I am an academician, but retired. I am interested in cosmology and the physics of galaxies. As the only selection was 'Nature', there are lot of things that I could be interested in, shown at my website, but most of them are wrong.
Galactic or extragalactic H I clouds, if not too massive, must be in pressure equilibrium with th... more Galactic or extragalactic H I clouds, if not too massive, must be in pressure equilibrium with the galactic coronal gas. Given the model of the corona and observed parameters of an H I cloud, one can find now the (two) possible distances of the cloud. Three examples are given, the solutions being either smaller than one kpc or about 30 - 60 kpc. Limitations and error bounds of the method are discussed.
Abstract. We study the properties of dark matter haloes of a LCDM model in different environments... more Abstract. We study the properties of dark matter haloes of a LCDM model in different environments. Using the distance of the 5th nearest neighbour as an environmental density indicator, we show that haloes in a high density environment are more massive, richer, have larger radii and larger velocity dispersions than haloes in a low density environment. Haloes in high density regions move with larger velocities, and are more spherical than haloes in low density regions. In addition, low mass haloes in the vicinity of the most massive haloes are themselves more massive, larger, and have larger rms velocities and larger 3D velocities than low mass haloes far from massive haloes. The velocities of low mass haloes near massive haloes increase with the parent halo mass. Our results are in agreement with recent findings about environmental effects for groups and clusters of galaxies from deep (SDSS and LCRS) surveys. Keywords: Cosmology: simulations – cosmology: large-scale structure of the...
The VIMOS Public Extragalactic Redshift Survey [VIPERS, Guzzo et al. (2014)] is using the VIMOS s... more The VIMOS Public Extragalactic Redshift Survey [VIPERS, Guzzo et al. (2014)] is using the VIMOS spectrograph at the ESO VLT to measure redshifts for ∼ 100, 000 galaxies with IAB < 22.5 and 0.5 < z < 1.2, over an area of 24 deg (split over the W1 and W4 fields of CFHTLS). VIPERS currently provides, at such redshifts, the best compromise between volume, number of galaxies and dense spatial sampling. We present here the first estimate of the power spectrum of the galaxy distribution, P(k), at redshifts z ∼ 0.75 and z ∼ 1, obtained from the ∼ 55, 000 redshifts of the PDR-1 data release. We discuss first constraints on cosmological quantities, as the matter density and the baryonic fraction, obtained for the first time at an epoch when the Universe was about half its current age.
Aims. If the concordanceCDM model is a true description of the universe, it should also properly ... more Aims. If the concordanceCDM model is a true description of the universe, it should also properly predict the properties and structure of dark matter haloes, where galaxies are born. Using N-body simulations with a broad scale of mass and spatial resolution, we study the structure of dark matter haloes, the distribution of masses and the spati al distribution of subhaloes within the main haloes. Methods. We carry out threeCDM simulations with different resolutions using the AMIGA code. Dark matter haloes are identified using an algorithm that is based on the adaptive grid structure of the simulation code. The haloes we find encompass the mass scales from 10 8 M⊙ to 10 15 M⊙. Results. We find that if we have to study the halo structure (search for s ubhaloes), the haloes have to contain at least 10 4 particles. For such haloes, where we can resolve substructure, we determined the subhalo mass function and found that it is close to a power law with the slope −0.9 (at present time), con...
Implications of the observed large scale structure on the physics of the early universe are descr... more Implications of the observed large scale structure on the physics of the early universe are described. A short review of Soviet work on the subject is given, and the present status of the fractal model of the large scale structure is discussed.
Galactic or extragalactic H I clouds, if not too massive, must be in pressure equilibrium with th... more Galactic or extragalactic H I clouds, if not too massive, must be in pressure equilibrium with the galactic coronal gas. Given the model of the corona and observed parameters of an H I cloud, one can find now the (two) possible distances of the cloud. Three examples are given, the solutions being either smaller than one kpc or about 30 - 60 kpc. Limitations and error bounds of the method are discussed.
Abstract. We study the properties of dark matter haloes of a LCDM model in different environments... more Abstract. We study the properties of dark matter haloes of a LCDM model in different environments. Using the distance of the 5th nearest neighbour as an environmental density indicator, we show that haloes in a high density environment are more massive, richer, have larger radii and larger velocity dispersions than haloes in a low density environment. Haloes in high density regions move with larger velocities, and are more spherical than haloes in low density regions. In addition, low mass haloes in the vicinity of the most massive haloes are themselves more massive, larger, and have larger rms velocities and larger 3D velocities than low mass haloes far from massive haloes. The velocities of low mass haloes near massive haloes increase with the parent halo mass. Our results are in agreement with recent findings about environmental effects for groups and clusters of galaxies from deep (SDSS and LCRS) surveys. Keywords: Cosmology: simulations – cosmology: large-scale structure of the...
The VIMOS Public Extragalactic Redshift Survey [VIPERS, Guzzo et al. (2014)] is using the VIMOS s... more The VIMOS Public Extragalactic Redshift Survey [VIPERS, Guzzo et al. (2014)] is using the VIMOS spectrograph at the ESO VLT to measure redshifts for ∼ 100, 000 galaxies with IAB < 22.5 and 0.5 < z < 1.2, over an area of 24 deg (split over the W1 and W4 fields of CFHTLS). VIPERS currently provides, at such redshifts, the best compromise between volume, number of galaxies and dense spatial sampling. We present here the first estimate of the power spectrum of the galaxy distribution, P(k), at redshifts z ∼ 0.75 and z ∼ 1, obtained from the ∼ 55, 000 redshifts of the PDR-1 data release. We discuss first constraints on cosmological quantities, as the matter density and the baryonic fraction, obtained for the first time at an epoch when the Universe was about half its current age.
Aims. If the concordanceCDM model is a true description of the universe, it should also properly ... more Aims. If the concordanceCDM model is a true description of the universe, it should also properly predict the properties and structure of dark matter haloes, where galaxies are born. Using N-body simulations with a broad scale of mass and spatial resolution, we study the structure of dark matter haloes, the distribution of masses and the spati al distribution of subhaloes within the main haloes. Methods. We carry out threeCDM simulations with different resolutions using the AMIGA code. Dark matter haloes are identified using an algorithm that is based on the adaptive grid structure of the simulation code. The haloes we find encompass the mass scales from 10 8 M⊙ to 10 15 M⊙. Results. We find that if we have to study the halo structure (search for s ubhaloes), the haloes have to contain at least 10 4 particles. For such haloes, where we can resolve substructure, we determined the subhalo mass function and found that it is close to a power law with the slope −0.9 (at present time), con...
Implications of the observed large scale structure on the physics of the early universe are descr... more Implications of the observed large scale structure on the physics of the early universe are described. A short review of Soviet work on the subject is given, and the present status of the fractal model of the large scale structure is discussed.
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Papers by E. Saar