Status Report

NASA Hubble Space Telescope Daily Report #3942

By SpaceRef Editor
September 12, 2005
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HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science


PERIOD COVERED: UT September 09-11, 2005 (DOY 252-254)


ACS/SBC 9806

Properties of the Intergalactic Medium near the Epoch of He-II Reionization

Our STIS spectral snapshot programs have found a rare case of a He-II Lyman-alpha absorption trough in a z=3.51, V=17.6 quasar. This is the highest redshift at which this feature has been observed. We propose to obtain a high-quality STIS spectrum that will enable us to {1} Investigate the evolution and properties of the intergalactic medium {IGM} over an epoch between z=2.8 and 3.5; {2} Search for signs of the reionization of the intergalactic helium; {3} Measure the intensity of the UV background radiation, and find clues toward its origin; and {4} Estimate the IGM baryonic density. The instrument has been changed from STIS to ASC prism.

NIC1/NIC2/NIC3 8793

NICMOS Post-SAA calibration – CR Persistence Part 4

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.

ACS/HRC 10752

Cycle 14 Focus Monitor

The focus of HST is measured primarily with ACS/HRC over full CVZ orbits to obtain accurate mean focus values via a well sampled breathing curve. Coma and astigmatism are also determined from the same data in order to further understand orbital effects on image quality and optical alignments. To monitor the stability of ACS to WFPC2 relative focii, we’ve carried over from previous focus monitor programs parallel observations taken with the two cameras at suitable orientations of previously observed targets, and interspersed them with the HRC CVZ visits.

FGS 10613

Calibrating the Mass-Luminosity Relation at the End of the Main Sequence

We propose to use HST-FGS1R to calibrate the mass-luminosity relation {MLR} for stars less massive than 0.2 Msun, with special emphasis on objects near the stellar/brown dwarf border. Our goals are to determine M_V values to 0.05 magnitude, masses to 5 than double the number of objects with masses determined to be less than 0.20 Msun. This program uses the combination of HST-FGS3/FGS1R at optical wavelengths and ground-based infrared interferometry to examine nearby, subarcsecond binary systems. The high precision measurements with HST-FGS3/FGS1R {to 1 mas in the separations} for these faint targets {V = 10–15} simply cannot be equaled by any ground based technique. As a result of these measurements, we are deriving high quality luminosities and masses for the components in the observed systems, and characterizing their spectral energy distributions from 0.5 to 2.2 Mum. Several of the objects included have M < 0.1 Msun, placing them at the very end of the stellar main sequence. Three of the targets are brown dwarf candidates, including the current low mass record holder, GJ 1245C, with a mass of 0.062 +/- 0.004 Msun. The payoff of this proposal is high because all 10 of the systems selected have already been resolved with HST- FGS3/FGS1R during Cycles 5--10 and contain most of the reddest objects for which masses can be determined.

FGS 10611

Precise Distances to Nearby Planetary Nebulae

We propose to carry out astrometry with the FGS to obtain accurate and precise distances to four nearby planetary nebulae. In 1992, Cahn et al. noted that “The distances to Galactic planetary nebulae remain a serious, if not THE most serious, problem in the field, despite decades of study.” Twelve years later, the same statement still applies. Because the distances to planetary nebulae are so uncertain, our understanding of their masses, luminosities, scale height, birth rate, and evolutionary state is severely limited. To help remedy this problem, HST astrometry can guarantee parallaxes with half the error of any other available approach. These data, when combined with parallax measurements from the USNO, will improve distance measurements by more than a factor of two, producing more accurate distances with uncertainties that are of the order of ~6%. Lastly, most planetary nebula distance scales in the literature are statistical. They require several anchor points of known distance in order to calibrate their zero point. Our program will provide “gold standard” anchor points by the end of 2006, a decade before any anticipated results from future space astrometry missions.

