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The multi-wavelength context: the link to radio astronomy

The multi-wavelength context: the link to radio astronomy. Anne J. Green. Overview of Talk. The nonthermal sky – the nexus between gamma-ray and radio astronomy New radio telescopes span wavelengths from 850 microns to 10m – >4 orders of magnitude A snapshot of some of interesting results

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The multi-wavelength context: the link to radio astronomy

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  1. The multi-wavelength context: the link to radio astronomy Anne J. Green

  2. Overview of Talk • The nonthermal sky – the nexus between gamma-ray and radio astronomy • New radio telescopes span wavelengths from 850 microns to 10m – >4 orders of magnitude • A snapshot of some of interesting results • What about the future? Radio observations to complement CTA. SKA pushes the boundaries?

  3. Synergies between CTA & radio telescopes • Both probe nonthermal processes • Both g-rays & radio synchrotron are produced by the same CR electron population • Both cover >4 decades in frequency space • Both need to manage massive data streams • Both champion “open skies” policy

  4. What radio astronomy contributes • Telescopes with high spatial, spectral, temporal resolution • Wide field of view images • Magnetic field structure and strength • Kinematics and dynamics of the ISM, IGM • Different phases of the gas – molecular, ionised, hot, neutral • No extinction from dust

  5. ALMA – Atacama Large Mm-submm Array • 66 dishes (diameter12m and 7m) when complete • Baselines 150m to ~16km • Frequency range 84 – 720 GHz • Angular resolution 13.5 mas – 1.5” @ 300 GHz • Field of view 21” @ 300 GHz Chajnantor plateau, Chile

  6. Molecular gas – star nurseries ALMA & HST

  7. Karl Jansky Very Large Array • 27 dishes (25m diameter) • Frequency range 1 to 50 GHz • Angular resolution 4 mas – 0.2” • Field of view 45’ @ 1 GHz • Sensitivity 2 – 6 mJy (1hr) • Dynamic range 106 San Agustin Plains, NM

  8. Cygnus A – radio galaxy E galaxy Super massive Black hole produces twin jets Radio lobes & hot spots from interaction with IGM z = 0.056 Distance 230 Mpc

  9. Low Frequency Arrays – LOFAR & MWA LOFAR Two frequency bands: 30 – 240 MHz Baselines 100m – 1500km 8 simultaneous beams Multi-sensor array (Next Talk) MWA Frequency range: 80 – 300 MHz Baselines 8m – 3 km Field of view 610 deg2 @ 150 MHz Time resolution 8 sec Angular resolution 2’ @ 150 MHz

  10. Square Kilometre Array • Dual site decision: Australia-NZ & Southern Africa • Multiple sensor technologies, wide field of view, one km2 area, baselines up to 3000 km • Angular resolution < 100 mas • Sensitivity 400 mJy in 1 minute • Phase 1: 70 MHz – 3 GHz, 10 – 20% area (2019)

  11. g-rays from TeV cosmic rays (p, He, etc) . CRs deflected by magnetic fields p+p → o → 2g p→ m →e + (nmnm ne )  GAS CLOUD Gamma-Rays (+ neutrinos) Observational Signature → Gamma-rays & gas are spatially correlated → mm-radio astronomy traces the gas .......we expect gamma-ray flux Fg ~ kCR Mgas

  12. . g-Rays from multi-TeV electrons Inverse-Compton (IC) TeV Gamma-Rays Synchrotron radio to X-Rays Accelerated TeV Electrons e +(soft) → e´ +  (TeV) inverse-Compton (IC) scattering e +G → e´ +  (GHz)Radio synchrotron (+ X-rays, optical, IR) Observational Signature → May be differences in TeV & radio morphologies → B-field estimates possible

  13. Cas A – very young SNR (Fermi LAT – Abdo et al. 2010) (Chandra composite) (VLA radio composite) g-rays from shell not compact object – via hadrons or electrons?

