An Ultimate Wide-field Hard X-ray Imaging Survey Proposed to EXIST

1. An Ultimate Wide-field Hard X-ray Imaging Survey Proposed to EXIST Energetic X-ray Imaging Survey Telescope Surveying the universe in space and time for Black Holes Josh Grindlay Harvard And EXIST Concept Study Team members at: Harvard-SAO, Caltech, Columbia, Livermore, NASA/GSFC/MSFC, Stanford/SLAC, UC Berkeley/San Diego/Santa Barbara/Santa Cruz, Washington Univ., Yale, Sonoma State, Ball Aerospace, Spectrum Astro, Cambridge/UK, CESR/Fr, Rome/It

2. Energetic X-ray Imaging Survey Telescope (EXIST) • Hard X-ray (~5-600 keV) all-sky imaging each orbit to measure: • Obscured AGN vs. z and accretion (BHs) vs. nuclear (stars) luminosity of universe • First (PopIII) stellar Black Holes producing Gamma Ray Bursts (GRBs) EXIST measures properties of BHs, e.g. Cen-A, every orbit: characteristic time variability (QPOs) constrain BH mass and spin. • Reference Design Mission parameters: • Extend ROSAT sens. (~0.05mCrab) to >100 keV: 8m2 imaging (1.2mm pixels) CZT • All-sky imaging (5’ resolution; ~10-50” positions): 3 coded aperture telescopes http:EXIST.gsfc.nasa.gov

3. Primary Science Questions for EXIST • EXIST will address fundamental questions about black holes: • When and how were the first stellar black holes formed? • What is the epoch of obscuration of massive black holes? • How are dormant black holes revealed by stellar disruption? • How many stellar BHs and IMBHs in the Local Group? • Survey will provide large samples of BHs from all sky survey • with duty cycle for each object of ~20-40% for unprecedented • Spatial-Temporal Survey for BH populations. • EXIST opens new discovery space: ~100X faster full-sky • imaging than previously or planned at any wavelength

4. EXIST Science Objectives: Details Survey BHs for obscuration and accretion luminosity Supermassive BH survey (Lx ~1044 erg/s to z ~1) IMBH survey in Local Group (ULX sources: spectra, QPOs) Stellar BH inventory in Galaxy (BHs in galactic bulge cusp; transients) BH Evolution Type 2 QSOs (z ~5 for most luminous) Accretion vs. stellar luminosity of universe (Lx vs. NH; Blazars) First (Pop III) BHs at z~15? (GRBs) Approaching BH event horizons Stars tidally disrupted by BHs (~10-30 HX flares/year if ~1% Laccr in HX) Spectra and QPOs of BHs (thermal accr. vs. non-thermal jets) Secondary science Supernova rate in Galaxy from full galactic disk Ti-44 survey Planck scale physics from GRB timing Pulsars: neutron star B fields from cyclotron lines Magnetars out to Virgo cluster! Novae (511keV survey)

5. Science Drivers for a Black Hole Finder • Most massive black holes are thought to exist in obscured regions at centers of galaxies • Obscured BHs likely outnumber all known BHs in AGN and in Galaxy • The best way to discover and study obscured BHs is by surveying the sky in the hard x-ray band Obscured Line of Site to Central Black Hole Emission Strongest in Hard X-ray Band

6. EXIST survey SAX/PDS Swift HEAO Key EXIST science: Obscured AGN ASCA and BeppoSAX and now Chandra and XMM find likely dominant contribution of absorbed AGN (z ≤1) to cosmic x-ray background: NGC1068 NGC6240 (Vignati et al 99) Chandra deep surveys find Type 2 QSOs and XMM deep survey of Lockman Hole finds most still unresolved XRB is from obscured AGN EXIST will find >1-3 obscured AGN/square degree and obtain first all-sky measure of Seyfert 2 QSO 2 luminosity function and constrain obscuration vs. z for supermassive BHs.

