1. Radio Galaxy Evolution ATCA image by L. Saripalli, R. Subrahmanyan and Udaya Shankar http://www.narrabri.atnf.csiro.au/public/images/j0116-473/ Carlo Stanghellini First MCCT-SKADS Training School 23-29 September 2007, Medicina (Bologna, Italy)

2. outline What is a radiogalaxy How radio galaxies work How they evolve at kpc/Mpc scale How to find the youngest ones How the young radio galaxies evolve (pc/kpc scale) Evidence of recurrency in the same galaxy of the radio source phenomenon Not covered here (just mentioned): central engine Accretion disk, torus Beamed objets

3. What is a Radio Galaxy? All galaxies emit radio emission in one or more ways -neutral hydrogen -supernovae remnants -cosmic rays -HII regions -weak emission from the nucleus They are not radio galaxies

4. Cygnus A A radio galaxy is a galaxy emitting a significant fraction of its energy in form of radio waves, with defined characteristics -size from pc to Mpc -morphological differences depending on radio power, optical luminosity & orientation -radio power 10 23 to 10 28 W/Hz

5. Toruń, Poland, 26-29 September 2006 First observed radio galaxy Cygnus A in 1944/1948 by Grote Reber Sullivan W., The Early Years of Radio Astronomy – 1984 -Cambridge Univ. Press

6. Double lobed structures made difficult optical identification in the early years At the end of the ’60 it was largely accepted that most radio sources in the sky were of extragalactic origin Extragalactic radio sources were roughly divided in extended when the radio emission extends outwards the galaxy and compact when it does not

7. Fanaroff and Riley ? Fanaroff & Riley 1974, MNRAS 167, 31 ? “The morphology of extragalactic radio sources of high and low luminosity” ? Sharp division in luminosity at 10^25 W/Hz/Sr (178 MHz) FR I FR II Owen and Ledlow 1994

8. Zoology Extended extragalactic radio sources showed a variety of morphologies when radio interferometers came in operation. Miley G., Annual review of astronomy and astrophysics. Volume 18. 1980, p. 165-218.

9. Other examples http://www.jb.man.ac.uk/atlas/ 3C83.1B 3C465 3C272.1 3C98 3C184.1 4C11.71

10. Other examples 3C349 3C283C315 3C305 A1552 3C338

11. Compact radio sources At high frequency (>5GHz) compact sources are the dominant population of the radio sky Also compact sources may be divided in two main classes, the flat spectrum radio sources and the GPS/CSS radio sources. Flat spectrum radio sources are not intrinsically small but instead they are large radio sources which appear small because they are seen along the jet, thus the lobes are shortened by projection and the core is amplified by relativistic effects GPS/CSS radio sources (in particular GPS/CSS radio *galaxies*) are truly small radio sources (less than a few kpc) still imbedded in the galactic ISM, showing double lobed structures as their larger counterparts. (more later)

12. Alfvén, H.; Herlofson, N. 1950, Cosmic Radiation and Radio Stars predictet synchrotron emission from cosmic objects Shklovskii 1953, explained the continuum radiation of the Crab Nebula as synchrotron radiation General Electric Synchrotron accelerator in 1946

13. Synchrotron emission and equipartition assumption Burbidge 1956, ApJ 124, 416 “On synchrotron radiation from Messier 87” “The observations by Baade (1956) of the polarization of the jet in M87 are convincing proof of the hypothesis that this optical radiation is synchrotron radiation emitted by relativistic electrons and positrons moving in magnetic fields…” Also equipartition conditions have been introduced in this paper of Burbidge

14. Physics of a radio galaxy Pionering models First attempts to describe the physics of a radio source took inspiration by the recent discovery of pulsars, and considered fast rotating massive objects as the source of a continuous supply of energy (Morrison 1969, ApJ 157, L73; Rees 1971, Nat.229, 312, Longair et al. 1973, MNRAS 164, 243) Longair et al. 1973

15. More detailed models Scheuer in 1974 (MNRAS 166, 513) presents a rather plausible model of a radio source “in which energy is carried from a nucleus to the radio components by a relativistic beam”. In the Sheuer model the nature of the beam is not of much importance, and it can consist of electromagnetic waves, fast particles, or the beam can be subtituted by a massive object ejected by the nucleus

