Multiple-Dish Pulsar Scintillation Studies Dana Simard, Caltech - - PowerPoint PPT Presentation

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Multiple-Dish Pulsar Scintillation Studies Dana Simard, Caltech - - PowerPoint PPT Presentation

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Multiple-Dish Pulsar Scintillation Studies Dana Simard, Caltech Scintillometry 2019 MPIfR @ Bonn, November 2019 Scintillometry is a powerful tool Pulsar scintillation provides a way to study Plasma structures in the ISM By testing models

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Multiple-Dish Pulsar Scintillation Studies

Dana Simard, Caltech Scintillometry 2019 MPIfR @ Bonn, November 2019

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Pulsar scintillation provides a way to study

  • Plasma structures in the ISM
  • By testing models of scintillation
  • By comparing locations of screens to other tracers
  • Pulsar magnetospheres
  • Screens can resolve pulsar magnetosphere
  • Compare separation of components or emission

heights to beam models

  • The distribution of scattering screens in the ISM
  • Understand the prevalence of screens
  • Compare to other structures and tracers of ionized
  • r neutral gas

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

Scintillometry is a powerful tool

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Pulsar scintillation provides a way to study

  • Plasma structures in the ISM
  • By testing models of scintillation
  • By comparing locations of screens to other tracers
  • Pulsar magnetospheres
  • Screens can resolve pulsar magnetosphere
  • Compare separation of components or emission

heights to beam models

  • The distribution of scattering screens in the ISM
  • Understand the prevalence of screens
  • Compare to other structures and tracers of ionized
  • r neutral gas

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

For all, we need the distance to the screen!

Scintillometry is a powerful tool

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SLIDE 4

The secondary spectrum doesn’t give us distances

B0834+06

What information do we have? Curvature of the arc: Locations of the apexes:

η = λ2 2c Deff V 2

eff,k

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

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SLIDE 5

The secondary spectrum doesn’t give us distances

B0834+06

What information do we have? Curvature of the arc: Locations of the apexes:

η = λ2 2c Deff V 2

eff,k

θ Veff

The locations of the images: The velocity of the scintillation pattern: What information do we need?

  • r

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

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SLIDE 6

The secondary spectrum doesn’t give us distances

B0834+06

What information do we have? Curvature of the arc: Locations of the apexes:

η = λ2 2c Deff V 2

eff,k

Measured with VLBI and used to reconstruct a scattering screen by Brisken et al. (2010 ApJ 708 232) Measured with simultaneous observations by

  • eg. Galt & Lyne (1972 MNRAS 158 281);

Rickett & Lang (1973 ApJ 185 945)

θ Veff

The locations of the images: The velocity of the scintillation pattern: What information do we need?

  • r

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

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SLIDE 7

V 𝜾1 𝜾2

Φjk = φj − φk + 2π λ Deff 2 (θ2

j − θ2 k)

Each point in the conjugate spectrum also has a phase:

fD

𝜾2, 𝜾1 𝜾1, 𝜾2

LoS, 𝜾1 LoS, 𝜾2

𝜾1, LoS 𝜾2, LoS

Phases imparted by the lens. Typically dominate the phase and cause phase wrapping. Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

The conjugate spectrum phases are dominated by dispersive ones

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SLIDE 8

V 𝜾1 𝜾2

Φjk = φj − φk + 2π λ Deff 2 (θ2

j − θ2 k)

Each point in the conjugate spectrum also has a phase: In the secondary spectrum:

S(τ, fD) = ˜ I(τ, fD)˜ I(−τ, −fD)

Each point has a phase:

ΦS,jk = Φjk + Φkj = 0

And there is no remaining phase information.

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

The secondary spectrum has no phase information

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SLIDE 9

V b A B 𝜾2, 𝜾1 𝜾1, 𝜾2

2 observed by A correlated with 1 observed by B 1 observed by A correlated with 2 observed by B

VAB*(𝜉,t) = FT[EA(𝜉,t) E*B(𝜉,t)]

~ 𝜾1 𝜾2

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

The FT of the Visibilities is no longer symmetric

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V B b A shorter by 𝜾1・b/2 shorter by 𝜾2・b/2

Φjk,AB∗ = Φjk,00∗ + 2π λ 1 2(θj + θk) · b

Brisken et al. 2010 ApJ 708 232

𝜾1 𝜾2

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

The phase of the VLBI secondary cross-spectrum depends on 𝜄

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V B b A longer by 𝜾2・b/2 Longer by 𝜾1・b/2

