The multi wavelength context the link to radio astronomy
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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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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

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)

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)

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