Status Report

NASA Hubble Space Telescope Daily Report #4211

By SpaceRef Editor
October 3, 2006
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NASA Hubble Space Telescope Daily Report #4211


– Continuing to collect World Class Science

PERIOD COVERED: UT October 02, 2006 (DOY 275)



ACS CCDs daily monitor

This program consists of a set of basic tests to monitor, the read noise, the development of hot pixels and test for any source of noise in ACS CCD detectors. The files, biases and dark will be used to create reference files for science calibration. This programme will be for the entire lifetime of ACS. Changes from cycle 13:- The default gain for WFC is 2 e-/DN. As before bias frames will be collected for both gain 1 and gain 2. Dark frames are acquired using the default gain {2}. This program cover the period May, 31 2006- Oct, 1-2006. The first half of the program has a different proposal number: 10729.

ACS/WFC 10763

The Guitar Nebula: A Bow Shock that Traces ISM Turbulence and Accelerates Relativistic Particles

We propose joint Chandra and HST observations of the Guitar Nebula, an extraordinary bow- shock nebula produced by a very high-velocity but otherwise ordinary pulsar. Prior HST observations show epoch dependent changes in shock structure that signify changing ISM conditions. An enigmatic jet or filament is seen in a Chandra ACIS image {year 2000}, unlike jets from the Crab or other young pulsars. New Chandra observations will reveal the relative motion of the jet and the pulsar {which has moved by 0.9 arcsec} and thus determine if self confinement or special structure in the ISM plays a dominant role in shaping the jet, and will constrain the particle acceleration mechanism. We request joint high-resolution HST observations to contemporaneously determine the ISM density profile.

ACS/WFC 10813

MgII Absorption Line Systems: Galaxy Halos or the Metal-Enriched IGM?

MgII QSO absorption lines detected in the spectra of background QSOs were used over a decade ago to infer that all redshift z > 0.2 galaxies have gaseous halos of radius ~ 60 kpc. The actual size of the halo was believed to be proportional to the luminosity of the galaxy. However, these conclusions are now much harder to understand in light of the results from numerical simulations which show how gas evolves in the universe. These models predict that gas and galaxies merely share the same filamentary structures defined by dark matter. If these models are correct, how are MgII systems and galaxies really related? We can better understand the distribution of absorbing gas if we FIRST select galaxies close to QSO sightlines and THEN search for MgII absorption at the redshift of the intervening galaxies. This is the antithesis of the original experiments which sought to find absorbing galaxies based on known MgII systems. The frequency with which we detect MgII lines from randomly selected galaxies should enable us to better understand if absorption arises in the halos of individual galaxies, or if MgII merely arises in the same IGM that galaxies inhabit. We have used ground-based telescopes to indentify twenty z = 0.31-0.55 galaxies within 14-51 kpc of a g < 20 QSO, and to search for MgII absorption at the galaxies' redshifts. Surprisingly, we find that only 50% of our QSOs show MgII absorption. In this proposal, we seek multi-color ACS images of twelve of the fields to i} correlate the incidence of MgII with galaxy morphology; ii} determine if absorption {or lack thereof} is related to galaxy disks or halos; iii} search for signs of galaxy interactions which may explain the large cross-sections of MgII systems; and iv} look for faint interloping galaxies closer to the line of sight than the one we identified. An important component of the program is to observe each field in the SDSS g-, r- and i-bands, to permit an estimate of the photometric redshift of any objects which lie closer to the QSO sightline than the identified galaxy, and which might actually be responsible for the absorption.

ACS/WFC 10876

SL2S: The Strong Lensing Legacy Survey

Strong Gravitational Lensing is an invaluable tool to constrain the absolute mass distribution of structures irrespective of their light distribution. Strong Lensing has successfully been applied to single galaxies lensing quasars into multiple images, and to massive clusters lensing background sources into giant arcs. More recently, the Sloan Lens ACS Survey also found numerous examples of isolated, yet massive ellipticals lensing background galaxies into Einstein rings. We have started the Strong Lensing Legacy Survey {SL2S} looking for strong lenses in the 170 sq. degree CFHT-Legacy Survey, using dedicated automated search procedures, optimized for detection of arcs and Einstein rings. Thanks to the unsurpassed combined depth, area and image quality of the CFHT-LS, we uncovered a new population of lenses: the intermediate mass halo and sub-halo lenses. This new population effectively bridges the gap between single galaxies and massive clusters. Here, we propose to obtain SNAPSHOT ACS images of the 50 first strong lens candidates with Einstein radii 2″< Re <9" {found in the first 45 sq. degrees of CFHT-LS data released}. The ACS images will allow us to model in details the mass distribution of this new population of lensing groups under various lensing configurations. Using ACS images, we ultimately hope to provide a better understanding of the formation of structures by studying the lensing signatures of the key population of galaxy groups.

