Pharos: distant beacons as cosmological probes

1. 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

2. The fate of baryons

3. The warm intergalactic medium Lya clouds WH green d~10 red d~104 H G

4. Cen et al. 2005

5. The warm intergalactic medium IGM density Dave’ et al 2000 IGM temperature IGM metallicity OVIII OVII Hellsten et al. 1998 ApJ, 509, 56

6. Cen et al. 2005

7. Cen et al. 2005

8. Cen et al. 2005

9. Cen et al. 2005

10. 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

11. 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

12. Cen et al. 2005

13. 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.)

14. 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

15. Reducing Uncertainties • GOAL: Reduce b and dN/dz uncertainties down to few % from current (+140,-70) % Needs 100 to 1000 Detections!

16. 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

17. 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

18. 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

19. How was the Warm IGM heated? Thermal broadening of O lines is ~50 km/s at T=4106 K Fang et al 2002

20. 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.

21. 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)

23. 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

24. 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….!

25. 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

26. 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

27. 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

28. 1-D Coded Masks Collimator Si -strip Detectors SuperAGILE in short Costa, Feroci & the Super-Agile Coll. Imposed by Agile

29. 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

30. 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)

31. Pharos goal Citterio & Pareschi

32. 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!!!

33. 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

34. 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

35. 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)

36. 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

37. 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

38. 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.

39. Results from low resolution spectroscopy High dust depletion High dust content Denser clouds DLAs Savaglio, Fall & Fiore 2002

40. 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

41. GRB021004 FORS1 R~1000 CIV CIV z=2.296 z=2.328 UVES R=40000 z=2.296 z=2.328

42. GRB021004 AlIII1854 AlII1670 SiIV1402 SiIV1393 CIV1550 CIV1548 z=2.321z=2.328

43. GRB021004 z=2.321z=2.328 MgII2803 FeII1608 FeII2344 FeII2374 FeII2382

44. GRB021004 AlIII1670 SiIV1393 SiIV1402 CIV1548 CIV1550 z=2.296 z=2.298 Constellation-X SWG Sept 2002

45. GRB021004 z=2.296z=2.298 MgII2796 MgII2803 FeII1608 FeII2344 FeII2374 FeII2382 Constellation-X SWG Sept 2002

46. Relative abundances in GRB021004

47. Comparison with CLOUDY models: Ionization parameter assuming solar abundances Constellation-X SWG Sept 2002

48. GRB020813 z=1.2545 MgII2796 MgII2803 FeII2344 FeII2374 FeII2382 FeII2600

49. 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.

50. …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!