GLAST Posters
High Energy Astrophysics Division (HEAD) 2006
Oct 4-7, San Francisco
1) Prospects for Observations of Microquasars with GLAST
Final poster (ppt)
R.Dubois, SLAC The Gamma-ray Large Area Space Telescope (GLAST) is a next generation high energy gamma-ray observatory due for launch in Fall 2007. The primary instrument is the Large Area Telescope (LAT), which will measure gamma-ray flux and spectra from 20 MeV to > 300 GeV and is a successor to the highly successful EGRET experiment on CGRO. The LAT will have better angular resolution, greater effective area, wider field of view and broader energy coverage than any previous experiment in this energy range. This poster will present performance estimates with particular emphasis on how these apply to studies of microquasars. The LAT's scanning mode will provide unprecedented unformity of sky coverage and permit measurements of light curves for any source. We will show results from recent detailed simulations that illustrate the potential of the LAT to observe microquasar variability and spectra, including source sensitivity and ability to detect orbital modulation.
2) Prospects for Pulsar Studies with the GLAST Large Area Telescope
Final poster (ppt)
Alice K. Harding (NASA Goddard) for the GLAST LAT Pulsar, PWN and SNR group
The Large Area Telescope (LAT) on the Gamma-ray Large Area Space Telescope (GLAST) will have unprecedented sensitivity and energy resolution for gamma-rays in the range of 30 MeV to 200 GeV.
GLAST is therefore expected to provide major advances in the understanding of high-energy emission from rotation-powered pulsars. As the only presently known galactic GeV source class, pulsars will be one of the most important sources for study with GLAST. The main science goals of the LAT for pulsar studies include an increase in the number of detected radio-loud and radio-quiet gamma-ray pulsars, including millisecond pulsars, giving much better statistics for elucidating population characteristics, measurement of the high-energy spectrum and the shape of spectral cutoffs and determining pulse profiles for a variety of pulsars of different age. Further, measurement of phase-resolved spectra and energy dependent pulse profiles of the brighter pulsars should allow detailed tests of magnetospheric particle acceleration and radiation mechanisms, by comparing data with theoretical models that have been developed. Additionally, the LAT will have the sensitivity to allow blind pulsation searches of nearly all unidentified EGRET sources, to possibly uncover more radio-quiet Geminga-like pulsars.
3) Supernova Remnant and Pulsar Wind Nebula Studies with the GLAST Large Area Telescope
Final version (pdf)
S. Funk , J. Cohen Tanugi, GLAST LAT Collaboration Pulsars
and Supernova remnants working group
Supernova remnants have long been considered to be responsible to
accelerate charged particles to ultra-relativistic energies in the shocks
of the expanding shells. These charged particles can subsequently emit
X-ray photons or Gamma-rays through interactions with magnetic fields and
surrounding material. In spite of recent detailed studies in these
wavebands, the nature of the parent population responsible for the
gamma-ray emission remains elusive. It is not yet evident, whether the
bulk of the gamma-rays are produced by Inverse Compton scattering of
electrons (e.g. on the CMBR), or by hadronic interactions and subsequent
pi0-decay. If the hadronic origin of the gamma-ray emission can be
established, this would be a great step towards the final proof that
shell-type SNRs are the long sought source of cosmic rays in the Galaxy.
The upcoming GLAST Large Area Telescope (LAT) will be able to distinguish
between leptonic and hadronic gamma-ray emission scenarios and we will
present predictions for expected signals from these objects. In addition
to the shell emission, supernova remnants containing energetic pulsars may
also show bright emission from pulsar wind nebulae (PWNe). With the recent
successes of TeV detection of PWNe, these promise to be an exciting source
class for the LAT, as well; we comment briefly on SNR with PWN components.
4) GLAST's Sensitivity to Gamma-Ray Bursts
David Band (GSSC/UMBC)
The Gamma-ray Large Area Space Telescope (GLAST) will advance the study of gamma-ray bursts. The spectral coverage of more than 7 energy decades and large fields-of-view of the Large Area Telescope (LAT; 20 MeV to >300 GeV) and the GLAST Burst Monitor (GBM; 10 keV to 30 GeV) will result in unprecedented spectral and temporal coverage of a large number of bursts. In addition, both detectors will localize the bursts. Semi-analytic calculations can characterize the burst populations to which each instrument will be sensitive.
