Status Report

NASA Hubble Space Telescope Daily Report #4671

By SpaceRef Editor
August 11, 2008
Filed under , ,


Continuing to collect World Class Science

PERIOD COVERED: 5am August 8 – 5am August 11, 2008 (DOY 221/0900z-224/0900z)


NIC1/NIC2/NIC3 8795

NICMOS Post-SAA Calibration – CR Persistence Part 6

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.

WFPC2 11807

Hubble WFPC2 Imaging of NGC 2074 in the Large Magellanic Cloud

We propose HST WFPC2 observations of the diffuse nebula NGC 2074 (which is possibly a SNR) in the LMC. We will exploit the spatial resolution provided by HST to image circumstellar ejecta of hot stars , where ground- based imaging is difficult, and cannot provide meaningful spatial information. The distribution of the ionized gas and dust will allow us to determine the morphology of the circumstellar nebulae. In addition, the image promises to be quite spectacular, endowing it with great outreach potential.

WFPC2 11804

WFPC2 Closeout Calibration — CTE Effects on Standard Star

Observations of the primary standard star GRW+70D5824 are made at several different places on the CCD to directly estimate the impact of CTE. All four CCDs are evaluated. Filters F170W and F555W are used to evaluate the effects of background and different PSF shapes / sizes.

WFPC2 11796

WFPC2 Cycle 16 Decontaminations and Associated Observations

This proposal is for the WFPC2 decons. Also included are instrument monitors tied to decons: photometric stability check, focus monitor, pre- and post-decon internals (bias, intflats, kspots, & darks), UV throughput check, VISFLAT sweep, and internal UV flat check.

NIC2 11548

NICMOS Imaging of Protostars in the Orion A Cloud: The Role of Environment in Star Formation

We propose NICMOS observations of a sample of 252 protostars identified in the Orion A cloud with the Spitzer Space Telescope. These observations will image the scattered light escaping the protostellar envelopes, providing information on the shapes of outflow cavities, the inclinations of the protostars, and the overall morphologies of the envelopes. In addition, we ask for Spitzer time to obtain 55-95 micron spectra of 75 of the protostars. Combining these new data with existing 3.6 to 70 micron photometry and forthcoming 5-40 micron spectra measured with the Spitzer Space Telescope, we will determine the physical properties of the protostars such as envelope density, luminosity, infall rate, and outflow cavity opening angle. By examining how these properties vary with stellar density (i.e. clusters vs groups vs isolation) and the properties of the surrounding molecular cloud; we can directly measure how the surrounding environment influences protostellar evolution, and consequently, the formation of stars and planetary systems. Ultimately, this data will guide the development of a theory of protostellar evolution.

NIC3 11334

NICMOS Cycle 16 Spectrophotometry

Observation of the three primary WD flux standards must be repeated to refine the NICMOS absolute calibration and monitor for sensitivity degradation. So far, NICMOS grism spectrophotometry is available for only ~16 stars with good STIS spectra at shorter wavelengths. There are more in the HST CALSPEC standard star data base with good STIS spectra that would also become precise IR standards with NICMOS absolute SED measurements. Monitoring the crucial three very red stars (M, L, T) for variability and better S/N in the IR. Apparent variability was discovered at shorter wavelengths during the ACS cross-calibration work that revealed a ~2% discrepancy of the cool star fluxes with respect to the hot primary WD standards. About a third of these stars are bright enough to do in one orbit, the rest require 2 orbits.

NIC1/NIC2/NIC3 11318

NICMOS Cycle 16 Multiaccum Darks

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 16. This proposal is a slightly modified version of proposal 10380 of cycle 13 and 9993 of cycle12 and is the same as Cycle 15. Covers the period from April 08 to November 08 (inclusive).

