1. Reu Sochias:14-16 Enero 2009 Luis Campusano, Dpt Astronom í a, Universidad de Chile Large Quasar Groups as Signposts of the galaxy Large Scale Structure at z>0.5

2. Reu Sochias:14-16 Enero 2009 Collaborators Roger Clowes, KA Harris (U Central Lancashire, UK) Gerry Williger Lutz Haberzett JT Lauroesch (U Louisville, USA) R Dav é (U Arizona), MJ Graham (Caltech), AM Koekemoer (STScI) Chris Haines (U Birminghan, UK), J Loveday (U Sussex), I Sochting (Oxford) and D. Valls-Gabaud (Observatoire de Paris, France).

3. Reu Sochias:14-16 Enero 2009 Galaxy LSS: the 2dF redshift survey (Figure credit: W. Schaap,U Groningen)

4. Reu Sochias:14-16 Enero 2009 Sponge like topology and Walls in galaxy distribution (z<0.3)

5. Reu Sochias:14-16 Enero 2009 BIG QUESTIONS NOTICE THAT GALAXY FORMATION IS NOT YET A SOLVED PROBLEM IS THERE INDEED A HOMOGENEITY SCALE IN THE UNIVERSE? (POSSIBILITY OF A FRACTAL STRUCTURE) WHAT ARE THE DETAILS OF THE ‘LOCAL’ LARGE SCALE STRUCTURES? FILAMENTS AND WAALS ALREADY IN PLACE AT HIGH REDSHIFTS?

6. Reu Sochias:14-16 Enero 2009 Galaxy LSS (2dF,SDSS,6dFS) Sheet-like LSS as the “Great Wall” of galaxies (Geller & Huchra 1989) are typical phenomena. Waals with average extent of 50-100 Mpc, comprising ~50% of the galaxies Low density regions or VOIDS ~50 Mpc in size The underdense regions are criss-crossed by FILAMENTS having a variety of richnesses

7. Reu Sochias:14-16 Enero 2009 Standard LCDM predictions Predicts weak non-linear structures at low-z of the dimensions of waals Simulations indicate Great-Wall like sheets become rare at z~1 (Evrad et al. 2002) Current extended redshift surveys do reach only to z~0.2-0.3. Direct observations of ‘Great-Waals’ at z~1 would provide a strong test for theory

8. Reu Sochias:14-16 Enero 2009 Grid Structures in numerical simulations: LCDM evolution

9. Reu Sochias:14-16 Enero 2009 Large Quasar Groups The largest structures seen so far in the early universe (z~0.4-2.0) With sizes in the range 70-250 Mpc, and membership ~5-20 Several of them have been followed-up, including searches of correlated galaxy distributions

10. Reu Sochias:14-16 Enero 2009 Large Quasars Groups Quasars may signal gas-rich mergers environments Large Quasar Groups (LQGs) are potentially unique structure markers on scales up to hundreds of Mpc LQGs allow the discovery of huge structures, and potentially allow the study of their quasars and galaxies in a wide variety of environments, from low to high densities LQGs may signal huge structures to z~3 and test if there are high-z Great-Waals

11. Reu Sochias:14-16 Enero 2009 Large Quasar Groups LQGs can contribute to constrain the various physical mechanisms (feedback, merger, etc) which produce the quasars LQG space density is 7 Gpc -3 at 0.3<z<1.9 (Pilipenko 2007) Implies LGQs are large perturbations, with 500-1000 LQGs on 100-200 Mpc scales at z<2.8 (Pilipenko 2007)

12. Reu Sochias:14-16 Enero 2009 Clowes-Campusano LQG At z~1.3 with a longest dimension of ~250 Mpc Several follow-up investigations have been done, revealing accompanying overdensities of galaxies in these LQGs In addition to the galaxy distribution, several clusters of galaxies have been found to be embeded in the LQGs After follow-up, a second LQG was discovered in the same direction at z~0.8

13. Reu Sochias:14-16 Enero 2009 Conclusions Large Quasar Groups can trace mass to at least z~2 and thus are powerful tools to study galaxy evolution and structure formation at high redshift Today’s quasar surveys over extended areas of the sky allow searches of LQGs LQGs are a tool to search for super-large structures to z>=2 and to further test the hypothesis of homogeneity of the Universe Theoretical models predict ‘Grear Waals” of >500 Mpc in size. LQGs may find an upper z-limit for the existence of “Great Waals’.

14. Reu Sochias:14-16 Enero 2009 FIN