NASA Hubble Space Telescope Daily Report #4448
Notice: Due to the conversion of some ACS WFC or HRC observations into WFPC2, or NICMOS observations after the loss of ACS CCD science capability in January, there may be an occasional discrepancy between a proposal’s listed (and correct) instrument usage and the abstract that follows it.
HUBBLE SPACE TELESCOPE DAILY REPORT # 4448
– Continuing to collect World Class Science
PERIOD COVERED: UT September 14, 15 & 16, 2007 (DOY 257, 258 & 259)
OBSERVATIONS SCHEDULED
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=3Ddate/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 DARKs. 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/SBC 11225
The Wavelength Dependence of Accretion Disk Structure
We can now routinely measure the size of quasar accretion disks using gravitational microlensing of lensed quasars. The next step to testing accretion disk models is to measure the size of accretion disks as a function of wavelength, particularly at the UV and X-ray wavelengths that should probe the inner, strong gravity regime. Here we focus on two four-image quasar lenses that already have optical {R band} and X-ray size measurements using microlensing. We will combine the HST observations with ground-based monitoring to measure the disk size as a function of wavelength from the near-IR to the UV. We require HST to measure the image flux ratios in the ultraviolet continuum near the Lyman limit of the quasars. The selected targets have estimated black hole masses that differ by an order of magnitude, and we should find wavelength scalings for the two systems that are very different because the Blue/UV wavelengths should correspond to parts of the disk near the inner edge for the high mass system but not in the low mass system. The results will be modeled using a combination of simple thin disk models and complete relativistic disk models. While requiring only 18 orbits, success for one system requires observations in both Cycles 16 and 17.
WFPC2 11217
The Light Echoes around V838 Monocerotis
V838 Monocerotis, which burst upon the astronomical scene in early 2002, is a completely unanticipated new object. It underwent a large-amplitude and very luminous outburst, during which its spectrum remained that of an extremely cool supergiant. A rapidly evolving set of light echoes around V838 Mon was discovered soon after the outburst, and quickly became the most spectacular display of the phenomenon ever seen. These light echoes provide the means to accomplish three unique types of measurements based on continued HST imaging during the event: {1} Study effects of MHD turbulence at high resolution and in 3 dimensions; {2} Construct the first unambiguous and fully 3-D map of a circumstellar dust envelope in the Milky Way; {3} Study dust physics in a unique setting where the spectrum and light curve of the illumination, and the scattering angle, are unambiguously known. We have also used our HST data to determine the distance to V838 Mon through direct geometric techniques. Because of the extreme rarity of light echoes, this is almost certainly the only opportunity to achieve such results during the lifetime of HST. We propose two visits during Cycle 16, in order to continue the mapping of the circumstellar dust and to accomplish the other goals listed above.
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 11155
Dust Grain Evolution in Herbig Ae Stars: NICMOS Coronagraphic Imaging and Polarimetry
We propose to take advantage of the sensitive coronagraphic capabilities of NICMOS to obtain multiwavelength coronagraphic imaging and polarimetry of primordial dust disks around young intermediate-mass stars {Herbig Ae stars}, in order to advance our understanding of how dust grains are assembled into larger bodies. Because the polarization of scattered light is strongly dependent on scattering particle size and composition, coronagraphic imaging polarimetry with NICMOS provides a uniquely powerful tool for measuring grain properties in spatially resolved circumstellar disks. It is widely believed that planets form via the gradual accretion of planetesimals in gas-rich, dusty circumstellar disks, but the connection between this suspected process and the circumstellar disks that we can now observe around other stars remains very uncertain. Our proposed observations, together with powerful 3-D radiative transfer codes, will enable us to quantitatively determine dust grain properties as a function of location within disks, and thus to test whether dust grains around young stars are in fact growing in size during the putative planet-formation epoch. HST imaging polarimetry of Herbig Ae stars will complement and extend existing polarimetric studies of disks around lower-mass T Tauri stars and debris disks around older main-sequence stars. When combined with these previous studies, the proposed research will help us establish the influence of stellar mass on the growth of dust grains into larger planetesimals, and ultimately to planets. Our results will also let us calibrate models of the thermal emission from these disks, a critical need for validating the properties of more distant disks inferred on the basis of spectral information alone.