WFPC2 11227

The Orbital Period for an Ultraluminous X-ray Source in NGC1313

The ultraluminous X-ray sources {ULXs} are extragalactic point sources with luminosities that exceed the Eddington luminosity for conventional stellar-mass black holes by factors of 10 – 100. It has been hotly debated whether the ULXs are just common stellar-mass black hole sources with beamed emission or whether they are sub-Eddington sources that are powered by the long-sought intermediate mass black holes {IMBH}. To firmly decide this question, one must obtain dynamical mass measurements through photometric and spectroscopic monitoring of the secondaries of these system. The crucial first step is to establish the orbital period of a ULX, and arguably the best way to achieve this goal is by monitoring its ellipsoidal light curve. The extreme ULX NGC1313 X-2 provides an outstanding target for an orbital period determination because its relatively bright optical counterpart {V = 23.5} showed a 15% variation between two HST observations separated by three months. This level of variability is consistent with that expected for a tidally distorted secondary star. Here we propose a set of 20 imaging observations with HST/WFPC2 to define the orbital period. This would be the first photometric measurement of the orbital period of a ULX binary. Subsequently, we will propose to obtain spectroscopic observations to obtain its radial velocity amplitude and thereby a dynamical estimate of its mass.

WFPC2 11222

Direct Detection and Mapping of Star Forming Regions in Nearby, Luminous Quasars

We propose to carry out narrow-band emission line imaging observations of 8 quasars at z=0.05-0.15 with the WFPC2 ramp filters and with the NICMOS narrow-band filters. We will obtain images in the [O II], [O III], H-beta, and Pa-alpha emission line bands to carry out a series of diagnostic tests aimed at detecting and mapping out star-forming regions in the quasar host galaxies. This direct detection of star-forming regions will confirm indirect indications for star formation in quasar host galaxies. It will provide a crucial test for models of quasar and galaxy evolution, that predict the co-existence of starbursts and “monsters” and will solve the puzzle of why different indicators of star formation give contradictory results. A secondary science goal is to assess suggested correlations between quasar luminosity and the size of the narrow-line region.

WFPC2 11218

Snapshot Survey for Planetary Nebulae in Globular Clusters of the Local Group

Planetary nebulae {PNe} in globular clusters {GCs} raise a number of interesting issues related to stellar and galactic evolution. The number of PNe known in Milky Way GCs, 4, is surprisingly low if one assumes that all stars pass through a PN stage. However, it is likely that the remnants of stars now evolving in Galactic GCs leave the AGB so slowly that any ejected nebula dissipates long before the star becomes hot enough to ionize it. Thus there should not be ANY PNe in Milky Way GCs–but there are four! It has been suggested that these PNe are the result of mergers of binary stars within GCs, i.e., that they are descendants of blue stragglers. The frequency of occurrence of PNe in external galaxies poses more questions, because it shows a range of almost an order of magnitude. I propose a Snapshot survey aimed at discovering PNe in the GC systems of Local Group galaxies more distant than the Magellanic Clouds. These clusters, some of which may be much younger than their counterparts in the Milky Way, might contain many more PNe than those of our own galaxy. I will use the standard technique of emission-line and continuum imaging, which easily discloses PNe.

WFPC2 11203

A Search for Circumstellar Disks and Planetary-Mass Companions around Brown Dwarfs in Taurus

During a 1-orbit program in Cycle 14, we used WFPC2 to obtain the first direct image of a circumstellar disk around a brown dwarf. These data have provided fundamental new constraints on the formation process of brown dwarfs and the properties of their disks. To search for additional direct detections of disks around brown dwarfs and to search for planetary-mass companions to these objects, we propose a WFPC2 survey of 32 brown dwarfs in the Taurus star-forming region.

WFPC2 11202

The Structure of Early-type Galaxies: 0.1-100 Effective Radii

The structure, formation and evolution of early-type galaxies is still largely an open problem in cosmology: how does the Universe evolve from large linear scales dominated by dark matter to the highly non-linear scales of galaxies, where baryons and dark matter both play important, interacting, roles? To understand the complex physical processes involved in their formation scenario, and why they have the tight scaling relations that we observe today {e.g. the Fundamental Plane}, it is critically important not only to understand their stellar structure, but also their dark-matter distribution from the smallest to the largest scales. Over the last three years the SLACS collaboration has developed a toolbox to tackle these issues in a unique and encompassing way by combining new non-parametric strong lensing techniques, stellar dynamics, and most recently weak gravitational lensing, with high-quality Hubble Space Telescope imaging and VLT/Keck spectroscopic data of early-type lens systems. This allows us to break degeneracies that are inherent to each of these techniques separately and probe the mass structure of early-type galaxies from 0.1 to 100 effective radii. The large dynamic range to which lensing is sensitive allows us both to probe the clumpy substructure of these galaxies, as well as their low-density outer haloes. These methods have convincingly been demonstrated, by our team, using smaller pilot-samples of SLACS lens systems with HST data. In this proposal, we request observing time with WFPC2 and NICMOS to observe 53 strong lens systems from SLACS, to obtain complete multi-color imaging for each system. This would bring the total number of SLACS lens systems to 87 with completed HST imaging and effectively doubles the known number of galaxy-scale strong lenses. The deep HST images enable us to fully exploit our new techniques, beat down low-number statistics, and probe the structure and evolution of early- type galaxies, not only with a uniform data-set an order of magnitude larger than what is available now, but also with a fully coherent and self-consistent methodological approach!