16. A twin-exhaust model for a double radio source In 1974 (MNRAS 169, 395) Blandford and Rees present “A twin-exhaust model for a double radio source” which is a further elaboration of the Scheuer model where the beam is composed by relativistic plasma Even if subsequent refinement of the model have been done, it remains valid in its basic assumption: -The energy is supplied by a light fluid composed of relativistic particles pervaded by electromagnetic fields which is generated in the nuclear region and collimates into two oppositely directed beams. -Each beam terminates, and reconverts much of its bulk energy into relativistic particle and fields at a working surface which advences outwards at a speed determined by a balance between the momentum flux in the beam and the ram pressure of the intergalactic medium. -The energy content of extended sources can be assumed to accumulate gradually over the whole lifetime, at rates ~<10^45 erg/sec. Cygnus A at 5GHz with the 5km radio telescope in Cambridge Hargrave & Ryle 1974

17. Standard basic model for FR II still widely accepted

18. Dentist drill ? Scheuer, 1982, IAUS 97, 163: ? Morphology and power of radio sources Carilli et al. 1999, Aj 118, 2581: “The generally accepted model for double hot spots is the dentist drill model in which the jet alters direction on timescales shorter than the timescale it would take for an "abandoned" hot spot to fade to the background surface brightness level because of expansion losses (10 5 yr)”

19. The unified schemes

20. Evolution of radio galaxies in the sixties Speculations about evolution of radio sources started also in the sixties. Kardashev, 1962, Sov. Astr. 6, 317 Schmidt, 1966, ApJ 146, 7 Kellermann, 1966, ApJ 146, 621 Van der Laan and Perola, 1969, A&A 3, 468 These studies were mainly based on the spectral properties of radio sources, and the evidence that the radiation came by relativistic electrons radiating by synchrotron emission It was recognized that the radiative losses of the relativistic plasma reflected in the spectral shape could give an estimate of the radio source age. Kardashev, 1962

21. Ages of the radio sources The radio source phenomenon has been soon recognized by the studies of spectral ageing to be a relatively short event lasting between 10^6 to 10^8 years Modern applications consist in the study of different regions of a radio source to trace the path of the electrons, and find the where the electrons are deposited or reaccelerated

22. B1943+546 100pc Core Jet Lobe Core Determination of LOCAL spectral aging: assuming: - no reacceleration - equipartition magnetic field - no expansion losses Determination of LOCAL spectral aging: assuming: - no reacceleration - equipartition magnetic field - no expansion losses Need pc-scale spectral index images via Multifrequency VLBA+Y1 observation Hot Spots 50pc Age=~1300 yr V_sep=0.28c Age=~1300 yr V_sep=0.28c

23. 1323+321

24. Begelman, Blandfrod and Rees 1984, Rev. Mod. Phys. 56, 255 Theory of extragalactic radio sources Methods of using the observations diagnostically to infer the pressures, densities, and fluid velocities within jets are explained

25. Begelman and Cioffi 1989, ApJ 345, L21 Overpressured cocoons in extragalactic radio sources Pressure of the cocoon high enough to confine the jet Also triggering of star formation which explains alignement of optical continuum emission with radio axis

26. Falle 1991, MNRAS 250, 581 Self similar jets General arguments and numerical calculations are used to show that the flow caused by a superconic gas jet is self-similar under certain conditions. pressure density

27. Shklovskii 1963, Soviet Astronomy 6, 465 On the Nature of Radio Galaxies Shlovskii introduces the P-D diagram which is the radio galaxy equivalent of the H-R diagram for stars

28. Baldwin 1982, IAUS 97, 21 Evolutionary tracks of extended radio sources Using Sheuer dynamical model and a decreasing density profile of the IGM Baldwin trace evolutionary tracks on the P-D diagram

29. Models of power and size evolution of an FR II Power evolution governed by adiabatic losses as lobes expands, synchrotron radiation losses in the lobe magnetic fields and inverse Compton (IC) losses off the cosmic microwave background photons Density of the ambient gas

