A High Resolution Intergalactic Explorer for the Soft XrayFarUV

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Pharos distant beacons as cosmological
probes
The Pharos of Alexandria, one of the Seven
Wonders of the ancient world, was the
tallest building on Earth (120m). Its
mysterious mirror, which reflection could be
seen more than 55 km off-shore fascinated
scientists for centuries.
Fabrizio Fiore, Fabrizio Nicastro INAF-OAR,
Martin Elvis SAO
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The fate of baryons
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The warm intergalactic medium
Lya clouds
WH
H
green d10 red d104
G
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Cen et al. 2005
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The warm intergalactic medium

IGM density
Dave et al 2000
IGM temperature
IGM metallicity
OVIII
OVII
Hellsten et al. 1998 ApJ, 509, 56
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Cen et al. 2005
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Cen et al. 2005
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Cen et al. 2005
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Cen et al. 2005
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Detection of the Local Warm IGMby Chandra
PKS2155 line of sight
Nicastro et al. 2002 ApJ

• HRC/LETG 63 ksec on 21mCrab source
• R400
• 700 counts/resolution element.
• PKS2155-304 z0.116 blazar Cal. target.
• Strong detection of OVII Ka 21.9A,
• NeIX Ka
• Weaker detection of OVIII Ka
• EW 10-20 mA
• FUSE detection of OVI 2s-gt2p
• All lines at z0, -135 km s-1 from FUSE

OVII
OVIII
NeIX
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Detection of Warm IGMby Chandra Mark421 line
of sight
The highest S/N grating spectrum
ever! 40-60mCrab source yielded 2500 counts per
resolution el. at 0.6 keV! Fluence of 10-4 erg
cm2! First detection of warm IGM at
zgt0 OVII(z0.011) EW0.05eV OVII(z0.027)
EW0.03eV ?1015 cm-2 ? NVII(z0.027)
EW0.05eV Nicastro et al.
2005
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Cen et al. 2005
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Ob(NOVIIgt7x1014 cm-2)

• Mkn 421 (2 Filaments.) z0.03
• Combined Mkn4211ES1028511 (3 Filaments)
• Consistent with ?missing 2.5 ? 0.4

(Nicastro et al., 2005, Nature, 433, 495
Steenbrugge et al., 2006, in prep.)
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Physics and Astrophysics of the Warm IGM

• How many lines? The baryon density at low
  redshift
• How is the Warm IGM heated?
• shocks? -gt Rgt6000
• What is the history of the heating?
• mirrors decline of Lyman a forest? -gt z1-
  2 X-ray forest
• Did chemical enrichment trace heating?
• tracks star formation rates? -gt Rgt6000
• Does the X-ray forest redshift structure match
  CDM predictions?
• trace later formation of large scale
  structures
• -gt z0.1-1 X-ray forest

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Reducing Uncertainties

• GOAL Reduce ?b and dN/dz uncertainties down to
  few from current (140,-70)

Needs 100 to 1000 Detections!
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Warm IGM Spectroscopy Goals
FWHM 20 km s-1
FUSE OVI
FWHM 660 km s-1
Chandra LETG OVII
goal

• Resolve Warm IGM line widths
• 50 km s-1, R 6000
• Span 0ltzlt2 for OVII, OVIII
• (OVIII Ka 18.97A OVIII Ka 22.09A)
• i.e. 18 - 66A, 0.19 keV - 0.7 keV minimum
• Extra line diagnostics
• NeIX (13.69A) 0.31 - 0.92 keV
• CVI (33.73A) 0.13 - 0.38 keV
• weak lines need high resolving power

5?1014 cm-2
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• The minimum detectable EW scales with the square
  root of ?E. Since the rest frame EW scales with
  (1z)EWobs and since for gratings ?E scales with
  E-1, the minimum detectable rest frame EW is
  nearly constant with z.
• Similar column densities can be probed with
  gratings in the z range 0-2

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Physics and Astrophysics of the Warm IGM

• How many lines? The baryon density at low
  redshift
• How is the Warm IGM heated?
• shocks? -gt Rgt6000
• What is the history of the heating?
• mirrors decline of Lyman a forest? -gt z1-
  2 X-ray forest
• Did chemical enrichment trace heating?
• tracks star formation rates? -gt Rgt6000
• Does the X-ray forest redshift structure match
  CDM predictions?
• trace later formation of large scale
  structures
• -gt z0.1-1 X-ray forest

