نتایج جستجو برای: galaxy evolution
تعداد نتایج: 389980 فیلتر نتایج به سال:
The morphologies of disk galaxies begin to deviate systematically from those of nearby galaxies at surprisingly low redshifts, possibly as low as z = 0.3. This corresponds to a time ∼ 3.5 Gyr in the past, which is only one quarter of the present age of the Universe. Beyond z = 0.5 (a look-back time of 5 Gyr) the effects of evolution on spiral structure are rather obvious: spiral arms are less w...
Far-infrared flux densities are newly extracted from the IRAS database for the RSA and CfA complete samples of Seyfert galaxies. These data are used to classify the Seyfert galaxies into those where the far-infrared continuum emission is dominated by the active galactic nucleus (AGN), circumnuclear starburst, or host galaxy. While AGN-dominant objects consist of comparable numbers of Seyfert 1 ...
A semi-analytic model is proposed that couples the Press-Schechter formalism for the number of galaxies with a prescription for galaxy-galaxy interactions that enables to follow the evolution of galaxy morphologies along the Hubble sequence. Within this framework, we calculate the chemo-spectrophotometric evolution of galaxies to obtain spectral energy distributions. We find that such an approa...
The main ingredients of recent semi-analytic models of galaxy formation are summarised. We present predictions for the galaxy clustering properties of a well specified ΛCDM model whose parameters are constrained by observed local galaxy properties. We present preliminary predictions for evolution of clustering that can be probed with deep pencil beam surveys.
The Milky Way Galaxy offers a unique opportunity for testing theories of galaxy formation and evolution. I discuss how large surveys, both photometric and spectroscopic, of Galactic stars are the keystones of investigations into such fundamental problems as the merging history – and future – of the Galaxy.
We investigate the evolution of angular momentum in simulations of galaxy formation in a cold dark matter universe. We analyse two model galaxies produced in the Nbody/hydrodynamic simulations of Okamoto et al. Starting from identical initial conditions, but using different assumptions for the baryonic physics, one of the simulations produced a bulge-dominated galaxy and the other one a disk-do...
We investigate the evolution of angular momentum in simulations of galaxy formation in a cold dark matter universe. We analyse two model galaxies generated in the Nbody/hydrodynamic simulations of Okamoto et al. Starting from identical initial conditions, but using different assumptions for the baryonic physics, one of the simulations produced a bulge-dominated galaxy and the other one a disc-d...
There exists a population of broad-line z∼2 QSOs which have heavily absorbed X-ray spectra. These objects constitute ∼10% of the population at luminosities and redshifts characteristic of the main producers of QSO luminosity in the Universe. Our follow up observations in the submm show that these QSOs are often embedded in ultraluminous starburst galaxies, unlike most unabsorbed QSOs at the sam...
This paper investigates whether nonlinear gravitational instability can account for the clustering of galaxies on large and small scales, and for the evolution of clustering with epoch. The local clustering spectrum is accurately established, and bias is not a great source of uncertainty: the real-space power spectra of optical and IRAS galaxies show only a weak scale-dependent relative bias of...
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