GLAST: Status and Science Prospects Peter F. Michelson Stanford University Gamma-ray Large Area Space Telescope Joint GLAST LAT-SWG Symposium, September 30, 2004

2 Outline LAT: 20 MeV – >300 GeV GBM: 10 keV – 25 MeV Large Area Telescope (LAT) GLAST Burst Monitor (GBM) launch: February 2007 GLAST: An International Science Mission – Large Area Telescope (LAT) – GLAST Burst Monitor (GBM) science opportunities: the need for multi-wavelength observations schedule highlights

3 GLAST is an International Mission NASA – Department of Energy Partnership on LAT LAT is being built by an international team Stanford University (SLAC & HEPL, Physics) Goddard Space Flight Center Naval Research Laboratory University of California, Santa Cruz University of Washington Ohio State University CEA/Saclay & IN2P3 (France) ASI & INFN (Italy) Hiroshima University, ISAS, RIKEN (Japan) Royal Inst. of Technology & Stockholm Univ. (Sweden) GBM is being built by US and Germany MPE, Garching (Germany) Marshall Space Flight Center Spacecraft and integration - Spectrum Astro Mission Management: NASA/GSFC Germany France Sweden Italy USA Japan

4 GLAST addresses a broad science menu Systems with supermassive black holes & relativistic jets Systems with supermassive black holes & relativistic jets Gamma-ray bursts (GRBs) Gamma-ray bursts (GRBs) Pulsars Pulsars Solar physics Solar physics Origin of Cosmic Rays Origin of Cosmic Rays Probing the era of galaxy formation Probing the era of galaxy formation Solving the mystery of the high-energy unidentified sources Solving the mystery of the high-energy unidentified sources Discovery! Particle Dark Matter? Other relics from the Big Bang? Discovery! Particle Dark Matter? Other relics from the Big Bang? Testing Lorentz invariance. New source classes Testing Lorentz invariance. New source classes

5 EGRET all-sky survey (E>100 MeV) diffuse extra-galactic background (flux ~ 1.5x10 -5 cm -2 s -1 sr -1 ) galactic diffuse (flux ~O(100) times larger) high latitude (extra-galactic) point sources (typical flux from EGRET sources O( ) cm -2 s -1 galactic sources (pulsars, un-ID’d) An essential characteristic: VARIABILITY in time! wide field of view, and the ability to repoint, important for study of transients. Features of the gamma-ray sky

6 Overview of GLAST Large Area Telescope Precision Si-strip Tracker (TKR) 18 XY tracking planes. Single-sided silicon strip detectors (228  m pitch) Measure the photon direction; gamma ID. Hodoscopic CsI Calorimeter(CAL) Array of 1536 CsI(Tl) crystals in 8 layers. Measure the photon energy; image the shower. Segmented Anticoincidence Detector (ACD) 89 plastic scintillator tiles. Reject background of charged cosmic rays; segmentation removes self- veto effects at high energy. Electronics System Includes flexible, robust hardware trigger and software filters. Systems work together to identify and measure the flux of cosmic gamma rays with energy 20 MeV - >300 GeV. e+e+ e–e–  Calorimeter Tracker ACD [surrounds 4x4 array of TKR towers]

7 Huge FOV (~20% of sky) Broadband (4 decades in energy, including unexplored region > 10 GeV) Unprecedented PSF for gamma rays (factor > 3 better than EGRET for E>1 GeV) Large effective area (9x larger than 1 GeV) Results in factor > improvement in sensitivityResults in factor > improvement in sensitivity much smaller deadtime per event (25  sec  factor 4,000 better than EGRET) No expendables long mission without degradation GLAST LAT High Energy Capabilities

8 GBM Detector (12) Sodium Iodide (NaI) Scintillation Detectors Major Purposes –Provide low-energy spectral coverage in the typical GRB energy regime over a wide FoV (10 keV – 1 MeV) –Provide rough burst locations over a wide FoV Bismuth Germanate (BGO) Scintillation Detector Major Purpose –Provide high-energy spectral coverage (150 keV – 25 MeV) to overlap LAT range over a wide FoV LAT

