scholarly journals FLUCTUATIONS IN A PRIMORDIAL ANISOTROPIC ERA

1998 ◽  
Vol 13 (03) ◽  
pp. 363-379 ◽  
Author(s):  
MÁRIO NOVELLO ◽  
LUCIANE R. DE FREITAS
Keyword(s):  
Phase Transition ◽  
Power Spectrum ◽  
Galaxy Formation ◽  
Formation Process ◽  
Current Knowledge ◽  
Efficient Process ◽  
Anisotropic Expansion ◽  
The Galaxy ◽  
The Universe ◽  
Fluid Configuration

The primordial Universe is treated in terms of a nonperfect fluid configuration endowed with an anisotropic expansion. The deGennes–Landau mechanism of phase transition acts as a very efficient process to provide the elimination of the previous anisotropy and to set the universe in the current isotropic FRW stage. The entropy produced, as a consequence of the phase transition, depends on the strength of the previous shear. We suggest the hypothesis that the germinal perturbations that will grow into the observed system of galaxies occurring in the anisotropic era. We present a model to deal with this idea that provides a power spectrum of fluctuations of the form [Formula: see text]. We compare this prediction of our model to the current knowledge on the galaxy formation process.

scholarly journals The evolution of massive galaxies in semi-analytical models of galaxy formation

2012 ◽  
Vol 8 (S295) ◽  
pp. 191-199
Author(s):  
Carlton M. Baugh
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Formation Process ◽  
Hierarchical Models ◽  
Gravitational Instability ◽  
Stellar Populations ◽  
Analytical Models ◽  
Massive Galaxies ◽  
Current State ◽  
The Galaxy

AbstractMassive galaxies with old stellar populations have been put forwards as a challenge to models in which cosmic structures grow hierarchically through gravitational instability. I will explain how the growth of massive galaxies is helped by features of hierarchical models. I give a brief outline of how the galaxy formation process is modelled in hierarchical cosmologies using semi-analytical models, and illustrate how these models can be refined as our understanding of processes such as star formation improves. I then present a brief survey of the current state of play in the modelling of massive galaxies and list some outstanding challenges.

The First Stars

2013 ◽  
Author(s):  
Abraham Loeb ◽  
Steven R. Furlanetto
Keyword(s):  
Phase Transition ◽  
Early Universe ◽  
Galaxy Formation ◽  
Big Bang ◽  
First Stars ◽  
Complex Chemical ◽  
Radiative Processes ◽  
Complex Processes ◽  
The Big Bang ◽  
The Universe

This chapter considers the emergence of the complex chemical and radiative processes during the first stages of galaxy formation. It studies the appearance of the first stars, their feedback processes, and the resulting ionization structures that emerged during and shortly after the cosmic dawn. The formation of the first stars tens or hundreds of millions of years after the Big Bang had marked a crucial transition in the early Universe. Before this point, the Universe was elegantly described by a small number of parameters. But as soon as the first stars formed, more complex processes entered the scene. To illustrate this, the chapter provides a brief outline of the prevailing (though observationally untested) theory for this cosmological phase transition.

scholarly journals Star clusters as tracers of galactic subsystems

1993 ◽  
Vol 153 ◽  
pp. 323-324
Author(s):  
B. Barbuy ◽  
E. Bica ◽  
S. Ortolani
Keyword(s):  
Spatial Distribution ◽  
Galaxy Formation ◽  
Formation Process ◽  
Globular Clusters ◽  
Star Clusters ◽  
Open Clusters ◽  
Horizontal Branch ◽  
The Galaxy ◽  
Magnitude Difference

We have obtained CCD BVRI colour-magnitude diagrams for a series of disk globular clusters, improving parameters and detecting a new one: Lyngå 7. Using the magnitude difference between turn-off and horizontal branch Δ(TO-HB) as an age discriminator, and their spatial distribution we compare old disk open clusters, young halo globular clusters, and metal-rich disk globular clusters, obtaining clues to the Galaxy formation process.

scholarly journals Observational Tests of the Galaxy Formation Process

2004 ◽  
Vol 294 (1-2) ◽  
pp. 3-8
Author(s):  
Gianfranco De Zotti ◽  
Gian Luigi Granato ◽  
Laura Silva ◽  
Luigi Danese
Keyword(s):  
Galaxy Formation ◽  
Formation Process ◽  
The Galaxy

THE LINK BETWEEN GALAXIES AND DARK MATTER

2011 ◽  
Vol 20 (10) ◽  
pp. 1771-1777
Author(s):  
HOUJUN MO
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Luminosity Function ◽  
The Other ◽  
Dark Matter Halos ◽  
Galaxy Formation And Evolution ◽  
The Galaxy ◽  
Galaxy Halo ◽  
Formation And Evolution ◽  
The Universe

Given that dark matter is gravitationally dominant in the universe, and that galaxy formation is closely related to dark matter halos, a key first step in understanding galaxy formation and evolution in the CDM paradigm is to quantify the galaxy-halo connection for galaxies of different properties. Here I will present results about the halo/galaxy connection obtained from two different methods. One is based on the conditional luminosity function, which describes the occupation of galaxies in halos of different masses, and the other is based on galaxy systems properly selected to represent dark halos.

scholarly journals Observational Data Related to the Largest Galaxies of the Universe: What they Tell?

