Active Galaxies, Shocks and High Energy Particles Carried out in collaboration with: Philip Best...

Active Galaxies, Shocks Active Galaxies, Shocks and High Energy Particlesand High Energy Particles

Carried out in collaboration with:Carried out in collaboration with:

Philip BestPhilip BestKatherine InskipKatherine InskipHuub RHuub Rööttgeringttgering

Active Galaxies and High Active Galaxies and High Energy ParticlesEnergy Particles

• Radio galaxies and radio quasars are source of Radio galaxies and radio quasars are source of high energy particles which are dispersed high energy particles which are dispersed throughout intergalactic spacethroughout intergalactic space

• Evidence for strong shocks in the environments of Evidence for strong shocks in the environments of powerful radio galaxies on very large scalespowerful radio galaxies on very large scales

• Statistics of different classes of powerful Statistics of different classes of powerful extragalactic radio sourceextragalactic radio source

• Can these considerations play a role in the study Can these considerations play a role in the study of high energy cosmic rays?of high energy cosmic rays?

Why the Radio Galaxies and Why the Radio Galaxies and Radio Quasars?Radio Quasars?

• Radio galaxies and radio quasars are only a small Radio galaxies and radio quasars are only a small fraction of the population of active galaxies. For fraction of the population of active galaxies. For example, radio quiet quasars are typically about example, radio quiet quasars are typically about 100 times more common.100 times more common.

• But, the powerful extragalactic radio sources have But, the powerful extragalactic radio sources have the key feature of accelerating huge fluxes of high the key feature of accelerating huge fluxes of high energy particles at very great distances from the energy particles at very great distances from the source of energy, the supermassive black holes in source of energy, the supermassive black holes in their nuclei.their nuclei.

The 3CR Radio GalaxiesThe 3CR Radio Galaxies

The brightest radio sources in the northern The brightest radio sources in the northern sky are contained in the sky are contained in the Third Cambridge Third Cambridge Catalogue of Radio SourceCatalogue of Radio Source, the , the 3CR 3CR catalogue (1962)catalogue (1962). .

Robert Laing, Julia Riley and I produced a Robert Laing, Julia Riley and I produced a revised version in 1983, the revised version in 1983, the 3CRR 3CRR cataloguecatalogue with improved completeness. with improved completeness. Virtually all the sources at |b|>10Virtually all the sources at |b|>10oo are are distant extragalactic objectsdistant extragalactic objects. .

The 3CR Radio SourcesThe 3CR Radio SourcesThe sample is The sample is flux-density limitedflux-density limited at S at S ≈≈ 10 Jy 10 Jy at 178 MHz and so contains a mixture of at 178 MHz and so contains a mixture of nearby low radio luminosity objects and nearby low radio luminosity objects and luminous distant objects. Being selected at a luminous distant objects. Being selected at a low frequency, virtually all of them are low frequency, virtually all of them are extended double radio sourcesextended double radio sources..

There are significant differences between the There are significant differences between the radio structures of the extragalactic sources as radio structures of the extragalactic sources as a function of radio luminosity – the a function of radio luminosity – the Fanaroff-Fanaroff-Riley effectRiley effect..

Fanaroff-Riley Classes I and IIFanaroff-Riley Classes I and II

FRIFRI FRIIFRII

Low Radio luminosityLow Radio luminosity High Radio luminosityHigh Radio luminosity

Fanaroff-Riley Classes I and IIFanaroff-Riley Classes I and II

There is a very marked There is a very marked transition between FRI transition between FRI and FRII as a function of and FRII as a function of radio luminosity.radio luminosity.

We will be principally We will be principally concerned with the FRII concerned with the FRII sources which are the sources which are the most luminous radio most luminous radio sources. They sources. They undoubtedly possess undoubtedly possess large-scale shocks.large-scale shocks.