WFPC2 11128
Time Scales Of Bulge Formation In Nearby Galaxies
Traditionally, bulges are thought to fit well into galaxy formation models of hierarchical merging. However, it is now becoming well established that many bulges formed through internal, secular evolution of the disk rather than through mergers. We call these objects pseudobulges. Much is still unknown about pseudobulges, the most pressing questions being: How, exactly, do they build up their mass? How long does it take? And, how many exist? We are after an answer to these questions. If pseudobulges form and evolve over longer periods than the time between mergers, then a significant population of pseudobulges is hard to explain within current galaxy formation theories. A pseudobulge indicates that a galaxy has most likely not undergone a major merger since the formation of the disk. The ages of pseudobulges give us an estimate for the time scale of this quiescent evolution. We propose to use 24 orbits of HST time to complete UBVIH imaging on a sample of 33 nearby galaxies that we have observed with Spitzer in the mid-IR. These data will be used to measure spatially resolved stellar population parameters {mean stellar age, metallicity, and star formation history}; comparing ages to star formation rates allows us to accurately constrain the time scale of pseudobulge formation. Our sample of bulges includes both pseudo- and classical bulges, and evenly samples barred and unbarred galaxies. Most of our sample is imaged, 13 have complete UBVIH coverage; we merely ask to complete missing observations so that we may construct a uniform sample for studying bulge formation. We also wish to compare the stellar population parameters to a variety of bulge and global galaxy properties including star formation rates, dynamics, internal bulge morphology, structure from bulge-disk decompositions, and gas content. Much of this data set is already or is being assembled. This will allow us to derive methods of pseudobulge identification that can be used to accurately count pseudobulges in large surveys. Aside from our own science goals, we will present this broad set of data to the community. Thus, we waive proprietary periods for all observations.
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.
NIC3 11080
Exploring the Scaling Laws of Star Formation
As a variety of surveys of the local and distant Universe are approaching a full census of galaxy populations, our attention needs to turn towards understanding and quantifying the physical mechanisms that trigger and regulate the large-scale star formation rates {SFRs} in galaxies.
WFPC2 11079
Treasury Imaging of Star Forming Regions in the Local Group: Complementing the GALEX and NOAO Surveys
We propose to use WFPC2 to image the most interesting star-forming regions in the Local Group galaxies, to resolve their young stellar populations. We will use a set of filters including F170W, which is critical to detect and characterize the most massive stars, to whose hot temperatures colors at longer wavelengths are not sensitive. WFPC2’s field of view ideally matches the typical size of the star-forming regions, and its spatial resolution allows us to measure individual stars, given the proximity of these galaxies. The resulting H-R diagrams will enable studies of star-formation properties in these regions, which cover largely differing metallicities {a factor of 17, compared to the factor of 4 explored so far} and characteristics. The results will further our understanding of the star-formation process, of the interplay between massive stars and environment, the properties of dust, and will provide the key to interpret integrated measurements of star-formation indicators {UV, IR, Halpha} available for several hundreds more distant galaxies. Our recent deep surveys of these galaxies with GALEX {FUV, NUV} and ground-based imaging {UBVRI, Halpha, [OIII] and [SII]} provided the identification of the most relevant SF sites. In addition to our scientific analysis, we will provide catalogs of HST photometry in 6 bands, matched corollary ground-based data, and UV, Halpha and IR integrated measurements of the associations, for comparison of integrated star-formation indices to the resolved populations. We envisage an EPO component.
NIC1/NIC2/NIC3 11060
NICMOS Photometric Stability Monitoring
This NICMOS calibration proposal carries out photometric monitoring observations during Cycle 15. The format is the same as the Cycle 14 version of the program {10725}, but a few modifications were made with respect to the Cycle 12 program 9995 and Cycle 13 program 10381. Provisions had to be made to adopt to 2-gyro mode {G191B2B was added as extra target to provide target visibility through most of the year}. Where before 4 or 7 dithers were made in a filter before we moved to the next filter, now we observe all filters at one position before moving to the next dither position. While the previous method was chosen to minimize the effect of persistence, we now realize that persistence may be connected to charge trapping and by moving through the filter such that the count rate increases, we reach equilibrium more quickly between charge being trapped and released. We have also increased exposure times where possible to reduce the charge trapping non- linearity effects.