30. Kaiser and Alexander 1997, MNRAS 286, 215 A self-similar model for extragalactic radio sources Model for extragalactic radio source with pressure-confined jet expanding in self similar way into a spherically symmetric atmosphere with density profile falling less steeply than 1/d^2 Stable laminar jets for jet powers above the FRI/FRII divide

31. Kaiser, Dennet-Thorpe and Alexander 1997, MNRAS 292, 723 Evolutionary tracks of FRII sources through the P-D diagram Hot spot pressure drives the source expansion along the jet axis and the cocoon pressure drives the expansion perpendicular to the jet axis Considering energy-losses for the relativistic electrons, evolutionary tracks through the power-linear size diagram are calculated Cocoons can have self similar growth The evolutionary tracks are found to be insensitive to the assumed form of the magnetic field evolution. Some evidence against protons as a major constituent of the jet material is also found.

32. Blundell, Rawlings and Willott 1999, AJ 117, 677 The nature and evolution of classical double radio sources from complete samples

33. Manolakou and Kirk 2002, A&A 391, 127 Modelling the spectral evolution of classical double radio sources Same picture as in Blundell et al. 1999, but assuming that adiabatic losses between the hot spot and the lobe are compensated by subsequent weaker shocks through which the plasma passes after the termination shock at the primary hot spot and before emerging in the lobe

34. Barai and Wiita 2006, MNRAS 372, 381 Testing Models of the individual and cosmological evolution of powerful radio galaxies Barai and Wiita 2007, ApJ 658, 217 Testing Models of Radio Galaxy Evolution and the Cosmological Impact of FR II Radio Galaxies They want to address cosmological aspects Radio Galaxies can have sustantial impacts on the formation, distribution and evolution of galaxies and large scale structure in the Universe Radio Galaxies trigger star formation in the IGM.The expanding radio lobes could have infused magnetic fields of significan strengths (10^-8G) in the IGM. The radio lobes can be also responsible to spread metals in the IGM Which part of the “relevant” Universe has been filled by the radio lobes? Self similar growth a reasonable aproximation

35. Barai and Wiita 2007, MNRAS 372, 381 Testing Models of the individual and cosmological evolution of powerful radio galaxies Barai and Wiita 2007, ApJ 658, 217 Testing Models of Radio Galaxy Evolution and the Cosmological Impact of FR II Radio Galaxies Simulated suveys are generated and allowed to evolve according the previous models No existing model gives exellent fits to all the data simultaneously However Kaiser et al. model is the best in fitting the observational data In the second paper Barai and Wiita present modified models allowing the growth of the hot-spot size. This improve the match between simulated and real data, but it is still not entirely statisfactory Jeyakumar and Saikia 2000

36. Earlier evolution ? The evolutionary models discussed so far where about the growth and evolution of an already established radio galaxy in the intergalactic medium while it is supplied with fresh electrom from the nucleus ? In the following we will consider the early phases of a radio source life, and possibility of recurrency of the radio source phenomenon

37. find young radio galaxies These sources are known as Compact Symmetric Objects (CSO, < 1kpc) and Medium Size Objects (MSO, 1-20 kpc). They generally have a convex radio spectrum (flux density versus frequency). To find young radio sources we may look for compact sources with the same morphology of the large ones (in the assumption they maintain their basic structure during their lifetime).

38. CSO/MSO and GPS/CSS  selection of CSOs and MSOs has severe problems.  They have in general a convex radio spectrum peaking around 1 GHz (CSO) or 100 MHz (MSO).  Selection based on the spectral shape is easier.  then Compact Steep Spectrum (CSS) and GHz Peaked Spectrum (GPS) radio sources.  selection of CSOs and MSOs has severe problems.  They have in general a convex radio spectrum peaking around 1 GHz (CSO) or 100 MHz (MSO).  Selection based on the spectral shape is easier.  then Compact Steep Spectrum (CSS) and GHz Peaked Spectrum (GPS) radio sources.

39. Turnover CSS/GPS/HFP radio sources

40. Are these objects really young?  Youth scenario – they are young (10^4 yr).  Frustration scenario – they are old (10^6 yr) and confined.  Recurrency – they die and start again.  Short lived – they die when still young.  Youth scenario – they are young (10^4 yr).  Frustration scenario – they are old (10^6 yr) and confined.  Recurrency – they die and start again.  Short lived – they die when still young.

