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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

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Pharos distant beacons as cosmological probes

Pharos:

distant beacons ascosmological 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


Pharos distant beacons as cosmological probes

The fate of baryons


Pharos distant beacons as cosmological probes

The warm intergalactic medium

Lya clouds

WH

green d~10

red d~104

H

G


Pharos distant beacons as cosmological probes

Cen et al. 2005


Pharos distant beacons as cosmological probes

The warm intergalactic medium

IGM density

Dave’ et al 2000

IGM temperature

IGM metallicity

OVIII

OVII

Hellsten et al. 1998 ApJ, 509, 56


Pharos distant beacons as cosmological probes

Cen et al. 2005


Pharos distant beacons as cosmological probes

Cen et al. 2005


Pharos distant beacons as cosmological probes

Cen et al. 2005


Pharos distant beacons as cosmological probes

Cen et al. 2005


Detection of the local warm igm by chandra pks2155 line of sight

Detection of the Local Warm IGMby Chandra: PKS2155 line of sight

Nicastro et al. 2002 ApJ

  • HRC/LETG 63 ksec on 21mCrab source

  • R=400

  • ~700 counts/resolution element.

  • PKS2155-304 z=0.116 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->2p

  • All lines at z~0, -135 km s-1 from FUSE

OVII

OVIII

NeIX


Detection of warm igm by chandra mark421 line of sight

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 z>0

OVII(z=0.011) EW=0.05eV

OVII(z=0.027) EW=0.03eV

1015 cm-2

NVII(z=0.027) EW=0.05eV

Nicastro et al. 2005


Pharos distant beacons as cosmological probes

Cen et al. 2005


B n ovii 7x10 14 cm 2

Ωb(NOVII>7x1014 cm-2)

  • Mkn 421 (2 Filaments.): z=0.03

  • Combined Mkn421+1ES1028+511 (3 Filaments):

    Consistent with missing =2.5  0.4

(Nicastro et al., 2005, Nature, 433, 495; Steenbrugge et al., 2006, in prep.)


Physics and astrophysics of the warm igm

Physics and Astrophysics of the Warm IGM

  • How many lines? The baryon density at low redshift

  • How is the Warm IGM heated?

    shocks?->R>=6000

  • What is the history of the heating?

    mirrors decline of Lyman a forest? -> z=1- 2 X-ray forest

  • Did chemical enrichment trace heating?

    tracks star formation rates? ->R>=6000

  • Does the `X-ray forest’ redshift structure match CDM predictions?

    trace later formation of large scale structures

    -> z=0.1-1 X-ray forest


Reducing uncertainties

Reducing Uncertainties

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

Needs 100 to 1000 Detections!


Warm igm spectroscopy goals

Warm IGM Spectroscopy Goals

FUSE OVI

FWHM= 20 km s-1

FWHM= 660 km s-1

Chandra LETG OVII

goal

  • Resolve Warm IGM line widths:

  • 50 km s-1, R = 6000

  • Span 0<z<2 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


Pharos distant beacons as cosmological probes

  • The minimum detectable EW scales with the square root of E. Since the rest frame EW scales with (1+z)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


Physics and astrophysics of the warm igm1

Physics and Astrophysics of the Warm IGM

  • How many lines? The baryon density at low redshift

  • How is the Warm IGM heated?

    shocks?->R>=6000

  • What is the history of the heating?

    mirrors decline of Lyman a forest? -> z=1- 2 X-ray forest

  • Did chemical enrichment trace heating?

    tracks star formation rates? ->R>=6000

  • Does the `X-ray forest’ redshift structure match CDM predictions?

    trace later formation of large scale structures

    -> z=0.1-1 X-ray forest


Pharos distant beacons as cosmological probes

How was the Warm IGM heated?

Thermal broadening of O lines

is ~50 km/s at T=4106 K

Fang et al 2002


Pharos distant beacons as cosmological probes

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.