Optical Absolute MagnitudeOptical Absolute Magnitude

The Nature of the Radio EmissionThe Nature of the Radio Emission

The radio emission is The radio emission is synchrotron radiationsynchrotron radiation, the emission of , the emission of extremely high energy electrons gyrating in a magnetic field. extremely high energy electrons gyrating in a magnetic field.

The electrons are produced by jets of relativistic material The electrons are produced by jets of relativistic material ejected from the active galactic nucleus.ejected from the active galactic nucleus.

The Radio Galaxy Cygnus AThe Radio Galaxy Cygnus A

The radio lobes are powered The radio lobes are powered by intense beams of relativistic by intense beams of relativistic

material originating in the material originating in the active nucleusactive nucleus

Cygnus A – X-ray imageCygnus A – X-ray image

NASA Chandra ObservatoryNASA Chandra Observatory

The image shows the distribution of hot intergalactic gas The image shows the distribution of hot intergalactic gas surrounding the radio source.surrounding the radio source.

The X-ray emission is the The X-ray emission is the bremsstrahlung of very hot bremsstrahlung of very hot

intergalactic gas which intergalactic gas which provides the pressure to provides the pressure to confines the lobes of the confines the lobes of the

radio galaxies.radio galaxies.

The Dynamics of Powerful FRII Radio SourcesThe Dynamics of Powerful FRII Radio Sources

• Kaiser and Alexander developed an analytic model to Kaiser and Alexander developed an analytic model to describe the dynamics of the evolution of these radio describe the dynamics of the evolution of these radio structures which are dominated by the hypersonic passage structures which are dominated by the hypersonic passage of the relativistic jets from the nucleus of the active galaxy.of the relativistic jets from the nucleus of the active galaxy.

The Quasar The Quasar 3C 2733C 273

In 1963, 3C 273, the In 1963, 3C 273, the first quasar, was first quasar, was discovered. About discovered. About 20% of the radio 20% of the radio sources in the sources in the 3CRR sample are 3CRR sample are radio-loud quasars. radio-loud quasars.

Virtually all of them Virtually all of them are all FRII radio are all FRII radio sources when sources when selected at low radio selected at low radio frequencies. frequencies.

Normal galaxies at the same distance as the quasar

Redshift distributions for 3CR radio galaxies Redshift distributions for 3CR radio galaxies and quasars – a complete sampleand quasars – a complete sample

Num

ber

Num

ber

Num

ber

Num

ber

0 0.5 1.0 1.5 2.00 0.5 1.0 1.5 2.0

Quasars and BLRGsQuasars and BLRGs

22

44

0 0.5 1.0 1.5 2.00 0.5 1.0 1.5 2.0

55

1010

RedshiftRedshift

Narrow Line Radio Narrow Line Radio GalaxiesGalaxies

Note that the radio Note that the radio galaxies and quasars galaxies and quasars span span the same range the same range of redshift.of redshift.

For the FRII sources, For the FRII sources, the distributions are the distributions are the same. the same.

Note the ratio of the Note the ratio of the numbers of FRII numbers of FRII

sourcessources

~ ~ 3:13:1

FRI FRIIB

LRG

Num

ber

Num

ber

Quasars and BLRGsQuasars and BLRGs44

22

Num

ber

Num

ber

Narrow line radio galaxiesNarrow line radio galaxies

0 0.5 1.00 0.5 1.0

55

1010

V/VV/Vmaxmax

The V/VThe V/Vmaxmax Test Test

The test shows that The test shows that the radio galaxies the radio galaxies and quasars are and quasars are piled up towards the piled up towards the limits of their limits of their observable volumes. observable volumes. This is direct This is direct evidence for the evidence for the strong evolution of strong evolution of these populations these populations with cosmic epochwith cosmic epoch. .

The Orientation-based Unification Scheme The Orientation-based Unification Scheme for 3CR Radio Galaxies and Quasarsfor 3CR Radio Galaxies and Quasars

Active galactic nucleusActive galactic nucleus

Obscuring Obscuring torustorus

QuasarQuasar QuasarQuasar

Radio galaxyRadio galaxy


BlazarBlazar BlazarBlazar

Relativistic jetRelativistic jet








For the 3CR FRII sources, orientation-based unification schemes are For the 3CR FRII sources, orientation-based unification schemes are remarkably successful.remarkably successful.