Φjk,AB∗ = Φjk,00∗ + 2π λ 1 2(θj + θk) · b Φkj,AB∗ = Φkj,00∗ + 2π λ 1 2(θj + θk) · b

𝜾1 𝜾2

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

The phase of the VLBI secondary cross-spectrum depends on 𝜄

Brisken et al. 2010 ApJ 708 232

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SLIDE 12

Φjk,AB∗ = Φjk,00∗ + 2π λ 1 2(θj + θk) · b Φkj,AB∗ = Φkj,00∗ + 2π λ 1 2(θj + θk) · b

equal but opposite V B b A 𝜾1 𝜾2

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

The phase of the VLBI secondary cross-spectrum depends on 𝜄

Brisken et al. 2010 ApJ 708 232

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SLIDE 13

Φjk,AB∗ = Φjk,00∗ + 2π λ 1 2(θj + θk) · b Φkj,AB∗ = Φkj,00∗ + 2π λ 1 2(θj + θk) · b Φ[ ˜ VAB∗(τ, fD) ˜ VAB∗(−τ, −fD)] = Φjk,AB∗ + Φkj,AB∗ = 2π λ (θj + θk) · b

V B b A 𝜾1 𝜾2

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

The phase of the VLBI secondary cross-spectrum depends on 𝜄

Brisken et al. 2010 ApJ 708 232

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SLIDE 14

60 −150 −100 −50 50 100 150 phase (deg)

Φ[ ˜ VAB∗(τ, fD) ˜ VAB∗(−τ, −fD)] = Φjk,AB∗ + Φkj,AB∗ = 2π λ (θj + θk) · b

−60 −40 −20 20 40 60 fD (mHz) 200 400 600 800 1000 1200 τ (µs)

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

The phase of the VLBI secondary cross-spectrum depends on 𝜄

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SLIDE 15

PSR B0834+06

Brisken et al. 2010 ApJ 708 232

First reconstructions of scattered image with VLBI

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

AR-GBT Distance to the screen: 0.65 Dpsr

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SLIDE 16

First reconstructions of scattered image with VLBI

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

Vela

Kirsten et al. in prep.

Distance to the screen: 0.73 Dpsr

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SLIDE 17

The secondary spectrum doesn’t give us distances

B0834+06

What information do we have? Curvature of the arc: Locations of the apexes:

η = λ2 2c Deff V 2

eff,k

Measured with VLBI and used to reconstruct a scattering screen by Brisken et al. (2010 ApJ 708 232) Measured with simultaneous observations by

  • eg. Galt & Lyne (1972 MNRAS 158 281);

Rickett & Lang (1973 ApJ 185 945)

θ Veff

The locations of the images: The velocity of the scintillation pattern: What information do we need?

  • r

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

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SLIDE 18

Correlating 2-station dyn spec measures the scintillation velocity

  • Galt & Lyne 1972 (MNRAS 158 281):

Measured the delay in the scintillation pattern of PSR B0329+54 between DRAO and Jodrell Bank over more than day to measure the velocity of the scintillation pattern

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

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SLIDE 19
  • Bignall et al. 2006 (ApJ 652 1050): Used the

delay between the scintillation pattern of PKS 1257-326 to constrain the direction and amount of anisotropy in the scattered disk

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

Correlating 2-station dyn spec measures the scintillation velocity

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SLIDE 20
  • Fadeev et al. 2018 (MNRAS 480 4199): Measure the scintillation pattern

velocity for PSR B0823+26 using the delay between GBT and WB and combine this w/ the arc curvature to measure distance to the screen

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

Correlating 2-station dyn spec measures the scintillation velocity

Velocity of the pattern: 610 km s−1 Distance to the screen: 0.77 +/- 0.03 Dpsr

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SLIDE 21

V shorter by 𝜾1・b/2 longer by 𝜾2・b/2 A b

Φjk,AA∗ = Φjk,00∗ + 2π λ 1 2(θj − θk) · b

𝜾1 𝜾2

Simard et al. 2019 MNRAS 488 4952 Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

The phase of the intensity cross secondary spectrum depends on 𝜄

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SLIDE 22

V longer by 𝜾1・b/2 shorter by 𝜾2・b/2 B b

Φjk,AA∗ = Φjk,00∗ + 2π λ 1 2(θj − θk) · b Φkj,BB∗ = Φkj,00∗ + 2π λ 1 2(θj − θk) · b