NIC2 11197

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 that 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 Phillip’s relation over cosmic time. High signal-to-noise measurements of 16 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. In Cycle 15 we obtained NICMOS photometry of 8 ESSENCE supernovae and are awaiting template observations to place them on the IR Hubble diagram. Here we request another 8 supernovae be studied in the final season of the ESSENCE search. 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.

NIC1/NIC2 11172

Defining Classes of Long Period Variable Stars in M31

We propose a thrifty but information-packed investigation {1440 exposures total} with NICMOS F205W, F160W and F110W providing crucial information about Long Period Variables in M31, at a level of detail that has recently allowed the discovery of new variable star classes in the Magellanic Clouds, a very different stellar population. These observations are buttressed by an extensive map of the same fields with ACS and WFPC2 exposures in F555W and F814W, and a massive ground-based imaging patrol producing well-sampled light curves for more than 400,000 variable stars. Our primary goal is to collect sufficient NIR data in order to analyze and classify the huge number of long-period variables in our catalog {see below} through Period-Luminosity {P/L} diagrams. We will produce accurate P/L diagrams for both the bulge and a progression of locations throughout the disk of M31. These diagrams will be similar in quality to those currently in the Magellanic Clouds, with their lower metallicity, radically different star formation history, and larger spread in distance to the variables. M31 offers an excellent chance to study more typical disk populations, in a manner which might be extended to more distant galaxies where such variables are still visible, probing a much more evenly spread progenitor age distribution than cepheids {and perhaps useful as a distance scale alternative or cross-check}. Our data will also provide a massive and unique color-magnitude dataset, and allow us to confirm the microlensing nature of a large sample of candidate lensed sources in M31. We expect that this study will produce several important results, among them a better understanding of P/L and P/L-color relations for pulsating variables which are essential to the extragalactic distance ladder, will view these variables at a common distance over a range of metallicities {eliminating the distance- error vs. metallicity ambiguity between the LMC and SMC}, allow further insight into possible faint-variable mass-loss for higher metallicities, and in general produce a sample more typical of giant disk galaxies predominant in many studies.

ACS/SBC 11151

Evaluating the Role of Photoevaporation of Protoplanetary Disk Dispersal

Emission produced by accretion onto the central star leads to photoevaporation, which may play a fundamental role in disk dispersal. Models of disk photoevaporation by the central star are challenged by two potential problems: the emission produced by accretion will be substantially weaker for low-mass stars, and photoevaporation must continue as accretion slows. Existing FUV spectra of CTTSs are biased to solar-mass stars with high accretion rates, and are therefore insufficient to address these problems. We propose use HST/ACS SBC PR130L to obtain FUV spectra of WTTSs and of CTTSs at low masses and mass accretion rates to provide crucial data to evaluate photoevaporation models. We will estimate the FUV and EUV luminosities of low-mass CTTSs with small mass accretion rates, CTTSs with transition disks and slowed accretion, and of magnetically-active WTTSs.