5) GLAST LAT and GRBs
Final version (pdf)
Author: GLAST/LAT GRB Science Group
Presenters: Eduardo do Couto e Silva and Johann Cohen-Tanugi (KIPAC/SLAC)
Abstract: The GLAST Large Area Telescope (LAT) is the next generation satellite experiment for high-energy gamma-ray astronomy. It employs a pair conversion technique to record photons in the energy range from 20 MeV to 300 GeV and higher. Its modular design consists of sixteen towers made of silicon trackers followed by segmented CsI electromagnetic calorimeters. Towers are surrounded by plastic scintillators acting as an anticoincidence shield that rejects unwanted charge particle background. The LAT will follow the steps from its predecessor, EGRET, and will explore the high energy gamma-ray sky with unprecedented capabilities.
The detection and observation of Gamma-Ray Bursts is one of the main scientific goals of the LAT. A full simulation chain has been developed by the LAT collaboration, starting from the simulation of the source to the detailed Montecarlo simulation of the instrument, and to the full reconstruction software. Analysis tools dedicated to the GRB science have been developed, as well as the simulation of the GLAST Burst Monitor, the second instrument on-board GLAST, dedicated to GRB's. In this contribution we show the expected LAT sensitivity obtained with such simulations, as well as some results from spectral and temporal analysis.
6) Evaluation of the celestial foreground in determination of the extragalactic diffuse gamma-ray emission (submitted)
Final poster (ppt)
Igor V. Moskalenko (Stanford), Troy A. Porter (UCSC), Seth Digel (SLAC)
The intensity and spectrum of the diffuse extragalactic emission in high-energy gamma rays have attracted long-standing experimental and theoretical interest. They relate to the luminosity functions of blazars and other active galaxies, as unresolved point sources, and to any truly
diffuse cosmological component. Any evaluation of the extragalactic diffuse emission relies on detailed understanding of the calibration and backgrounds of the gamma-ray telescope as well as the intensities of the foreground celestial components. We evaluate the celestial sources of the foreground and their impact on determination of the true diffuse extragalactic gamma-ray emission.
7) GLAST Large Area Telescope High-Energy Multiwavelength Planning
Final Poster, (ppt), (pdf)
Author list: D. J. Thompson, P. Caraveo, R. Sambruna, G. M. Madejski, R. W. Romani, K. S. Wood, on behalf of the GLAST LAT collaboration
Because gamma-ray astrophysics depends in many ways on multiwavelength studies, the Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) Collaboration is carrying out multiwavelength planning in preparation for the scheduled 2007 launch of the observatory. Many of these multiwavelength activities emphasize other areas of high-energy astrophysics. We identify the spectral bands that might be particularly important towards understanding the nature of gamma-ray sources. Some of the high-priority needs include: (1) simultaneous broad-spectrum blazar flare measurements; (2) characterization of gamma-ray transients, including gamma ray bursts; (3) X-ray timing of radio-quiet pulsars; (4) broad-spectrum variability studies of sources such as microquasars; (5) X-ray and TeV counterpart searches for unidentified gamma-ray sources. The LAT team welcomes cooperative efforts from observers at all wavelengths.
The LAT is an international project with U.S. support from NASA and the Department of Energy.
8) Detecting the EBL attenuation of Blazars with GLAST
Final version (ppt)
Luis C. Reyes
The Large Area Telescope (LAT) on board GLAST (Gamma-ray Large Area Space Telescope) due for launch in Fall 2007 will study the gamma-ray sky in the energy range 20 MeV to >300 GeV. GLAST-LAT's improved sensitivity with respect to previous missions will increase the number of known Blazars from about 100 to thousands, with redshifts up to z~5. Since Gamma rays with energy above 10 GeV interact via pair-production with photons from the Extragalactic Background Light (EBL), the systematic attenuation of GLAST-detected Blazars as a function of redshift would constitute and effective and unique probe to the optical-UV EBL density and its evolution over cosmic history. Based on the GLAST-LAT instrument performance, detailed simulations of expected blazar populations attenuated by EBL have been performed. In this poster we present an analysis of such simulations in order to measure the EBL attenuation, ensuing a clear distinction between competing EBL models.
9) GLAST Large Area Telescope Performance Monitoring and Calibrations On Orbit
Anders W. Borgland (ISOC/SLAC)
The Large Area Telescope (LAT) is one of the two instruments onboard the Gamma ray Large Area Space Telescope (GLAST), the next generation high energy gamma ray telescope, which is due to be launched in Fall of 2007. It is comprised of sixteen identical towers in a four by four grid, each tower containing a silicon tracker and a CsI calorimeter that together will give the incident direction of the pair-converting photon and the photon energy. The instrument is covered by an AntiCoincidence Detector (ACD) to reject charged particle background. Altogether, the LAT contains more than 800.000 channels in the trackers, 1536 CsI crystals and 97 ACD tiles and ribbons.
