Session 133. Cosmology with Large-Area Surveys
Invited, Wednesday, January 12, 2005, 3:40-5:10pm
- 133.02 The Large Synoptic Survey Telescope
- P.A. Pinto (Steward Observatory, University of Arizona)
The LSST is an 8.4 meter telescope with a ten square degree field and three gigapixel detector, backed up by a powerful data processing and archiving facility. Operating as a fully-automated survey, it will image the entire sky repeatedly and at a rapid pace, opening the time domain to astronomy by producing more than 20 terabytes of high-quality images per night. Rarely observed events will become commonplace, new and unanticipated events will be discovered, and the combination of LSST with contemporary space-based missions will provide powerful synergies. Adding the data accumulated over years of operation will provide multicolor maps of the entire sky to unprecedented depth, with every pixel tied to its own time history in the database. An "open data" project, it will have no proprietary scientific information or areas of study. The LSST will simultaneously address many of astronomy's fundamental problems, from planetary science to cosmology, and will open a window to new discoveries yet unknown. I will give an overview of the LSST project, the data to be obtained, and some of its principal science drivers and key science deliverables.
Poster, Wednesday, January 12, 2005, 9:20am-6:30pm, Exhibit Hall
- 108.01 The Large Synoptic Survey Telescope Science Requirements
- J. A. Tyson (University of California, Davis), LSST Team
The Large Synoptic Survey Telescope (LSST) is a wide-field telescope facility that will add a qualitatively new capability in astronomy and will address some of the most pressing open questions in astronomy and fundamental physics. The 8.4-meter telescope and 3 billion pixel camera covering ten square degrees will reach sky in less than 10 seconds in each of 5-6 optical bands. This is enabled by advances in microelectronics, software, and large optics fabrication. The unprecedented optical throughput drives LSST's ability to go faint-wide-fast. The LSST will produce time-lapse digital imaging of faint astronomical objects across the entire visible sky with good resolution.
For example, the LSST will provide unprecedented 3-dimensional maps of the mass distribution in the Universe, in addition to the traditional images of luminous stars and galaxies. These weak lensing data can be used to better understand the nature of Dark Energy. The LSST will also provide a comprehensive census of our solar system. By surveying deeply the entire accessible sky every few nights, the LSST will provide large samples of events which we now only rarely observe, and will create substantial potential for new discoveries. The LSST will produce the largest non-proprietary data set in the world.
Several key science drivers are representative of the LSST system capabilities: Precision Characterization of Dark Energy, Solar System Map, Optical Transients, and a map of our Galaxy and its environs. In addition to enabling all four of these major scientific initiatives, LSST will make it possible to pursue many other research programs. The community has suggested a number of exciting programs using these data, and the long-lived data archives of the LSST will have the astrometric and photometric precision needed to support entirely new research directions which will inevitably develop during the next several decades.
- 108.02 An Overview of the Large Synoptic Survey Telescope (LSST) System
- C.W. Stubbs (Harvard University), D. Sweeney (LSST Corp), J.A. Tyson
(UC Davis), LSST Collaboration
The Large Synoptic Survey Telescope will provide the astrophysics and astronomy communities with a leap in wide field survey capability. This paper will present a high-level overview of the project's design philosophy, structure, status and anticipated timeline. The LSST will be a community resource, with broad access to the data and no proprietary data witholding period. We encourage the community to think about they might exploit the LSST data, and in particular how frequent multiband imaging, to 24th magnitude, could enable innovative new science.
- 108.03 Optical Design for the 8.4m Large Synoptic Survey Telescope
- L. G. Seppala (LLNL), M. Liang, C. F. Claver (NOAO), J. Burge (U.
Arizona), K. Cook (LLNL/NOAO), L. Daggert (NOAO), S. Ellis (Photon Inc.), S.
