Reu Sochias:14-16 Enero 2009

Luis Campusano, Dpt Astronomía, Universidad de Chile

Large Quasar Groups as Large Quasar Groups as Signposts of the galaxy Large Signposts of the galaxy Large

Scale Structure at z>0.5Scale Structure at z>0.5

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 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).

Reu Sochias:14-16 Enero 2009

Galaxy LSS: the 2dF redshift survey (Figure credit: W.

Schaap,U Groningen)

Reu Sochias:14-16 Enero 2009

Sponge like topology and Walls in galaxy

distribution (z<0.3)

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?

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 galaxiesLow density regions or VOIDS ~50 Mpc in size

The underdense regions are criss-crossed by FILAMENTS having a variety of richnesses

Reu Sochias:14-16 Enero 2009

Standard LCDM predictions

Predicts weak non-linear structures at low-z of the dimensions of waalsSimulations 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

Reu Sochias:14-16 Enero 2009

Grid Structures in numerical simulations:

LCDM evolution

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

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 MpcLQGs 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 densitiesLQGs may signal huge structures to z~3 and test if there are high-z Great-Waals

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)

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 LQGsIn 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

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 redshiftToday’s quasar surveys over extended areas of the sky allow searches of LQGsLQGs are a tool to search for super-large structures to z>=2 and to further test the hypothesis of homogeneity of the UniverseTheoretical models predict ‘Grear Waals” of >500 Mpc in size. LQGs may find an upper z-limit for the existence of “Great Waals’.

Reu Sochias:14-16 Enero 2009 FINFIN