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Abstract. We use the model for the migration of planets introduced in Del Popolo et al. (2003, MNRAS, 339, 556) to calculate the observed mass and semimajor axis distribution of extra-solar planets. The assumption that the surface density in planetesimals is proportional to that of gas is relaxed, and in order to describe disc evolution we use a method which, using a series of simplifying assumptions, is able to simultaneously follow the evolution of gas and solid particles for up to 10 7 yr. The distribution of planetesimals obtained after 10 7 yr is used to study the migration rate of a giant planet through the model described in the present paper. The disk and migration models are used to calculate the distribution of planets as function of mass and semimajor axis. The results show that the model can give a reasonable prediction of planets' semi-major axes and mass distribution. In particular there is a pile-up of planets at a 0.05 AU, a minimum near 0.3 AU, indicating a paucity of planets at that distance, and a rise for semi-major axes larger than 0.3 AU, out to 3 AU. The semi-major axis distribution shows that the more massive planets (typically, masses larger than 4 M J ) form preferentially in the outer regions and do not migrate much. Intermediate-mass objects migrate more easily whatever the distance at which they form, and that the lighter planets (masses from sub-Saturnian to Jovian) migrate easily.

Optical CCD imaging with Hα and [SII] filters and spectroscopic observations of the galactic supernova remnant G85.9-0.6 have been performed for the first time. The CCD image data are taken with the 1.5 m RussianTurkish Telescope (RTT150) at TÜBİTAK National Observatory (TUG) and spectral data are taken with the Bok 2.3 m telescope on Kitt Peak, AZ.The images are taken with narrow-band interference filters Hα, [SII] and their continuum.[SII]/Hα ratio image is performed. The ratio obtained from [SII]/Hα is found to be ∼0.42, indicating that the remnant interacts with HII regions. G85.9-0.6 shows diffuse-shell morphology.[SII]λλ6716/6731 average flux ratio is calculated from the spectra, and the electron density N e is obtained to be 395 cm −3 . From [OIII]/Hβ ratio, shock velocity has been estimated, pre-shock density of n c = 14 cm −3 , explosion energy of E = 9.2 × 10 50 ergs, interstellar extinction of E(B − V ) = 0.28, and neutral hydrogen column density of N(HI) = 1.53 × 10 21 cm −2 are reported.

Abstract. In this paper, we discuss improvements of the Suto et al. (2000) model, in the light of recent theoretical developments (new theoretical mass functions, a more accurate mass-temperature relation and an improved bias model) to predict the clustering properties of galaxy clusters and to obtain constraints on cosmological parameters. We re-derive the two-point correlation function of clusters of galaxies for OCDM and ΛCDM cosmological models, and we compare these results with the observed spatial correlation function for clusters in RASS1 (ROSAT All-Sky Survey 1), and in XBACs (X-RAY Brighest Abell-Type) samples. The comparison shows that the best agreement is obtained for the ΛCDM model with Ω m = 0.3. The values of the correlation length obtained, (r 0 28.2 ± 5.2 h −1 Mpc for ΛCDM), are larger than those found in the literature and comparable with the results found in Borgani et al. (1999). In order to study the possible dependence of the clustering properties of the X-ray clusters on the observational characteristics defining the survey, we calculated the values of the correlation length r 0 in the catalogues where we vary the limiting X-ray flux S lim . The result shows an increase of r 0 with L lim , and correlation lengths that are larger than in previous papers in literature (e.g. Moscardini et al. 2001 (hereafter MMM);Suto et al. 2000). These differences are due essentially to the different M − T , mass function and bias model used in this paper. Then, we perform a maximum-likelihood analysis by comparing the theoretical predictions to a set of observational data in the X-ray band (RASS1 Bright Sample, BCS (Rosat Brightest Cluster Sample), XBACs, REFLEX (ROSAT-ESO Flux Limited X-Ray Sample)), similarly to MMM. In the framework of cold dark matter models, we compute the constraints on cosmological parameters, such as the matter density Ω m , the contribution to density due to the cosmological constant, Ω Λ , the power-spectrum shape parameter Γ and normalization σ 8 . If we fix Γ and σ 8 , at the values suggested by different observational datasets, we obtain (for flat cosmological models with varying cosmological constant Ω 0Λ = 1 − Ω 0m ) constraints on the matter density parameter: 0.25 ≤ Ω 0m ≤ 0.45 and 0.23 ≤ Ω 0m ≤ 0.52 at the 95.4 and 99.73 per cent levels, respectively, which is 20-30% larger than the values obtained MMM. Leaving Γ, and Ω m0 , free for the flat model, the constraints for Γ are 0.1 ≤ Γ ≤ 0.14, while for the open model 0.09 ≤ Γ ≤ 0.13. These values are smaller than those of MMM by about 20−30%. If we keep the values of Ω Λ fixed, we obtain the constraints in the Γ − σ 8 plane. For the open model with Ω 0m = 0.3 the 2σ region for Γ is 0.11-0.2 for σ 8 it is 0.7 and 1.55. For the flat model with Ω 0m = 0.3 the 2σ region has 0.13 ≤ Γ ≤ 0.2 and 0.8 ≤ σ 8 ≤ 1.6 The values of σ 8 obtained are larger than those of MMM by 20%. If we allow the shape parameter to vary, we find that the clustering properties of clusters are almost independent of the matter density parameter and of the p...

We derive the luminosity-temperature relation for clusters of galaxies by means of a modification of the self-similar model to take account of angular momentum acquisition by protostructures and of an external pressure term in the virial theorem. The fundamental result of the model is that gravitational collapse, which takes account of angular momentum acquisition, can explain the non self-similarity in the L-T relation, in disagreement with the largely accepted assumption that heating/cooling processes and similar are fundamental in the originating the non-self similar behavior (shaping) of the L-T relation.