scholarly journals On the connectivity of the cosmic web: theory and implications for cosmology and galaxy formation

2018 ◽  
Vol 479 (1) ◽  
pp. 973-993 ◽  
Author(s):  
Sandrine Codis ◽  
Dmitri Pogosyan ◽  
Christophe Pichon
Keyword(s):  
Galaxy Formation ◽  
Random Fields ◽  
High Redshift ◽  
Gaussian Random Fields ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Spatial Dimensions ◽  
History Of ◽  
The Mean ◽  
High Redshift Universe

ABSTRACT Cosmic connectivity and multiplicity, i.e. the number of filaments globally or locally connected to a given cluster is a natural probe of the growth of structure and in particular of the nature of dark energy. It is also a critical ingredient driving the assembly history of galaxies as it controls mass and angular momentum accretion. The connectivity of the cosmic web is investigated here via the persistent skeleton. This tool identifies topologically the ridges of the cosmic landscape which allows us to investigate how the nodes of the cosmic web are connected together. When applied to Gaussian random fields corresponding to the high-redshift universe, it is found that on average the nodes are connected to exactly κ = 4 neighbours in two dimensions and ∼6.1 in three dimensions. Investigating spatial dimensions up to d = 6, typical departures from a cubic lattice κ = 2d are shown to scale like the power 7/4 of the dimension. These numbers strongly depend on the height of the peaks: the higher the peak the larger the connectivity. Predictions from first principles based on peak theory are shown to reproduce well the connectivity and multiplicity of Gaussian random fields and cosmological simulations. As an illustration, connectivity is quantified in galaxy lensing convergence maps and large dark haloes catalogues. As a function of redshift and scale the mean connectivity decreases in a cosmology-dependent way. As a function of halo mass, it scales like 10/3 times the log of the mass. Implications on galactic scales are discussed.

scholarly journals Semi-Analytic Galaxy Formation: Understanding the High Redshift Universe

2001 ◽  
pp. 295-306
Author(s):  
C. M. Baugh ◽  
A. J. Benson ◽  
S. Cole ◽  
C. S. Frenk ◽  
C. G. Lacey
Keyword(s):  
Galaxy Formation ◽  
High Redshift ◽  
High Redshift Universe

On Estimation of the Mean and Covariance Parameter for Gaussian Random Fields

Statistics ◽  
1998 ◽  
Vol 31 (1) ◽  
pp. 1-20 ◽  
Author(s):  
P. Ibarrola ◽  
R. Różański ◽  
R. Vélez
Keyword(s):  
Random Fields ◽  
Gaussian Random Fields ◽  
The Mean

scholarly journals Adding an Extra Dimension to What Students See through the Light Microscope: A Lab Exercise Demonstrating Critical Analysis for Microscopy Students

2011 ◽  
Vol 10 (4) ◽  
pp. 430-435
Author(s):  
Ashley Garrill
Keyword(s):  
Extra Dimension ◽  
Light Microscope ◽  
Critical Analysis ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Learning Approach ◽  
Growth Data ◽  
Constant Rate ◽  
The Mean ◽  
Biology Curriculum

This article describes an undergraduate lab exercise that demonstrates the importance of students thinking critically about what they see through a microscope. The students are given growth data from tip-growing organisms that suggest the cells grow in a pulsatile manner. The students then critique this data in several exercises that incorporate aspects of a problem-based learning approach, envisaging growth not just in two dimensions, but in three dimensions. For some cells, what appears to be pulsatile growth could also be explained by growth at a constant rate up and down in the z-axis. Depending on the diffraction pattern generated by the tip of the cell, this movement in the z-axis could go undetected. This raises the possibility that pulsatile growth seen in some species may be an artifact generated by the limitations of the light microscope. Students were subsequently asked to rate their awareness of the need to think critically about what they see through a microscope, using a scale of 1 (unaware) to 5 (very much aware). Prior to doing the lab exercise, the mean rating was 2.7; this increased to 4.4 after the lab. The students also indicated a likelihood of being more critical in their thinking in other aspects of their biology curriculum.

scholarly journals Formation and Evolution of Nucleated Galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 172-174
Author(s):  
Kenji Bekki
Keyword(s):  
Galaxy Formation ◽  
Globular Clusters ◽  
High Redshift ◽  
Galaxy Mergers ◽  
Galaxy Formation And Evolution ◽  
Central Regions ◽  
Low Mass ◽  
Formation And Evolution ◽  
Nuclear Structures ◽  
High Redshift Universe

AbstractWe discuss how stellar galactic nuclei (SGN) form and evolve during galaxy formation and evolution based on chemodynamical simulations on the central regions (1-1000 pc) of galaxies. Our simulations demonstrate that dissipative formation of SGN through rapid transfer of gas into the central 10 pc of galaxies is more consistent with recent observations of SGN than dissipationless formation of SGN through merging of globular clusters (GCs). Nuclear structures in the remnants of major galaxy mergers between low-mass, nucleated spirals are found to depend strongly on the mass-ratio of massive black holes (MBHs) to SGN in spirals in the sense that the remnants have more distinct SGN in the mergers with the smaller MBH-to-SGN-mass-ratios. During the destruction of low-mass, nucleated galaxies by strong tidal fields of giant galaxies, SGN can remain intact. The stripped SGN can be observed as bright GCs around the giant galaxies. The color-magnitude relation of metal-poor GCs (referred to as “the blue tilt”) recently discovered for bright galaxies is similar to that of SGN, which suggests that the origin of the blue tilt is closely associated with the formation processes of SGN of gas-rich, low-mass dwarfs in the high redshift universe.