M. Kahn (SLAC), V. Krabbendam (NOAO), D. Sweeney (LSST Inc./LLNL), C. Stubbs
(Harvard), D. Wittman, J. A. Tyson (UC Davis)
The proposed 8.4m Large Synoptic Survey Telescope (LSST) facility will digitally survey the entire visible sky. It will explore the nature of dark matter and dark energy, open the faint optical transient time window and catalog earth-crossing asteroids >300m in diameter. This concept was strongly endorsed by the three National Academy of Sciences reports: .Connecting Quarks with the Cosmos., "Astronomy and Astrophysics in the New Millennium" and .New Frontiers in the Solar System.. In response to these endorsements we present the design of a modified 8.4m Paul-Baker or Laux(1) telescope that expands the etendue ("A - Omega") product to >300m2deg2, a factor of >50 beyond any existing facility. This evolved telescope design has increased etendue to meet the demanding science requirements for the LSST and simplifications in the optical prescription to enhance manufacturability. The optical design delivers a 3.5-degree diameter field of view (9.62 deg2) with superb <0.2 arcsec FWHM images over 5 spectral bands covering 400-1000 nm. The flat focal surface has a plate scale of 51 microns/arcsec (f/1.25), chosen to match the 10 microns pixel size of a large 0.65m diameter mosaic digital detector. The f/1.14 primary can be made using polishing techniques and metrology methods pioneered at the University of Arizona Mirror Lab for the 8.4m f/1.1 Large Binocular Telescope primaries. The 3.4 m convex secondary is twice the size of the largest convex secondary yet manufactured; the 1.7 m MMT f/5 secondary. We show a fabrication and testing plan for this optic. The corrective camera optics are significantly simplified from earlier designs in that all refractive elements have spherical surfaces. In addition the 3 mirror telescope system delivers, without the camera corrector optics, a spherical wavefront on axis that greatly helps in initial assembly and alignment.
1. R. N. Wilson, "Reflecting Optical Telescopes I", Springer A&A Library, 2000, Chapter 3.6.5.
- 108.04 LSST Telescope Design
- V. Krabbendam, C.F. Claver, L. Daggert, J. Sebag, D.R. Neill, R. Gomez
(NOAO), J.H. Burge, R. Tessieries, W. Davison, B. Cuerden (U. Arizona)
The proposed Large Synoptic Survey Telescope (LSST) has an 8.4 meter aperture with a 3.5 degree diameter field of view and must meet the challenging cadence requirements necessary to perform the LSST survey mission. The telescope optical system is based on a Paul-Baker three element design with a single captured focus for the dedicated instrument. The large mirrors, 8.4 m diameter primary, 3.2 m secondary, and 5.0 m tertiary, and the large 65 cm diameter focal plane camera are supported by a rigid steel structure with active control of alignment and mirror support. Analysis has demonstrated that wavefront information taken at multiple field positions within the focal plane can be used unambiguously to control the alignment of all components and the optical figures of the three large mirrors. A significant challenge for the Telescope design is the slew and settle requirement of 3 degrees in 5 seconds with subsequent moves every 30 seconds. Previous structural and thermal studies have been used to refine the telescope design. The structure has been designed to exhibit a first structural mode of nearly 10 hz. fully loaded with the optical system, the camera and anticipated parasitic masses in place. The LSST telescope development continues in concert with the parallel development of all aspects of the entire LSST Project.
- 108.05 The Optical and Mechanical Design of the LSST Camera
- L.C. Hale (LLNL)
The LSST Camera requires: three large (1.6 m, 1.1 m and 0.73 m) refractive optics; five 0.78 m auto-changing color filters; a mechanical shutter with 0.76 m aperture; a tiled sensor array at focus spanning 0.64 m with 3.2e9 pixels and their associated electrical devices with many thousands of interconnections; and various other items too numerous to mention. The optical elements require precise alignment and in some cases actuation such as focus adjustment. For example, the focal plane array, which operates at 180 K, must be flat to 10 µm P-V for any orientation of the telescope. Work has been underway to allocate space and package these items, devise workable concepts for the mechanisms, and design structural elements (e.g., optic mounts and housings) that can be manufactured precisely and adjusted as necessary to meet alignment and stability requirements. This poster presents work to date relating to the optical and mechanical design of the LSST camera.
- 108.06 Design Overview of the LSST Camera
- S. M. Kahn (SLAC), LSST Camera Team
The Large Synoptic Survey Telescope will be a large aperture, large field-of-view ground-based telescope operating in the visible band. It is designed to provide a synoptic survey of a major fraction of the sky in five color bands, on timescales ranging from minutes to days. The database generated by the LSST will be amenable to a wide variety of scientific analyses, ranging from searches for moving bodies in the solar system to the mapping of the dark matter distribution as a function of redshift through weak lensing.