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How was the Warm IGM heated? Thermal broadening
of O lines is 50 km/s at T4?106 K
Fang et al 2002
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Hydrodynamic simulations show that reasonable
warm intergalactic gas turbulence may be of 100
km s-1 up t0 200 km/s (implying a resolution of
1500-3000 to resolve these lines and measure the
Doppler term b. If the temperature of the gas
can be constrained through OVI, OVII and OVIII
line ratios the measure of b can provide
information on the heating history of the gas.
For example, if the gas were shock heated one
would expect that the gas temperature is
proportional to the square of the gas sound
speed, which in turn should be proportional to
the gas turbulence. By measuring b and T it
would be possible to check this idea and to
provide tests and constraints to hydrodynamic
models.
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Gamma-ray Bursts
Stupor Coeli Greatest Lighthouses of the Universe

• GRBs come from distant (zgt1) explosions

• Brighter than Crab Nebula for a few minutes

• brightest GRB fluence
• 10-5 erg
  cm-2 (1min-12hr)
• 10 Msec (4months) observing brightest z2
  quasar, flux 10-12 erg cm-2 s-1

• GRBs are best lighthouses to study intervening
  matter

BATSE all sky GRB map (http//f64nsstc.nasa.gov/ba
tse/grb/skymap)
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BeppoSAX GRBMWFC Frontera et al. 2000
Fiore et al. 2000
Assuming F(2-10)_at_30sec/Fpeak(50-300)0.01 and a
power law decay with ?-1.3
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GRBs are the best path
Fiore et al 2000 ApJL, astro-ph/0303444

• Most GRB have X-ray afterglows, a few can be
  very bright (fluencegt 1x10-5 erg s-1 )
• brightest z0.5-1 quasars (0.5 mCrab) take 2
  weeks to gather same fluence
• 1-2 GRB/yr at fluencegt1x10-5 erg/cm2
• 1 Msec obs of a half mCrab AGN
• 40 GRB/yr at fluencegt1x10-6 erg/cm2
• 100 ksec of a half mCrab AGN
• resolve lines, detect faint lines
• 100 GRB/yr at fluencegt1x10-7 erg/cm2
• detect X-ray forest

But Swift will tell.!
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44 GRB localized by Swift BAT 8 GRB localized by
BSAX WFC, Extrapolated from 30sec to 100 sec, 2.4
hr assuming ?-1.3
100 sec
2.4 hr
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Pharos Concept

• Goal R6000 (50 km s-1) soft (lt1 keV) X-ray
  spectroscopy
• Cosmological driver measure baryon density at
  low z
• Physics driver resolve thermal widths of X-ray
  lines
• Astronomy driver resolve internal galaxy motions

• Gamma-ray Burst (GRB) afterglows may produce many
  more X-ray photons than any other high redshift
  source (i.e. quasars).
• Requires acquisition within 10 minutes of GRB
• 1 minute goal, as Swift

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Pharos Rapid X-Ray-rich GRB Trigger Location

• Problem require lt1armin location acquisition
  in 0.5-1 minutes and require quasi-4p coverage
  conflicting goals
• Solution trigger in the 5-30 keV with 2 1-D
  Coded Masks

t0 s
t1-15 s
Trigger 5-30 keV light ASM Coded Mask 1
localization in 0.5-1 s
Rapid rough slew to 1 location

• 0.1-1 keV (5-10 mirror) short focal length
  reduces moment of inertia, ImR2
• (factor 25 for 2 m vs. 10 m)

GRB trigger must be on-board autonomous 5-30
keV triggers X-ray rich
X-ray spectrometer starts to take data Rgt5000 _at_
0.5 keV Out-of-plane Reflection Gratings
t30 s
Fine slew to lt1 arcmin position
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SuperAGILE in short
Costa, Feroci the Super-Agile Coll.
Imposed by Agile
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16 46x46 deg2 SAs cover Half Sky