7. Extragalactic Timing with EXIST First all-sky (every 95min) imaging and variability survey at any energy • QPOs from BHs: EXIST detects ~300-1000 AGN with FHX ≥2mCrab and timescales  ~1h -1y, constrain BH Mass & spin parameter a/M • Tidal disruption of stars spiralling into Dormant SMBHs with mass ~107 Mo: if 1% of Lacc in HX band, EXIST may see ~10-30 flares/yr out to ~100Mpc!(Grindlay 2004). Will measure population of 106-7 Mo dormant BHs in galaxy bulges! Sub-giants with WD cores areLISA gravitational wave triggers. QPO (& 3:2 resonance) vs. BH mass and a/M (Abramowicz, Kluzniak et al 2004) Artists conception of tidal disruption of star in RXJ1242-1119 detected with ROSAT (1991) and confirmed with Chandra (Komossa et al 2004).

8. Key Science: GRBs probe stellar BHs at z~5-20 • “Long”-GRBs are from SNIb,c and probable stellar BH formation • Likely very first stars were ~100Mo and collapse to BHs GRBs! EXIST could detect many GRBs to z~20 and probe PopIII stars: first BHs at re-ionization epoch suggested by WMAP and probe IGM. Photometric z from lum-lag And/or lum-Epeak correlations Response to E>100keV needed even for z~10! Flux vs. detected Epeak for GRBs from z=1 (top +) to 10 (bottom +) for Epeak =30, 100, 300, 1000keV if emitted at z=1 vs. sensitivities (Band 2004).

9. Key Science: Blazars, BHs-Jets & Cosmic Diffuse IR EXIST provides broad-band imaging and monitoring of all AGN classes, including Blazars. Hard x-ray (synchrotron) spectral breaks (~10-200keV) allow gamma-ray (~10 GeV - 10 TeV) spectral breaks measured by GLAST and VERITAS to constrain origin of diffuse IR background for Blazars at known redshift (gamma-rays pair-produce on the IR background photons). Time-variable spectral breaks required from simultaneous HX measurements. Probe of non-thermal jet-disk interaction EXIST VERITAS GLAST SSC model for Mkn 501 (Coppi & Aharonian 1999) EXIST will provide the continuous HX spectral-monitoring to study Blazars and non-thermal AGN to constrain diffuse IR (~10-100μ) background from obscured AGN andnuclear vs. accretion luminosity of the universe

10. Stellar BHs and IMBHs in Local Group • All bright stellar BHs in transients (Lx(>10 keV) ~1038 erg/s) detected throughout Galaxy, LMC/SMC and M31. Population of obscured binaries found with INTEGRAL: discrete, not diffuse, sources at >20 keV • Isolated stellar BHs in Galaxy and IMBHs in Local Group accreting via Bondi-Hoyle (with ~10-4 efficiency) from GMCs nearly Compton thick • BHs inGalactic Bulge nuclear cusp (cf. Alexander & Livio 2004) detected if Lx(>10 keV) ≥1035 erg/s as expected for wind-fed binaries or for CI Cam type outbursts (~1-2d) Chandra view of central Bulge (~ 2o x 1o)

11. EXIST Mission Reference Design • Free-Flyer (500km, i ~ 22º): • Zenith pointer (Survey mode) • 3-axis pointer (Observatory and survey) • 3 coded aperture telescopes (2.7m2 area & 60º x 75º each) for 8m2 & 180º x 75º fan-beam: full sky/orbit & >20% continuous coverage Nod direction, ┴ scan (+/-20o ea. ~10min) • Mission Parameters: • CZT tiled arrays: 8m² total area, • (20x20x5mm crystals, ea. with 16x16 pixels; 5 x 106 pixels!) • Passive and active shielding; 50º x 60º collimation/module • Mass, power, telemetry: 8500kg, 1400W, 1.5Mbs (X-band) • Delta-IV launch scan direction (orbit veloc. vector)

12. EXIST detectors and sensitivity • Detector is tiled Cd-Zn-Te (CZT) array: 20 x 20 x 5mm, 16 x 16 pixels direct-bonded to low noise ASIC • Detector modules (DMs): 4 x 4 CZT detectors per board-µProc. 8 x 8 DMs per sub-telescope (ST); actively collimated 50o x 60o 3 x 3 or 4 x 4 STs per Telescope • 3 coded aperture Telescopes (2.7m2 ea.) 1.5m focal length, 2.5mm mask pix 5arcmin resol., 10-50” loc. 0.05mCrab = 5 x 10-13 cgs, 5σ, 6-9mo, 20-40% duty cyc. Cutaway view of EXIST detectors in one telescope. EXIST sensitivities.