2020 ◽  
pp. 236-240
Author(s):  
H. A. Harutyunian
Keyword(s):  
Dark Energy ◽  
Observational Data ◽  
Galaxy Formation ◽  
Physical Mechanism ◽  
Baryonic Matter ◽  
Model Predictions ◽  
The Galaxy ◽  
Cd Galaxies ◽  
Mechanism Of Interaction ◽  
The Universe

The physical mechanism of interaction between dark energy and ordinary baryonic matter is used to show that Ambartsumian's cosmogonic paradigm on the galaxy formation gets new support. This mechanism is considered to compare the cD galaxies observational properties with the model predictions in the framework of the suggested paradigm.

scholarly journals Compact groups from semi-analytical models of galaxy formation – I. A comparative study of frequency and nature

2019 ◽  
Vol 492 (2) ◽  
pp. 2588-2605
Author(s):  
E Díaz-Giménez ◽  
A Taverna ◽  
A Zandivarez ◽  
G A Mamon
Keyword(s):  
Power Spectrum ◽  
Spatial Resolution ◽  
Galaxy Formation ◽  
Cosmological Parameters ◽  
Analytical Models ◽  
Compact Groups ◽  
Galaxy Interactions ◽  
Flux Limit ◽  
Unique Site ◽  
The Universe

ABSTRACT Compact groups (CGs) of galaxies are defined as isolated and dense galaxy systems that appear to be a unique site of multiple galaxy interactions. Semi-analytical models (SAMs) of galaxy formation are a prime tool to understand CGs. We investigate how the frequency and the 3D nature of CGs depends on the SAM and its underlying cosmological parameters. Extracting nine light-cones of galaxies from five different SAMs and selecting CGs as in observed samples, we find that the frequency and nature of CGs depends strongly on the cosmological parameters. Moving from the WMAP1 to the WMAP7 and Planck cosmologies (increasing density of the Universe and decreasing normalization of the power spectrum), the space density of CGs is decreased by a factor 2.5, while the fraction of CGs that are physically dense falls from 50 to 35 per cent. The lower σ8 leads to fewer dense groups, while the higher Ωm causes more chance alignments. However, with increased mass and spatial resolution, the fraction of CGs that are physically dense is pushed back up to 50 per cent. The intrinsic differences in the SAM recipes also lead to differences in the frequency and nature of CGs, particularly those related to how SAMs treat orphan galaxies. We find no dependence of CG properties on the flux limit of the mock catalogues nor on the waveband in which galaxies are selected. One should thus be cautious when interpreting a particular SAM for the frequency and nature of CGs.

scholarly journals Simulating galaxy formation in f(R) modified gravity: matter, halo, and galaxy statistics

2019 ◽  
Vol 490 (2) ◽  
pp. 2507-2520 ◽  
Author(s):  
Christian Arnold ◽  
Baojiu Li
Keyword(s):  
Correlation Function ◽  
Power Spectrum ◽  
Galaxy Formation ◽  
Mass Function ◽  
Back Reaction ◽  
Satellite Galaxy ◽  
Matter Power Spectrum ◽  
Hydrodynamical Simulation ◽  
The Galaxy ◽  
Galaxy Count

ABSTRACT We present an analysis of the matter, halo, and galaxy clustering in f(R)-gravity employing the SHYBONE full-physics hydrodynamical simulation suite. Our analysis focuses on the interplay between baryonic feedback and f(R)-gravity in the matter power spectrum, the matter and halo correlation functions, the halo and galaxy–host–halo mass function, the subhalo and satellite–galaxy count, and the correlation function of the stars in our simulations. Our studies of the matter power spectrum in full-physics simulations in f(R)-gravity show that it will be very difficult to derive accurate fitting formulae for the power spectrum enhancement in f(R)-gravity which include baryonic effects. We find that the enhancement of the halo mass function due to f(R)-gravity and its suppression due to feedback effects do not show significant back-reaction effects and can thus be estimated from independent general relativity-hydro and f(R) dark matter only simulations. Our simulations furthermore show that the number of subhaloes and satellite-galaxies per halo is not significantly affected by f(R)-gravity. Low-mass haloes are nevertheless more likely to be populated by galaxies in f(R)-gravity. This suppresses the clustering of stars and the galaxy correlation function in the theory compared to standard cosmology.

scholarly journals Jet-Induced Star Formation

2004 ◽  
Vol 217 ◽  
pp. 472-479 ◽  
Author(s):  
Wil van Breugel ◽  
Chris Fragile ◽  
Peter Anninos ◽  
Stephen Murray
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Positive Feedback ◽  
Formation Process ◽  
Radio Galaxy ◽  
Radio Galaxies ◽  
Observational Evidence ◽  
Active Galaxies ◽  
Induce Star Formation ◽  
The Galaxy

Jets from radio galaxies can have dramatic effects on the medium through which they propagate. We review observational evidence for jet-induced star formation in low (‘FR-I’) and high (‘FR-II’) luminosity radio galaxies, at low and high redshifts respectively. We then discuss numerical simulations which are aimed to explain a jet-induced starburst (‘Minkowski's Object’) in the nearby FR-I type radio galaxy NGC 541. We conclude that jets can induce star formation in moderately dense (10 cm−3), warm (104 K) gas; that this may be more common in the dense environments of forming, active galaxies; and that this may provide a mechanism for ‘positive’ feedback from AGN in the galaxy formation process.

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