Cosmological evolution, statistics of numbers and sizes, Cosmological evolution, statistics of numbers and sizes, asymmetries, presence of one/two sided jets. asymmetries, presence of one/two sided jets.

The host galaxies of radio quasars are the radio galaxies.The host galaxies of radio quasars are the radio galaxies.

The number counts and V/VThe number counts and V/Vmaxmax tests tests

indicate that there had been an indicate that there had been an enormous enormous increaseincrease in the numbers of radio sources at in the numbers of radio sources at large redshifts.large redshifts.

The radio quasars and the radio galaxies The radio quasars and the radio galaxies exhibit exhibit precisely the same form of evolution precisely the same form of evolution with cosmic epochwith cosmic epoch (or redshift). (or redshift).

The Evolution of the Radio The Evolution of the Radio Source PopulationsSource Populations

Determining the Evolution FunctionDetermining the Evolution Function

--

Pure luminosity Pure luminosity evolutionevolution

Deep radio Deep radio surveys confirm surveys confirm the decrease in the decrease in the comoving the comoving number density number density of radio sources of radio sources at large redshiftsat large redshifts

Dunlop and Peacock 1990Dunlop and Peacock 1990

Radio-Quiet Quasar StatisticsRadio-Quiet Quasar Statistics

Evolving Evolving luminosity luminosity functionfunction

7000 quasars. 7000 quasars. The observed The observed changes are changes are

consistent with consistent with luminosity luminosity evolution.evolution.

AAO 2dF AAO 2dF quasar survey quasar survey

(2000)(2000)

Boyle et al 2000Boyle et al 2000

Infrared Observations of GalaxiesInfrared Observations of Galaxies

Wavelength (Wavelength (m)m)0.1 1.0 100.1 1.0 10

Flu

x de

nsity

(W

mF

lux

dens

ity (

W m

-2-2 H

z H

z-1-1))

1010-33-33

1010-31-31

1010-32-32

Spectrum of giant elliptical galaxySpectrum of giant elliptical galaxy

Opt

ical

wav

eban

dsO

ptic

al w

aveb

ands

Infr

ared

wav

eban

dsIn

frar

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Galaxies are Galaxies are relatively brighter in relatively brighter in the the near infrared K near infrared K wavebandwaveband (2.2 (2.2 m) m) as compared with as compared with the optical the optical waveband. This is waveband. This is especially true of especially true of galaxies at large galaxies at large redshiftsredshifts. .

The K-z Relation for 3CR Radio The K-z Relation for 3CR Radio GalaxiesGalaxies

RedshiftRedshift

K (

2.2

mm

) ap

pare

nt m

agni

tude

K (

2.2

mm

) ap

pare

nt m

agni

tude

1212

1414

1616

1818

0.05 0.1 0.5 1.00.05 0.1 0.5 1.0

Expectations of standardworld models

Expectation of standard world models plus passive evolution of their stellar populations.

Lilly and Longair 1984Lilly and Longair 1984

Good News and Bad NewsGood News and Bad News• We planned a number of surveys to pin down We planned a number of surveys to pin down

the evolution of the optical, infrared and radio the evolution of the optical, infrared and radio properties of the radio source population. The properties of the radio source population. The K-z relation held out to z ~ 2.K-z relation held out to z ~ 2.

ButBut• in 1987, Chambers in 1987, Chambers et al.et al. and McCarthy and McCarthy et al.et al.

discovered that discovered that the optical images of the radio the optical images of the radio galaxies were aligned with their radio axes.galaxies were aligned with their radio axes. The The radio source activity was influencing the optical, radio source activity was influencing the optical, and possibly, infrared images.and possibly, infrared images.

