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1 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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Presentation on theme: "1 Astronomy, Radio Sources and Society Extragalactic radio sources and their importance for astronomy Leiden 10-13 June 2013 Ron Ekers CSIRO, Australia."— Presentation transcript:

1 1 Astronomy, Radio Sources and Society Extragalactic radio sources and their importance for astronomy Leiden June 2013 Ron Ekers CSIRO, Australia

2 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 QSOs. In recent years it has become apparent that they are also objects of considerable beauty. Ann. Rev. Astron. Astrophys,

3 January 7, 2013AAS Long Beach3 Mt Palomar th Anniversary of the Discovery of Quasars

4 Geese Hoyle, Burbidge and Narlikar

5 Linear size distribution of radio galaxies 5 n 3CR radiogalaxies a Linear plot with linear bins b Log plot with log bins Ekers & Miley 1977

6 23May2007Halley Lecture The Scientific Method n Developed during the 17 th century –Develop an hypothesis –Make predictions –Verify with observations (or discard hypothesis) n 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 Halleys comet in 1758 –Since than it made many predictions

7 Astronomy n Most astronomy papers today are explanations of observed phenomena. n Predictions usually fail and it is considered normal practice to adapt the theory to fit the observations. n These theories may not be wrong, but without predictions we have no reason to accept them n Many examples in our interpretation of radio galaxies n The role of the sceptic in science 7

8 Where we are going from here n Some of the enabling technology n Martin Rees and the Wireless Internet n Radio Galaxies from the beginning n QSO 50 th anniversary Blackholes n Some Extragalactic Radio Source Highlights n Galaxy formation and the early Universe 8

9 9 Cambridge One-Mile Telescope: 1962

10 10 First Cambridge Earth Rotation Synthesis Image n June 1961 n North pole survey n 4C aerials n 178 MHz n Computations and graphical display used EDSACII n 7 years after Christiansen

11 Benelux Cross 1963 n Joint Netherlands – Belgium n OEEC (now OECD) agreement n Christiansen et al design n 100x 30m + 1x 70m dish n 21cm n 1.5km

12 Science Goals for Benelux Cross n Oort - OECD Symposium (1961) –Primary goal »Enough sensitivity and resolving power to study the early universe through source counts

13 13 Westerbork: 1970 n Hogbom (Cambridge) + n Christiansen (Sydney) Benelux cross WSRT n 12 x 25m dishes –Two moveable –10 redundant spacings –Self calibration n Add 2 more 25m dishes later

14 LOFAR: The Low Frequency Array n Oort Workshop 1997 n George Miley proposal to ASTRON n Arnold van Ardenne already thinking about SKA-low and the aperture arrays n Actively promoted by George –Low Frequencies are Cheap! 14

15 LOFAR WILL EXPLORE NEW PARAMETER SPACE Lowest Radio Frequencies ( 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 Miley Tasmania 2008

16 June 2013Ekers, Radio Sources & Society16 From Cambridge to The Netherlands 1970 then to Australia 1996 n Steven Hawking: black holes radiate n Small black holes evaporate in less than the age of the Universe n Martin Rees: a radio pulse might be observable when they disappear n John OSullivan: and collaborators build a special instrument to look for the exploding black holes using Dwingeloo and Westerbork –there has to be a better way! n Fourier Transform on a chip – IEEE wireless internet standard

17 Cygnus A strongest radio source in sky n Hey 1946 –source with variable intensity –time scale of seconds to minutes –must be small diameter –the first radio star n 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

18 What is the Non-thermal Radio Emission? n A very confusing story n Misinterpretation of radio data added to the confusion n 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 n 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

19 Cliff Interferometer n Dover Heights, Sydney, Australia n 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

20 NGC5128

21 Centaurus A

22 Centaurus A ATCA Mosaic Feain et al 2011

23 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, 2013Kellermann AAS Long Beach23

24 Why was it so difficult to accept extra-galactic? n Letter from Bolton to Minkowski 20 May 1949 n There were no galaxy experts at CSIR and very few in Australia n It was easier to assume that the strange galaxies were unusual galactic objects n There were no known mechanisms to explain the powerful radio emission if extragalactic 24

25 Synchrotron Model for Radio Emission n 1949 Unsold: sunspots anomalous radiation –non-thermal –plasma oscillations n 1950 Alven & Herlofson: –synchrotron radiation from sunspots n 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 n Mostly ignored in the West but enthusiastically embraced in Russia by Ginzburg and later by Shklovski 25

26 3C 48, the first radio star n Small diameter source catalogue from Manchester –Henry Palmer & George Miley ? n Accurate position measured at OVRO n 1960 Tom Matthews and John Bolton identify 3C 48 with a stellar object n Greenstein, Munch, Sandage 200 spectra –Lots of unidentified spectral lines n 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, 2013Adapted from Kellermann AAS Long Beach 26

27 3C 273 identification January 7, 2013Kellermann AAS Long Beach27 Cyril Hazard Parkes lunar occultation