  14. SNR W49B & Starburst region W49A Brogan & Troland (2001) SNR W49B – bright X-rays, youngish SNR embedded in molecular cloud, a target for CRs accelerated in SNR shock to produce g-rays Starburst region W49A – massive stellar wind shocks likely source of particle acceleration

  15. Mature SNR – W28 & HII region Image: VLA, ATCA, MSX Brogan et al. (2006) Nanten2 12CO(J=2-1) image -10 to 25km/s (Nakashima et al 2008) SNR – shock interaction with molecular cloud – CRs source of grays Southern g-ray sources a mystery? From SNR or HII regions?

  16. SNR G347.3-0.5 (Age < 104 years) TeV image from H.E.S.S. Aharonian et al. (2006) SNR mapped in radio continuum (ATCA) and X-rays (ROSAT) Diffusive shock acceleration at forward shock (Lazendic et al. 2004; Ellison et al. 2001)

  17. H2 and HI gas study(Fukui et al. 2011) Regions of cold optically thick and self-absorbed HI H2 from Nanten CO(1-0) HI from ATCA/Parkes

  18. RXJ1713.7-3946: Molecular Cloud Cores Mopra observations CS(1-0) (N. Maxted) Core A Core C Core B → dense gas 104-5 cm-3 → mass 50 – 100 Msun

  19. TeV source & star formation region • Unidentified HESS source J1626-490 • Associated with CO cloud – maybe passive target for CR protons accelerated by nearby SNR?? • Suggests hadronic process. • Need for magnetic fields & turbulence estimates, detailed CO, HI Eger et al. (2011)

  20. Molecular gas with Mopra telescope (Burton)

  21. Molecular gas with Mopra telescope (Burton)

  22. HI Supershell in Galactic Plane McClure-Griffiths et al. (2000)

  23. Radio Polarisation studies of the ISM Polarised emission does not track total intensity (Gaensler et al. 2011)

  24. Magnetic fields & turbulence

  25. SNR G327.1-1.1 with a PWN (Next Talk) Composite SNR with central PWN

  26. Radio Galaxy - Centaurus A FRI galaxy – distance 3.8 Mpc Lobes sites of CR acceleration? SMBH ~ 55million Msun Images: Feain et al (2012) and TANAMI network (Muller et al. 2011)

  27. Centaurus A – H.E.S.S. & Fermi detections Cen A Lobes Fermi LAT Yang et al. (2012) Radio polarisation magnetic fields ~ 1mG Cen A Core H.E.S.S. Aharonian et al. (2009)

  28. Intermediate Black Hole (HLX-1) Host Galaxy ESO 243-49 Distance 95 Mpc X-ray luminosity plus assumptions on likely g-ray jet spectrum and CTA sensitivity allows possible detection of BH mass ~104 Msun out to ~60 Mpc. Three-way correlation interesting. IMBH may have major role in SMBH formation Farrell et al. (2009) Webb et al. (2012)

  29. GRBs the long & the short of it • Long – massive star collapse • Short – neutron stars merge • Hybrid bursts? Progenitors? • Radio properties of afterglow might help characterise progenitor. Chandra et al. (2010) measures z = 8.26 for GRB 090423

  30. 30% TeV sources no identified counterparts Higher positional accuracy needed to secure identification & avoid confusion (e.g. J1745-303) Strong & variable gamma-ray source with no obvious counterpart or explanation (H.E.S.S. J1422-174) Unidentified g-ray sources H.E.S.S. J1507-622 Tibolla et al. (2009)

  31. What are some future options? • Radio frequency bremsstrahlung from CR and g-ray atmospheric showers • Relativistic beamed pulses from CR and g-ray atmospheric showers • Overlapping simultaneous beams with PAFs track CR shower development through atmosphere • Radio synchrotron emission from secondary electrons • Detection of GRB prompt emission & (orphan) afterglows – wide field of view & storage buffers needed • Future large radio telescopes with time link to particle detectors for source filtering and storage buffer to search backwards – radio Cerenkov?

  32. Acknowledgements • Ron Ekers (CSIRO Astronomy & Space Science) • Gavin Rowell (University of Adelaide) • Michael Burton (University of NSW) • Sean Farrell (University of Sydney) • H.E.S.S. Source of the Month website

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