The Hubble Space TelescopeThe Hubble Space Telescope

Observations of the Observations of the 28 brightest 3CR radio 28 brightest 3CR radio galaxiesgalaxies in the northern sky in the redshift in the northern sky in the redshift interval interval 0.6 < z < 1.80.6 < z < 1.8. These should contain . These should contain clues to the origin of the strong clues to the origin of the strong cosmological evolutionary effects.cosmological evolutionary effects.

Optical Optical HST images : HST images : = 0.1 arcsec= 0.1 arcsecInfrared Infrared UKIRT images : UKIRT images : = 1 arcsec= 1 arcsecRadioRadio VLA images : VLA images : = 0.18 arcsec= 0.18 arcsec

= angular resolution= angular resolution

3C 266 z = 1.2723C 266 z = 1.272

InfraredInfrared image imageUKIRTUKIRT

2.2 microns2.2 microns

Old starsOld stars

HST HST optical optical imageimage


Blue linesBlue lines are the contours of radio emission are the contours of radio emission

3C 368 z = 1.1323C 368 z = 1.132



Blue linesBlue lines are the contours of radio emission are the contours of radio emission

UnrelatedUnrelatedforegroundforeground

starstar



3C 324 z = 1.2073C 324 z = 1.207Blue linesBlue lines are the contours of radio emission are the contours of radio emission





3C 280 z = 0.9963C 280 z = 0.996Blue linesBlue lines are the contours of radio emission are the contours of radio emission





The radio galaxies in the redshift The radio galaxies in the redshift interval 1 < z < 1.3interval 1 < z < 1.3

• There are There are 88 radio galaxies in the sample in radio galaxies in the sample in the redshift interval the redshift interval 1 to 1.31 to 1.3, when the , when the Universe was about Universe was about a thirda third its present age. its present age.

• They all have roughly the They all have roughly the same intrinsic radio same intrinsic radio luminosityluminosity..

• Their relative luminosities and sizes are Their relative luminosities and sizes are independent of the cosmological modelindependent of the cosmological model..

• They all display a They all display a strong alignment effectstrong alignment effect..

3C266

3C368

3C324

3C280

3C65

50 kpc

3C2673C267

3C3563C356

3C2523C252

50 kpc50 kpc

Evolution of Powerful Radio Evolution of Powerful Radio Galaxies - the optical movieGalaxies - the optical movie

All images on the same physical scaleAll images on the same physical scale

100 kpc100 kpc

Understanding the Alignment EffectUnderstanding the Alignment Effect

Possible causesPossible causes

• Jet-induced star formationJet-induced star formation• Scattering of the light of an obscured nucleus - Scattering of the light of an obscured nucleus -

unification schemes for active galaxiesunification schemes for active galaxies• ‘‘nebular emission’/shocks induced by the nebular emission’/shocks induced by the

passage of the radio jetpassage of the radio jet

Philip Best, Huub Rottgering and I began a long Philip Best, Huub Rottgering and I began a long campaign of 2-d imaging optical spectroscopy to campaign of 2-d imaging optical spectroscopy to understand the excitation mechanisms of the understand the excitation mechanisms of the aligned emission.aligned emission.

The Ionisation Diagnostic DiagramThe Ionisation Diagnostic Diagram

The large sources have emission line spectra The large sources have emission line spectra consistent with consistent with photoionisationphotoionisation. The smaller . The smaller sources are consistent with sources are consistent with shock excitationshock excitation..

Shock Excitation of Ambient Cool Shock Excitation of Ambient Cool Gas CloudsGas Clouds

Ingredients of the model:Ingredients of the model:

• Kaiser and Alexander model of the evolution of the Kaiser and Alexander model of the evolution of the shock frontshock front

• Dopita and Sutherland model of shock excitation of Dopita and Sutherland model of shock excitation of cool gas cloudscool gas clouds

• Mendoza analysis of shock waves entering cool Mendoza analysis of shock waves entering cool cloudsclouds

Shock Excitation of Ambient Cool Shock Excitation of Ambient Cool Gas CloudsGas Clouds

A self-consistent set of parameters can be found to A self-consistent set of parameters can be found to account for the structures in terms of the shock wave account for the structures in terms of the shock wave associated with the radio cocoon exciting and heating associated with the radio cocoon exciting and heating compact cool clouds.compact cool clouds.

