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Astronomy, Radio Sources and Society

Extragalactic radio sources and their importance for astronomy

Leiden 10-13 June 2013

Ron Ekers

CSIRO, Australia

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George Miley

The largest, the furthest, the most powerful, and to some of us the most fascinating objects known in

the Universe are to be found among the radio sources associated with some elliptical galaxies

and QSO’s. In recent years it has become apparent that they are also objects of considerable

beauty.

Ann. Rev. Astron. Astrophys, 1980

AAS Long Beach 3January 7, 2013 Mt Palomar 200”

50th Anniversary of the Discovery of Quasars

Geese

Hoyle, Burbidge and Narlikar

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Linear size distribution of radio galaxies

3CR radiogalaxies

a Linear plot with linear bins

↕

b Log plot with log bins

Ekers & Miley 1977

Halley Lecture23May2007

The Scientific Method

Developed during the 17th century– Develop an hypothesis – Make predictions– Verify with observations (or discard hypothesis)

Eg Newton's theory of gravity – at the time Newton died it was still merely a hypothesis– It explained everything from planets to falling apples– It was verified by the return of Halley’s comet in 1758– Since than it made many predictions

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Astronomy

Most astronomy papers today are explanations of observed phenomena.

Predictions usually fail and it is considered normal practice to adapt the theory to fit the observations.

These theories may not be wrong, but without predictions we have no reason to accept them

Many examples in our interpretation of radio galaxies The role of the sceptic in science

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Where we are going from here

Some of the enabling technology Martin Rees and the Wireless Internet Radio Galaxies from the beginning QSO 50th anniversary Blackholes Some Extragalactic Radio Source Highlights Galaxy formation and the early Universe

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Cambridge One-Mile Telescope: 1962

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First Cambridge Earth Rotation Synthesis Image

June 1961 North pole survey 4C aerials 178 MHz Computations and graphical

display used EDSACII 7 years after Christiansen

Benelux Cross1963

Joint Netherlands – Belgium OEEC (now OECD) agreement Christiansen et al design 100x 30m + 1x 70m dish 21cm 1.5km

Science Goals for Benelux Cross Oort - OECD Symposium

(1961)– Primary goal

» Enough sensitivity and resolving power to study the early universe through source counts

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Westerbork: 1970 Hogbom (Cambridge)

+ Christiansen (Sydney)

Benelux cross WSRT 12 x 25m dishes

– Two moveable– 10 redundant spacings– Self calibration

Add 2 more 25m dishes later

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LOFAR: The Low Frequency Array

Oort Workshop 1997 George Miley proposal to ASTRON Arnold van Ardenne already

thinking about SKA-low and the aperture arrays

Actively promoted by George– Low Frequencies are Cheap!

LOFAR WILL EXPLORE NEW PARAMETER SPACE• Lowest Radio Frequencies (< 50 MHz) (Wavelengths > 3 metre)

– Neglected cradle of radio astronomy

• Bill Erickson – a hero

– Coherent radiation processes

– Oldest synchrotron electrons – “Fossil”

– Absorption

• Huge Simultaneous Fields (tens of degrees with large-sky monitor triggering)

– Searches for rare variable and transient sources and cosmic air showers

– “Synoptic” telescope

• High Dynamic Range Radio Spectroscopy at 110 – 230 MHz

– Search for fingerprint of reionization

• Neutral hydrogen (HI) at z ~ 11 to z ~7

DESIGN OF LOFAR DRIVEN BY FEW KEY PROJECTS

George MileyTasmania 2008

16June 2013 Ekers, Radio Sources & Society

From Cambridge to The Netherlands 1970then to Australia 1996

Steven Hawking: black holes radiate Small black holes evaporate in less than the age

of the Universe Martin Rees: a radio pulse might be observable

when they disappear John O’Sullivan: and collaborators build a

special instrument to look for the exploding black holes using Dwingeloo and Westerbork – “there has to be a better way!”

Fourier Transform on a chip– IEEE 802.11 wireless internet standard

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Cygnus Astrongest radio source in sky

Hey 1946 – source with variable intensity– time scale of seconds to minutes– must be small diameter– the first “radio star”

What was it?– no optical counterpart– was the whole galactic plane was made of such stars?– no theory linking diffuse galactic emission to cosmic

rays

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What is the Non-thermal Radio Emission?

A very confusing story Misinterpretation of radio data added to the confusion some radio sources had small diameter (Hey).