𝜾1 𝜾2

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

The phase of the intensity cross secondary spectrum depends on 𝜄

Simard et al. 2019 MNRAS 488 4952

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V B b A

Φjk,AA∗ = Φjk,00∗ + 2π λ 1 2(θj − θk) · b Φ[˜ IAA∗(τ, fD)˜ IBB∗(−τ, −fD)] = Φjk,AA∗ + Φkj,BB∗ = 2π λ (θj − θk) · b Φkj,BB∗ = Φkj,00∗ + 2π λ 1 2(θj − θk) · b

𝜾1 𝜾2

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

The phase of the intensity cross secondary spectrum depends on 𝜄

Simard et al. 2019 MNRAS 488 4952

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SLIDE 24

−60 −40 −20 20 40 60 fD (mHz) 200 400 600 800 1000 1200 τ (µs) −

Φ[˜ IAA∗(τ, fD)˜ IBB∗(−τ, −fD)] = Φjk,AA∗ + Φkj,BB∗ = 2π λ (θj − θk) · b

60 −150 −100 −50 50 100 150 phase (deg)

Dana Simard 16 October 2019 SKA VLBI KSP Workshop

The phase of the intensity cross secondary spectrum depends on 𝜄

Simard et al. 2019 MNRAS 488 4952

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Visibilities: Intensities:

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

Phase pattern is different for two analyses

= 2π λ (θj − θk) · b

∗ ∗

= 2π λ (θj + θk) · b

Simard et al. 2019 MNRAS 488 4963

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𝜾j, l component 𝜾j, m component 𝜾k, l component 𝜾k, m component

  • After combining the

spectra from the visibilities and intensities, we can easily measure both angles on the sky

  • We note especially

that places where 𝜾k = 0 are very

  • apparent. This is

where off-axis mages are interfering with the central bright core

  • f the scattered flux

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

Combining VLBI + intensity analysis gives both angles

Simard et al. 2019 MNRAS 488 4963

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−30 −20 −10 10 20 30 l (mas) −30 −20 −10 10 20 30 m (mas)

  • By using the values of 𝜾j

where 𝜾k = 0 along with the power at that part of the secondary spectrum, we can reconstruct the scattered image of the pulsar

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

Combining VLBI + intensity analysis gives both angles

Simard et al. 2019 MNRAS 488 4963

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s = 1 − dlens dpsr

τ = dpsr 2c 1 − s s (θ2

j − θ2 k)

  • Since we also know both

angles, we can combine that with the delay to determine the distance at each pixel

Dana Simard 4 November 2019 Scintillometry 2019 @ MPIfR

Combining VLBI + intensity analysis gives distance for each point

Simard et al. 2019 MNRAS 488 4963

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SLIDE 29

4 November 2019 Scintillometry 2019 @ MPIfR Dana Simard

Combining VLBI + intensity analysis gives distance for each point

  • 1-D simulation of two screens at different distances but with

similar arc curvatures

Simard et al. 2019 MNRAS 488 4963

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SLIDE 30

4 November 2019 Scintillometry 2019 @ MPIfR Dana Simard

Combining VLBI + intensity analysis gives distance for each point

  • 1-D simulation of two screens at different distances but with

similar arc curvatures

Simard et al. 2019 MNRAS 488 4963

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Many ways to reconstruct scattering screens

  • A. Use VLBI to calculate 𝜾 at

the apexes of arclets.

  • B. Use simultaneous intensity

measurements at 2 or more dishes to measure Veff

  • C. Combine A. and B. to

measure 𝜾 at every point in the secondary spectrum. Need to be able to distinguish arclets due to interference with the central bright core. No need to determine which points are due to interference with the central bright core. No need to determine which points are due to interference with the central bright core. Need to measure the curvature

  • f the parabolic arc.

Need to measure the curvature

  • f the parabolic arc.

No need for a curvature measurement or evidence of parabolic arcs. Must record voltages (or correlate in real-time). No need to record voltages. Can take advantage of wide- band receivers and pulsar backends. Must record voltages (or correlate in real-time). Use when there is a single dominant screen. Use when there are multiple screens.

4 November 2019 Scintillometry 2019 @ MPIfR Dana Simard

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Questions?