Typical parameters:Typical parameters:

Particle density in IGMParticle density in IGM 0.03 cm0.03 cm-3-3 Particle density in cloudsParticle density in clouds 101022 cm cm-3-3

Filling factorFilling factor 1010-6-6

Velocity of shock in IGMVelocity of shock in IGM 0.02 c0.02 cVelocity of shock in cloudVelocity of shock in cloud 200 km s200 km s-1-1

The 6C sampleThe 6C sample

• The next step was to apply the same The next step was to apply the same techniques to fainter samples of radio techniques to fainter samples of radio sources – the 6C sample selected by sources – the 6C sample selected by Rawlings and Eales.Rawlings and Eales.

• The sample is about a factor of six fainter The sample is about a factor of six fainter than the 3CR sample.than the 3CR sample.

• The analysis was carried out with The analysis was carried out with Katherine Katherine InskipInskip and and Philip BestPhilip Best and there were three and there were three topics relevant to the work-shop.topics relevant to the work-shop.

Topic 1: Separating radio luminosity Topic 1: Separating radio luminosity from redshift changesfrom redshift changes

3CR3CR

6C6C

The 6C sample is about 6 times fainter than the 3CR sampleThe 6C sample is about 6 times fainter than the 3CR sample

6C1217+36

6C1017+37

6C0943+39

6C1129+37

6C1256+36

50 kpc

Spectroscopic Surveys of the Aligned Spectroscopic Surveys of the Aligned StructuresStructures

We have completed deep two-dimensional optical We have completed deep two-dimensional optical spectroscopic observations of all the z ~ 1 radio spectroscopic observations of all the z ~ 1 radio galaxies in the 3CR and 6C samples. galaxies in the 3CR and 6C samples.

These enable the physics of these phenomena to These enable the physics of these phenomena to be understood in some detail and related to the be understood in some detail and related to the dynamics of the radio sources.dynamics of the radio sources.

Work of Work of Katherine InskipKatherine Inskip, , Philip BestPhilip Best, Huub , Huub Rottgering, Steve Rawlings, Garret Cotter and Rottgering, Steve Rawlings, Garret Cotter and MSLMSL

The Ionisation Diagnostic DiagramThe Ionisation Diagnostic Diagram

The large sources have emission line spectra The large sources have emission line spectra consistent with photoionisation. The smaller consistent with photoionisation. The smaller sources are consistent with shock excitation.sources are consistent with shock excitation.

Kinematics and Radio SizeKinematics and Radio Size

The conclusion is in agreement with the broad range of velocities The conclusion is in agreement with the broad range of velocities

and velocity components present in the small sourcesand velocity components present in the small sources..

3CR large z – crosses6C matched sample – triangles3CR low z sample – filled stars

Kinematics versus RedshiftKinematics versus Redshift

3CR large z – crosses6C matched sample – triangles3CR low z sample – filled stars

Kinematics versus Radio PowerKinematics versus Radio Power

3CR large z – crosses6C sample – triangles3CR low z sample – filled stars

Evolution of the host galaxy Evolution of the host galaxy and/or environmentand/or environment

• Significant evolution of the host galaxy properties with redshift is Significant evolution of the host galaxy properties with redshift is required to explain the kinematics of the extended emission line regions.required to explain the kinematics of the extended emission line regions.

• Other observational evidence for evolutionOther observational evidence for evolution

• These suggest that:These suggest that:

• High-z radio sources often belong to richer cluster High-z radio sources often belong to richer cluster environments.environments.

• The alignment effect is less extreme at low-z.The alignment effect is less extreme at low-z.