The LSST camera will be the largest digital camera ever built. As such, its design presents a number of challenges. The field of view will be 3.5 degrees in diameter and will be sampled by a 3 billion pixel array of sensors. The entire array must be readout in under 2 s, which leads to demanding constraints on the sensor architecture and the readout electronics. In addition, given the fast optical beam (f 1.2), the build tolerances on the assembly and alignment of the focal plane are tight. The camera incorporates three very large refractive lenses, and an array of five large filters.
We will present an overview of the overall camera design, with an emphasis on key aspects of our development program. Parallel posters will discuss the details of the sensor development and of the opto-mechanical subsystems.
- 108.07 LSST Focal Plane and Detector Development
- J.C. Geary (Smithsonian Astrophysical Observatory), LSST Focal Plane
The LSST focal plane is the largest and most complex ever proposed for an astronomical instrument. The demands of the science to be done and the nature of the cadence and very wide field preclude the use of any existing imager, so a custom device must be developed. Both CCD and CMOS imagers are being considered. We present several background studies on the size, organization, imager characteristics, and packaging we intend to develop in order to populate and read out this giant imaging focal plane.
- 108.08 Independent Testing of Silicon PIN Detector Arrays for LSST
- D. F. Figer, M. Regan, E. Morse (STScI)
We report full detector characterization of Silicon PIN detector arrays for astronomical applications, with a special emphasis on their use for the Large Synoptic Survey Telescope (LSST). For the first time, we present measurements of dark current, read noise, linearity, persistence, quantum efficiency, well depth, and crosstalk. These properties are measured as functions of temperature (100-240K), wavelength, and read mode.
- 108.09 LSST Operational Cadence Simulation and Design
- K.H. Cook (Lawrence Livermore National Laboratory, National Optical
Astronomy Observatory), A. Saha, F. Pierfedrici, R. Allsman (National Optical
Astronomy Observatory), F. Delgado (Cerro Tololo Inter-Americal Observatory),
P.A. Pinto (Steward Observatory, University of Arizona)
With its unprecedented combination of collecting area and field of view, the LSST will image large areas of the sky frequently and to great depth. The cadence of these observations, the order in which different fields of view are observed in each color and the frequency with which they are revisited, will determine just how much sky will be covered, to what depth, and with what temporal sampling. This in turn will determine how useful LSST data will be to different investigations. The development of observing cadences is thus an important part of the LSST design process. A great many scientific programs require multiple, short exposures. As a result, detailed simulations of a decade of LSST operation demonstrate cadences which will satisfy a wide variety of scientific requirements simultaneously. They also demonstrate that there is surprisingly little conflict among the cadence demands of projects as diverse as whole-sky weak lens surveys, near-Earth asteroid, outer solar system, and supernova searches, and catching transients and characterizing variability on a wide variety of timescales. This shows that the LSST need not be .over-engineered. for any given project to be useful for doing many at the same time.
- 108.10 Analysis of the LSST image quality and effects seen through the atmosphere.
- C. F. Claver (NOAO), L. Rosenberg, S. Asztalos (LLNL), A. Becker (U.
Washington), J. R. Peterson (SLAC), D. Wittman, J. A. Tyson (UC Davis)
The 8.4m Large Synoptic Survey Telescope (LSST) is a new 3.5 degree field of view facility for the purpose of studying the nature of dark energy and matter along with the time varying nature of the optical universe. These science missions require precise knowledge and control of both the size and shape of the point spread function (PSF) delivered by the LSST. Here, we present analyses of three areas of image quality that are critical to the LSST: 1) the stability and angular correlation of the stellar PSF second moments as seen through a turbulent atmosphere typical of a high quality observing site and the baseline LSST optical design, 2) the ability to recover a synthetically induced gravitational shear signal on Hubble Deep Field data modified to mimic seeing and telescope aberrations, and 3) the effects of chromatic atmospheric refraction through the LSST filters on image shape and field registration. For the stability, angular correlation and chromatic refraction studies we compare our simulations with data obtained on modern new technology telescopes.