This poster details some of strategies and methods for calibrating the instrument on orbit, including both particle based calibrations, using Galactic Cosmic Rays (GCR) and CNO events, and charge injection, that will be necessary to ensure a satisfactory performance of the LAT in its energy range from 20 MeV to 300 GeV. It will also detail how we are planning to monitor the instrument performance during operations on orbit, including both low level detector monitoring and more high level analysis based monitoring using astrophysical sources.
10) The Search for Dark Matter and New Physics Using the Gamma Ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT)
Elliott D. Bloom (SLAC) - For the GLAST LAT Collaboration Dark Matter and New Physics Working Group.
Final poster (pdf)
The LAT Dark Matter and New Physics Working group has been developing approaches for the indirect detection of in situ annihilation of dark matter. Our work has assumed that a significant component of dark matter is a new type of Weakly Interacting Massive Particle (WIMP). The annihilation of two WIMPS results in the production of a large number of high energy gamma rays (> 1 GeV) that can be well measured in the GLAST LAT. These searches involve strategies for observation of the galactic center, galactic halo (optimized diffuse all sky analysis), galactic satellites (almost point, high latitude, sources), and cosmological signals in the extra-galactic diffuse. The spectra of these potential signals are considerably harder than most, if not all, astrophysical sources, have an endpoint at the mass of the WIMP, and are not power laws. In addition, there is the possibility to observe lines from annihilation into gamma-gamma and/or gamma-Z final states. The estimates of LAT sensitivity depends upon the WIMP model, the DM halo model and other astrophysics backgrounds. Thus estimates of LAT sensitivity can vary over orders of magnitude depending on which models are chosen. Preparations for these searches and other type of new physics searches will be presented.This work is supported by Stanford University and the Stanford Linear Accelerator Center (SLAC) under DoE contract number DE-AC 03-76-SFO0515 and NASA grant number NAS5-00147. Non-US sources of funding also support the efforts of GLAST LAT collaborators in France, Italy, Japan, and Sweden.
11) The Large Area Telescope (LAT) on the Gamma-ray Large Area Space Telescope (GLAST)
W.B. Atwood et al, representing the GLAST LAT team
Final poster (ppt)
The Gamma-ray Large Area Space Telescope, GLAST, is a mission to measure the cosmic gamma-ray flux in the energy range 20 MeV to >300 GeV, with supporting measurements for gamma-ray bursts from 10 keV to 25 MeV. With its launch in 2007, GLAST will open a new and important window on a wide variety of high energy phenomena, including black holes and active galactic nuclei; gamma-ray bursts; the origin of cosmic rays and supernova remnants; and searches for hypothetical new phenomena such as supersymmetric dark matter annihilations, Lorentz invariance violation, and exotic relics from the Big Bang. The Large Area Telescope (LAT), which provides the break-through high-energy measurements, consists of a pair conversion tracker, a hodoscopic crystal calorimeter, a segmented plastic scintillator anticoincidence shield, and a flexible trigger and data flow system. The LAT design is described, along with the expected science performance and the detailed simulations of particle interactions, event reconstruction, and classification of events on which the performance analysis is based.
12) Modeling the Interstellar Diffuse Gamma-Ray Emission for GLAST (submitted)
Final version of poster: (ppt), (pdf)
S. W. Digel (SLAC) for the GLAST LAT Collaboration Diffuse and Molecular Clouds Working Group
Interactions of cosmic rays with interstellar gas and photons make the Milky Way a bright, diffuse source of high-energy gamma rays. An accurate model of the diffuse emission is important for studies of point- and small extended sources of gamma rays as well as the extragalactic diffuse emission. It is also diagnostic of the distributions of gas and cosmic rays in the Milky Way. We present the model under development by the GLAST Large Area Telescope (LAT) team and demonstrate the sensitivity with which the model can be tuned using simulated flight data, to resolve ambiguities in the distribution of interstellar gas or refine the distribution of cosmic-ray sources. The model is implemented in the framework of the GALPROP code for cosmic-ray propagation and incorporates up-to-date surveys of the interstellar medium, as well as current models for the interstellar radiation field and updated production functions and inverse scattering calculations.
13) WIMP annihilation near a black hole (submitted)
Final poster (ppt)
Lawrence L. Wai (SLAC), Igor V. Moskalenko (Stanford)
We discuss the signatures of WIMP annihilation near a black hole. We show that under certain circumstances the signal may be detectable by indirect detection techniques.
