scholarly journals Luminosity Bias. II. The Cosmic Web of the First Stars

2013 ◽  
Vol 30 ◽  
Author(s):  
R. Barkana
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Relative Velocity ◽  
Large Scale ◽  
Neutral Hydrogen ◽  
Unique Form ◽  
Velocity Difference ◽  
First Stars ◽  
Formation And Evolution ◽  
The Universe

AbstractUnderstanding the formation and evolution of the first stars and galaxies represents one of the most exciting frontiers in astronomy. Since the universe was filled with neutral hydrogen at early times, the most promising method for observing the epoch of the first stars is using the prominent 21-cm spectral line of the hydrogen atom. Current observational efforts are focused on the reionisation era (cosmic age t ~ 500 Myr), with earlier times considered much more challenging. However, the next frontier of even earlier galaxy formation (t ~ 200 Myr) is emerging as a promising observational target. This is made possible by a recently noticed effect of a significant relative velocity between the baryons and dark matter at early times. The velocity difference suppresses star formation, causing a unique form of early luminosity bias. The spatial variation of this suppression enhances large-scale clustering and produces a prominent cosmic web on 100 comoving Mpc scales in the 21-cm intensity distribution. This structure makes it much more feasible for radio astronomers to detect these early stars, and should drive a new focus on this era, which is rich with little-explored astrophysics.

scholarly journals N-body Simulations of Galaxy Formation

1988 ◽  
Vol 130 ◽  
pp. 259-271
Author(s):  
Carlos S. Frenk
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Large Scale Structure ◽  
High Density ◽  
Galactic Halos ◽  
Body Techniques ◽  
Massive Halos ◽  
The Universe

Modern N-body techniques allow the study of galaxy formation in the wider context of the formation of large-scale structure in the Universe. The results of such a study within the cold dark matter cosmogony are described. Dark galactic halos form at relatively recent epochs. Their properties and abundance are similar to those inferred for the halos of real galaxies. Massive halos tend to form preferentially in high density regions and as a result the galaxies that form within them are significantly more clustered than the underlying mass. This natural bias may be strong enough to reconcile the observed clustering of galaxies with the assumption that Ω = 1.

scholarly journals Large-Scale Structure of the Universe in Unstable Dark Matter Models

1988 ◽  
Vol 130 ◽  
pp. 293-300
Author(s):  
A.G. Doroshkevich ◽  
A.A. Klypin ◽  
M.U. Khlopov
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Large Scale ◽  
Numerical Models ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Microwave Background ◽  
Physical Background ◽  
The Mean ◽  
The Universe

Processes of the formation and the evolution of the large-scale structure are discussed in the framework of unstable dark matter models. Six numerical models are presented. The projected distribution of simulated galaxies on the sky, wedge diagrams, correlation functions and the mean linear scale of voids are presented. Physical background of the hypothesis of unstable particles and possible observational tests are discussed. The level of the microwave background fluctuations is estimated analytically. Special attention is given to late stage of supercluster evolution and galaxy formation.

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.

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 Status of dark matter in the universe

2017 ◽  
Vol 26 (06) ◽  
pp. 1730012 ◽  
Author(s):  
Katherine Freese
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Gravitational Lensing ◽  
Gamma Ray ◽  
Galactic Center ◽  
Data Sets ◽  
Multiple Sources ◽  
Microwave Background ◽  
First Stars ◽  
The Universe

Over the past few decades, a consensus picture has emerged in which roughly a quarter of the universe consists of dark matter. I begin with a review of the observational evidence for the existence of dark matter: rotation curves of galaxies, gravitational lensing measurements, hot gas in clusters, galaxy formation, primordial nucleosynthesis and Cosmic Microwave Background (CMB) observations. Then, I discuss a number of anomalous signals in a variety of data sets that may point to discovery, though all of them are controversial. The annual modulation in the DAMA detector and/or the gamma-ray excess seen in the Fermi Gamma Ray Space Telescope from the Galactic Center could be due to WIMPs; a 3.5 keV X-ray line from multiple sources could be due to sterile neutrinos; or the 511 keV line in INTEGRAL data could be due to MeV dark matter. All of these would require further confirmation in other experiments or data sets to be proven correct. In addition, a new line of research on dark stars is presented, which suggests that the first stars to exist in the universe were powered by dark matter heating rather than by fusion: the observational possibility of discovering dark matter in this way is discussed.

scholarly journals Luminosity Bias: From Haloes to Galaxies

2013 ◽  
Vol 30 ◽  
Author(s):  
C. M. Baugh
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Large Scale ◽  
Large Scale Structure ◽  
Morphological Type ◽  
Intrinsic Properties ◽  
Matter Distribution ◽  
Local Universe ◽  
Galaxy Bias ◽  
The Universe

AbstractLarge surveys of the local Universe have shown that galaxies with different intrinsic properties such as colour, luminosity and morphological type display a range of clustering amplitudes. Galaxies are therefore not faithful tracers of the underlying matter distribution. This modulation of galaxy clustering, called bias, contains information about the physics behind galaxy formation. It is also a systematic to be overcome before the large-scale structure of the Universe can be used as a cosmological probe. Two types of approaches have been developed to model the clustering of galaxies. The first class is empirical and filters or weights the distribution of dark matter to reproduce the measured clustering. In the second approach, an attempt is made to model the physics which governs the fate of baryons in order to predict the number of galaxies in dark matter haloes. I will review the development of both approaches and summarise what we have learnt about galaxy bias.

