1. A New Pulsar Distance Scale and its Implications J. M. Cordes, Cornell University cordes@astro.cornell.edu COSPAR 11 October 2002 New electron density model (n e &  n e ) How is it different from Taylor & Cordes ’93 and other models? Ingredients and performance Implications: –Pulsar searches –Pulsar velocities –Luminosities (radio, X-ray,  -rays) VLBI astrometry = breakthrough Arecibo + GBT + VLA + Effelsburg + Jodrell = parallax machine Square Kilometer Array = Mother of all parallax machines w/ J. Lazio, S. Chatterjee, Z. Arzoumanian, D. Chernoff

2. New Model = NE2001 Cordes & Lazio Paper I = the model (astro-ph July ’02) Paper II = methodology & particular lines of sight Code + driver files (and paper I): www.astro.cornell.edu/~cordes/

3. Why detailed modeling? Distance scale for neutron stars –Neutron star populations (space density, luminosities) –Birth/death rates –Correlations with supernova remnants 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)

4. Integrated Measures DM  ds n e Dispersion Measure EM  ds n e 2 Emission Measure RM  ds n e B  Rotation Measure SM  ds C n 2 Scattering Measure Spectrum = C n 2 q - , q = wavenumber (temporal spectrum not well constrained, relevant velocities ~ 10 km/s)  = 11/3 (Kolmogorov value) Scales ~ 1000 km to > pc

5. Integrated Measures DM  ds n e Dispersion Measure EM  ds n e 2 Emission Measure RM  ds n e B  Rotation Measure SM  ds C n 2 Scattering Measure Spectrum = C n 2 q - , q = wavenumber (temporal spectrum not well constrained, relevant velocities ~ 10 km/s)  = 11/3 (Kolmogorov value) Scales ~ 1000 km to > pc

6. Integrated Measures DM  ds n e Dispersion Measure EM  ds n e 2 Emission Measure RM  ds n e B  Rotation Measure SM  ds C n 2 Scattering Measure Spectrum = C n 2 q - , q = wavenumber (temporal spectrum not well constrained, relevant velocities ~ 10 km/s)  = 11/3 (Kolmogorov value) Scales ~ 1000 km to > pc

7. Modeling the Galactic n e &  n e mean & fluctuations are modelled dSM = C n 2 ds  F n e 2 ds  F n e dDM F = “fluctuation parameter” varies widely over Galaxy  n e ~ C n (outer scale) 1/3 possible/probable  n e / n e ~ 1 not clear that  n e on all scales due to same process

8. Electron density of TC93 Taylor & Cordes (1993 ApJ, 411, 674)

9. Deficiencies of TC93 DM too small for distant, high latitude objects Distances overestimated for many objects in theGalactic plane (10% of now-known objects have DMs too large to be accounted for) Pulse broadening over/underestimated in some directions Spiral arms incompletely defined over Galaxy No Galactic center component

10. NE2001 x2 more lines of sight (D,DM,SM) [114 with D/DM, 471 with SM/D or DM] (Parkes MB in next version) Local ISM component (new) [12 parameters] Thin & thick disk components (as in TC93) [8 parameters] Spiral arms (revised from TC93) [21 parameters] Galactic center component (new) [3 parameters] (+auxiliary VLA/VLBA data ; Lazio & Cordes 1998) Individual `clumps’ of enhanced DM/SM (new) [5 parameters per clump] (Voids also) Improved fitting method (iterative likelihood analysis) penalty if distance or SM is not predicted to within the errors

11. Independent Pulsar Distances Parallaxes:Pulse timing Interferometry Associations:Supernova remnants Globular clusters HI Absorption:Galactic rotation

12. Very Long Baseline Array PSR B0919+06 S. Chatterjee et al. (2001)  = 88.5  0.13 mas/yr  = 0.83  0.13 mas D = 1.2kpc V = 505 km/s

13. Brisken et al. 2001; 2002

14. Model Components

15. Galactic Center Component

16. Thin disk

17. Thick disk (1 kpc)

18. Spiral arms

19. DM vs Galactic longitude for different latitude bins

21. 134 of 1143 TC93 distances are lower bounds

22. DM(psr)-DM(model,  )

23. Asymptotic DM

24. Differential TOA from Multipath: Quenching of pulsations for  d > P.

25. Pulsar Velocities Lyne & Lorimer 1994: Proper motions + TC93  ~ 500 km/s Unimodal distribution Cordes & Chernoff 1997: MSP analysis (TC93)  ~ 80 km/s Cordes & Chernoff 1998: High-field pulsars (TC93), < 10 Myr, 3D velocities (z/t) No correction for selection effects  bimodal V,  1 ~ 175 km/s,  2 ~ 700 km/s (14%) Arzoumanian, Chernoff & Cordes 2002: Full analysis (beaming, selection effects, TC93)  bimodal V,  1 ~ 90 km/s,  2 ~ 500 km/s (40%)