NIC3 11147

The Origin of Diffuse UV Light from Spiral Disks

The ultraviolet light from galaxies has been used as a beacon for tracing the cosmic star formation history of the Universe, yet we have an incomplete understanding of many characteristics of this light. Most of the UV emission from nearby, normal star–forming galaxies is unresolved and “diffuse”, and GALEX has shown that in spiral disks it permeates the inter-arm regions. The nature of this diffuse inter- arm component is under debate. Recent results suggest that it may arise from non- ionizing UV photons which originate in star forming regions in the spiral arms, travel in the plane of the galaxy, and then scatter off of diffusely distributed cold dust grains. Alternatively, an in-situ, unresolved stellar population could produce the observed inter-arm UV emission. This project seeks to establish which of the two competing scenarios is responsible for the bulk of this diffuse emission. We propose to use HST’s UV imaging capability (ACS/SBC) to obtain deep observations of selected fields in the nearby spiral galaxy M101, for which available (low angular resolution) data favor the ‘scattered light’ scenario. Our observations are designed to detect any faint, UV-luminous stellar population down to main sequence B5 stars. With these data, we will establish the nature of the bulk of the diffuse UV light in this spiral galaxy by: (i) quantifying the contribution from dust-scattered light; (ii) measuring the contribution to the ubiquitous diffuse ionized medium from in- situ ionizing stars; and (iii) providing constraints on the observed stellar mass function in the field. Only HST has the UV sensitivity and angular resolution to discriminate in-situ stellar populations from scattered light. The ultimate goal of this project is to re-‘calibrate’ the UV emission as a star formation rate indicator, which will need to account for any scattered component.

NIC1 11136

Resolving Ultracool Astrophysics with Brown Dwarf Binaries

We propose to obtain resolved far-red and near-IR photometry of 13 brown dwarf binaries with HST/NICMOS in order to study one of the long-standing puzzles in ultracool astrophysics, namely the rapid change in spectra from L dwarfs to T dwarfs at nearly constant effective temperature (a.k.a. the “L/T transition”). While many nearby brown dwarfs have been studied, use of such samples is inevitably hindered by the unknown ages, masses, and metallicities of the field population. Characterization of resolved ultracool binaries is a promising avenue for addressing this problem, by providing coeval systems of the same composition with comparable masses and temperatures. Our proposed HST/NICMOS (0.9-1.6 micron) observations will be combined with longer wavelength ground-based photometry and spectroscopy from Keck laser guide star adaptive optics. The resulting multiband (0.9-2.5 micron) dataset will be a unique resource for measuring the evolution of spectral energy distributions across the L/T transition, to test state-of-the-art atmospheric models, and to determine the physical process(es) that dominate the L/T transition. Understanding the L/T transition is important not only for testing brown dwarf atmospheres, but also provides a key pathway for understanding the same physical effects, namely the formation and removal of clouds, in the atmospheres of the extrasolar planets.

WFPC2 11134

WFPC2 Tidal Tail Survey: Probing Star Cluster Formation on the Edge

The spectacular HST images of the interiors of merging galaxies such as the Antennae and NGC 7252 have revealed rich and diverse populations of star clusters created over the course of the interaction. Intriguingly, our WFPC2 study of tidal tails in these and other interacting pairs has shown that star cluster birth in the tails does not follow a similarly straightforward evolution. In fact, cluster formation in these relatively sparse environments is not guaranteed — only one of six tails in our initial study showed evidence for a significant population of young star clusters. The tail environment thus offers the opportunity to probe star cluster formation on the edge of the physical parameter space {e.g., of stellar and gas mass, density, and pressure} that permits it to occur. We propose to significantly extend our pilot sample of optically bright, gas-rich tidal tails by a factor of 4 in number to include a more diverse population of tails, encompassing major and minor mergers, gas-rich and gas-poor tails, as well as early, late, and merged interaction stages. With 21 orbits of HST WFPC2 imaging in the F606W and F814W filters, we can identify, roughly age-date, and measure sizes of star clusters to determine what physical parameters affect star cluster formation. WFPC2 imaging has been used effectively in our initial study of four mergers, and it will be possible in this program to reach similar limits of Mv=-8.5 for each of 16 more tails. With the much larger sample we expect to isolate which factors, such as merger stage, HI content, and merger mass ratio, drive the formation of star clusters.

ACS/SBC 11110

Searching for Lyman Apha Emission from FUSE Lyman Continuum Candidates

We have recently been granted time on FUSE to characterize the escape fraction of hydrogen Lyman continuum (Lyc) photons from a morphologically diverse set of star forming galaxies. The FUSE program is designed to provide ~ 5 sigma detections of Lyc photons emitted from star forming galaxies with escape fractions ~5%. With this proposal we seek hydrogen Lyman alpha (Lya) observations of a representative subset of the FUSE program targets to constrain the observational relationship between Lyc, Lya, and hydrogen Balmer line emission in these systems. Such observations explore the detailed balance between the simple optically thin (Case A) and optically thick (Case B) limits in recombination theory. The ultimate goal of this program is to quantify the relationship between escaping Lya and Lyc emission and the first structures that form in the early universe.

