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Active Galaxies, Shocks and High Energy Particles

Active Galaxies, Shocks and High Energy Particles. Carried out in collaboration with: Philip Best Katherine Inskip Huub R ö ttgering. Radio galaxies and radio quasars are source of high energy particles which are dispersed throughout intergalactic space

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Active Galaxies, Shocks and High Energy Particles

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  1. Active Galaxies, Shocks and High Energy Particles Carried out in collaboration with: Philip Best Katherine Inskip Huub Röttgering

  2. Radio galaxies and radio quasars are source of high energy particles which are dispersed throughout intergalactic space • Evidence for strong shocks in the environments of powerful radio galaxies on very large scales • Statistics of different classes of powerful extragalactic radio source • Can these considerations play a role in the study of high energy cosmic rays? Active Galaxies and High Energy Particles

  3. Radio galaxies and radio quasars are only a small fraction of the population of active galaxies. For example, radio quiet quasars are typically about 100 times more common. • But, the powerful extragalactic radio sources have the key feature of accelerating huge fluxes of high energy particles at very great distances from the source of energy, the supermassive black holes in their nuclei. Why the Radio Galaxies and Radio Quasars?

  4. The 3CR Radio Galaxies The brightest radio sources in the northern sky are contained in the Third Cambridge Catalogue of Radio Source, the 3CR catalogue (1962). Robert Laing, Julia Riley and I produced a revised version in 1983, the 3CRR catalogue with improved completeness. Virtually all the sources at |b|>10o are distant extragalactic objects.

  5. The 3CR Radio Sources The sample is flux-density limited at S ≈ 10 Jy at 178 MHz and so contains a mixture of nearby low radio luminosity objects and luminous distant objects. Being selected at a low frequency, virtually all of them are extended double radio sources. There are significant differences between the radio structures of the extragalactic sources as a function of radio luminosity – the Fanaroff-Riley effect.

  6. FRI FRII Low Radio luminosity High Radio luminosity Fanaroff-Riley Classes I and II

  7. Fanaroff-Riley Classes I and II There is a very marked transition between FRI and FRII as a function of radio luminosity. We will be principally concerned with the FRII sources which are the most luminous radio sources. They undoubtedly possess large-scale shocks. Optical Absolute Magnitude

  8. The Nature of the Radio Emission The radio emission is synchrotron radiation, the emission of extremely high energy electrons gyrating in a magnetic field. The electrons are produced by jets of relativistic material ejected from the active galactic nucleus.

  9. The Radio Galaxy Cygnus A The radio lobes are powered by intense beams of relativistic material originating in the active nucleus

  10. The Radio Galaxy Cygnus A The radio lobes are powered by intense beams of relativistic material originating in the active nucleus

  11. The image shows the distribution of hot intergalactic gas surrounding the radio source. Cygnus A – X-ray image NASA Chandra Observatory The X-ray emission is the bremsstrahlung of very hot intergalactic gas which provides the pressure to confines the lobes of the radio galaxies.

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

  13. Normal galaxies at the same distance as the quasar In 1963, 3C 273, the first quasar, was discovered. About 20% of the radio sources in the 3CRR sample are radio-loud quasars. Virtually all of them are all FRII radio sources when selected at low radio frequencies. The Quasar 3C 273

  14. Quasars and BLRGs FRII FRI BLRG Narrow Line Radio Galaxies Note that the radio galaxies and quasars span the same range of redshift. For the FRII sources, the distributions are the same. Note the ratio of the numbers of FRII sources ~ 3:1 4 Number Redshift distributions for 3CR radio galaxies and quasars – a complete sample 2 0 0.5 1.0 1.5 2.0 10 Number 5 0 0.5 1.0 1.5 2.0 Redshift

  15. Quasars and BLRGs 4 The V/Vmax Test Number 2 10 The test shows that the radio galaxies and quasars are piled up towards the limits of their observable volumes. This is direct evidence for the strong evolution of these populations with cosmic epoch. Narrow line radio galaxies 5 Number 0 0.5 1.0 V/Vmax

  16. Radio galaxy Quasar Quasar Blazar Blazar Radio galaxy Active galactic nucleus The Orientation-based Unification Scheme for 3CR Radio Galaxies and Quasars Relativistic jet Obscuring torus

  17. Radio galaxy Quasar Quasar Blazar Blazar Radio galaxy Active galactic nucleus The Orientation-based Unification Scheme for 3CR Radio Galaxies and Quasars Obscuring torus • For the 3CR FRII sources, orientation-based unification schemes are remarkably successful. • Cosmological evolution, statistics of numbers and sizes, asymmetries, presence of one/two sided jets. • The host galaxies of radio quasars are the radio galaxies.