41. The density in the inner kpc From X-ray, infrared, HI at 21 cm, radio spectrum at low frequency, optical line diagnostic There is not a conclusive evidence to distinguish between the youth and the frustration scenarios

42. Core Hot-Spot Evidence for youth Owsianik et al. 1998 Evidence for youth Owsianik et al. 1998 2352+495

43. 0710+439 Owsianik et al. 1998

44. OQ208

45. Polatidis and Conway 2003

46. Proper motions Polatidis, Conway 2003 --- 10 detections (0.1-0.3 c) 3 upper limits (<0.1c) Gugliucci et al. 2005 --- 9 detections (0.4c ?), 8 upper limits (<0.2c) Dynamical ages 100-10000 years Polatidis, Conway 2003 --- 10 detections (0.1-0.3 c) 3 upper limits (<0.1c) Gugliucci et al. 2005 --- 9 detections (0.4c ?), 8 upper limits (<0.2c) Dynamical ages 100-10000 years

47. B1943+546 100pc Core Jet Lobe Core Determination of LOCAL spectral aging: assuming: - no reacceleration - equipartition magnetic field - no expansion losses Determination of LOCAL spectral aging: assuming: - no reacceleration - equipartition magnetic field - no expansion losses Need pc-scale spectral index images via Multifrequency VLBA+Y1 observation Hot Spots 50pc Age=~1300 yr V_sep=0.28c Age=~1300 yr V_sep=0.28c

48. Young Radio Sources

49. Dynamical ages and radiative ages agree and strongly favour the youth scenario but

50. Extended emission present in a fraction of GPS Recurrency? Not always

51. 1127+145 2.7 GHZ VLBA (RRFID)8.4 GHZ VLBA (RRFID)2.7 GHZ VLBA tapered 1.4 GHZ VLA B

52. 0738+313  0738+313 from mas to arcsec 15 GHz VLBA 15 GHz VLBA 1.4 GHz VLA B 5 GHz VLBI

53. 0738+313 z=0.631 z=2 z=3

54. What are the hosts of CSS/GPS?  CSS/GPS/(HFP) are a mix of galaxies and quasars.  Quasars rarely show a symmetric morphology, mostly core-jet at mas resolution.  Presence of weak extended emission (>10kpc) when deep observations are available.  CSS/GPS/(HFP) are a mix of galaxies and quasars.  Quasars rarely show a symmetric morphology, mostly core-jet at mas resolution.  Presence of weak extended emission (>10kpc) when deep observations are available.

55. Origin of the convex spectrum  In CSOs few similar rather homogeneous compact components (lobes and/or hot-spots) combine to make the typical global GHz peaked radio spectrum.  In some quasars a particular geometric configuration amplifies the brightness of a compact and homogeneous component close to the core, which dominates the radio spectrum and is responsible for the global GHz peaked shape.  In CSOs few similar rather homogeneous compact components (lobes and/or hot-spots) combine to make the typical global GHz peaked radio spectrum.  In some quasars a particular geometric configuration amplifies the brightness of a compact and homogeneous component close to the core, which dominates the radio spectrum and is responsible for the global GHz peaked shape.

56.  GPS galaxies are young radio sources (or confined).  GPS quasars are intrinsically similar to FS quasars.  In the framework of the study of the evolution of extragalactic radio sources, CSS/GPS/HFP quasars are objects contaminating the samples, and should be excluded.  GPS galaxies are young radio sources (or confined).  GPS quasars are intrinsically similar to FS quasars.  In the framework of the study of the evolution of extragalactic radio sources, CSS/GPS/HFP quasars are objects contaminating the samples, and should be excluded. Quasars and Galaxies are different objects

57. CSS/GPS/HFP quasars In the framework of evolution of radio sources from pc to Mpc scale, most GPS quasars are contaminating objects. Any inference based on complete samples of HFP/GPS/CSS radio sources should take in consideration this contamination, and should be limited to CSOs when information morphologies are available or limited to Galaxies, if mas morphologies are unknown. In the framework of evolution of radio sources from pc to Mpc scale, most GPS quasars are contaminating objects. Any inference based on complete samples of HFP/GPS/CSS radio sources should take in consideration this contamination, and should be limited to CSOs when information morphologies are available or limited to Galaxies, if mas morphologies are unknown.