ACS/WFC 10604

The Formation History of the M81 Spheroid

Spheroidal stellar populations {elliptical galaxies, bulges, and halos} contain a significant fraction of all stars and metals in the local universe. The mechanisms responsible for their formation are ultimately the ones which governed galaxy formation during early epochs. To begin understanding the M81 spheroid, we are currently studying the globular cluster population using HST/WFPC2 multiband imaging and ground based optical spectroscopy. To complete this effort, we propose to use ACS/WFC to obtain deep {I, V-I} color magnitude diagrams {to the horizontal branch} of two fields in M81 – one dominated by thick disk stars and the other halo stars. These observations will provide tight constraints on the formation timescales and chemical enrichment history of the field star population. Combined with results on the globular clusters, we will reconstruct the early formation history of M81, and compare with those found for other nearby, massive galaxies. Because M81 is the earliest type spiral galaxy {Sab} available for such a detailed study, it provides a unique opportunity to probe the connection between elliptical halos and lower mass spiral spheroids.

NIC2 10603

Multiwavelength Imaging of Edge-on Protoplanetary Disks: Quantifying the Growth of Circumstellar Dust

Young, edge-on circumstellar disks are uniquely valuable laboratories for the study of planet formation. In these objects, the central star is occulted from direct view, significant PSF artifacts are absent, and the disk is clearly seen as a central dust lane flanked by faint disk reflected light. The detailed morphology of these nebulae and its variation with wavelength provide crucial information on the disk internal structure and the properties of its constituent dust grains. A key observable is the slope defining the wavelength dependence of the dust scattering opacity, which becomes shallower when grain growth has taken place; multiwavelength resolved disk images are the key dataset enabling such measurements. Recent analyses of three different edge-on disks have revealed a diversity in their dust properties that is indicative of different degrees of dust grain evolution having taken place in each system. This characterization of disk grain growth, when applied comparatively to a larger sample of these objects, would enable the construction of an evolutionary sequence of young disks at successive stages on the road to planet formation. In pursuit of this goal, we have identified a sample of 15 edge-on disks previously discovered by HST or groundbased telescopes, but for which high fidelity, high spatial resolution images do not yet exist in both the optical and near-infrared. We propose broad-band multicolor imaging with NICMOS of all these targets, and ACS imaging of nine of these targets In combination with existing data, the proposed images will form a complete database of high resolution optical/near-IR images for these 15 disk systems. Scattered light modeling will be used to derive the disk structure and dust properties, yielding results that will be of fundamental importance for our understanding of grain properties during protoplanetary disk evolution.

ACS/WFC 10592

An ACS Survey of a Complete Sample of Luminous Infrared Galaxies in the Local Universe

At luminosities above 10^11.4 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 ACS/WFC imaging of a complete sample of 88 L_IR > 10^11.4 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, resolution, and field of view of ACS/WFC on HST enables a unique opportunity to study the detailed structure of galaxies that sample all stages of the merger process. Imaging will be done with the F439W and F814W filters {B and I-band} to examine as a function of both luminosity and merger state {i} the evidence at optical wavelengths of star formation and AGN activity and the manner in which instabilities {bars and bridges} in the galaxies may funnel material to these active regions, {ii} the relationship between star formation and AGN activity, and {iii} the structural properties {AGN, bulge, and disk components} and fundamental parameters {effective radius and surface brightness} of LIRGs and their similarity with putative evolutionary byproducts {elliptical, S0 and classical AGN host galaxies}. This HST survey will also bridge the wavelength gap between a Spitzer imaging survey {covering seven bands in the 3.6-160 micron range} and a GALEX UV imaging survey of these galaxies, but will resolve complexes of star clusters and multiple nuclei at resolutions well beyond the capabilities of either Spitzer or GALEX. The combined datasets will result in the most comprehensive multiwavelength study of interacting and merging galaxies to date.