Gamma ray bursts

Gamma-rayBursts

Stupor Coeli

Greatest Lighthouses of the Universe

  • GRBs come from distant (z>1) explosions

  • Brighter than Crab Nebula for a few minutes

  • brightest GRB fluence

  • = 10-5 erg cm-2 (1min-12hr)

  • = 10 Msec (4months) observing brightest z~2 quasar, flux: 10-12 erg cm-2 s-1

  • GRBs are best `lighthouses’ to study intervening matter

Constellation-X SWG Sept 2002

BATSE all sky GRB map (http://f64nsstc.nasa.gov/batse/grb/skymap)


Pharos distant beacons as cosmological probes

BeppoSAX GRBM+WFC Frontera et al. 2000 Fiore et al. 2000

Assuming F(2-10)@30sec/Fpeak(50-300)=0.01 and a power law decay with =-1.3


Grbs are the best path fiore et al 2000 apjl astro ph 0303444

GRBs are the best pathFiore et al 2000 ApJL, astro-ph/0303444

  • Most GRB have X-ray afterglows, a few can be very bright(fluence> 1x10-5 erg s-1 )

  • brightest z~0.5-1 quasars (0.5 mCrab) take 2 weeks to gather same fluence

  • 1-2 GRB/yr at fluence>1x10-5 erg/cm2

  • = 1 Msec obs of a half mCrab AGN

  • 40 GRB/yr at fluence>1x10-6 erg/cm2

  • =100 ksec of a half mCrab AGN

  • resolve lines, detect faint lines

  • 100 GRB/yr at fluence>1x10-7 erg/cm2

  • detect X-ray forest

But … Swift will tell….!


Pharos distant beacons as cosmological probes

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


Pharos concept

Primary Targets: GRB Afterglows; Secondary Targets: QSOs, Blazars

Pharos Concept

  • Goal:R=6000 (50 km s-1) soft (<1 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


Pharos rapid x ray rich grb trigger location

Pharos: Rapid X-Ray-rich GRB Trigger & Location

  • Problem: require <1armin 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

0.1-1 keV (5-10” mirror): short focal length reduces moment of inertia,I=mR2

(factor 25 for 2 m vs. 10 m)

t=0 s

t=1-15 s

Trigger

5-30 keV ‘light’ ASM Coded Mask1’ localization in 0.5-1 s

Rapid rough slewto 1’ location

GRB trigger must be on-board & autonomous: 5-30 keV triggers X-ray rich

X-ray spectrometer starts to take data R>5000 @ 0.5 keV:

Out-of-plane Reflection Gratings

t=30 s

Fine slew

to <1 arcmin position

Constellation-X SWG Sept 2002


Superagile in short

1-D Coded Masks

Collimator

Si -strip Detectors

SuperAGILE in short

Costa, Feroci & the Super-Agile Coll.

Imposed by Agile


16 46x46 deg 2 sa s cover half sky

16 46x46 deg2 “SA”s 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/IBIS=700 kg; Swift/BAT>100 kg; ISS/MAXI=490 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 + FOV=46x46 deg2

    • Sensitivity: 1 mCrab in 50 ks (5-10 keV) at 5σ

  • CHEAP!: 1 M$ to redo it

  • LIGHT!: Total weight ~ 80 kg


X ray mirror area

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 E<0.9 keV higher reflectivity than Au

Minimum mirror

Baseline mirror

1200 cm-2

60kg (incl. 40%support)

2000 cm-2

200 kg (incl. 40% support)


Pharos distant beacons as cosmological probes

Pharos goal

Citterio & Pareschi


X ray gratings

X-ray Gratings

  • R=6000 is technically achievable

    XMM RGS gratings behind Chandra mirror -> R=5000

    (subject to improved facet alignment)

  • Out-of-plane reflection gratingsgive higher dispersion (Cash 1991)

  • Need5” FWHM mirror assembly. Control ofgrating scattering crucial.

    (else wings fill in absorption lines)

MIT gratings

+ HRC efficiency

~25-30%

Calorimeter +

Filter efficiency

~50%

5” resolution R=5400!!!


Figure of merit comparison with other missions

Figure of Merit: Comparison with other Missions

FoM

  • No other missionmatches 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) xGF

GF= Gain in Fluence = 1 Pharos,SwiftDt=10m

GF=0.04 Chandra, XMM, Con-XDt=4-8hr

* assumes R=1000

# for a 4-8hr response time

x 24 for 10 min response


Pharos summary

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 formation1997

    • The recombination epoch2000

  • R=6000 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


Gamma ray bursts one of the great wonders of the universe

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 z~6-?