COSMIC STRINGS, HOT DARK MATTER AND THE LARGE-SCALE STRUCTURE OF THE UNIVERSE

1990 ◽  
Vol 05 (09) ◽  
pp. 1633-1651 ◽  
Author(s):  
ROBERT H. BRANDENBERGER ◽  
LEANDROS PERIVOLAROPOULOS ◽  
ALBERT STEBBINS
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Large Scale ◽  
Cosmic Strings ◽  
Unit Length ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Rotation Curves ◽  
The Universe

A review of recent results on large-scale structure and galaxy formation in a model with hot dark matter and cosmic strings is given. With cosmic strings seeding perturbations, many of the arguments against hot dark matter disappear. It is shown that spherical accretion about loops leads to dark matter haloes with flat velocity rotation curves. Velocity perturbations due to wakes behind long, moving strings lead to a network of planar overdensities with a distinguished scale of slightly less than 40×40 Mpc2. If the mass per unit length μ exceeds a certain bound, then the wakes become nonlinear by the present time. In this case, their thickness can be calculated.

scholarly journals The Cosmic Chemical Evolution as seen by the Brightest Events in the Universe

2009 ◽  
Vol 5 (S265) ◽  
pp. 139-146 ◽  
Author(s):  
Sandra Savaglio
Keyword(s):  
Chemical Evolution ◽  
Galaxy Formation ◽  
Gamma Ray ◽  
Host Galaxies ◽  
First Stars ◽  
Galaxy Surveys ◽  
Galaxy Formation And Evolution ◽  
Formation And Evolution ◽  
Field Galaxy ◽  
The Universe

AbstractGamma-ray bursts (GRBs) are the brightest events in the universe. They have been used in the last five years to study the cosmic chemical evolution, from the local universe to the first stars. The sample size is still relatively small when compared to field galaxy surveys. However, GRBs show a universe that is surprising. At z > 2, the cold interstellar medium in galaxies is chemically evolved, with a mean metallicity of about 1/10 solar. At lower redshift (z < 1), metallicities of the ionized gas are relatively low, on average 1/6 solar. Not only is there no evidence of redshift evolution in the interval 0 < z < 6.3, but also the dispersion in the ~30 objects is large. This suggests that the metallicity of host galaxies is not the physical quantity triggering GRB events. From the investigation of other galaxy parameters, it emerges that active star-formation might be a stronger requirement to produce a GRB. Several recent striking results strongly support the idea that GRB studies open a new view on our understanding of galaxy formation and evolution, back to the very primordial universe at z ~ 8.

scholarly journals A multi-messenger view of cosmic dawn: Conquering the final frontier

2021 ◽  
Vol 30 (14) ◽  
Author(s):  
Hamsa Padmanabhan
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Current Knowledge ◽  
Cosmological Parameters ◽  
Observational Cosmology ◽  
First Stars ◽  
Cosmological Principle ◽  
Normal Matter ◽  
The Universe ◽  
Einstein’S General Relativity

The epoch of Cosmic Dawn, when the first stars and galaxies were born, is widely considered as the final frontier of observational cosmology today. Mapping the period between Cosmic Dawn and the present-day provides access to more than 90% of the baryonic (normal) matter in the universe, and unlocks several thousand times more Fourier modes of information than available in today’s cosmological surveys. We review the progress in modeling baryonic gas observations as tracers of the cosmological large-scale structure from Cosmic Dawn to the present day. We illustrate how the description of dark matter haloes can be extended to describe baryonic gas abundances and clustering. This innovative approach allows us to fully utilize our current knowledge of astrophysics to constrain cosmological parameters from future observations. Combined with the information content of multi-messenger probes, this will also elucidate the properties of the first supermassive black holes at Cosmic Dawn. We present a host of fascinating implications for constraining physics beyond the [Formula: see text]CDM model, including tests of the theories of inflation and the cosmological principle, the effects of nonstandard dark matter, and possible deviations from Einstein’s general relativity on the largest scales.

scholarly journals Ab Initio Formation of Galaxies, Groups and Large-Scale Structure

2000 ◽  
Vol 174 ◽  
pp. 434-444
Author(s):  
Antonaldo Diaferio
Keyword(s):  
Dark Matter ◽  
Ab Initio ◽  
Structure Formation ◽  
Galaxy Formation ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Global Properties ◽  
Small Scales ◽  
First Time ◽  
The Universe

AbstractFor the first time, the combination of semi-analytic modelling of galaxy formation and N-body simulations of cosmic structure formation enables us to model, at the same time, both the photometric and the clustering properties of galaxies. Two Cold Dark Matter Universes provide a reasonable fit to the observed properties of galaxies, groups and clusters, including luminosities, colours, density and velocity biases. We show how the properties of galaxies and groups on small scales are inextricably connected with the global properties of the Universe.

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