Modeling the warm ionized ISM (primarily) Measureables:

1. The Fluctuating Ionized ISM: Galactic Distribution and Related IssuesJim Cordes (Cornell), Joe Lazio (NRL), Ramesh Bhat (Swinburne) Modeling the warm ionized ISM (primarily) Measureables: • what scales do we have evidence for? (kpc  few  100 km) • inversion into physical parameters (wavenumber spectrum, etc.) • # sightlines grossly undersamples Galactic structure Relationship between measures (DM, EM, SM) Galactic models • Prior vs fitted structures • NE2001 (Cordes & Lazio 2003); supercedes TC93 • NE200X: new data and new priors (esp. parallaxes out to 4 kpc) Constraints on the ionized IGM • Role of foreground plasma (IPM, ISM) Jim Cordes SINS Workshop

2. Why detailed modeling? • Distance scale for neutron stars • Neutron star populations (space density, velocities, luminosities) • Birth/death rates • Correlations with supernova remnants • Designing Radio Pulsar Surveys • Turbulence in Galactic plasma • Galactic magnetic fields (deconstructing Faraday rotation measures) • Interpreting scintillations of sources at cosmological distances (AGNs, GRBs) • Baseline model for exploring the intergalactic medium (dispersion & scattering in ISM, IGM) Jim Cordes SINS Workshop

3. Observables Jim Cordes SINS Workshop

4. Observables ℓ1= inner scale ℓ0= outer scale Jim Cordes SINS Workshop

5. Observables Jim Cordes SINS Workshop

6. Thin disk Thick disk Spiral arms Local ISM components Clumps of enhanced ne Voids of low ne Galactic Structures Necessary to Explain DM data Jim Cordes SINS Workshop

7. NE2001: Galactic Distribution of Free Electrons + Fluctuations Paper I = the model (astro-ph/0207156) Paper II = methodology & particular lines of sight (astro-ph/0301598) Code + driver files + papers: www.astro.cornell.edu/~cordes/NE2001 Jim Cordes SINS Workshop

8. Asymptotic DM Jim Cordes SINS Workshop

9. Empirical Distances vs. Model Distances Jim Cordes SINS Workshop

10. Possibly born in Cyg OB 6 ,b = 91.3o, 52.3o D = 2.450.25 kpc V = 1114-94+132 km s-1 P = 0.74 s B = 2x1012 G s = P/2Pdot = 2.36 Myr The highest measured velocity using direct distance measurement 2.5x further than electron density model based distance estimate (NE2001)

11. Constraints on spectrum: Small scales: (“micro tiny” ?) Scaling of DISS parameters with  angle, frequency, time Scintillation arcs DM(t) on months to years DM() in globular clusters RISS parameters Large scales: RM vs  EM, DM, SM on same LOS Bow shock contours (Guitar Neb) All scales: Cosmic ray scattering on B and linkage ne/ne ~ B/B  ~ 11/3 Estimated Wavenumber Spectrum for ne see also Armstrong, Rickett, Spangler 1995 Jim Cordes SINS Workshop

12. Methods for Probing ne on Small Scales Jim Cordes SINS Workshop

13. Summary of Constraints on Length Scales in WIM • Spectral index of wavenumber spectrum •   11/3  0.3 commonly inferred • Exceptions most likely due to special geometries or inner scale effects (e.g. “anomalous” pulse broadening) • Excess power inferred on ~ AU scales from refractive ISS probably due to deterministic structures • Outer scale: • At least ~ 100 AU from DM(t) measurments • ~ 0.01 pc in high scattering regions with EM obs • > 1 pc inferred from EM, DM, SM of thick disk component • Inner scale: • 100 to 103 km from visibility, pulse broadening measurements • Scintillation arcs (TBD) • N.b. proton gyro-radius Jim Cordes SINS Workshop

14. Pulse Broadening Bhat, Cordes et al. 2004, unpub. Jim Cordes SINS Workshop

15. Scaling of Pulse Broadening with DM and  Jim Cordes SINS Workshop

16. Scaling of pulse broadening with DM and  c.f. similar constraints on inner scale from Moran et al. 1990; Spangler and Gwinn 1990; Molnar et al. 1996 based on angular broadening measurements of AGNs and Cyg X-3 Jim Cordes SINS Workshop

17. Constraints from Arcs c.f. Dan Stinebring’s talk Large inner scales and media with single scales or steep wavenumber spectra (4) suppress arcs Jim Cordes SINS Workshop

18. dSM  F ne dDM F  (dne / ne )2 / f (outer scale)2/3 Evidence for variations in turbulence properties between inner & outer Galaxy large F F varies by 100 between inner and outer Galaxy  Change in porosity from different SFR? small F Jim Cordes SINS Workshop

19. NE200X • 3 more lines of sight with pulsar parallaxes Brisken, Chatterjee et al. published, unpublished • ~ 1000 more pulsar DM values • DM() on globular-cluster scales (dozens) • ~150 new pulse-broadening measurements • Use scintillation arcs for local ISM screens • More linkage between optical and radio tracers • Alternative Sun-GC distance • New spiral arm definitions Jim Cordes SINS Workshop