    • The fate of the baryons & large scale structure

      1999 Warm IGM simulations

      2001 1st Warm IGM detection (thank to Chandra)


Pharos distant beacons as cosmological probes

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


Galaxies in the age of star formation

peak of star formation

star formation rate

GRB Hosts

redshift, (1+z)

Galaxies in the Age of Star Formation

GRBs also probe normal high z galaxies

  • Star formation in the Universe peaked at z~2

  • Studies of z=>1-2 galaxies are biased against dusty environments.

  • GRB hosts are normal galaxies

Mann et al. 2002 MNRAS, 332, 549

  • GRB afterglowswill reveal host

  • Galaxy dynamics, abundances, & dust content at z>1

X-ray high resolution spectroscopy

Optical-near infrared high resolution spectroscopy


Pharos distant beacons as cosmological probes

GOALS

1- The GRB environment:size and density of the region surrounding a GRB can be constrained by monitoring the absorption line equivalentwidths (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.


Pharos distant beacons as cosmological probes

Results from low resolution spectroscopy

High dust

depletion

High dust content

Denser clouds

DLAs

Savaglio, Fall & Fiore 2002


Pharos distant beacons as cosmological probes

DATA

UVES spectra 3800-9400 A, slit 1”, resolution=42,000

GRB020813: z=1.245 - Exposure of 5000 sec. 24 hours after the GRB; R=20.4, B=20.8

GRB021004: z=2.328- Exposure of 7200 sec. 12 hours after the GRB; R=18.6, B=19


Pharos distant beacons as cosmological probes

GRB021004

FORS1 R~1000

CIV CIV

z=2.296 z=2.328

UVES R=40000

z=2.296 z=2.328


Pharos distant beacons as cosmological probes

GRB021004

AlIII1854

AlII1670

SiIV1402

SiIV1393

CIV1550

CIV1548

z=2.321z=2.328


Pharos distant beacons as cosmological probes

GRB021004

z=2.321z=2.328

MgII2803

FeII1608

FeII2344

FeII2374

FeII2382


Pharos distant beacons as cosmological probes

GRB021004

AlIII1670

SiIV1393

SiIV1402

CIV1548

CIV1550

z=2.296 z=2.298

Constellation-X SWG Sept 2002


Pharos distant beacons as cosmological probes

GRB021004

z=2.296z=2.298

MgII2796

MgII2803

FeII1608

FeII2344

FeII2374

FeII2382

Constellation-X SWG Sept 2002


Pharos distant beacons as cosmological probes

Relative abundances in GRB021004


Comparison with cloudy models

Comparison with CLOUDY models:

Ionization parameter assuming solar abundances

Constellation-X SWG Sept 2002


Pharos distant beacons as cosmological probes

GRB020813

z=1.2545

MgII2796

MgII2803

FeII2344

FeII2374

FeII2382

FeII2600


Pharos distant beacons as cosmological probes

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.


Pharos distant beacons as cosmological probes

…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!


Beacons of the recombination era

Beacons of the Recombination Era

GRBs may be the only bright z>6 sources

  • Gunn-Peterson trough found in z=6.28 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 z>6

  • Bromm & Loeb

  • First metal production, snapshot of IGM

  • No quasars at z>>6?

  • GRBs a unique probe of recombination epoch?

HST Deep Field (http://www.stsci.edu/ftp/science/hdf/hdf/html)


In the meantime

In the meantime…

Swift is due to launch on Sept 2004!!!

Swift will trigger medium resolution [email protected]

observations with Chandra and XMM-Newton,

[email protected] 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


Rapid grb trigger location

Rapid GRB Trigger & Location

  • Problem: require <1armin location + acquisition in 1-10 minutes and require quasi-4p coverage: conflicting goals

  • Solution: divide GRB trigger from location (as on BeppoSAX)

short focal length reduces moment of inertia,I=mR2

(factor 25 for 2 meters vs. 10 meters)

t=3s

t=30s

~20cm dia

x ~50cm length

Trigger

faceted CsI solid1o in seconds

t=0s

Rapid rough slew to 1o location

Locationsmall X-ray coded maskeg XMM pn chip with 10ox10o fov to obtain arcmin location in a few seconds

GRB trigger must be on-board & autonomous

t=40s

Fine slew

to <1 arcmin position

t=60s

X-ray spectrometer starts to take data


Con x pros cons

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

    • R=6000 vs R~400 or R~2000

    • Add GRB trigger/locator

      `Christmas tree’ effect


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