WFPC2 11038
Narrow Band and Ramp Filter Closeout
These observations are to improve calibration of narrow band and ramp filters. We also test for changes in the filter properties during WFPC2’s 14 years on-board HST.
FGS 10928
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.
NIC3 10921
Tangential Velocities of Objects in the Orion Nebula and Locating the Embedded Outflow Sources.
The Orion Nebula is arguably the Rosetta Stone for studying a very young star cluster and how the radiation and outflowing plasma from its stars interact with ambient material. It has been the subject of numerous HST imaging studies, which means that there is good opportunity for determining tangential velocities by obtaining second epoch images during Cycle 15, which may be the last cycle for which the WFPC2 is available. These velocities in the plane-of-the-sky will allow us to determine the patterns of outflow from micro-jets smaller than the Solar System to jet driven shocks more than a parsec from their sources. Combined with radial velocities, we’ll obtain spatial velocities, which are critical to determining where the embedded sources are located that produce the numerous HH objects coming from the Orion-S and BN-KL regions. We’ll also be able to determine the physics that is operating in the LL Ori type of outflows {where a bipolar jet is being distorted by a slow wind coming from the nebula}. We will also be able to search for runaway stars caused by the disintegration of young multiple-star systems. All of this is possible because the long-time base of the WFPC2 and ACS observations allow a new level of astrometric precision to be obtained and to be done efficiently by making coordinated parallel observations with all images.
NIC1 10889
The Nature of the Halos and Thick Disks of Spiral Galaxies
We propose to resolve the extra-planar stellar populations of the thick disks and halos of seven nearby, massive, edge-on galaxies using ACS, NICMOS, and WFPC2 in parallel. These observations will provide accurate star counts and color-magnitude diagrams 1.5 magnitudes below the tip of the Red Giant Branch sampled along the two principal axes and one intermediate axis of each galaxy. We will measure the metallicity distribution functions and stellar density profiles from star counts down to very low average surface brightnesses, equivalent to ~32 V-mag per square arcsec. These observations will provide the definitive HST study of extra-planar stellar populations of spiral galaxies. Our targets cover a range in galaxy mass, luminosity, and morphology and as function of these galaxy properties we will provide: – The first systematic study of the radial and isophotal shapes of the diffuse stellar halos of spiral galaxies – The most detailed comparative study to date of thick disk morphologies and stellar populations – A comprehensive analysis of halo and thick disk metallicity distributions as a function of galaxy type and position within the galaxy. – A sensitive search for tidal streams – The first opportunity to directly relate globular cluster systems to their field stellar population We will use these fossil records of the galaxy assembly process preserved in the old stellar populations to test halo and thick disk formation models within the hierarchical galaxy formation scheme. We will test LambdaCDM predictions on sub-galactic scales, where it is difficult to test using CMB and galaxy redshift surveys, and where it faces its most serious difficulties.
ACS/SBC 10872
Lyman Continuum Emission in Galaxies at z=3D1.2
Lyman continuum photons produced in massive starbursts may have played a dominant role in the reionization of the Universe. Starbursts are important contributors to the ionizing metagalactic background at lower redshifts as well. However, their contribution to the background depends upon the fraction of ionizing radiation that escapes from the intrinsic opacity of galaxies below the Lyman limit. Current surveys suggest escape fractions of a few percent, up to 10%, with very few detections {as opposed to upper limits} having been reported. No detections have been reported in the epochs between z=3D0.1 and z=3D2. We propose to = measure the fraction of escaping Lyman continuum radiation from 15 luminous z~1.2 galaxies in the GOODS fields. Using the tremendous sensitivity of the ACS Solar- blind Channel, we will reach AB=3D30 mag., allowing us to detect an escape fraction of 1%. We will correlate the amount of escaping radiation with the photometric and morphological properties of the galaxies. A non-detection in all sources would imply that QSOs provide the overwhelming majority of ionizing radiation at z=3D1.3, and = it would strongly indicate that the properties of galaxies at higher redshift have to be significantly different for galaxies to dominate reionization. The deep FUV images will also be useful for extending the FUV study of other galaxies in the GOODS fields.