58. Even excluding contaminating objects CSS/GPS/HFP are too many.  They should decrease in luminosity by an order of magnitude during evolution (Fanti et. al 1995, Odea et al. 1997)  Existance many short-lived objects (Readhead et al. 1994) Even excluding contaminating objects CSS/GPS/HFP are too many.  They should decrease in luminosity by an order of magnitude during evolution (Fanti et. al 1995, Odea et al. 1997)  Existance many short-lived objects (Readhead et al. 1994)

59. Cotton et al. 2003

60. HFP/GPS/CSS radio galaxies are truly young and are a “tool” to study the evolution of the extragalactic radio sources in their infancy

61. CSS/GPS/HFP samples Spencer et al. 89 CSS 3C/PW Fanti et al. (1990) Kunert et al. 2002 B3-VLA Fanti et al. 2001 Compact Low Pol - Stanghellini et al. half Jy Parkes – Snellen et al. 2002 Marecki et al 1999 WENSS-GPS Snellen et al. 1998 GPS 1Jy Stanghellini et al. 1998 CORALZ – Snellen et al. 2004 HFP Bright HFP Dallacasa et al 2000 Faint HFP Stanghellini/Dallacasa Flux density limit size

62. Evolution of young extragalactic radiosources Expansion, interaction with the ambient medium, luminosity evolution, age-size correlation:  current models on the evolution of the radio sources in their infancy derive by the model of Begelman, 1996.  self similarity, luminosity decreases with time. Expansion, interaction with the ambient medium, luminosity evolution, age-size correlation:  current models on the evolution of the radio sources in their infancy derive by the model of Begelman, 1996.  self similarity, luminosity decreases with time.

63. Begelman 1996 Baby Cygnus A's Cygnus A -- Studay of a Radio Galaxy, Proceedings of the Greenbank Workshop, held in Greenbank, West Virginia, 1-4 May, 1995 Self-similar hypothesis: cocoon will evolve with a fixed ratio of width to length Density profile Luminosity into FRI, FRII Expansion velocity weakly dependent on source size A fraction of sources die young

64. Alexander 2000, MNRAS 319, 8 Evolutionary models for radio sources from compact sources to classical doubles Atmosphere with a King profile Self similar expansion No cosmological evolution of the Luminosity Function Comparison of predicted distribution functions with observational data - Samples: Stanghellini et al. 1998 (GPS) and Fanti et al. 1990 (CSS) Luminosity increases in the GPS phase (<1kpc) Luminosity decreases afterwards GPS/CSS become FRII and FR I A fraction are short lived sources

65. Snellen et al. 2000 Samples: Snellen et al. 1998 (GPS), Stanghellini et al. 1998 (GPS), Fanti et al. 1990 (CSS) – only galaxies Luminosity evolution derived Local Luminosity Function of CSS/GPS Atmosphere with King profile Equipartition conditions, self similar expansion L increases in the GPS phase, then decreases, CSS/GPS become FRII and FR I strong comological evolution of the LF. NO need for short lived objects

66. Tinti & De Zotti 2006 They combine several samples of GPS galaxies: Dallacasa et al. 2000, Stanghellini et al. 1998, WENSS Snellen et al.1998, Half-Jy Snellen et al. 2002, CORALZ Snellen et al. 2004, Edwards and Tingay 2004, Bolton et al. 2004 (111 objects) NO self similarity L decreases with time GPS become only FRI NO need for cosmological evolution of LF

67.  The different models are constrained by the available samples of CSS/GPS/HFP radio sources  The problem of different predictions/results arises because the different groups introduce different assumptions to put the samples together  The different models are constrained by the available samples of CSS/GPS/HFP radio sources  The problem of different predictions/results arises because the different groups introduce different assumptions to put the samples together

