23 research outputs found
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 () 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 forest is studied using new HST
data for the quasar pair Q~1026--0045 A and B at = 1.438 and 1.520
respectively. The angular separation is 36 arcsec and corresponds to transverse
linear separations between lines of sight of kpc (
= 0.5) over the redshift range 0.833 < z < 1.438. From the observed numbers of
coincident and anti-coincident Ly absorption lines, we conclude that,
at this redshift, the Ly structures have typical dimensions of
kpc, larger than the mean separation of the two lines of
sight. The velocity difference, , between coincident lines is
surprisingly small (4 and 8 pairs with z_{abs}z_{abs}z_{abs}z_{abs}z_{abs}z_{abs}\alphah^{-1}_{50}$ kpc surrounding quasar A.Comment: 4 pages, 2 figures, A&A Letter acccepte
Large-scale structure formation for power spectra with broken scale invariance
We have simulated the formation of large-scale structure arising from
COBE-normalized spectra computed by convolving a primordial double-inflation
perturbation spectrum with the CDM transfer function. Due to the broken scale
invariance ('BSI') characterizing the primordial perturbation spectrum, this
model has less small-scale power than the (COBE-normalized) standard CDM model.
The particle-mesh code (with cells and particles) includes a
model for thermodynamic evolution of baryons in addition to the usual
gravitational dynamics of dark matter. It provides an estimate of the local gas
temperature. In particular, our galaxy-finding procedure seeks peaks in the
distribution of gas that has cooled. It exploits the fact that ``cold"
particles trace visible matter better than average and thus provides a natural
biasing mechanism. The basic picture of large-scale structure formation in the
BSI model is the familiar hierarchical clustering scenario. We obtain particle
in cell statistics, the galaxy correlation function, the cluster abundance and
the cluster-cluster correlation function and statistics for large and small
scale velocity fields. We also report here on a semi-quantitative study of the
distribution of gas in different temperature ranges. Based on confrontation
with observations and comparison with standard CDM, we conclude that the BSI
scenario could represent a promising modification of the CDM picture capable of
describing many details of large-scale structure formation.Comment: 15 pages, Latex using mn.sty, uuencoded compressed ps-file with 15
figures by anonymous ftp to ftp://ftp.aip.de/incoming/mueller/bsi.u