13. Reference Design Detectors, Telescopes & Launcher EXIST (revealed) in Delta-IV shroud Detector & active-collimator & Telescope-structure views (3 Telescopes + S/C: Ht x Diam ~8.6m x 4.7m)

14. Requirements to achieve ~0.05mCrab sensitivity • Very large detector area, Atot.~8m2, and long exposure time, Texpsince S/N ~ (Atot • Texp/B)1/2 for given background, B • Very large field of view, , in scan direction & need to scan since Texp ~ /(d/dt) for given orbital scan rate, d/dt, and scan needed to average over detector pixel-pixel variations (pixel-pixel systematics and background variations for N x N coded mask: reduce systematic noise sysby scanning source image(s) across ~2N x 2N detector pixels) • Imaging and mask design should yield 102-3 dynamic range sinceany instantaneous FOV will have 1 source @ 5-50 mCrab (N.B. “coding noise” systematics for N x N coded aperture (non-URA): sys~1/N, and further reduced by factor ~1/m0.5 for scan across m masks) Simulations show scanning greatly reduces systematics; Optimum scan strategies under study: scan + nod?

15. Simulated 3C273 field (scanning vs. pointing) 3C273 simulation: 0.5 - 1 year survey EXIST image (0.05mCrab, 5, 22o FoV). Scanning (left) vs. pointing (right), with 10% systematics (Grindlay and Hong 2003, SPIE)

16. EXIST technology development • Imaging and detector technology development • Coded aperture hard x-ray imaging • Developed on SR&T/balloon payloads (e.g. EXITE) • Demonstrated in space on SIGMA, INTEGRAL • Cd-Zn-Te (CZT) detectors • Backgrounds measured & CZT imagers for balloons • Large-area (0.5m²) CZT array to be flown on Swift (2004) • Medical & Security imaging lowering CZT costs ($50/cm2) • CZT imagers for 10-600 keV: EXITE coded aperture telescope (20-600 keV) in balloon gondola 64cm² prototype, image & Ba-133 spectra 60 keV image CZT3 prototype imager lines at 276, 302, 356, 383keV

17. Current EXIST technology develoment • CZT contacting and materials uniformity studies • Leakage current results follow for Imarad CZT with In vs. Pt contacts • ASIC development: • optimum depth sensing for >200keV imaging and large FoV projection Δx to image plane: both cathode PHA and anode timing? • Low power: <100µW per channel • sparse readout (peak pixel + neighbors, for optimum energy resolution and polarization sensitivityfor GRBs, Blazars and non-thermal jets: Polarization from azimuthal direction of single Compton scattered photons (probable at E >200 keV) in 5mm thick CZT. Image shown is GEANT simulation for 300 keV photons with polarization at 45o as recorded by 0.8mm pixels • CZT detector-ASIC coupling and tiling • next generation ASIC and prototype interface ready for testing Δx d

18. Trade studies on EXIST design (partial list) • Energy range: 10-600keV vs. • 5-600keV or 5-300keV? (single band) • Or 5-100keV (LE) and 100-600keV (HE)? • Field of view: uniform ~5sr vs. • segmented in narrow (LE) and wide (HE)? • Angular resolution: 5arcmin vs. • ~30arcsec (LE) and ~10arcmin (HE)? • Shielding and active collimation: full or partial? • Calibration and on-board data processing/distribution

19. Alternative Telescope and Field of View Designs Alternative fields of view and sky coverage Two telescope version of Reference Design

20. EXIST as BH Finder Probe: Summary • EXIST conductshigh priority science • Highest sensitivity full-sky probe of obscured BHs in universe • Ultimate sensitivity broad-band, high resolution study of GRBs at z~ 15 as probes of PopIII stars/stellar BHs and reionization epochs • Decadal Survey high ranking shows broad astrophysics interest • EXIST well suited as BH Finder Probe • Hard X-ray/All-sky imaging-monitoring provides most complete and unambiguous BH survey and followup study • Synergy with GLAST, NuSTAR, Con-X, JWST, JDEM and LSST • Technology and mission concept could support a 2011 launch • Concept Study can demonstrate mission viability • Detailed simulations & design trade studies to optimize science • Mission technology relatively understood; primary needs are CZT production, ASICs, imaging design, and digital processing