26. ACC ‘02 How might the results change using NE2001 instead of TC93?

27. Guitar Nebula & PSR B2224+65 Edot ~ 10 33 erg/s P~0.6 sec D(TC93) = 2 kpc  V  ~1700 km/s D(NE2001) = 1.7 kpc  V  ~1450 km/s H  Palomar 5-m image

28. Is the DM distance Realistic?

29. Is the DM distance Realistic? Yes Standoff radius and flux are consistent

30. Pulsar velocities using only objects with parallax measurements Distribution shows high- velocity tail and is “not inconsistent” with ACC results on high-field pulsars and CC97 on MSPs

31. New Parallax Programs 53 pulsars using VLBA antennas only at 1.4 GHz (systematics: ionospheric phase) Chatterjee, Brisken et al. (2002-2004) Currently can reach ~ 2 kpc 6 strong pulsars, VLBA-only at 5 GHz Ionosphere less important Chatterjee, Cordes et al. (2001-ongoing) VLBA + Arecibo + GBT + … Initial tests Expect to do ~100 pulsars in 5 years, some to 5 kpc Future: SKA  superior phase calibration, sensitivity, can reach >10 kpc

32. Parkes MB Feeds Arecibo Multibeam Surveys

33. I. Arecibo Galactic-Plane Survey |b| < 5 deg, 32 deg < l < 80 deg 1.5 GHz total bandwidth = 300 MHz digital correlator backend (1024 channels) (1st quadrant available = WAPP) multibeam system (7 feeds) ~300 s integrations, 3000 hours total Can see 2.5 to 5 times further than Parkes (period dependent) Expect ~500 to 1000 new pulsars

34. II. High Galactic Latitude Survey Millisecond pulsars (z scale height ~ 0.5 kpc) High-velocity pulsars (50% escape) (scale height =  ) NS-NS binaries (typical z ~ 5 kpc) NS-BH binaries (typical z ~ few kpc ?) Search for:

35. Surveys with Parkes, Arecibo & GBT. Simulated & actual Yield ~ 1000 pulsars.

36. SKA pulsar survey 600 s per beam ~10 4 psr’s

37. Comments & Summary NE2001 = large improvement over TC93 Caveat: HII regions, etc are grossly undersampled by the available LOS Need ~ 10 4 DMs to adequately model the MW VLBI (esp. with Arecibo, GBT, Jodrell, Effelsberg, etc) will yield many new parallaxes, obviating the need for DM distances for ~100 pulsars in a few yr New pulsar surveys will double sample in ~ 5 yr Other distance approaches possible (radio = standard candles if beaming accounted for) Expect tighter L X, L  with better distance models.

38. NE2001 Spiral Arms Electron density (log gray scale to enhance local ISM)

39. Electron density of TC93 Taylor & Cordes (1993 ApJ, 411, 674)

40. Deficiencies of TC93 DM too small for distant, high latitude objects Distances overestimated for many objects in theGalactic plane (10% of now-known objects have DMs too large to be accounted for) Pulse broadening over/underestimated in some directions Spiral arms incompletely defined over Galaxy No Galactic center component

42. Modeling the Galactic n e &  n e mean & fluctuations are modelled dSM = C n 2 ds  F n e 2 ds  F n e dDM F = “fluctuation parameter” varies widely over Galaxy  n e ~ C n (outer scale) 1/3 possible/probable  n e / n e ~ 1 not clear that  n e on all scales due to same process

43. INTERSTELLAR DISPERSION DM =  0 D ds n e (s) Known for ~1200 pulsars DM ~ 2 to 1100 pc cm -3 Variable at ~10 -3 pc cm -3 Variations with d,l,b show obvious Galactic structure

44. Interstellar Scattering Effects Used Angular broadening (seeing) Pulse broadening Diffractive interstellar scintillations (DISS)  d = / l d, l d = diffraction scale => Scattering Measure SM

45. Estimated Wavenumber Spectrum for  n e Similar to Armstrong, Rickett & Spangler (1995) Slope ~ -11/3 Spectrum = C n 2 q -  SM = LOS integral of C n 2

46. Independent Pulsar Distances Parallaxes:Pulse timing Interferometry Associations:Supernova remnants Globular clusters HI Absorption:Galactic rotation

47. Very Long Baseline Array PSR B0919+06 S. Chatterjee et al. (2001)  = 88.5  0.13 mas/yr  = 0.83  0.13 mas D = 1.2kpc V = 505 km/s

48. Independent Pulsar Distances Parallaxes:Pulse timing Interferometry Associations:Supernova remnants Globular clusters HI Absorption:Galactic rotation

49. Brisken et al. 2001

50. www.astro.cornell.edu/~shami/psrvlb

51. n e in local ISM (Brisken PhD thesis) ~ 50 nearby pulsars for future VLBI +AO+GBT parallaxes