14) The GLAST Approach To Gamma-ray Source Identification (submitted)
Draft poster (ppt)
Patrizia A. Caraveo (INAF-IASF) & Olaf Reimer (Stanford University) for the GLAST LAT Collaboration Science Working Group on Unidentified Sources
Basic source parameters, such as position, positional accuracy, flux, spectral shape or hardness ratio, variability on various timescales, will be cross-correlated with a number of existing catalogues and deep multifrequency observations to survey individual gamma-ray sources for potential counterparts. Figure-of-merit estimates will be used to assess the likelihood of counterpart candidates. Positional coincidence and variability timescale will be the most obvious parameters on the figure-of-merit ranking. The LAT superior positional accuracy will substantially reduce the sources' error boxes, thus strengthening the positional coincidence criterion. However, additional pieces of information, possibly related to any given potential source class, will also play a role. Chance occurrence probability as well as energetic plausibility of an individual association will further constraint the FoM estimate. Positional coincidence with a pulsar with a rotational energy loss too low to sustain the source flux should lead to an unacceptably low value of the overall FoM. A variable high-latitude source, whose position is compatible with a known AGN, will be labelled as a putative AGN, while a steady source in the galactic plane, whose position is compatible with a young, energetic pulsar, will be scrutinized for the characteristic pulsar timing signature as the definitive proof of identification or for source extension reminiscent of a high-energy plerion. If the cross correlation process does not yield a likely counterpart, or if the source has failed the acceptance tests devised for a given class of gamma-ray emitters, the source will be studied in-depth by the LAT Unidentified source WG, who will be responsible for the organization and efficient interpretation of results from a multiwavelength campaign aimed at finding (or discriminating between) potential counterpart candidates. The searches will be conducted mainly in nearby regions of the electromagnetic spectrum, i.e. in the VHE and soft to hard X-ray domains, characterized by more accurate source positioning.
15) GLAST and Ground-Based Gamma-Ray Astronomy
Final poster (ppt)
Julie McEnery (NASA/GSFC) + TBD for the GLAST LAT Collaboration.
The launch of the Gamma-ray Large Area Space Telescope next year together with the advent of a new generation of ground-based gamma-ray detectors such as VERITAS, HESS, MAGIC and CANGAROO, will usher in a new era of high-energy gamma-ray astrophysics. GLAST and the ground based gamma-ray observatories will provide highly complementary capabilities for spectral, temporal and spatial studies of high energy gamma-ray sources. Joint observations will cover a huge energy range, from 20 MeV to over 20 TeV. The LAT will survey the entire sky every three hours, allowing it both to perform uniform, long-term monitoring of variable sources and to detect flaring sources promptly. Both functions complement the high-sensitivity pointed observations provided by ground-based detectors. Finally, the large field of view of GLAST will allow a study of gamma-ray emission on large angular scales and identify interesting regions of the sky for deeper studies at higher energies. In this poster, we will discuss the science returns that might result from joint GLAST/ground-based gamma-ray observations and illustrate them with detailed source simulations.
16) Automated Science Processing for GLAST LAT Data (submitted)
Draft poster (ppt)
James Chiang (GSSC), Seth Digel, Eduardo do Couto e Silva (SLAC/KIPAC),
and Olaf Reimer (Stanford University) for the GLAST LAT ISOC
Automated Science Processing (ASP) will be performed by the GLAST Large Area Telescope (LAT) Instrument Science Operations Center (ISOC) on data from the satellite as soon as possible in the ground processing pipeline. ASP will consist of time-critical science analyses. These include refinement of gamma-ray burst positions, timing, flux and spectral properties, off-line searches for
untriggered GRBs and gamma-ray afterglows, longer time scale monitoring of a standard set of sources (AGNs, X-ray binaries), and searches for previously unknown flaring sources in the LAT band. We describe the design of ASP and the scientific products; and we show results of a prototype implementation, driven by the standard LAT data processing pipeline, as applied to simulated LAT and GBM data.
17) The GLAST LAT Instrument Science Operations Center (submitted)
Robert Cameron, Eduardo do Couto e Silva and Richard Dubois (SLAC) for the GLAST LAT ISOC
Operations support and science data processing for the Large Area Telescope (LAT) instrument on the Gamma-ray Large Area Space Telescope (GLAST) will be provided by the LAT Instrument Science Operations Center (ISOC) at the Stanford Linear Accelerator Center (SLAC). The ISOC supports GLAST mission operations in cooperation with other GLAST mission ground system elements and supports the science activities of the LAT collaboration.
