LOFAR

1. LOFAR LOw Frequency Array => most distant, high redshift Universe !? Consortium of international partners… Dutch ASTRON USA Haystack Observatory (MIT) USA Naval Research Lab … `best site’ = WA … … … Novel `technology telescope’ - array design => no moving parts (cheap) - huge, fast data network - huge collecting area - multi-beaming

2. ~ 400 km Dutch View

3. a Lofar `station’

4. LOFAR VLA ALMA GMRT ground based radio techniques 350m 10 MHz ATCA

5. LOFAR ground based radio techniques 350m 10 MHz

6. …this workshop… mml astronomy… ALMA LOFAR Simularities: sky noise atmosphere Gal. Synchrotron rapid phase variation atmosphere ionosphere Differences: solid angle of tiny (l/D of dish) nearly all sky receiving element survey …. mosaic all-sky calibration

7. Top 4 LOFAR astronomical science drivers • 21cm emission/absorption from Epoch of Reionisation • mapping the neutral clouds in IGM as first sources of ionising radiation appear at redshifts between 7 and 20(?)

8. t < 1 … (Gunn-Peterson Effect) UV Top LOFAR astronomical science drivers • 21cm emission/absorption from Epoch of Reionisation • mapping of neutral residue of IGM as first sources of ionising radiation appear at redshifts between 7 and 20(?) Z = 20 ……………. 15 ………. 10 8 7 6 cold HI HII 70 MHz 90 MHz 130 160 190 MHz

9. WMAP result => Z ~ 15 to 20 2 EoRs ??? … or… prolonged, patchy EoR ??? Z = 20 15 10 8 7 6 cold HI warm HI HII HII Pop III stars: @ 500 Solar mass

10. LOFAR and SKA… distributed star formation Quasar 10 arcmin

11. Top 4 LOFAR astronomical science drivers • 21cm emission/absorption from Epoch of Reionisation • mapping of neutral clouds in IGM as first sources of ionising radiation appear at redshifts between 7 and 20(?) • Highest redshift radio sources • Steep spectrum selection (a < -2) => 1 source per sample of ~30,000 • => catalog of background radio sources for intervening HI absorption

12. Spectral Index Redshift

13. Spectral Index Redshift

14. Mapping intervening protogalaxies in 21cm absorption SKAMP-III compatible !

15. Top 4 LOFAR astronomical science drivers • 21cm emission/absorption from Epoch of Reionisation • mapping of neutral clouds in IGM as first sources of ionising radiation appear at redshifts between 7 and 20(?) • Highest redshift radio sources • Steep spectrum selection (a < -2) => 1 source per sample of ~30,000 • => catalog of background radio sources for intervening HI absorption • 3-D mapping of the Galactic non-thermal emission • uses free-free absorption by known extended thermal sources • will determine the origin of the Galactic cosmic ray flux

16. Radio sky in 408 MHz continuum (Haslam et al) (Dominated by synchrotron emission from relativistic electrons)

17. Optically thick thermal plasma … HII regions holes in the Galactic radio sky…

18. mapping the synchrotron emission in front of … and behind the opaque thermal sources ….

19. Top 4 LOFAR astronomical science drivers • 21cm emission/absorption from Epoch of Reionisation • Mapping of neutral clouds in IGM as first sources of ionising radiation appear at redshifts between 7 and 20(?) • Highest redshift radio sources • Steep spectrum selection (a < -2) => 1 source per sample of ~30,000 • => catalog of background radio sources for intervening HI absorption • 3-D mapping of the Galactic non-thermal emission • uses free-free absorption by known extended thermal sources • will determine the origin of the Galactic cosmic ray flux • Transient and bursting sources • no moving parts => nearly instantaneous response to trigger events • central core is an all-sky (hemisphere) monitor • sensitive to non-thermal, coherent emission events, should they exist(?)

20. The SUN Coronal Mass Ejections, CMEs

22. #3 #1 very tough to achieve sensitivity: high risk / high gain #2 Frank’s 3 favorites LOFAR astronomical science drivers • Highest redshift radio sources • Steep spectrum selection (a < -2) => 1 source per sample of 10,000 • => catalog of background radio sources for intervening HI absorption • 21cm emission/absorption from Epoch of Reionisation • Tomography of neutral residue of IGM as first sources of ionising radiation appear at redshifts between 7 and 20(?) • 3-D mapping of the Galactic non-thermal emission • uses free-free absorption by known extended thermal sources • will determine the origin of the Galactic cosmic ray flux • Transient and bursting sources • no moving parts => nearly instantaneous response to trigger events • central core is an all-sky (hemisphere) monitor • sensitive to non-thermal, coherent emission events, should they exist(?)

24. Dipole + ground plane conducting ground plane

25. i2pft I e o Dipole + ground plane equivalent to dipole plus mirror image i2pft -I e o

26. i2pft I e o h h Dipole element response equivalent to dipole plus mirror image i2pft -I e o

27. i2pft I e o h h 2 P(q) ~ sin [2ph cos(q)/l] Dipole q = zenith angle equivalent to dipole plus mirror image i2pft -I e o (maximize response at q=0 if h=l/4 )

28. i2pft I e o h Dipole q f azimuth 2 2 2 P(q) ~ sin [2ph cos(q)/l] {1 - sin q sin f }

29. q q q q f f f f

30. The `sin projection’ of hemisphere onto a plane: The Sky above dipole

31. ‘sin projection’ line of constant zenith angle

32. ‘sin projection’

33. ‘sin projection’ gives little weight to sky close to horizon !

34. X Y

35. Y X

36. Y X Dipole over ground plane Tuned for 150 MHz

37. Dipole Tuned for 150 MHz • 150 • 180 210 MHz 240 MHz

38. What are these things?

39. Crossed Dipoles for dual polarization conducting plane

40. LOFAR-Low Band dipole element Droopy Dipoles for broad-band, dual polarization

41. 4x4 array of dipoles on ground plane - the ‘LOFAR-High band’ element h s s (many analogies to gratings for optical wavelengths)

42. 4x4 Tuned for 150 MHz sin projection

43. ZA = 0 deg 15 30 45 60 75

44. 4x4 Patterns • ZA = 30 deg • tuned for 150 MHz • 120 150 • 180 210 240

45. Lofar stations ???

46. a `station’ = 101 `4x4 tiles’ Size in l

47. a `station’ as 101 omni-directional elements Size in l

48. Station Beam:no 4x4 envelope

49. Station Beam: using 4x4 envelope

50. Station Beam: 4x4 envelope and taper