GLAST MISSION ELEMENTS GN - - DELTA 7920H White Sands TDRSS SN S & Ku Telemetry 1 kbps - S  sec HEASARC GSFC LAT Instrument Operations Center GBM Instrument Operations Center GRB Coordinates Network Alerts Data, Command Loads Schedules Archive Mission Operations Center (MOC) GLAST Science Support Center GLAST Spacecraft Large Area Telescope & GBM GPS GLAST MISSION ELEMENTS

10 Science Mission Elements Science Working Group (chair, S. Ritz, Project Scientist) –membership includes Interdisciplinary Scientists, instrument team PIs and instrument team representatives –bi-monthly telecons and ~bi-annual sit-down meetings, along with science symposia to engage the community. Users Committee (chair: J. Grindlay) –independent of the SWG. External review/feedback on science tools planning and progress. –includes members from both the astrophysics and high-energy particle physics communities who are likely users of GLAST data. GLAST Science Support Center (GSSC) –located at Goddard. Supports guest observer program, provides training workshops, provides data and software to community, archives to HEASARC, joint software development with Instrument Teams.

11 After the initial on-orbit checkout, verification, and calibrations, the first year of science operations will be an all-sky survey. –first year data used for detailed instrument characterization, refinement of the alignment, and key projects (source catalog, diffuse background models, etc.) needed by the community –data on transients will be released, with caveats –repoints for bright bursts and burst alerts enabled –extraordinary ToO’s supported –limited first-year guest observer program –workshops for guest observers on science tools and mission characteristics for proposal preparation Observing plan in subsequent years driven by guest observer proposal selections by peer review. All data released through the science support center (GSSC). Operations Phases

12 The next-generation ground-based and space-based experiments are well matched. Complementary capabilities ground-based space-based ACTEAS Pair angular resolutiongoodfair good duty cyclelowhigh high arealargelarge small field of viewsmalllarge large +can reorient energy resolutiongoodfair good, w/ smaller systematic uncertainties Gamma-ray Observatories (credit: A. Morselli et al.)

13 Anticenter Region Geminga IC 443 Crab PKS

14 3 rd EGRET Catalog GLAST Survey: ~10,000 sources (2 years) AGN - blazars unidentified pulsars LMC

15 Gamma-ray Sources: Inherently Multiwavelength Nature rarely produces monoenergetic particle beams. Broad range of particle energies leads to broad range of photon energies. –Example:  o production Charged particles rarely interact by only one process. Different processes radiate in different energy bands. –Example: synchrotron- Compton processes High-energy particles needed to produce  -rays can radiate in lower-energy bands as they lose energy. –Contrast: nonthermal X-ray source can have high-energy cutoff In the MeV range and above, sources are non-thermal:  produced by interactions of energetic particles  produced by interactions of energetic particles GLAST LAT Multiwavelength Coordinator: Dave Thompson

16 GLAST Schedule Launch February 2007 –Kennedy Space Flight Center Science operation beginsMay 2007 Delta II launch

17 MW Approaches for GLAST Sources Two broad areas: 1.Identification for known source classes; discovery of new classes. “What are they?” 2.Exploration of identified sources. “What can we learn from them?” Source ClassNumber seen by EGRET Number anticipated with GLAST Rotation-powered pulsars 6 definite 3 possible Blazars80 definite 50 possible >2000 Normal galaxies24-5 Gamma-ray bursts5>500 Unidentified sources170? Supernova remnants/plerions 1 likely ~5 possible >10 Radio galaxies1 likely 1 possible ? X-ray binaries/microquasars 1 likely 1 possible ? Starburst galaxies0? Clusters of galaxies0?

of the 271 sources in the EGRET 3 rd catalog are “unidentified” Cygnus region (15x15 deg) Unidentified Sources EGRET source position error circles are ~0.5°, resulting in counterpart confusion. GLAST will provide much more accurate positions, with ~30 arcsec - ~5 arcmin localizations, depending on brightness.

