# Presentation: 804752

## 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

## 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)***

**Reference Design Mission parameters:**
- Extend ROSAT sens. (~0.05mCrab) to >100 keV: ***8m******2 ******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 ***
***imaging than previously or planned at any wavelength***

## 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)

## 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 dominant
- 	contribution of absorbed AGN (z ≤1) to cosmic x-ray background:

- NGC1068
- NGC6240
- (Vignati et al 99)

**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.

**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-sky****** (every 95min) imaging and variability survey at ******any****** energy***
**	****	****	****	****	****	****	****	****	**
**QPOs from BHs: EXIST detects ~300-1000 AGN with F****HX ****≥2mCrab and timescales ******** ~1h -1y, constrain *****BH Mass & spin parameter a/M***
**          **
**Tidal disruption of stars spiralling**
**	**** ****into Dormant SMBHs with mass **
**	****~10****7**** M****o****:***** if 1% of L******acc ******in HX band, ***
***	******EXIST may see ~10-30 flares/yr ***
***	******out to ~100Mpc!****** ***(Grindlay 2004).
- 	***Will measure population of 10******6-7 ******M******o ***
***	******dormant BHs in galaxy bulges!***
***	******Sub-giants with WD cores are****** ******LISA ***
***	******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).**

## 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 ~100M****o**** 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-E****peak ****correlations**
**Response to E>100keV**
**needed even for z~10!**

**Flux vs. detected E****peak ****for GRBs from z=1 (top +) **
**to 10 (bottom +) for E****peak ****=30, 100, 300, 1000keV**
**if 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 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 and***** ******nuclear vs. accretion luminosity of the universe***

## Stellar BHs and IMBHs in Local Group

**All bright stellar BHs in transients (Lx(>10 keV) ~10****38 ****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 in***** *****Galactic Bulge***** nuclear cusp (cf. Alexander & Livio 2004) detected if Lx(>10 keV) ****≥****10****35 ****erg/s as expected for wind-fed binaries or for****	****CI Cam type outbursts (~1-2d)**

**Chandra view**
**of central Bulge**
**(~ 2****o****  x 1****o****)**

## EXIST Mission Reference Design

***Free-Flyer (500km, i ~ 22***o):
**Zenith pointer (Survey mode)**
**3-axis pointer (Observatory *****and *****survey)**
**3 coded aperture telescopes (2.7m****2 ****area &   60o x 75o each) for 8m****2****  & 180o x 75o fan-beam:           full sky/orbit & *****>20% continuous coverage***** **

***Mission Parameters:***
**CZT tiled arrays: 8m2 total area, **
** ****(****20x20x5mm crystals, ea. with 16x16 pixels; *****5 x 10******6 ******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)**

***Nod direction, ******┴ ******scan***
**(+/-20****o ****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 50****o**** x 60****o**** **
**	****	****3 x 3  or  4 x 4 STs per Telescope**
**3 coded aperture Telescopes (2.7m****2**** ea.) **
**	****	****1.5m focal length, 2.5mm mask pix**
**	****	****	****5arcmin resol., 10-50” loc.**
**	****	****	****0.05mCrab = 5 x 10****-13**** cgs, ****	****	****5****σ****, 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-IV***** shroud**

**Detector & 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, A****tot****.~8m****2****, and long exposure time, T****exp**** ****	**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 ~2N x 2N 	detector pixels)
**Imaging and mask design should yield ********10****2-3 ****dynamic range**
- 		since** **any 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?***

## Simulated 3C273 field (scanning vs. pointing)

***3C273 simulation*****: 0.5 - 1 year survey EXIST image (0.05mCrab, 5********, ****22****o ****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
- (20-600 keV) in balloon gondola

**64cm2 prototype,  image & Ba-133 spectra**

- lines at 276, 302, 356, 383keV

- CZT3 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 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 sensitivity****  *for 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

**Δ****x**

**d**

## 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**

## 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 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