An Ultimate Widefield Hard Xray Imaging Survey Proposed

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 EXIST - 1 EXIST

Energetic X-ray Imaging Survey Telescope (EXIST) Hard X-ray (~5 -600 ke. V) all-sky imaging each orbit to measure: • Obscured AGN vs. z and accretion (BHs) vs. nuclear (stars) luminosity of universe • First (Pop. III) 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. 05 m. Crab) to >100 ke. V: 8 m 2 imaging (1. 2 mm pixels) CZT • All-sky imaging (5’ resolution; ~10 -50” positions): 3 coded aperture telescopes http: EXIST. gsfc. nasa. gov EXIST - 2 EXIST

Primary Science Questions for 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: ~100 X faster full-sky imaging than previously or planned at any wavelength EXIST - 3 EXIST

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 (511 ke. V survey) EXIST - 4 EXIST

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 Þ 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 EXIST - 5 EXIST

Key EXIST science: Obscured AGN ASCA and Beppo. SAX and now Chandra and XMM find likely dominant contribution of absorbed AGN (z ≤ 1) to cosmic x-ray background: EXIST survey SAX/PDS Swift NGC 1068 NGC 6240 HEAO (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. EXIST - 6

Extragalactic Timing with EXIST First all-sky (every 95 min) imaging and variability survey at any energy • QPOs from BHs: EXIST detects ~3001000 AGN with FHX ≥ 2 m. Crab and timescales ~1 h -1 y, 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 ~100 Mpc! (Grindlay 2004). Will measure population of 106 -7 Mo dormant BHs in galaxy bulges! QPO (& 3: 2 resonance) vs. BH mass and a/M (Abramowicz, Kluzniak et al 2004) Sub-giants with WD cores are LISA gravitational wave triggers. Artists conception of tidal disruption of star in RXJ 1242 -1119 detected with ROSAT (1991) and confirmed with Chandra (Komossa et al 2004). EXIST - 7 EXIST

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 ~100 Mo and collapse to BHs GRBs! EXIST could detect many GRBs to z~20 and probe Pop. III stars: first BHs at re-ionization epoch suggested by WMAP and probe IGM. Photometric z from lum-lag And/or lum-Epeak correlations Flux vs. detected Epeak for GRBs from z=1 (top +) to 10 (bottom +) for Epeak =30, 100, 300, 1000 ke. V if emitted at z=1 vs. sensitivities (Band 2004). EXIST - 8 Response to E>100 ke. V needed even for z~10! EXIST

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 (~10200 ke. V) allow gamma-ray (~10 Ge. V - 10 Te. V) 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 GLAST VERITAS 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 and nuclear vs. accretion luminosity of the universe EXIST - 9

Stellar BHs and IMBHs in Local Group • All bright stellar BHs in transients (Lx(>10 ke. V) ~1038 erg/s) detected throughout Galaxy, LMC/SMC and M 31. Population of obscured binaries found with INTEGRAL: discrete, not diffuse, sources at >20 ke. V • Isolated stellar BHs in Galaxy and IMBHs in Local Group accreting via Bondi-Hoyle (with ~10 -4 efficiency) from GMCs nearly Compton thick • BHs in Galactic Bulge nuclear cusp (cf. Alexander & Livio 2004) detected if Lx(>10 ke. V) ≥ 1035 erg/s as expected for wind-fed binaries or for CI Cam type outbursts (~1 -2 d) Chandra view of central Bulge (~ 2 o x 1 o) EXIST - 10 EXIST

EXIST Mission Reference Design Free-Flyer (500 km, i ~ 22º): • Zenith pointer (Survey mode) • 3 -axis pointer (Observatory and survey) • 3 coded aperture telescopes (2. 7 m 2 area & 60º x 75º each) for 8 m 2 & 180º x 75º fan-beam: full sky/orbit & >20% continuous coverage Mission Parameters: • CZT tiled arrays: 8 m² total area, (20 x 5 mm crystals, ea. with 16 x 16 pixels; 5 x 106 pixels!) pixels Nod direction, ┴ scan (+/-20 o ea. ~10 min) scan direction (orbit veloc. vector) • Passive and active shielding; 50º x 60º collimation/module • Mass, power, telemetry: 8500 kg, 1400 W, 1. 5 Mbs (X-band) • Delta-IV launch EXIST - 11 EXIST

EXIST detectors and sensitivity • Detector is tiled Cd-Zn-Te (CZT) array: 20 x 5 mm, 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 50 o x 60 o 3 x 3 or 4 x 4 STs per Telescope Cutaway view of EXIST detectors in one telescope. • 3 coded aperture Telescopes (2. 7 m 2 ea. ) 1. 5 m focal length, 2. 5 mm mask pix 5 arcmin resol. , 10 -50” loc. 0. 05 m. Crab = 5 x 10 -13 cgs, 5σ, 6 -9 mo, 20 -40% duty cyc. EXIST sensitivities. EXIST - 12 EXIST

Reference Design Detectors, Telescopes & Launcher Detector & active-collimator & Telescope-structure views (3 Telescopes + S/C: Ht x Diam ~8. 6 m x 4. 7 m) EXIST - 13 EXIST (revealed) in Delta-IV shroud EXIST

Requirements to achieve ~0. 05 m. Crab sensitivity • Very large detector area, Atot. ~8 m 2, and long exposure time, Texp since 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 sys by scanning source image(s) across ~2 N x 2 N detector pixels) • Imaging and mask design should yield 102 -3 dynamic range since any instantaneous FOV will have 1 source @ 5 -50 m. Crab (N. B. “coding noise” systematics for N x N coded aperture (non-URA): sys ~1/N, and further reduced by factor ~1/m 0. 5 for scan across m masks) Simulations show scanning greatly reduces systematics; Optimum scan strategies under study: scan + nod? EXIST - 14 EXIST

Simulated 3 C 273 field (scanning vs. pointing) 3 C 273 simulation: simulation 0. 5 - 1 year survey EXIST image (0. 05 m. Crab, 5 , 22 o Fo. V ). Scanning (left) vs. pointing (right), with 10% systematics (Grindlay and Hong 2003, SPIE) EXIST - 15 EXIST

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. 5 m²) CZT array to be flown on Swift (2004) –Medical & Security imaging lowering CZT costs ($50/cm 2) EXITE coded aperture telescope (20 -600 ke. V) in balloon gondola • CZT imagers for 10 -600 ke. V: 64 cm² prototype, image & Ba-133 spectra CZT 3 prototype imager EXIST - 16 60 ke. V image lines at 276, 302, 356, 383 ke. V EXIST

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 >200 ke. V imaging and large Fo. V projection Δx to image plane: both cathode PHA and anode timing? Δx d Low power: <100µW per channel - sparse readout (peak pixel + neighbors, for optimum energy resolution and polarization sensitivity for GRBs, Blazars and non-thermal jets: Polarization from azimuthal direction of single Compton scattered photons (probable at E >200 ke. V) in 5 mm thick CZT. Image shown is GEANT simulation for 300 ke. V photons with polarization at 45 o as recorded by 0. 8 mm pixels • CZT detector-ASIC coupling and tiling - EXIST - 17 next generation ASIC and prototype interface ready for testing EXIST

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

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

EXIST as BH Finder Probe: Summary • EXIST conducts high 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 Pop. III 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, Nu. STAR, 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 EXIST - 20 EXIST