19 us source E  lower us source E  higher AGN, the EBL, and Cosmology IF IF AGN spectra can be understood well enough, they may provide a means to probe the era of galaxy formation: ( Stecker, De Jager & Salamon; Madau & Phinney; MacMinn & Primack ) If  c.m. energy > 2m e c 2, pair creation attenuates flux. For flux of  -rays with energy, E, this cross-section is maximized when the partner, , is For 10 GeV- TeV  -rays, this corresponds to a partner photon energy in the optical - UV range. Density is sensitive to time of galaxy formation. source E  lower source E  higher Salamon & Stecker, ApJ 493, 547 (1998) opaque No significant attenuation below 10 GeV

20 GLAST will see thousands of blazars - instead of peculiarities of individual sources, look for systematic effects vs redshift. key energy range for cosmological distances (TeV-IR attenuation more local due to opacity). GLAST Can Probe the Optical-UV EBL How many blazars have intrinsic roll- offs in this energy range ( GeV)? (An important question by itself for GLAST!) Power of statistics is the key. Must measure the redshifts for a large sample of these blazars! Caveats Primack & Bullock Salamon & Stecker No EBL Chen, Reyes, and Ritz, ApJ, in press effect is model-dependent (this is good):

21 MW Planning Group Recommendations Complete a southern hemisphere catalog of flat spectrum radio sources out to 8.4 GHz or higher frequencies, at least down to 100 mJy, and preferably to 30 mJy. Complete a program of optical identifications and redshift measurements for all known flat-spectrum radio sources brighter than 100 mJy at 8 GHz. Use pulsar models to develop a prioritized list of radio pulsars to be monitored. Start the timing program before the GLAST launch. Sponsor observations with the CfA telescope of special directions such as tangent directions of spiral arms. Encourage observations of the Galactic center region and a search for southern intermediate-latitude clouds. Pre-launch MW Planning:

22 MW Planning Group Recommendations Plan campaigns with Chandra, XMM, Astro E2, and (if selected) NuSTAR for high- energy X-ray studies of unidentified gamma-ray source error boxes. Plan pulsar search proposals for X-ray telescopes Plan coordinated proposals with optical and radio observatories for follow-on observations of LAT sources. The LAT blazar program should collaborate with existing blazar study groups wherever possible, for both Target of Opportunity campaigns and pre-planned MW campaigns. Plan a dedicated radio timing program for the pulsars expected to be brightest and most interesting GLAST sources. Plan follow-on proposals for radio, optical, or X-ray telescope time for LAT sources identified as pulsars in order to develop the most complete MW picture possible for these pulsars. MW Activities starting early in the Post-launch Phase: MW Activities throughout the GLAST Mission:

23 Summary BEFORE LAUNCHBEFORE LAUNCH – expand the list of known blazars, start radio timing program for pulsars EARLY IN THE MISSIONEARLY IN THE MISSION – radio and X-ray observations, in particular, to help identify gamma-ray sources. THROUGHOUT THE MISSIONTHROUGHOUT THE MISSION – monitoring and coordinated MW campaigns for flaring sources, regular timing for pulsars GLAST science will be maximized by multi-wavelength observations

24 photons with E>10 GeV are attenuated by the diffuse field of UV-Optical- IR extragalactic background light (EBL)  +   e + + e - a dominant factor in determining the EBL is the time of galaxy formation Chen & Ritz, ApJ (2000) Salamon & Stecker, ApJ 493, 547 (1998) opaque No significant attenuation below 10 GeV Constraints on extragalactic background light (EBL) from  -ray blazars

25 Gamma-ray Observatories “sensitivity”

26 High energy source sensitivity: all-sky scan mode 100 sec * 1 orbit * ^ 1 day^ ^“rocking” all-sky scan: alternating orbits point above/below the orbit plane EGRET Fluxes - GRB (100sec) - PKS flare - 3C279 flare - Vela Pulsar - Crab Pulsar - 3EG (SNR  Cygni?) - 3EG C279 lowest 5  detection - 3EG (AGN) - Mrk Weakest 5  EGRET source During the all-sky survey, GLAST will have sufficient sensitivity after O(1) day to detect (5  ) the weakest EGRET sources. *zenith-pointed