Luis Campusano, Dpt Astronom í a , Universidad de Chile

1. Large Quasar Groups as Signposts of the galaxy Large Scale Structure at z>0.5 Luis Campusano, Dpt Astronomía, Universidad de Chile

2. Collaborators Roger Clowes, KA Harris (U Central Lancashire, UK)Gerry Williger Lutz Haberzett JT Lauroesch (U Louisville, USA)R Davé (U Arizona), MJ Graham (Caltech), AM Koekemoer (STScI)Chris Haines (U Birminghan, UK), J Loveday (U Sussex), I Sochting (Oxford)andD. Valls-Gabaud (Observatoire de Paris, France).

3. Galaxy LSS: the 2dF redshift survey (Figure credit: W. Schaap,U Groningen)

4. Sponge like topology and Walls in galaxy distribution (z<0.3)

5. 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? BIG QUESTIONS

6. 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 Galaxy LSS (2dF,SDSS,6dFS)

7. 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 Standard LCDM predictions

8. Grid Structures in numerical simulations: LCDM evolution

9. 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 Large Quasar Groups

10. Quasars may signal gas-rich mergers environments LQGs may signal huge structures to z~3 and test if there are high-z Great-Waals 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 Large Quasars Groups

11. 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) Large Quasar Groups

12. At z~1.3 with a longest dimension of ~250 Mpc After follow-up, a second LQG was discovered in the same direction at z~0.8 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 Clowes-Campusano LQG

13. 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 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’. Today’s quasar surveys over extended areas of the sky allow searches of LQGs Conclusions

14. FIN