Jim Cordes SINS Workshop The Fluctuating Ionized ISM: Galactic Distribution and Related Issues Jim 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) 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop 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) 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Observables 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Observables ℓ1= inner scale ℓ0= outer scale 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Observables 9/21/2018 Jim Cordes SINS Workshop
Galactic Structures Necessary to Explain DM data Thin disk Thick disk Spiral arms Local ISM components Clumps of enhanced ne Voids of low ne 9/21/2018 Jim Cordes SINS Workshop
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 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Asymptotic DM 9/21/2018 Jim Cordes SINS Workshop
Empirical Distances vs. Model Distances 9/21/2018 Jim Cordes SINS Workshop
The highest measured velocity using direct distance measurement Possibly born in Cyg OB 6 ,b = 91.3o, 52.3o D = 2.450.25 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) The orbit of B1508+55 with respect to the Cygnus Superbubble and the Cygnus OB associations using an age of 2.34 Myr and a radial velocity of 200 km/s. The solid dot denotes the pulsars current position and the thick solid line its orbit traced back in time. The dashed circle represents the Cygnus superbubble while the solid ellipses are the Cygnus OB associations with positions and extents as tabulated by Uyaniker et al. (2001). From left to right and top to bottom these are OB 7, OB 6, OB 4, OB 2, OB 8, OB 9, OB 1, OB 3 and OB 5. The starred symbols are the Supernova remnants identified in this region. The solid horizontal line is the galactic plane with the horizontal dashed lines representing the pulsar scaleheight determined by ACC at the distance of the Cygnus superbubble. l,b = 91.3, 52.3 deg + D = 2.45 kpc => (x,y,z) = (1.50, 8.53, 1.94) kpc X || l=90 deg, y || l=180deg, z perpendicular to the Galactic plane
Estimated Wavenumber Spectrum for ne 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 see also Armstrong, Rickett, Spangler 1995 9/21/2018 Jim Cordes SINS Workshop
Methods for Probing ne on Small Scales Technique Quantity Good for: Results Scaling of visibility function with baseline (b) = spectrum index ℓi = inner scale ℓi few x 100 km Image anisotropy (vector b) anisotropy of ne Up to 3:1 for high scattering Scaling of DISS parameters with d() d() , ℓi ℓi 300 – 800 km Scintillation Arcs arc parameters , ℓi, anisotropy of ne Existence <4, inner scale “small” DM vs time DM vs angle on sky DM(t) DM() , ℓ0 = outer scale , outer scale 11/3 ℓ2 > 10 AU RISS and DISS modulation indices DM, EM, SM on same LOS & distance EM, DM,SM ℓ0 =outer scale filling factor RM vs angle on sky RM() , ℓ0 Constraints on ℓ0 9/21/2018 Jim Cordes SINS Workshop
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 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Pulse Broadening Bhat, Cordes et al. 2004, unpub. 9/21/2018 Jim Cordes SINS Workshop
Scaling of Pulse Broadening with DM and 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop 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 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Constraints from Arcs c.f. Dan Stinebring’s talk Large inner scales and media with single scales or steep wavenumber spectra (4) suppress arcs 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop 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 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop 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 9/21/2018 Jim Cordes SINS Workshop
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 Pulsars as gravitational laboratories and gravitational wave detectors are one of the five key areas. The primary source classes to be bound are (a) relativistic binaries (NS-NS, NS-BH) (b) Millissecond pulsars The Galactic center is a primary target: (a) Identifying radio pulsars there and timing them requires observations at > 9 GHz to combat radio-wave scattering; (b) current instrumentation appears to have insufficient sensitivity to detect pulsars at these frequencies in the GC (c.f. attempts with Parkes (64m), Effelsberg (100m) and the GBT (100m) The yield from a Galactic survey of binary pulsars and MSPs is terrific! Not shown on the slide are the prospects for detecting single, giant pulses from local group galaxies and probably as far as the Virgo cluster. Such pulses can be used to characterize the local intergalactic medium. SKA SKA Blue points: SKA simulation Black points: known pulsars only 6! ~104 pulsar detections 9/21/2018 Jim Cordes SINS Workshop
Scattering in the IGM? (Lazio, Cordes, Fey in preparation) SM vs Galactic latitude AGNs pulsars 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop 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 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop 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 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Extra Slides 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop 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 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Local ISM components & results 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Model Components 9/21/2018 Jim Cordes SINS Workshop
Galactic Center Component 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Thin disk 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Thick disk (1 kpc) 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Spiral arms 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop DM vs Galactic longitude for different latitude bins 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop DM vs Galactic longitude for different latitude bins 9/21/2018 Jim Cordes SINS Workshop
134 of 1143 TC93 distances are lower bounds 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop DM(psr)-DM(model, ) 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Asymptotic DM 9/21/2018 Jim Cordes SINS Workshop
Estimated Wavenumber Spectrum for ne 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 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Pulse Broadening 9/21/2018 Jim Cordes SINS Workshop
Constraints on the Inner Scale From DISS Scaling 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop 9/21/2018 Jim Cordes SINS Workshop
Is the DM distance Realistic? Yes Standoff radius and flux are consistent 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Galactic Center Region Sgr A* = 3106 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 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop Observables l1= inner scale l0= outer scale 9/21/2018 Jim Cordes SINS Workshop
Jim Cordes SINS Workshop 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 9/21/2018 Jim Cordes SINS Workshop