- 108.11 The LSST Data Processing Pipeline
- T. Axelrod (Steward Observatory), A. Connolly (U. Pittsburgh), Z.
Ivezic (U. Washington), J. Kantor (LSST Corp.), R. Lupton (Princeton Univ.),
R. Plante (NCSA), C. Stubbs (Harvard Univ.), D. Wittman (UC Davis)
In science observing mode, the LSST telescope and camera system will deliver a 2.8Gpixel image every 12 sec, a data rate of about 0.5 GByte/sec. The data processing pipeline must process this incoming data to produce the LSST's primary data products: the calibrated image archive; the detection catalog; the object catalog; and real-time alerts. Additionally, the quality of the incoming data must be rapidly assessed and fed back to the observatory control system. The pipeline must be flexible enough to allow addition of new processing stages and replacement of existing algorithms with improved ones, and must be robust in the face of the failure of hardware components such as disk drives. We present a preliminary design of the primary LSST data products, and of the data processing pipeline. The mapping of the pipeline onto computing hardware is discussed, along with estimates of the computational, I/O, and network bandwidths required.
- 108.12 LSST : Image Subtraction & Transient Detection Techniques
- A.C. Becker (U. Washington), A. Rest (CTIO), G. Miknaitis (U.
Washington), R.C. Smith (CTIO), C. Stubbs (Harvard)
The LSST will open a window to new classes of optical variability with its enterprising combination of depth, cadence, and sky coverage. The recent detection of faint, short timescale events suggests a wealth of phenomena occurring below the sky background and within the intervals when one returns to look at a given part of the sky. The LSST should detect thousands of these short timescale (< 1000 second) events per night; the transient detection pipeline must recognize events and disseminate alerts on a timescale short enough to enable followup. In addition, even a small misclassification allowance will result in a flood of false positives. This requires making use of current datasets to examine and classify the spectrum of astronomical variability. We describe here successes, failures, and lessons learned in difference imaging survey data from the Deep Lens, Sloan, SuperMACHO, ESSENCE, MCELS, and MACHO surveys. This includes the need to propagate noise and bad/saturated pixel masks through image convolution stages, which allows for the setting of correct detection thresholds. As well, variability pipelines must enable efficiency analysis for the calculation of event rates. Particular attention must be paid to the quality and stability of the system PSF, a requirement both for weak lensing science and for image subtraction techniques.
- 108.13 LSST and Astronomy in 2020
- A.S. Szalay (The Johns Hopkins University), T. Axelrod (University of
Arizona), J. Gray (Microsoft Research), R.H. Lupton (Princeton University), R.
Astronomy, like High Energy Physics, will bring GB/sec instruments on line within the next decade. As the example of the LHC shows, both technical and political forces imply a multi-tiered architecture in which all data is replicated for reliabilty and performance at several Tier-1 centers and extracts will be stored at many Tier-2 sites. This suggests a world-wide federation of about 10 peta-scale sites, each associated with an LSST-class instrument, interconnected with high-speed networking, forming the core of the Virtual Observatory. Unlike HEP, there is great interest in cross-correlating astronomy data from multiple instruments and telescopes. Users need easy access to data from all sites and some will want to build their own Tier-2 archives. The real-time nature of LSST (and probably other instruments) forces substantial archive and processing facilities co-located with the telescopes.
- 108.14 LSST and Cosmology: Supernovae and Cosmic Shear As Complementary Probes of Dark Energy
- L. Knox, A. Albrecht (UCD), Y.-S. Song (U Chicago), J. A. Tyson, D.
Weak lensing observations and supernova observations, combined with CMB observations, can both provide powerful constraints on dark energy properties. We find luminosity distances inferred from 2000 supernovae and large-scale (l &t; 1000) angular power spectra inferred from redshift-binned cosmic shear maps of half of the sky place complementary constraints on w0 and wa where w(z) = w0 + wa(a-1). Further, each set of observations can constrain higher-dimensional parameterizations of w(z) and constrains these in different ways. To quantify these abilities we consider eigenmodes of the w(z) error covariance matrix. The best-determined mode for each dataset has a standard deviation of about 0.03. This error rises quite slowly with increasing eigenmode number for the lensing data, reaching one only by the 7th mode. The eigenmode shapes also have interesting differences indicating that lensing is better at probing higher z while supernovae have their chief advantage at lower z.
- 108.15 Cosmology with Shear Selected Galaxy Clusters in LSST
- Z. Haiman, S. Wang (Columbia University & Brookhaven National
Labs), J. Khoury (Massachussetts Institute of Technology), J. F. Hennawi (UC
Berkeley), M. May (Brookhaven National Laboratory), D.N. Spergel (Princeton
University), J. A. Tyson (UC Davis)
LSST can identify over a hundred thousand galaxy clusters from weak lensing shear maps. This cluster sample will have statistically well-controlled mass estimates, and can place precise and robust constraints on cosmological parameters. We use a Fisher matrix approach to forecast the level of these constraints. We utilize cosmological N-body simulations to include the mass--shear relation, including its scatter and false projections, in our mock selection procedure. We find that by combining measurements of the evolution of cluster abundance, (dN/dz), and the spatial power spectrum, (P[k]), degeneracies among cosmological parameters, and also between cosmological parameters and systematic errors in the analysis, can be broken, yielding percent-level constraints on individual parameters. We focus on the evolution of the dark energy equation of state, dw/dz, and on a measurement of the neutrino mass. Combining the cluster data with CMB anisotropy measurements by Planck results in tighter constraints than possible from either experiment alone. The LSST cluster constraints are also complementary to those from LSST shear tomography and from SN studies.
- 108.16 Dark Energy Constraints from Lensing Tomography with LSST
- M. Takada (Tohoku U.), G. Bernstein (U Penn), W. Hu, D. Huterer (U
Chicago), B. Jain (U Penn), L. Knox, T. Tyson, D. Wittman (UC Davis)
We estimate the dark energy constraints achievable with a weak lensing survey that could be carried out with the Large Synoptic Survey Telescope. The technique used in our forecasts is lensing tomography with the auto and cross power spectra of the lensing shear. The power spectra depend on the growth function and angular diameter distances, which are both sensitive to the equation of state of dark energy. We include the effect of statistical and some systematic errors in our parameter forecasts for LSST. We identify the limiting systematics in being able to achieve the precision possible with a survey that covers a large fraction of the sky. In this study we use only the simplest lensing statistics; the constraints can be improved by using other complementary measures from the same dataset.
- 108.17 Weak Lensing Cosmology with LSST: Three-Point Shear Correlations
- M. Jarvis (U. Penn.), M. Takada (Tohoku U.), B. Jain, G. Bernstein (U.
We present an analysis of the three-point correlation function for weak lensing shear data. The shear three-point function is an independent measurement from the two-point function and thus adds to the total signal-to-noise obtainable from weak lensing data. Furthermore, it is shown that the constraints on cosmological parameters are along somewhat different degeneracies than the two-point function, so the combination of the two statistics is significantly more powerful than either one individually. Predictions of the constraining power are given for the proposed Large Synoptic Survey Telescope (LSST). We also present the actual marginal detection from the 75 square degree CTIO Lensing Survey and the E/B mode analysis of this dataset.
- 108.18 Supernova Science from a "Standard" LSST Cadence
- P. M. Garnavich (Notre Dame), R. C. Smith (CTIO), G. Miknaitis (U.
Wash.), C. W. Stubbs (CfA), N. B. Suntzeff, J. L. Preito (CTIO), P. Pinto (U.
The Large Synoptic Survey Telescope (LSST) will likely have several cadences, but one of the most general will be a cadence which covers a large portion of the available sky repeatedly in a limited number of filters in a short period of time, for example every 3 to 5 nights. Such a cadence is useful not only for identifying and tracking moving sources such as Near Earth Objects (NEOs), but also for identifying and following moderately long-term (month timescale) transient events such as supernovae. Given a sample general cadence, we investigate the number of type Ia and core-collapse supernovae likely to be discovered per year with LSST. We also investigate the resulting light curve and multi-filter sampling and how these data might best be used for studying SN rates, dark energy models and other science programs based on obtaining a large sample of supernovae.
- 108.19 Core Collapse Supernovae Observed with the LSST
- N. B. Suntzeff, R. C. Smith (CTIO/NOAO), M. Hamuy, M. M. Phillips
(LCO/OCIW), T. Tyson (U.C. Davis)
Attention has been focused on the opportunities for precision cosmology using Type Ia supernovae discovered and followed on the LSST. Core collapse supernovae - Types II and Ib/c - will also be discovered in equal numbers with a redshift limit of z~0.9 for a typical Type II. The LSST will be able to measure precise stellar death rates for massive stars to this redshift. Coupled with spectroscopy, distances can be measured using the "standard candle" method of Hamuy & Pinto (2002), and the Expanding Photosphere Method, allowing for an alternate method for measuring acceleration provided that the distance errors can be reduced from the present scatter of ~ 0.3mag. Finally, a large dataset of Type Ib/c supernovae can be used search for evidence of the class of supernovae responsible for GRBs, but whose axis of gamma emission is not aligned with the direction toward the Earth.
- 108.20 An LSST Deep Supernova Cosmology Program
- P.A. Pinto (Steward Observatory, University of Arizona), C.R. Smith
(National Optical Astronomy Observatory), P.M. Garnavich (Harvard-Smithsonian
Center for Astrophysics)
Because of its rapid observing cadence and large aperture, the LSST presents an ideal tool for studying type Ia supernovae and exploiting them as cosmological tools to redshifts near unity. We present a series of simulations of an observing program which would use the LSST in a different mode from it usual cadence. It would use a small fraction of each night to do a deep supernova search in a "staring mode," with 10-20 minutes total exposure per day on each of several ten-square-degree fields. Assuming no evolution in the type Ia supernova rate, a year-long campaign will yield close to 2000 supernovae in each field with a mean redshift near 0.75, with 60-100 photometric points per lightcurve in five photometric bands. We discuss the use of this dataset for constraining the dark energy equation of state and especially any variation it might have with direction on the sky.
- 108.21 LSST Solar System Survey ñ Cadence and Sky Coverage Requirements
- A. W. Harris (Space Science Institute), E. L. G. Bowell (Lowell
Solar system goals with LSST include cataloging small Potentially Hazardous Asteroids (PHAs), surveying the main belt asteroid population to extraordinarily small size (where radiation pressure effects may play a dominant role in sculpting orbital distributions and spin states), discovering comets far from the sun where their nuclear properties can be discerned without coma, and surveying the Centaur and Kuiper Belt populations. The present planned observing strategy is to "visit" each field (8 sq. deg. net non-overlapped) with two successive exposures of ~ 12 sec, reaching to at least V magnitude 24. An intra-night revisit time of not less than ~20 minutes will distinguish stationary transients from even very distant (~ 70 AU) solar system bodies. The nightly cadence should be two, or possibly 3, revisits spaced by about half an hour. In order to link observations and determine orbits, each sky area must be re-visited on two, or better 3, nights during a month, spaced by about 5 days. Formally, two visits on two nights (2/2) is sufficient for orbit determination, but 2/3, 3/2, or 3/3 cadences would yield detection threshold improvements nearly enough to offset the additional time taken, provide redundancy for missed detections, and result in better orbit determination. We therefore recommend the 2/3 cadence, or even 3/3 if possible. We have explored the efficiency of the PHA survey with less than all-sky coverage. It appears that covering a band of the ecliptic ±10° in latitude and ±120° in longitude from the opposition point, less a swath ±20° in galactic latitude through the ecliptic plane, is sufficient to achieve nearly "all-sky" efficiency of surveying, requiring only ~ 4,000 sq. deg. per month. However, much of this area must be imaged at air mass >1.5, unsuitable for some of the other scientific goals of LSST. It appears that a survey in r band only of < 2000 sq. deg. per month that must be reached at higher air mass, combined with coverage in g, r, and i filters done as a part of the astrophysical surveying, can meet the goals of the solar system survey.
- 108.22 Mapping the Solar System with LSST
- Z. Ivezic (University of Washington), M. Juric, R. Lupton (Princeton
University), A. Connolly, J. Kubica, A. Moore (University of Pittsburgh), A.