• The distribution of cool gas clouds varies with zThe distribution of cool gas clouds varies with z• Interactions between the IGM and the radio jets are less Interactions between the IGM and the radio jets are less

important at low-zimportant at low-z..

Relevance to Acceleration of Relevance to Acceleration of High Energy ParticlesHigh Energy Particles

• Note that these observations provide direct Note that these observations provide direct evidence for the existence of very large-scale evidence for the existence of very large-scale shock waves in these radio galaxies on scales up shock waves in these radio galaxies on scales up to at least 100-200 kpc.to at least 100-200 kpc.

• According to the standard shock picture of According to the standard shock picture of particle acceleration, the maximum energies particle acceleration, the maximum energies scale as the dimension of the shock.scale as the dimension of the shock.

• Hence, possible to accelerate particles to, say, Hence, possible to accelerate particles to, say, 101055 times those in supernovae. times those in supernovae.

Topic 2: Optical-Infrared Colour Topic 2: Optical-Infrared Colour EvolutionEvolution

Colours Colours corrected for corrected for

emission lines emission lines and point and point sources in sources in

nucleinuclei

Averages in Averages in equal redshift equal redshift

bins.bins.

The lines are the loci of passively evolving galaxies with The lines are the loci of passively evolving galaxies with formation redshifts 3 (solid line) to 20 (uppermost locus)formation redshifts 3 (solid line) to 20 (uppermost locus)

Optical-Infrared Colour EvolutionOptical-Infrared Colour Evolution

• Direct evidence for on-going star formation Direct evidence for on-going star formation activity throughout the lifetime of the radio galaxy.activity throughout the lifetime of the radio galaxy.

• The optical-infrared colours of the 3CR and 6C The optical-infrared colours of the 3CR and 6C samples are remarkably similar despite the fact samples are remarkably similar despite the fact that the alignment effect is much weaker in the 6C that the alignment effect is much weaker in the 6C as compared with the 3CR sample.as compared with the 3CR sample.

• Are the infrared luminosities of the 3CR galaxies Are the infrared luminosities of the 3CR galaxies enhanced because of the alignment effect and/or enhanced because of the alignment effect and/or associated star formation activity?associated star formation activity?

Topic 3: The K-z Relation for 6C Topic 3: The K-z Relation for 6C Radio Galaxies - Eales and RawlingsRadio Galaxies - Eales and Rawlings

• The 6C survey was about 6 The 6C survey was about 6 times fainter than 3CR.times fainter than 3CR.

• The K-z relation agrees with The K-z relation agrees with the 3CR relation at z < 0.5.the 3CR relation at z < 0.5.

• The 6C galaxies are about The 6C galaxies are about 0.8 mag fainter than the 0.8 mag fainter than the 3CR galaxies at z ~ 1.3CR galaxies at z ~ 1.

• The 6C K-z relation is The 6C K-z relation is consistent with no evolution.consistent with no evolution.

o 6C3CR

RedshiftRedshift

K (

2.2

mm

) a

ppa

ren

t ma

gn

itude

K (

2.2

mm

) a

ppa

ren

t ma

gn

itude

1212

1414

1616

1818

0.01 0.1 1.0 100.01 0.1 1.0 10

2020No evolutionNo evolution

Comparison of the 3C and 6C GalaxiesThe 6C galaxies are less luminous and smaller than the

3C galaxies

3C 6C

Features of the New Analysis of the Features of the New Analysis of the K-z relationK-z relation

• Analyses repeated using wider range of Analyses repeated using wider range of cosmological models.cosmological models.

• Use of the latest galaxy evolution codes of Use of the latest galaxy evolution codes of Bruzual and Charlot (GISSEL).Bruzual and Charlot (GISSEL).

• Variation of parametersVariation of parameters

• Epoch of star formation.Epoch of star formation.

• Metallicity.Metallicity.

• Starbursts associated with the radio source events.Starbursts associated with the radio source events.