– Hey was correct but it was incorrectly assumed that all radio emission was the sum of these radio stars

It was assumed that the radio stars were like the sun– this was also incorrect.– they were galactic nebula (SNR) and extra galactic

(AGN)

Cliff Interferometer 1948

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Dover Heights, Sydney, Australia Piha and Leigh, New Zealand

Cliff interferometer CSIRO, Australia - NZ (1948)Built to identify the radio stars (John Bolton)Identification of the Crab Nebula super novae remnantDiscovery of extragalactic radio sources at great distances

Centaurus A – NGC5128 and Virgo A – M87

NGC5128

Centaurus A

Centaurus AATCA MosaicFeain et al 2011

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The First Radio Galaxies

1949 : The first radio galaxies? “Positions of Three Discrete Sources of Galactic

Radio-Frequency Radiation” - (Bolton, Stanley, and Slee, Nature 164, 101)» NGC 5128 and NGC 4486 (M87) have not been

resolved into stars, so there is little direct evidence that they are true galaxies. If the identification of the radio sources are accepted, it would indicate that they are within our own Galaxy.

January 7, 2013 Kellermann AAS Long Beach

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Why was it so difficult to accept extra-galactic?

Letter from Bolton to Minkowski 20 May 1949

There were no galaxy experts at CSIR and very few in Australia

It was easier to assume that the strange galaxies were unusual galactic objects

There were no known mechanisms to explain the powerful radio emission if extragalactic

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Synchrotron Model for Radio Emission

1949 Unsold: sunspots anomalous radiation – non-thermal– plasma oscillations

1950 Alven & Herlofson: – synchrotron radiation from sunspots

1950 Kiepenhauer (visiting Yerkes)– proposed the ISM rather than stars– needed magnetic field and high energy charged particles– He knew there was evidence for both

» optical polarization and cosmic rays

Mostly ignored in the West but enthusiastically embraced in Russia by Ginzburg and later by Shklovski

3C 48, the first radio star

Small diameter source catalogue from Manchester– Henry Palmer & George Miley ?

Accurate position measured at OVRO 1960 Tom Matthews and John Bolton

identify 3C 48 with a stellar object Greenstein, Munch, Sandage 200” spectra

– Lots of unidentified spectral lines Alan Sandage AAS paper (Dec 29, 1960),

– Remote possibility that it may be a distant galaxy of stars. But there is general agreement … that it is a relatively nearby star. S&T, 21, l48

January 7, 2013 Adapted from Kellermann AAS Long Beach

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3C 273 identification

January 7, 2013 Kellermann AAS Long Beach

Cyril HazardParkes lunar occultation

AAS Long Beach 28

50th Anniversary of the Discovery of Quasars

January 7, 2013 Mt Palomar 200”

3C273 Parkes Occultation 1962

Striking difference in radio spectra

Component A

S = -0.9

Component B

S = 0.0

Core – Jet morphology

Slide prepared by Jan Oort

3C273VLA 5GHz 1998

3C273Optical HST

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First Texas Symposium onRelativistic Astrophysics

Gravitational Collapse and Relativistic Astrophysics– Dallas, Texas, Dec 16-18 1963 – only gravity of a massive object in the

nucleus of a galaxy could provide the energy

Fred Hoyle: – relativists with their sophisticated work

were not only magnificent cultural ornaments but might actually be useful to science!

– The University of Chicago Press, 1965

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The Nuclei of Galaxies

1943: Carl Seyfert (Clevland, Ohio)– “Enhanced activity in the nuclei of 6

extragalactic nebulae– No citations for 18 years!

1958: Viktor Ambartsumian (Armenia)– Championed the role of the galaxy nuclei

1961: Vitaly Ginzburg (Russia)– Showed that gravitational energy could

power a radio galaxy

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The Energy Source

Old models disappear fairly quickly– Galaxies in collision (Baade & Minkowski) Bad theory– Nuclear energy– Electromagnetic flares

Redshift controversy lasts for many years– Many argued that the quasars are nearby Bad theory– New physics was better than the incredible luminosity– But all predictions failed

Gravitational energy from a collapsed object– Ginzburg, Hoyle, Fowler, Zeldovich, Novikov.....– This was a paradigm shift– But what kind of condensed object?

Black Holes

Chandrasekhar (1931) – paper rejected by ApJ– “A star of large mass cannot pass into the white dwarf

stage, one is left speculating on other possibilities” Eddington – the authority

– “a star would have to go on radiating and radiating, and contracting and contracting….I think there should be a law of nature to stop matter behaving in this absurd way”

Oppenheimer (1939) – exercise in abstraction– “the star closes itself off from any communication…only

its gravitational field persists”

NGC326 – pressing jetBinary Black hole?