20. The SKA as a Pulsar/Gravity/ISM Machine • Relativistic binaries (NS-NS, NS-BH) for probing strong-field gravity • Orbit evolution of pulsars around Sgr A* • Millisecond pulsars < 1.5 ms (EOS) • MSPs suitable for gravitational wave detection • 100s of NS masses (vs. evolutionary path, EOS, etc) • Galactic tomography of electron density and magnetic field; definition of Milky Way’s spiral structure • Target classes for multiwavelength and non-EM studies (future gamma-ray missions, gravitational wave detectors) Millisecond Pulsars Relativistic Binaries Today Future Today Future SKA SKA Blue points: SKA simulation Black points: known pulsars only 6! ~104 pulsar detections Jim Cordes SINS Workshop

21. Scattering in the IGM? (Lazio, Cordes, Fey in preparation) SM vs Galactic latitude AGNs pulsars Jim Cordes SINS Workshop

22. IGS Summary • Contribution from IGM is still very uncertain • IPS contribution • General IGM: no knowledge of what the level of turbulence really is, though the ingredients (ionized gas, shocks, winds) are there • Intervening galaxies: will contribute to some LOS  selected lines of sight • Empirically: accuracy of foreground Galactic model is crucial and perhaps not sufficient • Progress: • Angular broadening vs l,b for large number of AGNS • Search for AGNs and measure scattering through known galaxies and clusters • Secondary spectrum analyses of IDVs and GRB afterglows to get best estimates of angular size “seen” by the ISM • LOFAR, SKA: can measure large numbers of sources though wide-field studies Jim Cordes SINS Workshop

23. Summary • Strong evidence exists for an inner scale on LOS toward heavily scattered pulsars (few  100 km)…not inconsistent with the proton gyro-radius of WIM (or ion-inertial scale) in typical ISM B fields • The fluctuation parameter F = (ne/ne)2 / f ℓ02/3 varies by a factor of 100 between the solar circle and inner Galaxy; this may reflect the larger SFR in the inner Galaxy • Available LOS indicate the broad structures needed for a Galactic model for ne and ne (thin, thick disks, spiral arms, strong GC component, clumps and voids) (NE2001) • A new model NE200X (X=6, maybe 7) is in the works that will make use of new parallaxes, pulse broadening, new methods for modeling the local ISM (arcs) • VLBI on large samples (esp. IDV sample) can constrain or detect IGM scattering • The SKA will provide adequate LOS to critically sample most HII structures in the Galaxy, define spiral arms from pulsar birth sites Jim Cordes SINS Workshop

24. Extra Slides Jim Cordes SINS Workshop

25. NE2001 • Goal is to model ne(x) and Cn2(x)  Fne2(x)in the Galaxy • Input data = {DM, EM, SM, [DL, DU] = distance ranges} • Prior input: • Galactic structure, HII regions, spiral-arm loci • Multi- constraints on local ISM (H, NaI, X-ray) • Figures of merit: • N> = number of objects with DM > DM (model) (minimize) • Nhits = number of LOS where predicted = measured distance: d(model)  [DL, DU] (maximize) • L = likelihood function using distances & scattering (maximize) • Basic procedure: get distances right first, then get scattering (turbulence) parameters Jim Cordes SINS Workshop

26. Local ISM components & results Jim Cordes SINS Workshop

27. Model Components Jim Cordes SINS Workshop

28. Galactic Center Component Jim Cordes SINS Workshop

29. Thin disk Jim Cordes SINS Workshop

30. Thick disk (1 kpc) Jim Cordes SINS Workshop

31. Spiral arms Jim Cordes SINS Workshop

32. DM vs Galactic longitude for different latitude bins Jim Cordes SINS Workshop

33. DM vs Galactic longitude for different latitude bins Jim Cordes SINS Workshop

34. 134 of 1143 TC93 distances are lower bounds Jim Cordes SINS Workshop

35. DM(psr)-DM(model, ) Jim Cordes SINS Workshop

36. Asymptotic DM Jim Cordes SINS Workshop

37. Constraints on spectrum: Small scales: Scaling of DISS parameters with  angle, frequency, time Scintillation arcs DM(t) on month to years DM() in globular clusters RISS parameters Large scales: RM vs  EM, DM, SM on same LOS Bow shock contours (Guitar Neb) All scales: Cosmic ray scattering on B and linkage ne/ne ~ B/B Slope ~ -11/3 Estimated Wavenumber Spectrum for ne Jim Cordes SINS Workshop

38. Pulse Broadening Jim Cordes SINS Workshop

39. Constraints on the Inner Scale From DISS Scaling Jim Cordes SINS Workshop

40. Jim Cordes SINS Workshop

41. Jim Cordes SINS Workshop

42. Is the DM distance Realistic? Yes Standoff radius and flux are consistent Jim Cordes SINS Workshop

43. Galactic Center Region Sgr A* = 3106 black hole with a surrounding star cluster with ~ 108 stars. Many of these are neutron stars. Detecting pulsars in Sgr A* is difficult because of the intense scattering screen in front of Sgr A*. Multipath differential arrival times d ~ 2000 ν-4 sec Solution: high sensitivity at high frequency 327 MHz VLA image Jim Cordes SINS Workshop

44. Jim Cordes SINS Workshop

45. Observables l1= inner scale l0= outer scale Jim Cordes SINS Workshop

46. Scaling of pulse broadening with DM and  c.f. similar constraints on inner scale from Moran et al. 1990; Spangler and Gwinn 1990; Molnar et al. 1996 based on angular broadening measurements of AGNs and Cyg X-3 Jim Cordes SINS Workshop