The ISOC will be responsible for monitoring the health and safety of the LAT, preparation of command loads for the LAT, maintaining and updating embedded flight software which controls the LAT detector and data acquisition flight hardware, maintaining the LAT configuration and calibration, and applying event reconstruction processing to downlinked LAT data to recover information about detected gamma-ray photons. The SLAC computer farm will be used to process the large volume of LAT event data and generate science products to be made available to the LAT collaboration through the ISOC and the broader scientific community through the GLAST Science Support Center at GSFC. Science operations in the ISOC will optimize the performance of the LAT and oversee automated science processing of LAT data to detect and monitor transient gamma-ray sources. We describe the use of collaboration-wide data challenges to test and exercise LAT data processing before launch.
19) Studying Gamma-ray Blazars With The GLAST LAT (submitted)
Draft of poster (pdf)
Benoit Lott (SLAC/CENBG) on behalf of the "Blazars and other AGNs" Science Group, GLAST collaboration
Thanks to its sensitivity (4 10^-9 ph (E> 100 MeV) cm^-2 s^-1 for one year), the GLAST LAT should detect many more (up to several thousands) gamma-ray blazars than currently known. This large blazar sample will make detailed population studies possible. In addition, the LAT large field-of-view combined with the scanning mode will provide a very uniform exposure over the whole sky. This feature will allow a continuous monitoring of several tens of blazars and enable flare alerts to be issued. The poster will present the LAT performance relevant to blazar studies, more particularly related to timing and spectral properties. Major specific issues regarding the blazar phenomenon that the LAT data should shed light on thanks to these capabilities will be discussed. The poster will also describe the different approaches foreseen to address these issues. The associated data required in other bands, to be collected in contemporaneous/simultaneous multiwavelength campaigns will be mentioned as well.
20) The GLAST Burst Monitor on the Gamma-Ray Large Area Space Telescope (submitted)
Valerie Connaughton1, P. N. Bhat1, M. S. Briggs1, R. Diehl2, G. Fishman3, J. Greiner2, R. M. Kippen4, A. von Kienlin2, C. Kouveliotou5, G. Lichti2, C. A. Meegan3, W. S. Paciesas1, R. D. Preece1, H. Steinle2, C. Wilson-Hodge3
1UAH, 2MPE, Germany, 3NASA-MSFC, 4LANL, 5NASA.
The Gamma-Ray Large Area Space Telescope (GLAST) is scheduled for launch in Fall 2007. Its main instrument, the Large Area Telescope (LAT), is complemented by the GLAST Burst Monitor (GBM) for one of the major scientific objectives of the GLAST mission. Together, the instruments provide unprecedented coverage of gamma-ray bursts in the 10 keV to 300 GeV energy range. GBM consists of 12 NaI and 2 BGO detectors. It has now been built, tested, and delivered to SpectrumAstro in Arizona, where it is being integrated with the spacecraft and the LAT.
21) The CGRaBS Blazars: Preparation for GLAST
S. E. Healey, R. W. Romani, P. F. Michelson, E. F. Schlafly, and the CGRaBS team (Stanford/KIPAC)
We present progress on an all-sky (|b| > 10°) survey of radio blazars likely to be detected at high energies by the GLAST mission. Our parent population is a sample of ~11,000 flat-spectrum radio sources, which have been imaged at 8 GHz. From this, we use the radio and X-ray properties to select a Candidate Gamma-RAy Blazar Sample (CGRaBS) of the ~1500 sources most like the EGRET gamma-ray blazars. We expect that these sources will be prominent among the 3000-10000 blazars that should be detected by the LAT on GLAST, scheduled for launch in 2007. We report here on progress toward optical characterization of the sample, with spectroscopy obtained largely at the Hobby*Eberly Telescope. This blazar sample is dominated by FSRQs, with ~10% BL Lacs. We show our redshift distribution to date, with sources extending up to z > 5, and describe some SEDs of blazars from the sample, which support the idea that a strong Compton peak should be detectable up to gamma-ray energies. With an expanded observing campaign ramping up in 2006/2007, we expect to reach reasonable completion before GLAST launch. This sample should be very valuable for study of the blazar population and its evolution as well as an important tool for selecting key objects for multiwavelength studies coordinated with the gamma-ray observations.
22) GLAST'S Sensitivity to Gamma-Ray Bursts
Poster (ppt)
David L. Band (GSFC/UMBC)
The Gamma-ray Large Area Space Telescope (GLAST) willadvance the study of gamma-ray bursts. The spectral coverage of more than 7 energy decades and large fields-of-view of the Large Area Telescope (LAT; <20 MeV to >300 GeV) and the GLAST Burst Monitor (GBM; 10 keV to 30 GeV) will result in unprecedented spectral and temporal coverage of a large number of bursts. In addition, both detectors will localize the bursts. Semi-analytic calculations can characterize the burst populations to which each instrument will be sensitive.