  18. The Evolution of the Radio Source Populations The number counts and V/Vmax tests indicate that there had been an enormous increase in the numbers of radio sources at large redshifts. The radio quasars and the radio galaxies exhibit precisely the same form of evolution with cosmic epoch (or redshift).

  19. Pure luminosity evolution Determining the Evolution Function Deep radio surveys confirm the decrease in the comoving number density of radio sources at large redshifts - Dunlop and Peacock 1990

  20. AAO 2dF quasar survey (2000) Radio-Quiet Quasar Statistics Evolving luminosity function 7000 quasars. The observed changes are consistent with luminosity evolution. Boyle et al 2000

  21. Infrared wavebands Optical wavebands Spectrum of giant elliptical galaxy Galaxies are relatively brighter in the near infrared K waveband (2.2 mm) as compared with the optical waveband. This is especially true of galaxies at large redshifts. Infrared Observations of Galaxies 10-31 Flux density (W m-2 Hz-1) 10-32 10-33 0.1 1.0 10 Wavelength (mm)

  22. Expectations of standard world models Expectation of standard world models plus passive evolution of their stellar populations. The K-z Relation for 3CR Radio Galaxies 18 16 K (2.2 mm) apparent magnitude 14 12 0.05 0.1 0.5 1.0 Lilly and Longair 1984 Redshift

  23. We planned a number of surveys to pin down the evolution of the optical, infrared and radio properties of the radio source population. The K-z relation held out to z ~ 2. • But • in 1987, Chambers et al. and McCarthy et al. discovered that the optical images of the radio galaxies were aligned with their radio axes. The radio source activity was influencing the optical, and possibly, infrared images. Good News and Bad News

  24. The Hubble Space Telescope Observations of the 28 brightest 3CR radio galaxies in the northern sky in the redshift interval 0.6 < z < 1.8. These should contain clues to the origin of the strong cosmological evolutionary effects. Optical HST images : q = 0.1 arcsec Infrared UKIRT images : q = 1 arcsec Radio VLA images : q = 0.18 arcsec q = angular resolution

  25. HST optical image 0.8 microns Blue lines are the contours of radio emission 3C 266 z = 1.272 Infrared image UKIRT 2.2 microns Old stars

  26. HST optical image 0.8 microns Unrelated foreground star Blue lines are the contours of radio emission 3C 368 z = 1.132 Infrared image UKIRT 2.2 microns

  27. Infrared image UKIRT 2.2 microns HST optical image 0.8 microns Blue lines are the contours of radio emission 3C 324 z = 1.207

  28. HST optical image 0.8 microns Blue lines are the contours of radio emission Infrared image UKIRT 2.2 microns 3C 280 z = 0.996

  29. The radio galaxies in the redshift interval 1 < z < 1.3 There are 8 radio galaxies in the sample in the redshift interval 1 to 1.3, when the Universe was about a third its present age. They all have roughly the same intrinsic radio luminosity. Their relative luminosities and sizes are independent of the cosmological model. They all display a strong alignment effect.

  30. 3C266 3C368 3C324 3C280 3C65 50 kpc

  31. 50 kpc 3C267 3C252 3C356

  32. Evolution of Powerful Radio Galaxies - the optical movie 100 kpc All images on the same physical scale

  33. Possible causes • Jet-induced star formation • Scattering of the light of an obscured nucleus - unification schemes for active galaxies • ‘nebular emission’/shocks induced by the passage of the radio jet Understanding the Alignment Effect Philip Best, Huub Rottgering and I began a long campaign of 2-d imaging optical spectroscopy to understand the excitation mechanisms of the aligned emission.

  34. The Ionisation Diagnostic Diagram The large sources have emission line spectra consistent with photoionisation. The smaller sources are consistent with shock excitation.