52. Current features of local ISM in NE2001 model Parallax distances estimated correctly by model

53. Current features of local ISM in NE2001 model Parallax distances estimated correctly by model

54. DM vs Galactic longitude for different latitude bins

55. DM vs Galactic latitude for different longitude bins SM vs latitude

56. NE2001 Spiral Arms Electron density (log gray scale to enhance local ISM)

58. Selected Applications Galactic pulsar populations pulsar velocities e.g. J1740+1000 = 114 kyr at z ~ 0.4 kpc Bow shock nebulae to probe density variations Guitar Nebula HST obs. Galactic turbulence anisotropy of fluctuations relation to  B and CR prop’n IGM in local group M33 giant pulses from Crab-like pulsars  DM,SM IGM on cosmological scales scattering/scint’n of AGNs by intervening galaxies, Ly  clouds, turbulence in cluster gas HII regions at EOR GRB & IDV scintillations source sizes vs. t ambient medium IGM

59. Scattering of high z AGNs: Interstellar + Intergalactic ? -2.2 Lazio et al. (unpublished)

60. Surveys with Parkes, Arecibo & GBT. Simulated & actual Yield ~ 1000 pulsars.

61. SKA pulsar survey 600 s per beam ~10 4 psr’s

62. Summary New electron density model (NE2001) to be released soon (paper draft, software) www.astro.cornell.edu/~cordes/NE2001 (also web site at NRL with web-based tools)www.astro.cornell.edu/~cordes/NE2001 Large VLBI program initiating to measure PM, parallaxes out to 5 kpc in some cases IGM scattering: angular broadening vs. z Use bow shock nebulae to probe  n e. PMB pulsars for next version of model

63. J1740+1000 Seen through NPS Also AGNs with enhanced RISS Dynamic spectrum (DISS) with time scale smaller than expected z /  s ~ 4000 km/s

64. H  Images of Pulsar Bow Shocks Guitar Nebula (1600 km/s) MSP J0437-47 (100 km/s)

65. NE2001 Spiral Arms Electron density (log gray scale to enhance local ISM)

66. Hybrid ISS/VLBI Methods (Cordes & Rickett 1998, ApJ, 507,846) Exploit different D dependences of ISS and proper motion estimates of pulsar velocities: V  = D  (proper motion) V  = A W(D  d  1/2 /  t d A depends on wavenumber spectrum & spatial distribution W depends on spatial distribution Can solve for (or constrain) D and W(D) (info on spatial distribution of  n e )

67. Parkes MB Feeds Arecibo Multibeam Surveys

68. I. Arecibo Galactic-Plane Survey |b| < 5 deg, 32 deg < l < 80 deg 1.5 GHz total bandwidth = 300 MHz digital correlator backend (1024 channels) (1st quadrant available = WAPP) multibeam system (7 feeds) ~300 s integrations, 3000 hours total Can see 2.5 to 5 times further than Parkes (period dependent) Expect ~500 to 1000 new pulsars

69. II. High Galactic Latitude Survey Millisecond pulsars (z scale height ~ 0.5 kpc) High-velocity pulsars (50% escape) (scale height =  ) NS-NS binaries (typical z ~ 5 kpc) NS-BH binaries (typical z ~ few kpc ?) Search for:

70. NE2001 = New Model Cordes & Lazio (to be submitted [in 2001]) x2 more lines of sight (D,DM,SM) [114, 931, 471 data points] Local ISM component (new) [12 parameters] Thin & thick disk components (as in TC93) [8 parameters] Spiral arms (revised from TC93) [21 parameters] Galactic center component (new) [3 parameters] (+auxiliary VLA/VLBA data ; Lazio & Cordes 1998) Individual `clumps’ of enhanced DM/SM (new) [3 parameters x 20 LOS] Improved fitting method (iterative likelihood analysis) penalty if distance or SM is not predicted to within the errors

71. NE2001 Spiral Arms Electron density (log gray scale to enhance local ISM)

74. INTERSTELLAR DISPERSION DM =  0 D ds n e (s) Known for ~1200 pulsars DM ~ 2 to 1100 pc cm -3 Variable at ~10 -3 pc cm -3 Variations with d,l,b show obvious Galactic structure

75. Pulse broadening (recent Arecibo results, R. Bhat et al)  ~ D  2 /2c  -4 Low DM pulsar, no broadening High DM pulsar with broadening

76. Interstellar Scattering Effects Angular broadening (seeing) Pulse broadening Diffractive interstellar scintillations (DISS)  d = / l d, l d = diffraction scale Refractive interstellar scintillations (RISS)  r = k -1    = geometrical optics refraction TOA fluctuations (multiple effects) Superresolution phenomena: stars twinkle, planets don’t  pulsars show DISS, AGNs don’t, GRBs do RISS: pulsars, AGNs, GRBs …

77. Pulse broadening Pulse broadening vs DM Angular broadening Diffractive Scintillation Dynamic spectrum Visibility functions: