{ }From three quasar samples with a total of 1038 objects in the redshift range $1.0 \div 2.2$ we measure the variance $\sigma^2$ of counts in cells of volume $V_u$. By a maximum likelihood analysis applied separately on these samples we obtain estimates of $\sigma^2(\ell)$, with $\ell \equiv V_u^{ 1/3}$. The analysis from a single catalog for $\ell = ~40~h^{ -1}$ Mpc and from a suitable average over the three catalogs for $\ell = ~60,~80$ and $100~h^{ -1}$ Mpc, gives $\sigma^2(\ell) = 0.46^{ +0.27}_{ -0.27}$, $0.18^{ +0.14}_{ -0.15}$, $0.05^{ +0.14}_{ -0.05}$ and $0.12^{ +0.13}_{ -0.12}$, respectively, where the $70\%$ confidence ranges account for both sampling errors and statistical fluctuations in the counts. This allows a comparison of QSO clustering on large scales with analogous data recently obtained both for optical and IRAS galaxies: QSOs seem to be more clustered than these galaxies by a biasing factor $b_{ QSO}/b_{ gal} \sim 1.4 - 2.3$.
Categories: astro-ph