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High Energy meets Low Energy an introduction to radio interferometry

High Energy meets Low Energy an introduction to radio interferometry. Ignasi Reichardt IFAE Thursday meeting, March 19 th 2009. Radioastronomy. “ Exploring the sky at wavelengths from 10m to 0.4mm (30MHz – 800GHz) ”. Radiative processes and sources. Pulsars. Synchrotron. Spectral lines.

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High Energy meets Low Energy an introduction to radio interferometry

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  1. High Energy meets Low Energyan introduction to radio interferometry Ignasi Reichardt IFAE Thursday meeting, March 19th 2009

  2. Radioastronomy “Exploring the sky at wavelengths from 10m to 0.4mm (30MHz – 800GHz)”

  3. Radiative processes and sources Pulsars Synchrotron Spectral lines Free-Free Thermal

  4. Detection Principle

  5. Detection Principle Johnson noise Antenna Temperature Noise voltage

  6. Detection Principle OFF ON S = g(TAON– TAOFF)

  7. Detection Principle Local Oscillator: VL ~ cos(2πνLt + φL) VI ~ cos(2π(νS-νL )t + φL + φS) Noise voltage: VS ~ cos(2πνRt + φR) <Vi2> = <(VS+VL)2> = <VS2> + < VL2>

  8. Nice pictures? Cas-A (SNR) Cyg-A (AGN)

  9. Interferometry <V1·V2> = <VS2>eiφ ~ Seiφ <V1·V2> = <VS2> ~ S V1 = VA + VS V2 = VB + VS

  10. Interferometry S S Interferometer output: S·exp[2πiLsinθ(νS-νL)/c] Extra phase: 2πsinθL/λ Interferometer output: S·exp(2πisinθL/λ) θ L

  11. Interferometry S2 S2 Uncompensated path for S2 : Δφ = 2π(L/λ)cosθΔθ S1 S1 g: Angular Resolution! Δθ θ L

  12. DEC y θ = (x2 + y2)1/2 x RA Interferometry Two sources: STOT = S1 + S2e2πigΔθ Many sources: STOT = S1 + S2e2πigΔθ2+ ... + SNe2πigΔθN Extended source: STOT = ∫b(θ)e2πigθ dθ 2D sky: STOT = ∫b(x, y)e2πi(ux +vy)dxdy

  13. v g(t) u v g = (u2 + v2)1/2 u Filling the (u, v) plane

  14. Filling the (u, v) plane

  15. Very Long Baseline Interferometry

  16. Extremely Long Baselines?

  17. Provided by Daniel Mazin PRELIMINARY! VLA – 90cm M87: γ-rays meet radio waves

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