68. what is needed?  Selection and characterization of a large sample of HFP/GPS/CSS radio sources with symmetric morphology, at a low flux density limit, and a wide range in turnover frequency, to test and discriminate the proposed models.  Detection of proper motions in a large sample of HFP/GPS/CSS to investigate trends, make some statistics, and constrain the models  Selection and characterization of a large sample of HFP/GPS/CSS radio sources with symmetric morphology, at a low flux density limit, and a wide range in turnover frequency, to test and discriminate the proposed models.  Detection of proper motions in a large sample of HFP/GPS/CSS to investigate trends, make some statistics, and constrain the models New instruments are important to go to weaker flux densities and higher resolutions

69. Evidence that the radio sources are a recurrent phenomenon in elliptical galaxies Thanks to Karl Heinz Mack for the next slides

70. 1155+266 Owen & Ledlow 1997 Double Double Radio Galaxies

71. J1835+620 Spectral ages: 3.5 · 10 6 yr for outer lobes 2.3 · 10 6 yr for inner lobes expansion velocity: 0.2 … 0.25 c  Spectral ages are not consistent with an exhausted primary phase of activity  Outer lobes are still supplied by an underlying jet  Inner structure result of a dramatic increase of core activity Lara et al. 1999

72. 3C338 3C338 is FRI source in cooling flow cluster A2199 Non-symmetric cooling flow disrupted the radio jet and created the low-brightness emission. Radio emission identified with the dominant diffuse optical nucleus VLA 5 GHz: core source dominates (α = 0.7) barely resolved symmetric jets connect core and hotspots (~6 kpc), moderately steep spectrum (α = 0.7 … 1.1) Detached extended lobes and relic jet structure (α = 1.7 … 3.0) Giovannini et al. 1998 Ge & Owen (1994)

73. Multi-epoch VLBI studies of 3C338 Multi-epoch morphological comparison at 8.4 GHz: Assuming that central peak is true core:  Average velocity of new ejecta: v > 0.38 …0.41c No visible connection between jets and diffuse features  Extended emission is relic structure and not related to the present nuclear activity Relic structure embedded in strong cooling flow  low adiabatic losses Giovannini et al. 1998

74. X-shaped sources Possible scenarios: Backflow from the active lobes into the wings (Leahy & Williams 1984, Capetti et al. 2002) Slow conical precession of the jet axis (Parma, Ekers & Fanti 1985, Mack et al. 1994) Reorientation of jet axis with continuing flow (Dennett-Thorpe et al. 2002) Reorientation of jet axis with stopped or reduced jets (Dennett-Thorpe et al. 2002, Klein et al. 1998) Reorientation of spin axis due to minor merger (Merritt & Ekers 2002)  Wings are relics of radio jets, active lobes are younger No single model plausible to explain X-shaped sources as a class (Lal & Rao 2007)

75. Centaurus A / Virgo A – type sources ATNF - CSIRO

76. Virgo A / Centaurus A – type sources Similarity betwen Vir A and Cen A: Structure in three components abrupt changes in position angle Vir A: ejection of inhomogeneous jets by a precessing nucleus or continuous ejection of jets bent due to interaction with the environment (Feigelson et al. 1981) Change of orientation of the ejection during different epochs (Klein 1998) Cen A: bursting bubble model: Jet deflected during a jet-cloud inter- action and restarted via de Laval nozzle (Morganti et al. 1999)

77. Recurrent activity and restarting sources exist and are observed DDRGs seem to be most obvious manifestation of the phenomenon open issue: outer structures still replenished or full interruption? 3C338: 67 kpc Owen & Eilek 1998 Saripalli et al. 2004 B1545-321: 1 Mpc NRAO/AUI/STScI NGC326: 312 kpc Owen et al. 1999 Virgo A: 70 kpc Close relatives: new emission on smaller scales (e.g. B1144+35, 3C338) More distant relatives: X-shaped sources Cen A / Vir A types Caveat: recurrent activity everywhere?

78. The Duty Cycle of Radio Galaxies NRAO/AUI/STScI NGC326: 312 kpc Carilli et al. 1991 Cygnus A: 130 kpc Mack et al.1998 3C236: 4.6 Mpc Jamrozy et al. 2004 B2 0924+30: 400 kpc Owen et al. 1999 Virgo A: 70 kpc Orienti et al. 2004 B1242+410: :175 pc Mack et al.2005 3C299: 970 kpc Saripalli et al. 2004 B1545-321: 1 Mpc 3C338: 67 kpc Owen & Eilek 1998