28 50 th Anniversary of the Discovery of Quasars January 7, 2013AAS Long Beach28 Mt Palomar 200

29 3C273 Parkes Occultation Striking difference in radio spectra Component A S = -0.9 Component B S = 0.0 Core – Jet morphology Slide prepared by Jan Oort

30 3C273 VLA 5GHz

31 3C273 Optical HST 31

32 First Texas Symposium on Relativistic Astrophysics n Gravitational Collapse and Relativistic Astrophysics –Dallas, Texas, Dec –only gravity of a massive object in the nucleus of a galaxy could provide the energy n 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,

33 The Nuclei of Galaxies n 1943: Carl Seyfert (Clevland, Ohio) –Enhanced activity in the nuclei of 6 extragalactic nebulae –No citations for 18 years! n 1958: Viktor Ambartsumian (Armenia) –Championed the role of the galaxy nuclei n 1961: Vitaly Ginzburg (Russia) –Showed that gravitational energy could power a radio galaxy 33

34 The Energy Source n Old models disappear fairly quickly –Galaxies in collision (Baade & Minkowski) Bad theory –Nuclear energy –Electromagnetic flares n 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 n Gravitational energy from a collapsed object –Ginzburg, Hoyle, Fowler, Zeldovich, Novikov..... –This was a paradigm shift –But what kind of condensed object? 34

35 Black Holes n 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 n 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 n Oppenheimer (1939) – exercise in abstraction –the star closes itself off from any communication…only its gravitational field persists

36 NGC326 – pressing jet Binary Black hole? n Martin Rees 1978 –One black hole already pushes credibility – two was a step too far

37 NGC326 – pressing jet Binary Black Hole? n Martin Rees 1978 –One black hole already pushes credibility – two was a step too far n Binary Black holes? –Evidence for super massive binary black hole mergers and Gravitational wave predictions Murgia et al, A&A 380, (2001) Merritt & Ekers Science (2002) VLA 1.4GHz

38 38 Suspected SMBH binaries n 3C75-type sources: wide binaries

39 39 Periodic outbursts interpreting Pks n Binary black-hole in bound orbit n periodicly plunges through the accretion disk –will maintain its spin axis so gets a new accretion disk each plunge PKS – Quasar with Xray/radio jet

40 Hercules A VLA and HST 40 Baum et al (2012)

41 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

42 Fornax A on optical image

43 Fornax A Depolarization

44 Nov 2010Ron Ekers Fornax A and the ant like feature n Need a turbulant magneto-ionic medium n RM > 20 rad m -2 n Size 14 n Eg –Ne =.03 cm -3 –B = 2 μG –L = 100pc –M = 10 9 Mo n Bland-Hawthorne ApJ 447, L77 (1995) –Halpha detection at v = 1610km/s

45 NGC6251 Alignment 45 n VLBI cores aligned to within a few degrees over scale changes of 5x10 6 n Hence maintains axis for at least 10 8 years

46 3C273 superluminal expansion predicted & observed 46

47 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 48 HIPASS 21cm Continuum Preliminary continuum image, courtesy Mark Calabretta (CSIRO ATNF) Centaurus A - closest AGN

49 Centaurus A ATCA Mosaic 600kpc n 1.4GHz continuum n full polarization n 4 x 750m array configuration n 406 pointings, hexagonal grid n FOV 45 deg 2 n θ~45 n ~0.26mJy/beam (0.1K) Ilana Feain

50 Cen A Mosaic N lobe May

51 Centaurus A composite May

52 Centaurus A middle lobe X-ray XMM Newton May

53 Centaurus A middle lobe radio continuum and HI May Morganti

54 H alpha May Ellis and Bland-Hawthorne

55 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

56 The evolution of radio galaxies BIG BANG NOW

57 July 2005Ilana Klamer - ASA57 n our ATCA observations confirm that high-z radio galaxy spectra are not curved but USS spectra dont steepen at all… The K-correction interpretation is inconsistent with observations Klamer (Feien) MNRAS (2006)

58 27 Nov 1999R D Ekers58 Evolution of density fluctuations z=6 z=0 ρ (1+z) 3 Δρρ clus ρ=0ρ=0 ρ=0 ρ const

59 13 July 05R D Ekers59 Radio Galaxy - 4C41.17 redshift 3.8 n Alignment of radio jets (contours) with other tracers of star formation –VLA radio image × HST F702 × HST F569 × Ly-α van Breugel (1985)

60 13 July 2005R D Ekers60 Klamer et al Radio PADust PACO PA Alignment with Radio Axis Predicted an alignment in 4C41.17 Observed Δpa = 8 o

61 Survey of CO in High z Radio Galaxies n 13 high redshift radio galaxies –1.4 < z < 2.8 n CO (1-0) aligned with radio axis! Emonts, Miley et al

62 Conclusion March 2013Ekers62 The power of science is its ability to make predictions but science itself will evolve in unpredictable ways


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