1. Geodetic VLBI Lecture 3 18 October 2010

2. Lecture plan 1. Quasars as astrophysical objects 2. Redshift 3. Spectral analysis 4. Super luminous relativistic jets 5. Practical issues 6. Exercises 18 October 2010

3. Lecture plan 1. Quasars as astrophysical objects 2. Redshift 3. Spectral analysis 4. Super luminous relativistic jets 5. Practical issues 6. Exercises 18 October 2010

4. Quasars We use quasars for geodetic and astrometric research, but it is necessary to remember that the quasars are large and distant astrophysical objects. We should learn all their properties. 18 October 2010

5. Quasars (definition) A quasi-stellar radio source ("quasar") is a very energetic and distant galaxy with an active galactic nucleus (AGN). They are the most luminous objects in the universe. 18 October 2010

6. Quasars (definition) Quasar – a very energetic and distant galaxy with an active galactic nucleus; Quasar – the nucleus of the host galaxy 18 October 2010

7. Quasar 18 October 2010

8. Active Galactic Nuclei (AGN) It’s likely that the core of an AGN contains a supermassive black hole surrounded by an accretion disk. As matter spirals in the black hole, electro- magnetic radiation and plasma jets spew outward from the poles. Active galactic nuclei are a category of exotic objects that includes: luminous quasars, Seyfert galaxies, and blazars. 18 October 2010

9. Lecture plan 1. Quasars as astrophysical objects 2. Redshift 3. Spectral analysis 4. Super luminous relativistic jets 5. Practical issues 6. Exercises 18 October 2010

10. Doppler effect Frequency decreases if the body moves out of the observer. Wavelength increases Frequency increases if the body moves towards the observer. Wavelength decreases. 18 October 2010

11. Red shift Frequency increases if the body moves towards the observer. Wavelength decreases. All spectral lines shift to the red part of spectrum. So, we observe “red shift” 18 October 2010

12. Cosmological red shift Red shift, V>0, z>0 Blue shift, V<0, z<0 18 October 2010

13. Calculation of redshift 18 October 2010

14. The Expansion of the Universe Distances between galaxies are increasing uniformly. There is no need for a center of the universe. 18 October 2010

15. The Expansion of the Universe Friedman-Lemaitre- Robertson-Walker (FLRW) metric a(t) – expansion parameter 18 October 2010

16. Cosmological red shift Minkovsky metric FLRW metric 18 October 2010

17. Hubble’s law: v = HR where H is called Hubble’s constant. Hubble’s Law Hubble’s constant is related to a scale factor a that’s proportional to the distance between galaxies: Hubble also found a linear relation between distance and recession velocity! 18 October 2010

18. Hubble’s measurements Hubble also measured spectra of standard candles, observing that most were red-shifted. He realized that this was a Doppler shift. The universe is expanding! 18 October 2010

19. “Distance – redshift” relation Minkovsky metric Hubble law For local vicinity Distance – redshift 18 October 2010

20. “Distance – redshift” relation FLRW metric Hubble law 18 October 2010

21. “Distance – redshift” relation 18 October 2010

22. Lecture plan 1. Quasars as astrophysical objects 2. Redshift 3. Spectral analysis 4. Super luminous relativistic jets 5. Practical issues 6. Exercises 18 October 2010

23. Super luminous relativistic jets It’s likely that the core of an AGN contains a supermassive black hole surrounded by an accretion disk. As matter spirals in the black hole, electro-magnetic radiation and plasma jets spew outward from the poles. 18 October 2010

24. Super luminous relativistic jets The jets were found at the late 60 th 18 October 2010 They cause apparent motion of quasars, or “fake” proper motion For decades this “fake” proper motion was considered as the only kind of the proper motion detectable by observations

25. ICRF source instability (structure) Geoscience Australia 18 October 2010 Quasar 2201+315

26. Geoscience Australia 18 October 2010 Instability of ICRF sources ( 2201+315, in sky plane, 2001-2004)

27. Geoscience Australia 18 October 2010 Kellermann et al. (2004) Position angle of the brightest jet ~ 158º Geodetic VLBI: Position angle ~ 148º apparent proper motion ~ 0.6 mas/year

28. Apparent proper motions Motion of radio source jets mimic physical proper motions; Such fake motions can reach 100-1000  as/year; Expected systematic <50  as/year; We could discover systematics through the irregular apparent proper motions, for instance, using the expansion on spherical functions 18 October 2009

29. Search for systematic has been done (Gwinn, Eubanks et al. 1997; MacMillan 2005) Motivation – detection of the secular aberration drift – 4-5 μ arcsec/year (predicted many authors; Bastian, 1995) Geoscience Australia 25 September 2009

30. 4C39.25 25 September 2009 The longer period of time, the better proper motion

31. Lecture plan 1. Quasars as astrophysical objects 2. Redshift 3. Spectral analysis 4. Super luminous relativistic jets 5. Practical issues 6. Exercises

32. Identification of quasars (radio/optics) It is very important for many reasons 1.To tie radio and optical reference frames 2.To measure red shift 3.…

33. Identification of quasars (radio/optics) … we need to be sure that the observed object is a quasar rather than a star on foreground

34. 2318-087 System Aladin Optic – radio Potential confusion with the close star 2318-087 Faint in optics ~23 mag Strong in radio: total flux is about 0.2-0.3 Jy in S-,X-bands

35. Blue rays 2318-087 SuperCosmos (photographic plates)

36. SuperCosmos Red rays 2318-087

37. Identification of quasars More problems nearby the Galaxy plane

38. Radio source 1923+210 Flux >1 Jy in S-,X-band A lot of observations made by VLBI But! Galactic latitude b=+2

39. 1923+210 - VLBI image

40. 1923+210 Galactic latitude b=+2 This radio source looks very attractive in radio, but Galactic latitude b=+2

41. SuperCosmos Blue rays 1923+210

42. NTT image of 1923+210 1923+210 ? Several objects in the field SuperCosmos Blue rays (photographic plates) NTT image (CCD)

43. NTT image of 1923+210 Several objects in the field No one is a quasar! Galactic extinction is ~8 mag 1923+210 is not visible in optics! We measured 3 spectra

44. Quasar spectra Z=1.55 No Ly 

45. Quasar spectra Z=2.51 Ly 

46. Quasar spectra Z=3.16 Ly  Very faint object Ly  does not dominates

47. Quasar spectra Z=3.38 Ly  Faint object but Ly  dominates Break after Ly β

48. Lecture plan 1. Quasars as astrophysical objects 2. Redshift 3. Spectral analysis 4. Super luminous relativistic jets 5. Practical issues 6. Exercises

49. Exercise 1 Calculation of redshift Answer???

50. Exercise 2 Distance to galaxy with redshift Z=0.0030 H=60 km/sec·Mpc Answer??? 15 Mpc