NIC2 11101

The Relevance of Mergers for Fueling AGNs: Answers from QSO Host Galaxies

The majority of QSOs are known to reside in centers of galaxies that look like ellipticals. Numerical simulations have shown that remnants of galaxy mergers often closely resemble elliptical galaxies. However, it is still strongly debated whether the majority of QSO host galaxies are indeed the result of relatively recent mergers or whether they are completely analogous to inactive ellipticals to which nothing interesting has happened recently. To address this question, we recently obtained deep HST ACS images for five QSO host galaxies that were classified morphologically as ellipticals {GO-10421}. This pilot study revealed striking signs of tidal interactions such as ripples, tidal tails, and warped disks that were not detected in previous studies. Our observations show that at least some “elliptical” QSO host galaxies are the products of relatively recent merger events rather than old galaxies formed at high redshift. However, the question remains whether the host galaxies of classical QSOs are truly distinct from inactive ellipticals and whether there is a connection between the merger events we detect and the current nuclear activity. We must therefore place our results into a larger statistical context. We are currently conducting an HST archival study of inactive elliptical galaxies {AR- 10941} to form a control sample. We now propose to obtain deep HST/WFPC2 images of 13 QSOs whose host galaxies are classified as normal ellipticals. Comparing the results for both samples will help us determine whether classical QSOs reside in normal elliptical galaxies or not. Our recent pilot study of five QSOs indicates that we can expect exciting results and deep insights into the host galaxy morphology also for this larger sample of QSOs. A statistically meaningful sample will help us determine the true fraction of QSO hosts that suffered strong tidal interactions and thus, whether a merger is indeed a requirement to trigger nuclear activity in the most luminous AGNs. In addition to our primary science observations with WFPC2, we will obtain NICMOS3 parallel observations with the overall goal to select and characterize galaxy populations at high redshifts. The imaging will be among the deepest NICMOS images: These NICMOS images are expected to go to a limit a little over 1 magnitude brighter than HUDF-NICMOS data, but over 13 widely separated fields, with a total area about 1.5 times larger than HUDF- NICMOS. This separation means that the survey will tend to average out effects of cosmic variance. The NICMOS3 images will have sufficient resolution for an initial characterization of galaxy morphologies, which is currently one of the most active and promising areas in approaching the problem of the formation of the first massive galaxies. The depth and area coverage of our proposed NICMOS observations will also allow a careful study of the mass function of galaxies at these redshifts. This provides a large and unbiased sample, selected in terms of stellar mass and unaffected by cosmic variance, to study the on-going star formation activity as a function of mass {i.e. integrated star formation} at this very important epoch.


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


11428 – FGS 1 Loss of Lock

Following a successful GSACQ(1,2,1) at 222/13:10:37, loss of lock was observed at 13:30:47 with QF1STOPF and QSTOP flags set and take data flag down.

Observation affected: WFPC 100 to 105, proposal 11101, NICMOS 135, proposal #08795.

11429 – GSACQ(2,0,2) failed, scan step limit exceeded on FGS 2

GSACQ(2,0,2) at 223/18:10:27 failed to RGA hold due to scan step limit exceeded on FGS 2. No 486 ESB or NSSCI status buffer messages were received, #44 commands did not update from their values prior to LOS. QF2SSLEX and QF2STOPF stop flags were received at 18:14:34.

Observations affected: NICMOS 173 to 175, proposal 11548.

11430 – GSACQ(1,0,1) failed

GSACQ(1,0,1) at 223/19:46:26 failed to RGA control with QF1STOPF and QSTOP flags set at 19:51:10. Two 486 ESB “1805” messages (T2G_MOVING_TARGET_DETECTED) were received at 19:52:51.

Observations affected: NICMOS 177 to 178, proposal 11548.



                       SCHEDULED      SUCCESSFUL      FAILURE TIMES

FGS GSacq               27                   25
FGS REacq               14                   14
OBAD with Maneuver      82                   82
LOSS of LOCK                                           @222/1331z


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