What Are Stalled Preplanetary Nebulae? An ACS SNAPshot Survey

Essentially all planetary nebulae {PNs} are aspherical, whereas the mass-loss envelopes of AGB stars are strikingly spherical. Our previous SNAPshot surveys of a morphologically unbiased sample of pre-planetary nebulae {PPNs} — objects in transition between the AGB and PN evolutionary phases — show that roughly half our observed targets are resolved, with bipolar or multipolar morphologies. Spectroscopic observations of our sample confirm that these objects have not yet evolved into planetary nebulae. Thus, the transformation from spherical to aspherical geometries has already fully developed by the time these dying stars have become PPNs. Although our current studies have yielded exciting results, they are limited in two important ways — {1} the number of well-resolved objects is still small {18}, and the variety of morphologies observed relatively multitudinous, hence no clear trends can yet be established between morphology and other source properties {e.g., near-IR, far-IR colors, stellar spectral type, envelope mass}, and {2} the current samples are strongly biased towards small PPNs, as inferred from their low 60-to-25 micron flux ratios [R{60/25}<1]. However, the prototype of objects with R{60/25}>1, the Frosty Leo Nebula, has a puzzlingly large post-AGB age {almost 10^4 yr} and a fairly cool central star, very different from the expectations of single-star stellar evolutionary models. A proposed, but still speculative, hypothesis for such objects is that the slow evolution of the central star is due to backflow of material onto the mass-losing star, retarding its evolution towards the PN phase. This hypothesis has significant consequences for both stellar and nebular evolution. We therefore propose a survey of PPNs with R{60/25}>1 which is heavily weighted towards the discovery of such “stalled PPNs”. Supporting kinematic observations using long-slit optical spectroscopy {with the Keck}, millimeter and radio interferometric observations {with OVRO, VLA & VLBA} are being undertaken. The results from this survey {together with our previous work} will allow us to draw general conclusions about the complex mass-outflow processes affecting late stellar evolution, and will provide crucial input for theories of post-AGB stellar evolution. Our survey will produce an archival legacy of long-standing value for future studies of dying stars.


Probing Evolution And Reionization Spectroscopically {PEARS}

While imaging with HST has gone deep enough to probe the highest redshifts, e.g. the GOODS survey and the Ultra Deep Field, spectroscopic identifications have not kept up. We propose an ACS grism survey to get slitless spectra of all sources in a wide survey region {8 ACS fields} up to z =27.0 magnitude, and an ultradeep field in the HUDF reaching sources up to z =28 magnitude. The PEARS survey will: {1} Find and spectrocopically confirm all galaxies between z=4-7. {2} Probe the reionization epoch by robustly determining the luminosity function of galaxies and low luminosity AGNs at z = 4 – 6. With known redshifts, we can get a local measure of star formation and ionization rate in case reionization is inhomogeneous. {3} Study galaxy formation and evolution by finding galaxies in a contiguous redshift range between 4 < z < 7, and black hole evolution through a census of low-luminosity AGNs. {4} Get a robust census of galaxies with old stellar populations at 1 < z < 2.5, invaluable for checking consistency with heirarchical models of galaxy formation. Fitting these galaxies' spectra will yield age and metallicity estimates. {5} Study star-formation and galaxy assembly at its peak at 1< z < 2 by identifying emission lines in star-forming galaxies, old populations showing the 4000A break, and any combination of the two. {6} Constrain faint white dwarfs in the Galactic halo and thus measure their contribution to the dark matter halo. {7} Derive spectro-photometric redshifts by using the grism spectra along with broadband data. This will be the deepest unbiased spectroscopy yet, and will enhance the value of the multiwavelength data in UDF and the GOODS fields to the astronomical community. To this end we will deliver reduced spectra to the HST archives.

