Retorne
Título
:
A strong constraint on Omega, Lambda and possible quintessence using 2dF quasar
structures as standard rulers
Conferencista:
Gary Mamon, IAP
Data
:
Quarta-feira, 26/09/01 15H30M
Local
:
Auditório L.B.F. Clauzet - Água Funda
Sumário
:
The internal kinematics of groups and clusters have long been used to
constrain the density parameter of the Universe Omega to values of roughly 0.3
times the critical density, value confirmed by the study of the baryonic
content of these systems. The use of supernovae as standard candles has more
recently shown that the cosmological constant Lambda is positive, leading to an
accelerating Universe. Finally very recent analyses of the Cosmic Microwave
Background lead to an angular fluctuation spectrum highly consistent with a flat
Universe, i.e. Omega + Lambda = 1. Taking any two of these findings together
yields Omega = 0.3 and Lambda = 0.7.
I will describe how B. Roukema and I have been constraining these
cosmological parameters, using very large scale structures (larger than 50 Mpc)
as standard rulers in the comoving frame that expands with the Universe. Our
first results on a semi-reliable quasar sample yielded Omega = 0.3. More
recently, we have used the much more reliable 10QZ sample obtained with the 2dF
quasar survey. With fewer hypotheses, we obtain simultaneous constraints on
Omega and Lambda, consistent with the values given above, from 240 Mpc features.
Our study represesents the first joint constraint on Omega and Lambda from a
single sample and with a single method. I will also show our constraint on
quintessence. Tighter constraints are expected when the 2dF and SDSS surveys
reach completion.