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

EXIST - 1 EXISTEXIST

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 HolesSurveying the universe in space and time for Black Holes

Josh GrindlayHarvard

And EXIST Concept Study Team members at: 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


Energetic X-ray Imaging Survey Telescope (EXIST)

Hard X-ray (~5-600 keV) all-sky imaging Hard X-ray (~5-600 keV) all-sky imaging each orbit each orbit to measure: to measure: •Obscured AGNObscured AGN vs. z and accretion (BHs) vs. nuclear (stars) luminosity of universe•First (PopIII) stellar Black HolesFirst (PopIII) stellar Black Holes producing Gamma Ray Bursts (GRBs)

Reference Design Mission parameters: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

EXIST measures properties of BHs, e.g. Cen-A, every orbit:characteristic time variability (QPOs) constrain BH mass and spin.


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 EXIST opens new discovery space: ~100X faster full-sky imaging than previously or planned at any wavelengthimaging than previously or planned at any wavelength


EXIST Science Objectives: Details

Survey BHs for obscuration and accretion luminositySupermassive 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 EvolutionType 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 horizonsStars tidally disrupted by BHs (~10-30 HX flares/year if if ~1% Laccr in HX)Spectra and QPOs of BHs (thermal accr. vs. non-thermal jets)

Secondary scienceSupernova rate in Galaxy from full galactic disk Ti-44 surveyPlanck scale physics from GRB timingPulsars: neutron star B fields from cyclotron linesMagnetars out to Virgo cluster!Novae (511keV survey)


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


Key EXIST science: Obscured AGN

ASCA and BeppoSAX and now Chandra and XMM find likely dominantcontribution of absorbed AGN (z ≤1) to cosmic x-ray background:

NGC1068NGC1068NGC6240NGC6240(Vignati et al 99)(Vignati et al 99)

EXIST will find >1-3 obscured AGN/square degree and obtain first all-skyall-sky measure of Seyfert 2 QSO 2 luminosity function

and constrain obscuration vs. zobscuration vs. z for supermassive BHs.

EXIST survey

HEAOHEAO

SwiftSwift

SAX/PDSSAX/PDS

Chandra deep surveys find Type 2 QSOs and XMM deep survey of Lockman Hole finds most still unresolved XRB is from obscured AGN


Extragalactic Timing with EXIST

First all-skyall-sky (every 95min) imaging and variability survey at anyany energy

• QPOs from BHs: EXIST detects ~300-1000 AGN with FHX ≥2mCrab and timescales ~1h -1y, constrain BH Mass BH Mass & spin parameter a/M& 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). (Grindlay 2004). Will measure population of 10Will measure population of 106-7 6-7 MMo o dormant BHs in galaxy bulges!dormant BHs in galaxy bulges!

Sub-giants with WD cores areSub-giants with WD cores are LISA LISA gravitational wave triggersgravitational 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).


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 BHsfirst BHs at re-ionization epoch suggested by WMAP and probe IGM.

Photometric z from lum-lagAnd/or lum-Epeak correlations

Response to E>100keVneeded even for z~10!

Flux vs. detected Epeak for GRBs from z=1 (top +) to 10 (bottom +) for Epeak =30, 100, 300, 1000keVif emitted at z=1 vs. sensitivities (Band 2004).


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 interactionProbe of non-thermal jet-disk interaction

EXIST

VERITASGLAST

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 universenuclear vs. accretion luminosity of the universe


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 Population of obscured binaries found with INTEGRAL: discrete, not diffuse, sources at >20 keVfound 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 inBHs in Galactic BulgeGalactic 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 viewof central Bulge(~ 2o x 1o)


EXIST Mission Reference DesignFree-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 >20% continuous coveragecoverage

Mission Parameters:•CZT tiled arrays: 8m² total area, (20x20x5mm crystals, ea. with 16x16 pixels; 5 x 105 x 106 6 pixelspixels!)

•Passive and active shielding; 50º x 60º collimation/module

•Mass, power, telemetry: 8500kg, 1400W, 1.5Mbs (X-band)

•Delta-IV launch

scan directionscan direction(orbit veloc. vector)

Nod direction, Nod direction, ┴ ┴ scanscan(+/-20o ea. ~10min)


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 pix5arcmin 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.


Reference Design Detectors, Telescopes & Launcher

EXIST (revealed) in Delta-IVDelta-IV shroudDetector & active-collimator & Telescope-structure views (3 Telescopes + S/C: Ht x Diam ~8.6m x 4.7m)


Requirements to achieve ~0.05mCrab sensitivity

• Very large detector area, Atot.~8m2, 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 scansince 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 variationspixel-pixel systematics and background variations for N x N coded mask: reduce systematic noise sys by scanning source image(s) across ~2N x 2N detector pixels)

• Imaging and mask design should yield 102-3 dynamic rangesince any instantaneous FOV will have 1 source @ 5-50 mCrab

(N.B. “coding noise” systematics“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?


Simulated 3C273 field (scanning vs. pointing)

3C273 simulation3C273 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)


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 EXITE coded aperture telescope (20-600 keV) in balloon gondola(20-600 keV) in balloon gondola

64cm² prototype, image & Ba-133 spectralines at 276, 302, 356, 383keVCZT3 prototype imager 60 keV image


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 sensingdepth sensing for >200keV imaging and large FoV

projection Δx to image plane: both cathode PHA and anode timing?

- Low power: <100µW per channel

- sparse readoutsparse readout (peak pixel + neighbors, for optimum energy resolution and polarization sensitivitypolarization sensitivity for GRBs, Blazars and non-thermal jets:

Polarization from azimuthal direction of single Compton Polarization from azimuthal direction of single Compton scattered photons (probable at E >200 keV) in 5mm thick scattered photons (probable at E >200 keV) in 5mm thick CZT. Image shown is GEANT simulation for 300 keV CZT. Image shown is GEANT simulation for 300 keV photons with polarization at 45photons with polarization at 45oo as recorded by 0.8mm pixels as recorded by 0.8mm pixels

• CZT detector-ASIC coupling and tiling- next generation ASIC and prototype interface ready for testing

Δxd


Trade studies on EXIST design (partial list)

• Energy range: 10-600keV vs. 5-600keV or 5-300keV? (single band)5-600keV or 5-300keV? (single band) Or Or 5-100keV (LE) and 100-600keV (HE)?5-100keV (LE) and 100-600keV (HE)?

• Field of view: uniform ~5sr vs. segmented in narrow (LE) and wide (HE)? segmented in narrow (LE) and wide (HE)?

• Angular resolution: 5arcmin vs. ~30arcsec (LE) and ~10arcmin (HE)?~30arcsec (LE) and ~10arcmin (HE)?

• Shielding and active collimation: full or partialfull or partial?

• Calibration and on-board data processing/distribution


Alternative Telescope and Field of View Designs

Two telescope version of

Reference Design

Alternative fields of view and sky coverage


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 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 LSSTSynergy 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

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

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