ACS/HRC 10525

Characterizing the Near-UV Environment of M Dwarfs: Implications for Extrasolar Planetary Searches and Astrobiology

We propose SNAP observations with the ACS HRC PR200L prism, designed to measure the near ultraviolet emission in a sample of 107 nearby M dwarfs. The sample spans the mass range from 0.1 – 0.6 solar masses {temperature range 2200K – 4000K} where the UV energy distributions vary widely between active and inactive stars. The strength and distribution of this UV emission can have critical consequences for the atmospheres of attendant planets. Our proposed observations will provide desperately needed constraints on models of the habitability zone and the atmospheres of possible terrestrial planets orbiting M dwarf hosts, and will be used to sharpen TPF target selection. In addition, the NUV data will be used in conjunction with existing optical, FUV and X-ray data to constrain a new generation of M dwarf atmospheric models, and to explore unanswered questions regarding the dynamo generation and magnetic heating in these low-mass stars.

ACS/WFC 10497

Cepheid Calibrations of the Luminosity of Two Reliable Type Ia Supernovae and a Re- determination of the Hubble Constant

We propose to determine the luminosity of two type Ia supernovae {SNe Ia}, 1995al in NGC 3021 and SN 2002fk in NGC 1309, by observing Cepheids in their spiral hosts. Modern CCD photometry yields an extremely tight Hubble diagram for SNe Ia with a precisely determined intercept {i.e., Delta H_0/H_0}. Yet, the measurement of the true Hubble constant via SNe Ia is limited by the calibration derived from problematic and unreliable SN data. Most of the SNe Ia calibrated by HST to date are significantly compromised by the systematics of photographic photometry, high reddening and SN peculiarity, and by the photometric anomolies associated with WFPC2. The extended reach of ACS now provides opportunities to more reliably calibrate SNe Ia and H_0. Our Cepheid calibration of a reliable SN Ia dataset, SN 1994ae, using ACS in Cycle 11 resulted in a 15% increase in H_0 from the value derived by the HST SN Ia Calibration Program. Yet, there remains a terribly small sample of reliable SN Ia data sets on which to base such a crucial cosmological result. SN 1995al and SN 2002fk are two of the best observed SNe Ia both with little reddening. They provide two opportunities to use ACS for placing the calibration of H_0 via SN Ia on firmer footing and potentially improve its precision.


A Search for Debris Disks in the Coeval Beta Pictoris Moving Group

Resolved observations of debris disks present us with the opportunity of studying planetary evolution in other solar systems. We propose to search for debris disks in the Beta Pictoris moving group {8-20 Myrs, 10-50 pc away} , which provides a coeval sample of multiple spectral types, and it has already produced two magnificent resolved debris disks: AU Mic and Beta Pic. Such coeval sample will provide us with a snapshop of the crucial time in disk evolution in which the disk makes the transition from optically thick to optically thin, and it will be useful to study the stellar mass dependence of the disk evolution.

ACS/WFC 10475

An ACS H-alpha Survey of the Carina Nebula

We propose an H-alpha ACS imaging survey covering 540 square arcminutes of the Carina Nebula, including an unbiased survey of the bright core, and several prominent dust pillars in the rich southern region of the nebula. Carina provides an important link between well-studied nearby H II regions like Orion, and more distant mini-starbusts like 30 Doradus. CVZ orbits will allow extremely efficient use of HST to map a large area of this complex and important region — more than 95 percent of the proposed survey will be observed by HST for the first time. This survey will provide a complete census of microjets, proplyds, and silhouette disks with diameters as small as 200 AU, enough to spatially resolve disks like those in Orion, and will provide the first catalog of outflows {jets} from embedded low-mass stars, thin filamentary shocks, and wind-wind collisions in Carina. An accurate census of these phenomena is needed to characterize the star formation activity and gas dynamics as a function of position in the nebula, and to determine if models for protoplanetary disk evaporation from Orion are applicable in more extreme regions. Our previous ground-based optical and IR surveys have already revealed dozens of candidates for this type of activity — but this is just the tip of the iceberg. Our proposed HST/ACS survey promises to be a bonanza for understanding ongoing low-mass star formation influenced by extremely high-mass stars.


ACS CCDs daily monitor – Cycle 13 – Part 2

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 program will be for the entire lifetime of ACS.

