Galaxy Clusters & Large Scale Structure

1. Galaxy Clusters & Large Scale Structure Coma Cluster =A1656 Ay 16, April 3, 2008

2. Galaxies Are Not Randomly Distributed in Space Fundamental discovery (and debate) in the 20th century is that Galaxies cluster. On small scales: Binaries ~100 kpc intermediate scales: Groups ~1 Mpc larger scales: Clusters few Mpc even larger scales: Superclusters 10’s Mpc largest seen: Voids + Cosmic Web ~50 Mpc

3. M51 = Whirlpool = NGC 5194+95 NOAO

5. Seyfert’s Sextet

6. Stefan’s Quintet

7. Abell 1689

8. Coma Cluster

9. Coma in X-rays

10. Mass Estimators: 3 πΣσP2 RP • MV= • MP = ΣRi (Vi-VG)2 with fPM =10.2 and γ = 1.5 (Heisler, Tremaine & Bahcall 1985, ApJ 298, 8) 2 G fPM π G (N – γ)

12. Hydrostatic Equilibrium Abell 2142 in X-rays CXO

13. Gravitational Lensing

14. Cluster Mass Estimates Now three techniques agree fairly well for the same clusters -- Galaxy Dynamics, Gas Hydrostatic Equilibrium + Gravitational Lensing masses give a mean M/L of around 300 in blue light (solar units) and 100 in infrared light. This is important for cosmology as it implies (1) that there’s lots of Dark Matter on large scales, and (2) that  matter is ~ 0.25.

15. Perseus Cluster Shocks in the hot Gas (Fabian+)

16. Abell 2597 shocks and bubbles

17. Large Scale Structure The study of the galaxy distribution on large scales started out with maps.

18. Election ’06 Congressional Districts

19. Its all in the display: Election ’04 By County R/B By County color range By state scaled by population

20. Messier’s map: What do you see?

21. W. Herschel

22. New General Catalogue + Index Catalogues

23. Fritz Zwicky et al. CGCG

24. Zwicky’s Catalog

25. Early “Modern” Views • Hubble: The Large Scale is “Sensibly Uniform,” one cluster per 50 square degrees. “General Field of galaxies, isolated groups and clusters. versus • Zwicky “Clusters are Common” “cluster cells separated by saddles or minima ... and … not … flatlands”

26. Statistics of Clustering Many different “statistical” measures. Peebles and Totsuji & Kihara introduced the correlation function -- a measure of the excess probability of finding a galaxy near another galaxy --- in the early 1970’s.

27. Correlation Functions 2D Angular Correlation Function dP = N [1 + w()] d where N = surface density of galaxies  = angular separation and  = solid angle (area of sky)

29. 3D Spatial Correlation Function dP = n [ 1 + (r) ] dV where n is now the volume density dV is the volume element and r is some measure of separation e.g. s = [d2 + ((v1 - v2)/H)2 ]1/2

30. Hubble’s Discovery of Expansion

32. Redshift Surveys 3747 +/- 20 CfA Survey

33. 3D Maps of the Local Universe Not much progress until the mid 1970’s! Catalogs existed from Photographic Surveys- 2D only (Zwicky++; Vorontosov-Velyaminov++) In 1972 the largest “complete” galaxy redshift sample had only ~250 galaxies Key was innovations in detector technology: computers + digital detectors sensitive radio receivers

34. Larsonwasn’t quite right…

35. The Little Telescope that could. Tillinghast 1.5-m

36. The Z Machine Davis, Tonry, Latham & Huchra Based on a concept by Shectman & Gunn

38. Spectral features in galaxies

40. CfA2 Slice

41. 1985 CfA 2 deLapparent, Geller & Huchra

42. CfA2 1995

44. 6dF Fiber Positioner, SRC Schmidt, Coonabarabran

45. Great Wall LSC We are here Pisces-Perseus KS < 11.25

47. M. Westover

48. Magenta V < 1000 km/s • Blue 1000 < V < 2000 km/s • Green 2000 < V < 3000 km/s

49. Red3000 < v < 4000 Red 3000 < v < 4000 Blue 4000< v < 5000 Green 5000 < v < 6000

50. Red 6000 < v < 7000 Blue 7000 < v < 8000 Green 8000 < v < 9000