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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

The multi-wavelength context: the link to radio astronomy

Anne J. Green

Overview of talk

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?

Synergies between cta radio telescopes

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

What radio astronomy contributes

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

Alma atacama large mm submm array

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

Molecular gas star nurseries

Molecular gas – star nurseries


Karl jansky very large array

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

Cygnus a radio galaxy

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

Low frequency arrays lofar mwa

Low Frequency Arrays – LOFAR & MWA


Two frequency bands: 30 – 240 MHz

Baselines 100m – 1500km

8 simultaneous beams

Multi-sensor array

(Next Talk)


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

Square kilometre array

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)

The multi wavelength context the link to radio astronomy

g-rays from TeV cosmic rays (p, He, etc)


CRs deflected by magnetic fields

p+p → o → 2g

p→ m →e + (nmnm ne ) 


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

G rays from multi tev electrons


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

Cas a very young snr

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?

Snr w49b starburst region w49a

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

Mature snr w28 hii region

Mature SNR – W28 & HII region


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?

Snr g347 3 0 5 age 10 4 years

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)

The multi wavelength context the link to radio astronomy

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

The multi wavelength context the link to radio astronomy

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

Tev source star formation region

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)

Molecular gas with mopra telescope burton

Molecular gas with Mopra telescope (Burton)

Molecular gas with mopra telescope burton1

Molecular gas with Mopra telescope (Burton)

Hi supershell in galactic plane

HI Supershell in Galactic Plane

McClure-Griffiths et al. (2000)

Radio polarisation studies of the ism

Radio Polarisation studies of the ISM

Polarised emission does not track total intensity

(Gaensler et al. 2011)

Magnetic fields turbulence

Magnetic fields & turbulence

Snr g327 1 1 1 with a pwn

SNR G327.1-1.1 with a PWN

(Next Talk)

Composite SNR with central PWN

Radio galaxy centaurus a

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)

Centaurus a h e s s fermi detections

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)

Intermediate black hole hlx 1

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)

Grbs the long the short of it

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

Unidentified g ray sources

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)

What are some future options

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?



  • 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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