Confrontation of a Double Inflationary Cosmological Model with Observations

CDM models with non-scale-free step-like spectra of adiabatic perturbations produced in a realistic double inflationary model are compared with recent observational data. The model contains two additional free parameters relatively to the standard CDM model with the flat ($n=1$) initial spectrum. Results of the COBE experiment are used for the determination of a free overall spectrum normalization. Then predictions for the galaxy biasing parameter, the variance for "counts in cells", the galaxy angular correlation function, bulk flow peculiar velocities and the Mach number test are obtained. Also considered are conditions for galaxy and quasar formation. Observational data strongly restricts allowed values for the two remaining model parameters. However, a non-empty region for them satisfying all considered tests is found.Comment: 17 pages and 4 figures obtainable by request, LaTex, AIP 93-1

HST Observations of the QSO pair Q1026-0045A,B

The spatial distribution of the Ly$\alpha$ forest is studied using new HST data for the quasar pair Q~1026--0045 A and B at $z_{em}$ = 1.438 and 1.520 respectively. The angular separation is 36 arcsec and corresponds to transverse linear separations between lines of sight of $\sim300h^{-1}_{50}$ kpc ($q_{o}$ = 0.5) over the redshift range 0.833 < z < 1.438. From the observed numbers of coincident and anti-coincident Ly$\alpha$ absorption lines, we conclude that, at this redshift, the Ly$\alpha$ structures have typical dimensions of $\sim500h^{-1}_{50}$ kpc, larger than the mean separation of the two lines of sight. The velocity difference, $\Delta V$, between coincident lines is surprisingly small (4 and 8 pairs with $\Delta V < 50 and 200 km/s respectively). Metal line systems are present at$z_{abs}$= 1.2651 and 1.2969 in A,$z_{abs}$= 0.6320, 0.7090, 1.2651 and 1.4844 in B. In addition we tentatively identify a weak Mg II system at$z_{abs}$= 0.11 in B. It is remarkable that the$z_{abs}$= 1.2651 system is common to both lines of sight. The system at$z_{abs}$= 1.4844 There is a metal-poor associated system at$z_{abs}$= 1.4420 along the line of sight to A with complex velocity profile. We detect a strong Ly$\alpha$absorption along the line of sight to B redshifted by only 300 km/s relatively to the associated system. It is tempting to interpret this as the presence of a disk of radius larger than 300$h^{-1}_{50}$ kpc surrounding quasar A.Comment: 4 pages, 2 figures, A&A Letter acccepte