NIC1/NIC2/NIC3 10381

Photometric Stability

This NICMOS calibration proposal carries out photometric monitoring observations during Cycle 13. The format of the program is identical to that of the Cycle 12 program 9995

NIC1/NIC2/NIC3 10380

Cycle 13 NICMOS dark current, shading profile, and read noise monitoring program

The purpose of this proposal is to monitor the dark current, read noise, and shading profile for all three NICMOS detectors throughout the duration of Cycle 13. This proposal is an essentially unchanged continuation of PID 9993 which cover the duration of Cycle 12.


CCD Hot Pixel Annealing

Hot pixel annealing will continue to be performed once every 4 weeks. The CCD TECs will be turned off and heaters will be activated to bring the detector temperatures to about +20C. This state will be held for approximately 12 hours, after which the heaters are turned off, the TECs turned on, and the CCDs returned to normal operating condition. To assess the effectiveness of the annealing, a bias and four dark images will be taken before and after the annealing procedure for both WFC and HRC. The HRC darks are taken in parallel with the WFC darks. The charge transfer efficiency {CTE} of the ACS CCD detectors declines as damage due to on-orbit radiation exposure accumulates. This degradation has been closely monitored at regular intervals, because it is likely to determine the useful lifetime of the CCDs. We will now combine the annealling activity with the charge transfer efficiency monitoring and also merge into the routine dark image collection. To this end, the CTE monitoring exposures have been moved into this proposal . All the data for this program is acquired using internal targets {lamps} only, so all of the exposures should be taken during Earth occultation time {but not during SAA passages}. This program emulates the ACS pre-flight ground calibration and post-launch SMOV testing {program 8948}, so that results from each epoch can be directly compared. Extended Pixel Edge Response {EPER} and First Pixel Response {FPR} data will be obtained over a range of signal levels for both the Wide Field Channel {WFC}, and the High Resolution Channel {HRC}.


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


9942 – GSacq (1,2,1) results in Fine Lock Backup @253/0536z GSacq(1,2,1) scheduled at 253/05:32:36 resulted in fine lock backup 2,0,2) due to scan step limit exceeded on FGS 1. OBAD#1 showed values of V1=101.90 V2=-65.70 V3=154.12 RSS=196.09 OBAD#2 showed values of 1=-0.79 V2=-3.15 V3=0.69 RSS=3.32

9943 – Gsacq(1,2,1) was not attempted @253/0718z GSacq(1,2,1) scheduled at 253/07:17:49 was not attempted. We received at ESB message 1806 ( open loop timer expired) at 07:13:38 which caused the transition from T2G to M2G.

9944 – SG2BDC (Gyro 2 Bad Disp Ct) Out of Limits @253/1240z At 2005.253/12:40:22 SG2BDC (Gyro 2 Bad Disp Ct) flagged Red Hi. Mnemonic limit is set at 0. Occured just prior to OBAD scheduled @ 253/12:41:14, during orbit day, no SAA events, and no maneuvers taking place. Historical request showed count of one (1) at the time indicated. Notified on-call PCS SE.


17536-1 – Qcl Copy for 252/11:19:59 OBAD (First steps executed @252/1127z

17538-0 – GenSlew for Proposal 10487 – Slot4 @252/1601z

17539-0 – GenSlew for Proposal 10487 – Slot5 @252/1602z


                     SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS Gsacq              34             33        253/0718z 
FGS Reacq              10             10
OBAD with Maneuver     77             77


Operations Request 17536-1 for T3 Attitude Corrections was completed successfully at 252/11:27:12.

At 252/11:19:30, the macro to copy the Command Generator QcI to the Final QcI was executed. The OBAD w/maneuver at 252/11:19:59 was successful and the read-only flags were restored to “read-only” at 252/11:27:12. The subsequent guide star acquisition at 252/11:41:47 was successful.

SpaceRef staff editor.