1. Pharos: distant beacons as cosmological probes Fabrizio Fiore, Fabrizio Nicastro INAF-OAR, Martin Elvis SAO 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.

2. The fate of baryons

3. Ly  clouds WH H G green  ~10 red  ~10 4 The warm intergalactic medium

4. Cen et al. 2005

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

6. Cen et al. 2005

10. 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 , NeIX K  Weaker detection of OVIII K  EW 10-20 mA FUSE detection of OVI 2s->2p All lines at z~0, -135 km s -1 from FUSE  Detection of the Local Warm IGM by Chandra: PKS2155 line of sight OVII NeIX OVIII Nicastro et al. 2002 ApJ

11. Detection of Warm IGM by 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 cm 2 ! First detection of warm IGM at z>0 OVII(z=0.011) EW=0.05eV OVII(z=0.027) EW=0.03eV  10 15 cm -2  NVII(z=0.027) EW=0.05eV Nicastro et al. 2005

12. Cen et al. 2005

13. Ω b (N OVII >7x10 14 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  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 d N /dz uncertainties down to few % from current (+140,-70) %GOAL: Reduce  b and d N /dz uncertainties down to few % from current (+140,-70) % Needs 100 to 1000 Detections! Needs 100 to 1000 Detections!

16. Resolve Warm IGM line widths: 50 km s -1, R = 6000 Span 0<z<2 for OVII, OVIII: (OVIII K  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 Warm IGM Spectroscopy Goals FWHM= 20 km s -1 Chandra LETG OVII FUSE OVI goal FWHM= 660 km s -1 5  10 14 cm -2

17. The minimum detectable EW scales with the square root of  E. Since the rest frame EW scales with (1+z)EW obs 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  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  10 6 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. Constellation-X SWG Sept 2002 Gamma-ray Bursts BATSE all sky GRB map (http://f64nsstc.nasa.gov/batse/grb/skymap) 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 Stupor Coeli Greatest Lighthouses of the Universe

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 path Fiore 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/cm 2 = 1 Msec obs of a half mCrab AGN 40 GRB/yr at fluence> 1x10 -6 erg/cm 2 =100 ksec of a half mCrab AGN resolve lines, detect faint lines 100 GRB/yr at fluence>1x10 -7 erg/cm 2 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. Constellation-X SWG Sept 2002 Pharos: Rapid X-Ray-rich GRB Trigger & Location 0.1-1 keV (5-10” mirror): short focal length reduces moment of inertia, I=mR 2 (factor 25 for 2 m vs. 10 m) Problem: require <1armin location + acquisition in 0.5-1 minutes and require quasi-4  coverage: conflicting goals Solution: trigger in the 5-30 keV with 2 1-D Coded Masks Trigger 5-30 keV ‘light’ ASM Coded Mask 1 ’ localization in 0.5-1 s Rapid rough slew Rapid rough slew to 1 ’ location Fine slew to <1 arcmin position X-ray spectrometer starts to take data R>5000 @ 0.5 keV: Out-of-plane Reflection Gratings GRB trigger must be on-board & autonomous: 5-30 keV triggers X-ray rich t=0 s t=1-15 s t=30 s

28. SuperAGILE in short 1-D Coded Masks Collimator Si  -strip Detectors Energy Range15-40 keV Energy Resolution  7-8 keV FWHM Geometric Area1360 cm 2 Max Effective Area  280 cm 2 Field of View (ZR)2 x (68° x 107°) Angular Resolution 6 arcmin (on-axis) Source Location Accuracy  2-3 arcmin for bright sources Point Source Sensitivity  10 mCrab (50 ks, on axis) Timing Accuracy  5  s Imposed by Agile Costa, Feroci & the Super-Agile Coll.

29. 16 46x46 deg 2 “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 deg 2  Sensitivity: 1 mCrab in 50 ks (5-10 keV) at 5 σ  CHEAP!: 1 M$ to redo it  LIGHT!: Total weight ~ 80 kg

30. X-ray Mirror Area Baseline mirrorMinimum mirror 1200 cm -2 2000 cm -2 60kg (incl. 40%support) 200 kg (incl. 40% support) Low energy band allows wide grazing angles (up to 3-4 degrees) and short focal length: 2-2.5 meters – larger A eff Use Ni coating for E<0.9 keV higher reflectivity than Au

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 gratings give higher dispersion (Cash 1991) Need 5” FWHM mirror assembly. Control of grating scattering crucial. (else wings fill in absorption lines) 5” resolution R=5400!!! MIT gratings + HRC efficiency ~25-30% Calorimeter + Filter efficiency ~50%

33. Figure of Merit: Comparison with other Missions 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 = A eff (cm2) x  peak x R (0.5 keV) x GF XMM 1RGS # 2100 Chandra LETG # 5000 Chandra HETG # 9000 Swift1000 Con-X 1 unit # * 123,000 Con-X 4 units # * 500,000 Minimal Pharos600,000 Baseline Pharos2,500,000 * assumes R=1000 # for a 4-8hr response time x 24 for 10 min response FoM GF= Gain in Fluence = 1 Pharos,Swift  t=10m GF=0.04 Chandra, XMM, Con-X  t=4-8hr

34. Pharos Summary GRB afterglows combine 4 themes of early 21 st Century astrophysics: 1997 –The most energetic events in the Universe 1997 1999 –The fate of the baryons & large scale structure 1999 1997 – Galaxies in the age of star formation 1997 2000 – The recombination epoch 2000 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 21 st Century astrophysics: –Among the most energetic events in the Universe 1997 1 st GRB redshift (thank to BeppoSAX) 1997 1 st 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-? 2000-200? Gunn-Peterson trough at z~6-? –The fate of the baryons & large scale structure 1999 Warm IGM simulations 1999 Warm IGM simulations 2001 1 st Warm IGM detection (thank to Chandra) 2001 1 st 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. Galaxies in the Age of Star Formation Mann et al. 2002 MNRAS, 332, 549 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 GRB afterglows will reveal host Galaxy dynamics, abundances, & dust content at z>1 redshift, (1+z) star formation rate GRB Hosts peak of star formation GRBs also probe normal high z galaxies 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 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.

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

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=2.321 z=2.328

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

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

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

46. Relative abundances in GRB021004

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

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!

51. Beacons of the Recombination Era HST Deep Field (http://www.stsci.edu/ftp/science/hdf/hdf/html) 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 M sol `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 GRBs may be the only bright z>6 sources No quasars at z>>6? GRBs a unique probe of recombination epoch?

52. In the meantime… Swift is due to launch on Sept 2004!!! Swift will trigger medium resolution R=400@1keV observations with Chandra and XMM-Newton, R=1000@6keV observations with AstroE2 A few events/yr with Fluence  10 -6 erg cm 2 A dozen events/yr with Fluence  3  10 -7 erg cm 2 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

54. Rapid GRB Trigger & Location short focal length reduces moment of inertia, I=mR 2 (factor 25 for 2 meters vs. 10 meters) conflicting goalsProblem: require <1armin location + acquisition in 1-10 minutes and require quasi-4  coverage: conflicting goals Solution: divide GRB trigger from location (as on BeppoSAX) Trigger faceted CsI solid 1 o in seconds Rapid rough slew Rapid rough slew to 1 o location Location Location small X-ray coded mask eg XMM pn chip with 10 o x10 o fov to obtain arcmin location in a few seconds Fine slew to <1 arcmin position X-ray spectrometer starts to take data GRB trigger must be on-board & autonomous ~20cm dia x ~50cm length t=0s t=3st=30s t=60s t=40s

55. 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