Dynamical aspects of galaxy clustering

1980 ◽  
Vol 296 (1419) ◽  
pp. 339-345 ◽  
Keyword(s):  
Galaxy Formation ◽  
Gravitational Instability ◽  
Mass Density ◽  
Big Bang ◽  
Density Fluctuations ◽  
Galaxy Clustering ◽  
Origin And Evolution ◽  
Statistical Measures ◽  
Instability Theory ◽  
The Universe

Some recent work on the origin and evolution of galaxy clustering is reviewed, particularly within the context of the gravitational instability theory and the hot big-bang cosmological model. Statistical measures of clustering, including correlation functions and multiplicity functions, are explained and discussed. The close connection between galaxy formation and clustering is emphasized. Additional topics include the dependence of galaxy clustering on the spectrum of primordial density fluctuations and the mean mass density of the Universe.

scholarly journals Probing the Cosmic Frontier of Galaxies

2015 ◽  
Vol 11 (A29B) ◽  
pp. 808-811
Author(s):  
Pascal A. Oesch
Keyword(s):  
Galaxy Formation ◽  
Mass Density ◽  
Formation Rate ◽  
Big Bang ◽  
Ir Camera ◽  
Blank Field ◽  
Open Questions ◽  
First Galaxies ◽  
The Big Bang ◽  
The Universe

AbstractUnderstanding when and how the first galaxies formed and what sources reionized the universe are key goals of extragalactic astronomy. Thanks to deep surveys with the powerful WFC3/IR camera on the HST, the observational frontier of galaxy build-up now lies at only ~450 Myr after the Big Bang, at redshifts z ~10-12. In combination with deep data from Spitzer/IRAC we can now probe the evolution of the stellar mass density over 96% of cosmic history. However, detecting and characterizing galaxies at these early epochs is challenging even for HST and the sample sizes at the earliest redshifts are still very small. The Hubble Frontier Fields provide a prime new dataset to improve upon our current, sparse sampling of the UV luminosity function at z>8 from blank fields to answer some of the most pressing open questions. For instance, even the evolution of the cosmic star-formation rate density at z>8 is still debated. While our measurements based on blank field data indicate that galaxies with SFR>0.7 Msol/yr disappear quickly from the cosmic record between z~8 and z~10, other previous results, e.g., from the CLASH survey favor a more moderate decline. Here, we briefly review the recent progress in studying galaxy build-up out to z~10 from the combined blank field and existing Frontier Field datasets and discuss their implications for primordial galaxy formation and cosmic reionization.

Neutrinos and the dark matter problem

1994 ◽  
Vol 346 (1678) ◽  
pp. 121-135 ◽  
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Mass Density ◽  
Rest Mass ◽  
Density Fluctuations ◽  
Fine Tuning ◽  
Cosmological Argument ◽  
The Mean ◽  
The Universe

Theoretical and experimental arguments suggest that the mean mass density of our universe is close to the closure value and that most of the mass in the universe consists of weakly interacting non-baryonic particles. Among the plethora of candidates that have been proposed as the dark matter, the neutrino remains the only particle known to exist, even though the issue of a neutrino mass remains unresolved. It was shown several years ago that neutrinos alone cannot provide the dark matter because physical processes in the early universe would have wiped out primordial density fluctuations on the scale of galaxies and below. The idea that cosmic strings or textures may seed galaxy formation in a neutrino-dominated universe has not yet been demonstrated to be viable. On the other hand, a model in which the bulk of the dark matter is cold and neutrinos with a mass of ca . 10 eV provide a ca . 30% contribution can, in principle, overcome many of the objections against the standard cold dark matter cosmogony. Although subject to the usual ‘fine-tuning’ criticism, these mixed dark matter models represent the best cosmological argument in favour of a non-zero rest mass for the neutrino.

Linear Growth of Cosmological Perturbations

2013 ◽  
Author(s):  
Abraham Loeb ◽  
Steven R. Furlanetto
Keyword(s):  
Galaxy Formation ◽  
Big Bang ◽  
Density Fluctuations ◽  
Microwave Background ◽  
Cosmological Recombination ◽  
Small Density ◽  
Evolution Of Structure ◽  
First Galaxies ◽  
The Big Bang ◽  
The Universe

This chapter shows that, after cosmological recombination, the Universe had entered the “dark ages,” during which the relic cosmic microwave background (CMB) light from the Big Bang gradually faded away. During this “pregnancy” period (which lasted hundreds of millions of years), the seeds of small density fluctuations planted by inflation in the matter distribution grew until they eventually collapsed to make the first galaxies. In addition to the density evolution, the second key “initial condition” for galaxy formation is the temperature of the hydrogen and helium gas that had likewise collapsed into the first galaxies. Here, the chapter describes the first stages of these processes and introduces the methods conventionally used to describe the fluctuations. It follows the evolution of structure in the linear regime, when the perturbations are small.

scholarly journals Anisotropy of the Microwave Background and Biased Galaxy Formation

1988 ◽  
Vol 130 ◽  
pp. 43-50
Author(s):  
Nick Kaiser
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
Microwave Background ◽  
Galaxy Clustering ◽  
Clear View ◽  
Hot Gas ◽  
Density Perturbations ◽  
The Universe ◽  
Theoretical Developments

Fluctuations in the microwave background will have been imprinted at z ≃ 1000, when the photons and the plasma decoupled. On angular scales greater than a few degrees these fluctuations provide a clear view of any primordial density perturbations, and therefore a clean test of theories which invoke such fluctuations from which to form the structure we see in the universe. On smaller angular scales the predictions are less certain: reionization of the gas may modify the spectrum of the primordial fluctuations, and secondary fluctuations may be generated.Here I shall review some recent theoretical developments. A brief survey is made of the currently popular theories for the primordial perturbations, with emphasis on the predictions for large scale anisotropy. One major uncetainty in the predictions arises from the normalisation of the fluctuations to e.g. galaxy clustering, and much attention is given to the question of ‘biased’ galaxy formation. The effect of reionization on the primordial fluctuations is discussed, as is the anisotropy generated from scattering off hot gas in clusters, groups and galaxies.

