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Nov 16, 2013 (3 years and 10 months ago)

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1

Astronomy,

Radio Sources and Society

Extragalactic radio
s
ources and their
importance for astronomy

Leiden 10
-
13 June 2013



Ron Ekers

CSIRO,
Australia

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

2

January 7, 2013

AAS Long Beach

3

Mt Palomar 200”

50
th

Anniversary of the Discovery of Quasars

Geese



Hoyle, Burbidge and
Narlikar

Linear size distribution


of radio galaxies

5


3CR
radiogalaxies

a
Linear plot with
linear bins



b
Log plot with log
bins


Ekers & Miley 1977

23May2007

Halley Lecture

The Scientific Method


Developed during
the 17
th

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

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

7

Where we are going from here


Some of the enabling technology


Martin Rees
and the
Wireless Internet


Radio Galaxies from the beginning


QSO 50
th

anniversary


Blackholes


Some Extragalactic Radio Source Highlights


Galaxy formation and the early Universe

8

9

Cambridge One
-
Mile Telescope:
1962

10

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 Cross

1963


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

13

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

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!

14

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

June 2013

Ekers,
Radio Sources & Society

16

From Cambridge to The Netherlands 1970

then 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

Cygnus A

strongest 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

17

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)

18

Cliff Interferometer 1948

19


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 remnant

Discovery of extragalactic radio sources at great distances

Centaurus

A


NGC5128 and
Virgo
A


M87

NGC5128

Centaurus

A

Centaurus

A

ATCA
Mosaic

Feain et al 2011

The First Radio Galaxies


1
949 : The first radio galaxies?


“Positions of Three Discrete Sources of Galactic
Radio
-
Frequency Radiation”
-

(Bolton, Stanley,
and
Slee
, Nature
1
64,
1
0
1
)

»
NGC 5
1
28 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

23

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



24

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

25

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

26

3C 273 identification


January 7, 2013

Kellermann

AAS Long Beach

27

Cyril Hazard

Parkes lunar occultation

50
th

Anniversary of the Discovery
of Quasars


January 7, 2013

AAS Long Beach

28

Mt Palomar 200”

3C273

Parkes

Occultation 1962

29


Striking difference
in radio spectra


Component A



S =

-
0.9


Component B



S =

0.0


Core


Jet
morphology

Slide prepared by Jan
Oort

3C273

VLA 5GHz 1998

30

3C273

Optical HST

31

First Texas Symposium on

Relativistic 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

32

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


33

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?


34

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 jet

Binary Black hole?


Martin Rees
1978


One black hole already
pushes credibility


two
was a step too far

NGC326


pressing jet

Binary 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

38

Suspected SMBH binaries


3C75
-
type sources: wide binaries

39

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

Hercules A

VLA and HST

40

Baum et al (2012)

41

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
μ
G


L = 100pc


M = 10
9

Mo


Bland
-
Hawthorne
ApJ

447, L77 (1995)


Halpha

detection at v = 1610km/s

NGC6251

Alignment

45


VLBI cores aligned to
within a few degrees
over scale changes of
5x10
6



Hence maintains axis
for at least 10
8

years

3C273 superluminal expansion

predicted & observed

46

47

Relativistic outflow in
AGN

M87


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!

48

HIPASS

21cm Continuum

Preliminary continuum image, courtesy Mark Calabretta (CSIRO ATNF)

Centaurus A
-

closest AGN

Centaurus A

ATCA Mosaic

600kpc


1.4GHz continuum



full polarization


4 x 750m array
configuration


406
pointings
, hexagonal
grid



FOV 45 deg
2


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 lobe

X
-
ray XMM Newton

May 2012

52

Centaurus

A middle lobe

radio continuum and HI

May 2012

53

Morganti

H alpha

May 2012

54

Ellis and Bland
-
Hawthorne

LOFAR SCIENCE DRIVER 2: SURVEYS

2.1 ULTRA STEEP SPECTRUM SOURCES



PROBE OF GALAXY AND CLUSTER FORMATION

e.g. Blumenthal & Miley 1988

Radio spectrum

Cygnus A

Larger redshifts > higher frequencies > steeper spectra

LOFAR WILL DETECT STEEPEST SPECTRA

(MOST DISTANT SOURCES)

e.g. Blumenthal & Miley 1988

The evolution of radio galaxies

BIG 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

ρ
clus

ρ
=
0

ρ
=0

13 July 05

R D Ekers

59

Radio Galaxy
-

4C41.17

redshift 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)

13 July 2005

R D Ekers

60

Klamer et al. 2004

Radio PA

Dust PA

CO PA

Alignment with Radio Axis

Predicted an alignment in 4C41.17

Observed
Δ
pa = 8
o

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

61

Conclusion

March 2013

Ekers

62

The power of science is its ability
to make predictions

but science itself will evolve in
unpredictable ways