sec during Cycle 17. Hypothetically, the effect could be caused by short-duration stray light, say ~500-sec in duration. During the latter part of Cycle 17, operation of WFC3 was changed to additionally block the light path to the detector with the CSM. This program acquires a small number of darks at the longer SMOV exposure times (1800 sec) in order to check whether the effect repeats in the new operating mode.

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).

SpaceRef staff editor.