Harris (STScI), T. Bowell (Lowell Observatoy), G. Bernstein (University of
Pennsylvania), C. Stubbs (Harvard University), LSST Collaboration
The currently considered LSST cadence, based on two 10 sec exposures, may result in orbital parameters, light curves and accurate colors for over a million main-belt asteroids (MBA), and about 20,000 trans-Neptunian objects (TNO). Compared to the current state-of-the-art, this sample would represent a factor of 5 increase in the number of MBAs with known orbits, a factor of 20 increase in the number of MBAs with known orbits and accurate color measurements, and a factor of 100 increase in the number of MBAs with measured variability properties. The corresponding sample increase for TNOs is 10, 100, and 1000, respectively. The LSST MBA and TNO samples will enable detailed studies of the dynamical and chemical history of the solar system. For example, they will constrain the MBA size distribution for objects larger than 100 m, and TNO size distribution for objects larger than 100 km, their physical state through variability measurements (solid body vs. a rubble pile), as well as their surface chemistry through color measurements. A proposed deep TNO survey, based on 1 hour exposures, may result in a sample of about 100,000 TNOs, while spending only 10% of the LSST observing time. Such a deep TNO survey would be capable of discovering Sedna-like objects at distances beyond 150 AU, thereby increasing the observable Solar System volume by about a factor of 7. The increase in data volume associated with LSST asteroid science will present many computational challenges to how we might extract tracks and orbits of asteroids from the underlying clutter. Tree-based algorithms for multihypothesis testing of asteroid tracks can help solve these challenges by providing the necessary 1000-fold speed-ups over current approaches while recovering 95% of the underlying asteroid populations.
- 108.23 Estimating the Astrometric Accuracy of LSST
- D. Monet (USNO), I. Platais (JHU), LSST Team
Astrometry accuracy is an important component of the LSST Design Reference Mission. Indeed, LSST astrometry will deliver parallaxes, proper motion amplitudes, and perturbations at the milliarcsecond level (or better) for stars as faint as R=26. It is not too early to start developing the astrometric Requirements for the LSST design, creating a network of deep astrometric standards, and for simulating and designing the software pipeline. Among the more challenging problems involve dealing with the short exposure times, segmented focal plane, and atmospheric refraction. Astrometric accuracy must be maintained and quantified from the small scales (sub-pixel) to the largest (computing coordinates in the ICRS). Current plans will be discussed, and suggestions from potential users (needs, algorithms, architecture, etc.) will be solicited.
- 108.24 Multiple Dimensions of LSST Transient Detection: How do we detect things that go bump in the night that we have not yet thought of?
- W.T. Vestrand (LANL), A. Becker (Univ. of Washington), S. Perkins, J.
Theiler (LANL), J. A. Tyson (UC Davis), A. Rest, C. Smith (CTIO), C. Stubbs
(Harvard), N. B. Suntzeff (CTIO), P. R. Wozniak (LANL)
A salient challenge for the Large Synoptic Survey Telescope (LSST) is how to recognize important transients, in real time, in a scene full of normal variations. The data stream will simply be too large for efficient transient identification by human analysts. The broad continuum of properties for both extraneous artifacts and interesting transients make them difficult to deal with on a piecemeal basis with hard-wired code. Further, understanding of the time domain is too incomplete to predict confidently the properties of important changes. We examine the potential of modern Machine Learning (ML) techniques for solving this problem. In particular, we discuss the application of ML techniques for automated anomaly detection that can identify transients without an a priori description. Many anomalies will be instrumentation errors; automating their identification will allow prompt action to maintain LSST data quality. But some of the anomalies are likely to be things that go bump in the night that we have not yet thought of.
- 108.25 Science Education with the LSST
- S.H. Jacoby (LSSTC), L.M. Khandro, A.M. Larson (UW), D.W. McCarthy
(UA), S.M. Pompea (NOAO), M.M. Shara (AMNH)
LSST will create the first true celestial cinematography - a revolution in public access to the changing universe. The challenge will be to take advantage of the unique capabilities of the LSST while presenting the data in ways that are manageable, engaging, and supportive of national science education goals. To prepare for this opportunity for exploration, tools and displays will be developed using current deep-sky multi-color imaging data. Education professionals from LSST partners invite input from interested members of the community. Initial LSST science education priorities include: . Fostering authentic student-teacher research projects at all levels, . Exploring methods of visualizing the large and changing datasets in science centers, . Defining Web-based interfaces and tools for access and interaction with the data, . Delivering online instructional materials, and . Developing meaningful interactions between LSST scientists and the public.