ACS/WFC 10886

The Sloan Lens ACS Survey: Towards 100 New Strong Lenses

As a continuation of the highly successful Sloan Lens ACS {SLACS} Survey for new strong gravitational lenses, we propose one orbit of ACS-WFC F814W imaging for each of 50 high- probability strong galaxy-galaxy lens candidates. These observations will confirm new lens systems and permit immediate and accurate photometry, shape measurement, and mass modeling of the lens galaxies. The lenses delivered by the SLACS Survey all show extended source structure, furnishing more constraints on the projected lens potential than lensed-quasar image positions. In addition, SLACS lenses have lens galaxies that are much brighter than their lensed sources, facilitating detailed photometric and dynamical observation of the former. When confirmed lenses from this proposal are combined with lenses discovered by SLACS in Cycles 13 and 14, we expect the final SLACS lens sample to number 80–100: an approximate doubling of the number of known galaxy-scale strong gravitational lenses and an order-of-magnitude increase in the number of optical Einstein rings. By virtue of its homogeneous selection and sheer size, the SLACS sample will allow an unprecedented exploration of the mass structure of the early-type galaxy population as a function of all other observable quantities. This new sample will be a valuable resource to the astronomical community by enabling qualitatively new strong lensing science, and as such we will waive all but a short {3-month} proprietary period on the observations.

ACS/WFC/NIC2 10496

Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters

We propose a novel HST approach to obtain a dramatically more useful “dust free” Type Ia supernovae {SNe Ia} dataset than available with the previous GOODS searches. Moreover, this approach provides a strikingly more efficient search-and-follow-up that is primarily pre- scheduled. The resulting dark energy measurements do not share the major systematic uncertainty at these redshifts, that of the extinction correction with a prior. By targeting massive galaxy clusters at z > 1 we obtain a five-times higher efficiency in detection of Type Ia supernovae in ellipticals, providing a well-understood host galaxy environment. These same deep cluster images then also yield fundamental calibrations required for future weak lensing and Sunyaev-Zel’dovich measurements of dark energy, as well as an entire program of cluster studies. The data will make possible a factor of two improvement on supernova constraints on dark energy time variation, and much larger improvement in systematic uncertainty. They will provide both a cluster dataset and a SN Ia dataset that will be a longstanding scientific resource.

ACS/WFC/NIC3 10632

Searching for galaxies at z>6.5 in the Hubble Ultra Deep Field

We propose to obtain deep ACS {F606W, F775W, F850LP} imaging in the area of the original Hubble Ultra Deep Field NICMOS parallel fields and – through simultaneous parallel observations – deep NICMOS {F110W, F160W} imaging of the ACS UDF area. Matching the extreme imaging depth in the optical and near-IR bands will result in seven fields with sufficiently sensitive multiband data to detect the expected typical galaxies at z=7 and 8. Presently no such a field exist. Our combined optical and near-IR ultradeep fields will be in three areas separated by about 20 comoving Mpc at z=7. This will allow us to give a first assessment of the degree of cosmic variance. If reionization is a process extending over a large redshift interval and the luminosity function doesn’t evolve strongly beyond z=6, these data will allow us to identify of the order of a dozen galaxies at 6.5 < z <8.5 - using the Lyman break technique - and to place a first constrain on the luminosity function at z>6.5. Conversely, finding fewer objects would be an indication that the bulk of reionization is done by galaxies at z=6. By spending 204 orbits of prime HST time we will capitalize on the investment of 544 prime orbits already made on the Hubble Ultra Deep Field {UDF}. We have verified that the program as proposed is schedulable and that it will remain so even if forced to execute in the 2-gyro mode. The data will be non-proprietary and the reduced images will be made public within 2 months from the completion of the observations.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration – CR Persistence Part 5

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.

NIC2 10893

Sweeping Away the Dust: Reliable Dark Energy with an Infrared Hubble Diagram

We propose building a high-z Hubble Diagram using type Ia supernovae observed in the infrared rest-frame J-band. The infrared has a number of exceptional properties. The effect of dust extinction is minimal, reducing a major systematic tha may be biasing dark energy measurements. Also, recent work indicates that type Ia supernovae are true standard candles in the infrared meaning that our Hubble diagram will be resistant to possible evolution in the Phillips relation over cosmic time. High signal-to-noise measurements of 9 type Ia events at z~0.4 will be compared with an independent optical Hubble diagram from the ESSENCE project to test for a shift in the derived dark energy equation of state due to a systematic bias. Because of the bright sky background, H-band photometry of z~0.4 supernovae is not feasible from the ground. Only the superb image quality and dark infrared sky seen by HST makes this test possible. This experiment may also lead to a better, more reliable way of mapping the expansion history of the universe with the Joint Dark Energy Mission.