• Current Size and Thickness Imposed by Agile
• Presence of Agile anticoincidence limits current
  sensitivity by 1.5-2
• Only 5.5 kg (can be improved)
• Integral/IBIS700 kg Swift/BATgt100 kg
  ISS/MAXI490 kg
• Current Energy Range 15-40 keV
• -Low Energy Threshold halved just doubling the
  points of read-outs ? 7-40 keV for free!!
• -High Energy Threshold increases with thickness
• 650 ?m Si-thickness FOV46x46 deg2
• Sensitivity 1 mCrab in 50 ks (5-10 keV) at 5s
• CHEAP! 1 M to redo it
• LIGHT! Total weight 80 kg

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X-ray Mirror Area

• Low energy band allows wide grazing angles (up to
  3-4 degrees) and
• short focal length 2-2.5 meters larger Aeff
• Use Ni coating for Elt0.9 keV higher reflectivity
  than Au

Baseline mirror
Minimum mirror
1200 cm-2
2000 cm-2
60kg (incl. 40support)
200 kg (incl. 40 support)
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Pharos goal
Citterio Pareschi
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X-ray Gratings

• R6000 is technically achievable
• XMM RGS gratings behind Chandra mirror -gt
  R5000
• (subject to improved facet alignment)
• Out-of-plane reflection gratings give higher
  dispersion (Cash 1991)
• Need 5 FWHM mirror assembly. Control of grating
  scattering crucial.
• (else wings fill in absorption lines)

MIT gratings HRC efficiency 25-30 Calorimete
r Filter efficiency 50
5 resolution R5400!!!
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Figure of Merit Comparison with other Missions
FoM

• No other mission matches R 6000 in X-rays
• WHIM and high z galaxy dynamics unavailable.
• Other missions can still detect WHIM systems in
  GRBs
• Compare a figure of merit

FoM Aeff (cm2) x epeak x R (0.5 keV) x GF
GF Gain in Fluence 1 Pharos,Swift
Dt10m GF0.04 Chandra, XMM, Con-X Dt4-8hr
assumes R1000 for a 4-8hr response time x
24 for 10 min response
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Pharos Summary

• GRB afterglows combine 4 themes of
• early 21st Century astrophysics
• The most energetic events in the Universe 1997
• The fate of the baryons large scale structure
  1999
• Galaxies in the age of star formation 1997
• The recombination epoch 2000
• R6000 X-ray spectroscopy opens up all of these
  new physics and astrophysics
• A small, short, soft X-ray telescope is enough
• Rapid GRB trigger autonomous slewing essential

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Gamma ray bursts one of the great wonders of
the Universe

• GRBs combine 4 themes of
• early 21st Century astrophysics
• Among the most energetic events in the Universe
• 1997 1st GRB redshift (thank to BeppoSAX)
• Galaxies in the age of star formation
• metal abundances, dynamics, gas ionization,
  dust
• The recombination epoch
• 2000-200? Gunn-Peterson trough at z6-?
• The fate of the baryons large scale structure
• 1999 Warm IGM simulations
• 2001 1st Warm IGM detection (thank to Chandra)

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Minutes after the GRB event their afterglows are
the brightest sources in the sky at cosmological
redshift. Afterglows can be used to
probe the high redshift Universe through the
study of the intervening matter along the line of
sight. Two possible applications Galaxies in
the age of star-formation through high resolution
spectroscopy of UV lines The warm intergalactic
medium through high resolution X-ray spectroscopy
of highly ionized C,O,Ne lines
GRB010222 10
Crab! Crab 1mCrab i.e. a bright AGN
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Galaxies in the Age of Star Formation
GRBs also probe normal high z galaxies

• Star formation in the Universe peaked at z2

• Studies of zgt1-2 galaxies are biased against
  dusty environments.

• GRB hosts are normal galaxies

Mann et al. 2002 MNRAS, 332, 549

• GRB afterglows will reveal host
• Galaxy dynamics, abundances, dust content at
  zgt1