- 108.26 Mapping the Milky Way and Intergalactic Space with LSST
- K. Olsen (CTIO/NOAO), Z. Ivezic (Univ. of Washington), D. Monet (USNO),
D. Zaritsky (Univ. of Arizona), M. Shara (American Museum of Natural History),
A. Saha (NOAO), LSST Collaboration
The LSST will produce an accurate multi-color digital map of half the sky down to V~26.5, while time-spaced sampling of each field will provide variability, proper motions, and parallax measurements for objects brighter than V~24. These photometric, astrometric, and variability data will enable the construction of a detailed and robust map of the Milky Way, allowing exploration of its star formation, chemical enrichment, and accretion histories on a grand scale. For example, the parallax data will allow a complete census of all the stars above the hydrogen-burning limit that are closer than 500 pc, and RR Lyrae stars will be detectable through their variability to a distance limit of 400 kpc. Accurate colors will allow the estimate of photometric distance, and hence the three-dimensional number density distribution, for over a billion main-sequence stars to a distance limit of 100 kpc, and proper motion measurements will provide strong constraints on their kinematics. The LSST will also be able to detect novae out to the Virgo and Fornax clusters, providing an abundant stellar tracer of intergalactic space out to large distances. The LSST Milky Way and nova maps will revolutionize our understanding of the Milky Way and of intergalactic space, and in turn will have a significant impact on the theories of galaxy formation and evolution.
- 108.27 Strong Lensing Studies with the LSST
- C. D. Fassnacht (UC Davis), P. J. Marshall, A. E. Baltz, R. D.
Blandford (KIPAC), P. L. Schechter (MIT), J. A. Tyson (UC Davis)
The LSST will obtain hundreds of images of 20,000 square degrees, integrating to 26.5 AB mag in each of 5-6 bands. Photometric redshifts will be available for the ~3 billion detected galaxies. The data set will provide deep multicolor photometry and variability monitoring. One of the many strengths of the LSST will be its ability to use strong gravitational lensing to study dark matter distributions on galaxy and cluster scales.
The unprecedented combination of depth and area will be exploited to find rare objects, such as clusters in which background sources are lensed into multiple images. By sampling the gravitational potential at several radii in these systems, the LSST imaging will allow accurate, high-angular resolution reconstructions of cluster mass distributions. Our simulations predict that the LSST dataset will provide at least an order of magnitude increase in the number of such systems known. Other rare lensed image configurations will provide important insights into cosmography and source astrophysics. These include multiply-imaged supernovae, multiple-plane lensing, and unusual strong lenses with higher-order catastrophes.
In addition to the rare objects that will be found in the LSST survey, the survey images will produce at least an order of magnitude increase in galaxy-scale lenses. The LSST strategy of repeated imaging of the survey area will provide automatic monitoring of these lensed sources. Combined with a knowledge of the Hubble Constant and model constraints from space-based imaging, the measurement of time delays will provide a sensitive probe of the overall matter distribution in the lensing galaxies. Furthermore, these systems can provide information on the clumping of matter on sub-galaxy scales, through the investigation of flux-ratio anomalies and time-domain variations due to microlensing.
- 108.28 AGN Science with the LSST
- R.F. Green (KPNO), D.P. Schneider (Penn State), P.S. Osmer (Ohio State), D.E. Vanden Berk (Penn State)
The LSST, with its unprecedented combination of sky coverage, photometric and astrometric accuracy, sensitivity, broad wavelength coverage, and time sampling, will provide a new window into the nature of AGNs. Well-defined, large (> 107 objects) samples of AGNs at 0 < z < 6 can be constructed via three approaches: location in color-color space, variability, and lack of proper motion. The samples will allow determination of the AGN luminosity function down to Seyfert luminosities out to z ~ 4. The near-infrared wavelength coverage/high sensitivity of LSST enables detection of the population of red quasars, and the proper motion criteria will be particularly effective at separating z > 4 AGNs from brown dwarfs. The time baseline coupled with the sample size will produce a data set that can be used to address the physics of the AGN accretion process, including insights into the lifetime of AGNs.