NIC3 11064


Now that the spectrophotometric capabilities of the NICMOS grism have been established, cycle 15 observations are needed to refine the sensitivity estimates, to check for sensitivity loss with time, to improve the accuracy of the linearity correction, to improve the secondary flux standards by re-observation, and to expand the G206 data set now that the sky subtraction technique has been shown to produce useful fluxes for some of the fainter secondary standards. These faint secondary IR standards will be a significant step towards establishing flux standards for JWST, as well as for SNAP, Spitzer, and SOFIA. 1.Re-observe the 3 primary WDs GD71, G191B2b, & GD153 twice each, once at the beginning and once near the end of the 18 month cycle. To date, we have only 2 observation of each star, while the corresponding STIS data set for these primary standards ranges from 6 to 23 obs. No observations exist for GD71 or GD153 with G206, so that the current G206 sensitivity is defined solely by G191B2B. Purposes: Refine sensitivities, measure sens losses. Orbits: 2 for each of 6 visits = 12 2. Re-observe WD1057 & WD1657 plus another P041C lamp-on visit to improve the scatter in the non-lin measurements per Fig. 8 of NIC ISR 2006-02. The WD stars require 2 orbits each, while the lamp-on test is done in one. The very faintest and most crucial standard WD1657 has 2 good visits already, so to substantially improve the S/N, two visits of two orbits are needed. Include G206 for P041C in the lamp-off baseline part of that orbit. Orbits: WD1057-2, WD1657-4, P041C-1 –> 7 3. Re-observe 9 secondary standards to improve S/N of the faint ones and to include G206 for all 9. BD+17 {3 obs} is not repeated in this cycle. Four are bright enough to do in one orbit: VB8, 2M0036+18, P330E, and P177D. Orbits:2*5+4=14 Grand Total orbits over 18 month cycle 15 is 12+6+14=32 {Roelof will submit the P041C lamp-on visit in a separate program.}

NIC3 11068

NICMOS A-Star Spectrophotometric Observations

Now that the Cohen A-star fluxes have been verified in the IR by the four cycle 14 NICMOS grism observations from program 10754, verification of four more of these Cohen SEDs will be done in Cycle 15. All 8 stars are selected from the Spitzer IRAC photometric calibration target lists, {Tables 1-2} in Reach et al. 2005, PASP, 117,978; and all 8 A-stars are near the north ecliptic pole, ie near the JWST continuous viewing zone. The baseline plan for JWST NIRSpec calibration is to use the Cohen modeled flux beyond the 2.5micron NICMOS limit. Because of intrinsic variation within the same spectral type there is some statistical scatter expected in the precision of the Cohen flux extrapolation that is based on models. Thus, the ensemble JWST flux calibration based on an average over 8 stars should be sqrt{8} more accurate than a sensitivity based on just one A-star. In addition to JWST calibration, this program supports spectrophotometric cross calibration of HST and Spitzer. The targets are chosen to be faint enough for unsaturated observations with JWST NIRSpec, yet still bright enough for high signal to noise in relatively short observations with HST+NICMOS and with Spitzer+IRAC.

WFPC2 10748

WFPC2 CYCLE 14 Standard Darks

This dark calibration program obtains dark frames every week in order to provide data for the ongoing calibration of the CCD dark current rate, and to monitor and characterize the evolution of hot pixels. Over an extended period these data will also provide a monitor of radiation damage to the CCDs.


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


10457 – GSAcq(1,3,1) results in finelock backup (1,0,1)

The GSAcq(1,3,1) scheduled at 275/10:50:00 – 10:58:04 resulted to finelock backup (1,0,1) using FGS-1 due to stop flag (QF3STOPF) on FGS-3 at 275/10:54:39. Pre-acquisition OBADs had (RSS) attitude error corrections values of 1200.58 and 11.32 arcseconds. Post-acquisition OBAD/MAP had 3-axis (RSS) value of 11.32 a-s.

10458 – REAcq (2,1,2) failed to RGA control

REAcq (2,1,2) scheduled at 275/22:16:59-22:24:17 failed to RGA control due to stop flag on FGS 2. No 486 ESB’s were noted. OBAD #1: RSS= 18.64 a-s OBAD #2: RSS= 8.52 a-s OBAD MAP: RSS= 15.87 a-s

REAcq (2,1,2) scheduled at 275/23:59:04-276/00:06:21 failed to RGA control due to stop flag on FGS 2. OBAD #1: RSS= 1557.75 a-s OBAD #2: RSS= 4.06 a-s OBAD MAP was not scheduled

REAcq (2,1,2) scheduled at 276/01:40:10-01:47:27 failed to RGA control due to stop flag on FGS 2. OBAD #1: RSS= 1516.12 a-s OBAD #2: RSS= 5.58 a-s OBAD MAP was not scheduled



                          SCHEDULED      SUCCESSFUL 
FGS GSacq                07                     07 
FGS REacq                 07                    04 
OBAD with Maneuver   28                     28 


SpaceRef staff editor.