X-ray high resolution spectroscopy Optical-near
infrared high resolution spectroscopy
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GOALS 1- The GRB environment size and density
of the region surrounding a GRB can be
constrained by monitoring the absorption line
equivalent widths (Perna Loeb 1998). This can
be used to discriminate among competing GRB
progenitor scenarios. 2- Metal column densities,
gas ionization and kinematics These studies
have so far relied upon either Lyman Break
Galaxies or Damped Lyman Alpha systems. However,
it is not clear if these systems are truly
representative of the whole high-z galaxy
population. GRB afterglows can provide new,
independent tools to study high z galaxies.
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Results from low resolution spectroscopy
High dust depletion High dust content Denser
clouds
Savaglio, Fall Fiore 2002
DLAs
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DATA UVES spectra 3800-9400 A, slit 1,
resolution42,000 GRB020813 z1.245 - Exposure
of 5000 sec. 24 hours after the GRB R20.4,
B20.8 GRB021004 z2.328- Exposure of 7200 sec.
12 hours after the GRB R18.6, B19
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GRB021004 FORS1
R1000 CIV
CIV z2.296 z2.328

UVES R40000 z2.296 z2.328
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GRB021004
AlIII1854

AlII1670 SiIV1402 SiIV1393 CIV1550
CIV1548
z2.321 z2.328
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GRB021004
z2.321 z2.328 MgII2803

FeII1608 FeII2344 FeII2374 FeII2382
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GRB021004

AlIII1670

SiIV1393 SiIV1402 CIV1548 CIV1550

z2.296 z2.298
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GRB021004

z2.296 z2.298 MgII2796 MgII2803

FeII1608 FeII2344 FeII2374 FeII2382
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Relative abundances in GRB021004
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Comparison with CLOUDY models
Ionization parameter assuming solar
abundances
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GRB020813
z1.2545
MgII2796 MgII2803
FeII2344 FeII2374
FeII2382 FeII2600
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Summary High resolution UVES observations can
provide reliable ion column densities. The
GRB021004 higher z systems have much fainter low
ionization lines (FeII, MgII) than the GRB020813
systems (and most other GRBs), and strong high
ionization lines. The photoionization results of
CLOUDY yield ionization parameters constrained in
a relatively small range with no clear trend with
the system velocity. This can be interpreted as
density fluctuations on top of a regular R-2 wind
density profile.
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but this is only the begining! With Swift we
will have many more prompt triggers, say 20/yr
during the Paranal night and we will use the
VLT in Rapid Response Mode (10-20 minutes to go
on the GRB!) so .. stay tuned for many more
results on GRB host galaxies!
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Beacons of the Recombination Era
GRBs may be the only bright zgt6 sources

• Gunn-Peterson trough found in z6.28 quasar
  Epoch of reionization
• Becker et al., Djorgovski et al.

• Primordial star formation (PopIII) may create
  100-1000s Msol stars Madau, Norman et al.

• Quickly produce hypernovae GRBs?

• 10 of GRBs may be at zgt6
• Bromm Loeb
• First metal production, snapshot of IGM

• No quasars at zgtgt6?
• GRBs a unique probe of recombination epoch?

HST Deep Field (http//www.stsci.edu/ftp/science/h
df/hdf/html)
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In the meantime
Swift is due to launch on Sept 2004!!!
Swift will trigger medium resolution R400_at_1keV
observations with Chandra and XMM-Newton,
R1000_at_6keV observations with AstroE2 A few
events/yr with Fluence?10-6 erg cm2 A dozen
events/yr with Fluence?3?10-7 erg cm2 Warm
IGM Statistics of OVII lines first reliable
measure of ?B at low z Host galaxy
ISM Observations with the calorimeters of
AstroE2 will measure metal column densities, gas
ionization parameter, gas dynamics
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Rapid GRB Trigger Location

• Problem require lt1armin location acquisition
  in 1-10 minutes and require quasi-4p coverage
  conflicting goals
• Solution divide GRB trigger from location (as on
  BeppoSAX)

20cm dia x 50cm length
t3s
t30s
Trigger faceted CsI solid 1o in seconds
t0s
Rapid rough slew to 1o location
Location small X-ray coded mask eg XMM pn chip
with 10ox10o fov to obtain arcmin location in a
few seconds

• short focal length reduces moment of inertia,
  ImR2
• (factor 25 for 2 meters vs. 10 meters)

GRB trigger must be on-board autonomous
t40s
Fine slew to lt1 arcmin position
t60s
X-ray spectrometer starts to take data
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Con-X Pros Cons

• Pros
• Real project 2010 launch
• Next new MIDEX launch 200X
• Includes 1-10 keV
• 10 -100 keV spectra

• Cons
• 1min vs 12 hr slews
• R6000 vs R400 or R2000
• Add GRB trigger/locator
• Christmas tree effect