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 New Results on DLA Systems: Statistics

2015 ◽  
Vol 11 (S319) ◽  
pp. 40-40
Author(s):  
Sandhya Rao ◽  
David Turnshek ◽  
Eric Monier ◽  
Gendith Sardane
Keyword(s):  
Galaxy Formation ◽  
Mass Density ◽  
Neutral Hydrogen ◽  
Gas Content ◽  
Neutral Gas ◽  
Quasar Spectra ◽  
Galaxy Formation And Evolution ◽  
Formation And Evolution ◽  
Space Data ◽  
The Universe

AbstractThe damped Lyman-α absorption-line systems (DLAs) that are observed in quasar spectra arise in neutral-gas-rich regions of intervening galaxies. With the highest neutral hydrogen column densities observed (N(HI) ⩾ 2 × 1020 atoms cm−2), they are known to trace the bulk of the neutral gas content of the Universe, and are thus powerful probes of galaxy formation and evolution. However, DLAs are extremely rare, and since the Lyman-α line falls in the UV for redshifts z < 1.65, not many are known at low redshift due to the limited availability of space data. Our HST surveys for DLAs in strong MgII absorbers have been successful at showing that MgII can be used as an unbiased tracer of DLAs. We present new results on their incidence, or redshift number density, dn/dz, and cosmological neutral gas mass density, ΩDLA, at redshifts 0.11 ⩽ z ⩽ 1.65, and incorporate results from higher and lower redshift studies in the literature to derive the evolution of neutral gas in the Universe.

scholarly journals Origin of strong magnetic fields in Milky Way-like galaxies

2015 ◽  
Vol 11 (S317) ◽  
pp. 274-275
Author(s):  
Alexander M. Beck
Keyword(s):  
Magnetic Fields ◽  
Galaxy Formation ◽  
Milky Way ◽  
Cosmic Time ◽  
Strong Magnetic Fields ◽  
Origin And Evolution ◽  
The Universe

AbstractMagnetic fields are observed on all scales in the Universe (see e.g. Kronberg 1994), but little is known about the origin and evolution of those fields with cosmic time. Seed fields of arbitrary source must be amplified to present-day values and distributed among cosmic structures. Therefore, the emergence of cosmic magnetic fields and corresponding dynamo processes (see e.g. Zel'dovich et al. 1983; Kulsrud et al. 1997) can only be jointly understood with the very basic processes of structure and galaxy formation (see e.g. Mo et al. 2010).

The cosmic microwave background radiation and galaxy formation

1986 ◽  
Vol 64 (2) ◽  
pp. 147-151 ◽  
Author(s):  
Joseph Silk
Keyword(s):  
Galaxy Formation ◽  
Background Radiation ◽  
Gravitational Instability ◽  
Virgo Cluster ◽  
Inflationary Cosmology ◽  
Density Parameter ◽  
Microwave Background ◽  
Scale Invariant ◽  
Instability Theory ◽  
Microwave Background Radiation

Observational limits on the microwave-background-radiation anisotropy on various angular scales are reviewed. Comparison is made with the predictions of the gravitational-instability theory of galaxy formation from primordial fluctuations in the very early universe. There is no entirely satisfactory theory that presently reconciles inflationary cosmology predictions of the flatness of the universe and of the scale-invariant primordial fluctuation spectrum with the limits on the amplitude of the anisotropy (δT/T), with the Virgo-cluster motion inferred from the dipole anisotropy, and with astronomical determinations of the cosmological density parameter.

scholarly journals Abundances of hydrogen and helium isotopes in the Protosolar Cloud

2009 ◽  
Vol 5 (S268) ◽  
pp. 71-79 ◽  
Author(s):  
Johannes Geiss ◽  
George Gloeckler
Keyword(s):  
Solar Wind ◽  
Solar System ◽  
Big Bang ◽  
The Sun ◽  
Density Profiles ◽  
Origin And Evolution ◽  
Naturally Occurring ◽  
System 2 ◽  
The Big Bang ◽  
The Universe

AbstractFor our understanding of the origin and evolution of baryonic matter in the Universe, the Protosolar Cloud (PSC) is of unique importance in two ways: 1) Up to now, many of the naturally occurring nuclides have only been detected in the solar system. 2) Since the time of solar system formation, the Sun and planets have been virtually isolated from the galactic nuclear evolution, and thus the PSC is a galactic sample with a degree of evolution intermediate between the Big Bang and the present.The abundances of the isotopes of hydrogen and helium in the Protosolar Cloud are primarily derived from composition measurements in the solar wind, the Jovian atmosphere and “planetary noble gases” in meteorites, and also from observations of density profiles inside the Sun. After applying the changes in isotopic and elemental composition resulting from processes in the solar wind, the Sun and Jupiter, PSC abundances of the four lightest stable nuclides are given.

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