  35. Shock Excitation of Ambient Cool Gas Clouds • Ingredients of the model: • Kaiser and Alexander model of the evolution of the shock front • Dopita and Sutherland model of shock excitation of cool gas clouds • Mendoza analysis of shock waves entering cool clouds

  36. A self-consistent set of parameters can be found to account for the structures in terms of the shock wave associated with the radio cocoon exciting and heating compact cool clouds. Typical parameters: Particle density in IGM 0.03 cm-3 Particle density in clouds 102 cm-3 Filling factor 10-6 Velocity of shock in IGM 0.02 c Velocity of shock in cloud 200 km s-1 Shock Excitation of Ambient Cool Gas Clouds

  37. The next step was to apply the same techniques to fainter samples of radio sources – the 6C sample selected by Rawlings and Eales. • The sample is about a factor of six fainter than the 3CR sample. • The analysis was carried out with Katherine Inskip and Philip Best and there were three topics relevant to the work-shop. The 6C sample

  38. The 6C sample is about 6 times fainter than the 3CR sample Topic 1: Separating radio luminosity from redshift changes 3CR 6C

  39. 6C1217+36 6C1017+37 6C0943+39 6C1129+37 6C1256+36 50 kpc

  40. We have completed deep two-dimensional optical spectroscopic observations of all the z ~ 1 radio galaxies in the 3CR and 6C samples. These enable the physics of these phenomena to be understood in some detail and related to the dynamics of the radio sources. Work of Katherine Inskip, Philip Best, Huub Rottgering, Steve Rawlings, Garret Cotter and MSL Spectroscopic Surveys of the Aligned Structures

  41. The Ionisation Diagnostic Diagram The large sources have emission line spectra consistent with photoionisation. The smaller sources are consistent with shock excitation.

  42. 3CR large z – crosses 6C matched sample – triangles 3CR low z sample – filled stars Kinematics and Radio Size The conclusion is in agreement with the broad range of velocities and velocity components present in the small sources.

  43. Kinematics versus Redshift 3CR large z – crosses 6C matched sample – triangles 3CR low z sample – filled stars

  44. Kinematics versus Radio Power 3CR large z – crosses 6C sample – triangles 3CR low z sample – filled stars

  45. Evolution of the host galaxy and/or environment • Significant evolution of the host galaxy properties with redshift is required to explain the kinematics of the extended emission line regions. • Other observational evidence for evolution • These suggest that: • High-z radio sources often belong to richer cluster • environments. • The alignment effect is less extreme at low-z. • The distribution of cool gas clouds varies with z • Interactions between the IGM and the radio jets are less important at low-z.

  46. Relevance to Acceleration of High Energy Particles • Note that these observations provide direct evidence for the existence of very large-scale shock waves in these radio galaxies on scales up to at least 100-200 kpc. • According to the standard shock picture of particle acceleration, the maximum energies scale as the dimension of the shock. • Hence, possible to accelerate particles to, say, 105 times those in supernovae.

  47. Topic 2: Optical-Infrared Colour Evolution Colours corrected for emission lines and point sources in nuclei Averages in equal redshift bins. The lines are the loci of passively evolving galaxies with formation redshifts 3 (solid line) to 20 (uppermost locus)

  48. Optical-Infrared Colour Evolution • Direct evidence for on-going star formation activity throughout the lifetime of the radio galaxy. • The optical-infrared colours of the 3CR and 6C samples are remarkably similar despite the fact that the alignment effect is much weaker in the 6C as compared with the 3CR sample. • Are the infrared luminosities of the 3CR galaxies enhanced because of the alignment effect and/or associated star formation activity?

  49. o 6C No evolution 3CR 20 Topic 3: The K-z Relation for 6C Radio Galaxies - Eales and Rawlings 18 K (2.2 mm) apparent magnitude 16 The 6C survey was about 6 times fainter than 3CR. The K-z relation agrees with the 3CR relation at z < 0.5. The 6C galaxies are about 0.8 mag fainter than the 3CR galaxies at z ~ 1. The 6C K-z relation is consistent with no evolution. 14 12 0.01 0.1 1.0 10 Redshift

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