ACS/SBC 10864
Mapping the Gaseous Content of Protoplanetary and Young Planetary Systems with ACS
One of the key problems in planetary system formation is understanding how rapidly, and over what time interval Jovian planets can form. Dust in the protoplanetary disk is critical in planetesimal formation, but it is the gas which produces giant planets, and which is essential for their migration. However, compared to data on the circumstellar dust, information on the gas component is sparse, especially in the planet-formation zone. This severely limits our ability to put observational constraints on giant planet formation, except to note that the process must be largely complete by 12 Myr, given the paucity of Herbig Ae or classical T Tauri stars older than 10-12 Myr. In the FUV, photo-excited molecular hydrogen transitions have the requisite contrast to the stellar photosphere, accretion shock, and reflection nebulosity, and can be traced 50-100 AU from the exciting stars in both envelopes and outflow cavities and protoplanetary disks. Central disk cavities, an expected consequence of planet formation, larger than 0.1″ are directly detectable in HST FUV spectra, while smaller cavities may be detected by comparison with protoplanetary disks which are still accreting onto their stars. We propose augmenting existing HST coronagraphic imagery of 6 Herbig Fe and T Tauri disks with ACS Solar-Blind Channel Lyman alpha imagery and slitless spectroscopy simultaneously sampling the disk in molecular hydrogen and small-grain reflection nebulosity. These data will be used to quantify the amount of vertical stratification in these disks, to map the mass-loss geometry from the star, and to determine whether removal of molecular material precedes, lags, or is contemporary with clearing of the dust.
NIC2 10527
Imaging Scattered Light from Debris Disks Discovered by the Spitzer Space Telescope Around 20 Sun-like Stars
We propose to use the high contrast capability of the NICMOS coronagraph to image a sample of newly discovered circumstellar disks associated with sun-like stars. These systems were identified by their strong thermal infrared emission with the Spitzer Space Telescope as part of the Spitzer Legacy Science program titled, “The Formation and Evolution of Planetary Systems {FEPS}.” Modelling of the thermal excess emission in the form of spectral energy distributions alone cannot distinguish between narrowly confined high opacity disks and broadly distributed, low opacity disks. However, our proposed NICMOS observations can, by imaging the light scattered from this material. Even non- detections will place severe constraints on the disk geometry, ruling out models with high optical depth. Unlike previous disk imaging programs, our program contains a well defined sample of solar mass stars covering a range of ages from ~10Myrs to a few Gyrs, allowing us to study the evolution of disks from primordial to debris for the first time. These results will greatly improve our understanding of debris disks around Sun-like stars at stellar ages nearly 10x older than any previous investigation. Thus we will have fit a crucial piece into the puzzle concerning the formation and evolution of our own solar system.
NIC2 10487
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.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.
HSTARS:
10993 – REACQ(1,2,2) failed, scan step limit exceeded on FGS 1
REACQ(1,2,2) at 257/20:50:56 failed due to scan step limit exceeded on FGS 1 at 22:55:06. Initial GSACQ(1,2,2) at 21:17:23 was successful.
10994 – GSAcq(2,1,1) failed to RGA Hold (Gyro Control)
Upon acquisition of signal (AOS) at 260/01:50:01, the GSAcq(2,1,1) scheduled at 260/01:39:25 – 01:47:29 had failed to RGA Hold due to a Search Radius Limit Exceeded Error on FGS-2.
Pre-acquisition OBADs attitude correction values not available due to LOS. Post-acq OBAD/MAP has (RSS) value of 66.26 arcseconds.
Subsequent REacq(2,1,1) at 260/04:50:04 failed to RGA Hold due to a Search Radius Limit Exceeded Error on FGS-2. REacqs at 260/0314:51, 260/06:28:38 were successful.
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL
FGS GSacq 18 17
FGS REacq 24 22
OBAD with Maneuver 82 82
SIGNIFICANT EVENTS:
Flash Report: NICMOS Defocus Test
The 1st observation for the NICMOS on-orbit PAM defocus test was successfully completed Thursday. STScI has performed a quick-look analysis of the science data and they are happy with the initial results. A second flash report will be sent out after the second set of observations.