Martin Rees 1978– One black hole already

pushes credibility – two was a step too far

NGC326 – pressing jetBinary Black Hole?

Martin Rees 1978– One black hole already

pushes credibility – two was a step too far

Binary Black holes?– Evidence for super massive

binary black hole mergers and Gravitational wave predictions

Murgia et al, A&A 380, 102-116 (2001)

Merritt & Ekers Science (2002)

VLA 1.4GHz

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Suspected SMBH binaries

3C75-type sources: wide binaries

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Periodic outbursts interpreting Pks0637-752

Binary black-hole in bound orbit periodicly plunges through the accretion disk

– will maintain its spin axis so gets a new accretion disk each plunge

PKS0637-752 – Quasar with Xray/radio jet

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Hercules A VLA and HST

Baum et al (2012)

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NGC1265 head tail radio source

• Head tail radio source• Rosetta stone for radio

galaxies- Provided the time stamp- Radio source aging

model was incorrect- Fixed by re-acceleration

Fornax A on optical image

Fornax A Depolarization

Nov 2010 Ron Ekers

Fornax A and the ant like feature

Need a turbulant magneto-ionic medium RM > 20 rad m-2

Size 14” Eg

– Ne = .03 cm-3

– B = 2 μG – L = 100pc– M = 109 Mo

Bland-Hawthorne ApJ 447, L77 (1995)– Halpha detection at v = 1610km/s

NGC6251Alignment

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VLBI cores aligned to within a few degrees over scale changes of 5x106

Hence maintains axis for at least 108 years

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3C273 superluminal expansionpredicted & observed

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Relativistic outflow in AGNM87

• One sided Doppler boost but components have v/c < 1 !

• components are slow moving shocks not measuring bulk flow

• evidence for original interpretation is now lost!

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HIPASS 21cm Continuum

Preliminary continuum image, courtesy Mark Calabretta (CSIRO ATNF)

Centaurus A - closest AGN

Centaurus AATCA Mosaic

600kpc

1.4GHz continuum full polarization4 x 750m array

configuration406 pointings, hexagonal

gridFOV 45 deg2

θ~45’’ ~0.26mJy/beam (0.1K)

Ilana Feain

Cen A Mosaic N lobe

May 2012 50

Centaurus A composite

May 2012 51

Centaurus A middle lobeX-ray XMM Newton

May 2012 52

Centaurus A middle loberadio continuum and HI

May 2012 53

Morganti

H alpha

May 2012 54

Ellis and Bland-Hawthorne

LOFAR SCIENCE DRIVER 2: SURVEYS2.1 ULTRA STEEP SPECTRUM SOURCES –

PROBE OF GALAXY AND CLUSTER FORMATION e.g. Blumenthal & Miley 1988

Radio spectrumCygnus A

Larger redshifts > higher frequencies > steeper spectraLOFAR WILL DETECT STEEPEST SPECTRA

(MOST DISTANT SOURCES)

e.g. Blumenthal & Miley 1988

The evolution of radio galaxiesBIG BANG

NOW

July 2005 Ilana Klamer - ASA 57

our ATCA observations confirm that high-z radio galaxy spectra are not curved

but USS spectra don’t steepen at all…

The K-correction interpretation is inconsistent with observations

Klamer (Feien) MNRAS (2006)

27 Nov 1999 R D Ekers 58

Evolution of density fluctuations

z=6 z=0

ρ (1+z)3

Δρ ρclusρ=0

ρ=0

ρ ≈ const

ρ ≈ const

R D Ekers 5913 July 05

Radio Galaxy - 4C41.17redshift 3.8

Alignment of radio jets (contours) with other tracers of star formation– VLA radio image

HST F702

HST F569

Ly-α van Breugel (1985)

R D Ekers 6013 July 2005

Klamer et al. 2004

Radio PA Dust PA CO PA

Alignment with Radio Axis

Predicted an alignment in 4C41.17Observed Δpa = 8o

Survey of CO in High z Radio Galaxies

13 high redshift radio galaxies– 1.4 < z < 2.8

CO (1-0) aligned with radio axis!

Emonts, Miley et al 2013

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Conclusion

March 2013

The power of science is its ability to make predictions

but science itself will evolve in unpredictable ways