Bruzual and Charlot GISSEL Galaxy Bruzual and Charlot GISSEL Galaxy

Evolution ModelsEvolution Models

2 mz=1

z=3

z=2

Other world models, including passive Other world models, including passive

evolutionevolution 00

1.0 0.01.0 0.00.3 0.0 0.3 0.0 0.1 0.00.1 0.00.0 0.00.0 0.0 0.3 0.70.3 0.70.3 0.30.3 0.30.1 0.9 0.1 0.9 0.1 0.30.1 0.3

3CR Radio Galaxy Stellar Masses3CR Radio Galaxy Stellar Masses

McLure, Best et al 2005McLure, Best et al 2005

Empirical rather than Empirical rather than B-C evolutionary B-C evolutionary

modelsmodels

Galaxies in General versus RedshiftGalaxies in General versus Redshift

Glazebrook et al. 2005 Gemini Deep Deep Survey + K20

The Bulge-Black Hole ConnectionThe Bulge-Black Hole Connection

Häring and Rix (2004Häring and Rix (2004))

For nearby galaxies, For nearby galaxies, there is a close there is a close linear relation linear relation

between the masses between the masses of the central black of the central black holes and the mass holes and the mass

of the bulge (or of the bulge (or spheroid) of the spheroid) of the

galaxy. Typically it is galaxy. Typically it is found thatfound that

MMBHBH/M/Msphsph = 0.002 = 0.002








For the 3CR sample and others, orientation-based unification For the 3CR sample and others, orientation-based unification schemes are remarkably successful.schemes are remarkably successful.

Cosmological evolution, statistics of numbers and sizes, Cosmological evolution, statistics of numbers and sizes, asymmetries, presence of one/two sided jets. asymmetries, presence of one/two sided jets.

The host galaxies of radio quasars are the radio galaxies.The host galaxies of radio quasars are the radio galaxies.

The Bulge-Black Hole Connection for The Bulge-Black Hole Connection for 3CR Radio Galaxies and Quasars3CR Radio Galaxies and Quasars

McLure McLure et alet al (2005 (2005))

Because of the Because of the success of the success of the orientation-based orientation-based unification unification scheme, it is scheme, it is possible to derive: possible to derive:

• spheroid masses spheroid masses for the radio for the radio galaxiesgalaxies

• black hole masses black hole masses for the quasarsfor the quasars. .

Probability of a Galaxy Becoming a Radio Probability of a Galaxy Becoming a Radio Galaxy from the Sloan Digital Sky SurveyGalaxy from the Sloan Digital Sky Survey

Best et al 2005Best et al 2005

Philip Best and his Philip Best and his colleagues colleagues

showed that the showed that the fraction of radio-fraction of radio-

loud active loud active galaxies is galaxies is a very a very strong function of strong function of the mass of the the mass of the

galaxies and galaxies and consequently of consequently of

their central black their central black hole masses.hole masses.

3CR FRII

Radio Galaxy Activity and Bursts of Radio Galaxy Activity and Bursts of Star FormationStar Formation

Best et al 2005Best et al 2005

• The probability of a massive galaxy being an FR2 The probability of a massive galaxy being an FR2 radio galaxy is about 1%. radio galaxy is about 1%.

• The typical age of these sources is about 10The typical age of these sources is about 107-87-8 years. years.

• Hence, at small redshifts, there would need to be 1 to Hence, at small redshifts, there would need to be 1 to 10 radio source events during the lifetime of the 10 radio source events during the lifetime of the source.source.

• But we need to account for the relic bursts of star But we need to account for the relic bursts of star formation which give rise to the scatter in the optical-formation which give rise to the scatter in the optical-infrared colours.infrared colours.

• The strong evolution of the source population implies The strong evolution of the source population implies more radio source events of a given luminosity in the more radio source events of a given luminosity in the past. past.

Active Galaxies, Shocks and High Energy Particles Carried out in collaboration with: Philip Best...

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