The mean number of maxima above high levels in Gaussian random fields

1976 ◽  
Vol 13 (02) ◽  
pp. 377-379 ◽  
Author(s):  
A. M. Hasofer
Keyword(s):  
Asymptotic Formula ◽  
Random Fields ◽  
Gaussian Random Fields ◽  
Gaussian Field ◽  
General Proof ◽  
The Mean

An asymptotic formula for the mean number of maxima above a level of an n-dimensional stationary Gaussian field has been given by Nosko without proof. In this note a short general proof of this formula is given.

scholarly journals AGNs at the cosmic dawn: predictions for future surveys from a ΛCDM cosmological model

2020 ◽  
Vol 492 (2) ◽  
pp. 2535-2552
Author(s):  
Andrew J Griffin ◽  
Cedric G Lacey ◽  
Violeta Gonzalez-Perez ◽  
Claudia del P Lagos ◽  
Carlton M Baugh ◽  
...  
Keyword(s):  
Black Holes ◽  
Galaxy Formation ◽  
Near Infrared ◽  
Accretion Rate ◽  
High Redshift ◽  
Host Galaxies ◽  
Accretion Rates ◽  
Infrared Wavelengths ◽  
The Masses ◽  
High Redshift Universe

ABSTRACT Telescopes to be launched over the next decade and a half, such as JWST, EUCLID, ATHENA, and Lynx, promise to revolutionize the study of the high-redshift Universe and greatly advance our understanding of the early stages of galaxy formation. We use a model that follows the evolution of the masses and spins of supermassive black holes (SMBHs) within a semi-analytic model of galaxy formation to make predictions for the active galactic nucleus luminosity function at $z$ ≥ 7 in the broadband filters of JWST and EUCLID at near-infrared wavelengths, and ATHENA and Lynx at X-ray energies. The predictions of our model are relatively insensitive to the choice of seed black hole mass, except at the lowest luminosities (Lbol < 1043 erg s−1) and the highest redshifts ($z$ > 10). We predict that surveys with these different telescopes will select somewhat different samples of SMBHs, with EUCLID unveiling the most massive, highest accretion rate SMBHs, Lynx the least massive, lowest accretion rate SMBHs, and JWST and ATHENA covering objects inbetween. At $z$ = 7, we predict that typical detectable SMBHs will have masses, MBH ∼ 105–8 M⊙, and Eddington normalized mass accretion rates, $\dot{M}/\dot{M}_{\mathrm{Edd}}\sim 0.6{-}2$. The SMBHs will be hosted by galaxies of stellar mass M⋆ ∼ 108–10 M⊙, and dark matter haloes of mass Mhalo ∼ 1011–12 M⊙. We predict that the detectable SMBHs at $z$ = 10 will have slightly smaller black holes, accreting at slightly higher Eddington normalized mass accretion rates, in slightly lower mass host galaxies compared to those at $z$ = 7, and reside in haloes of mass Mhalo ∼ 1010–11 M⊙.

On Estimation of the Mean and Covariance Parameter for Gaussian Random Fields

Statistics ◽  
1999 ◽  
Vol 31 (1) ◽  
pp. 1-20
Author(s):  
P. Ibarrola ◽  
R. Rózanski ◽  
R. Vélez
Keyword(s):  
Random Fields ◽  
Gaussian Random Fields ◽  
The Mean

scholarly journals Star Formation Through Cosmic Time

2006 ◽  
Vol 2 (S235) ◽  
pp. 261-267
Author(s):  
Michael A. Dopita
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Globular Clusters ◽  
High Redshift ◽  
Cosmic Time ◽  
Star Formation History ◽  
Massive Black Holes ◽  
Massive Galaxies ◽  
History Of ◽  
Population Iii Stars

AbstractThis paper reviews the star formation history of the Universe, from the first stars to the current day, with emphasis on the critical analysis of the techniques that have been used to determine it, especially considering the role of dust. We consider the first population of stars, the Population III stars, were formed at redshifts ranging as high as z ~ 60, the formation of the Globular Clusters, the main epoch of galaxy formation. In the sub-mm galaxies and high-redshift radio galaxies the collapse of massive galaxies was surprisingly rapid, and that the growth of super-massive black holes at their centers provides the energy input to eject the galactic interstellar medium while at the same time precipitating a final burst of star formation and the ejection of their ISM so that the subsequent evolution of these galaxies is passive.

About approximation of 3-D random fields and statistical simulation

2003 ◽  
Vol 11 (3) ◽  
Author(s):  
Zoya O. Vyzhva
Keyword(s):  
Random Fields ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Statistical Simulation ◽  
Gaussian Random Fields ◽  
Statistical Characteristics ◽  
Mean Square ◽  
The Mean ◽  
Isotropic Random ◽  
Three Dimensional Space

The estimator of the mean-square approximation of 3-D homogeneous and isotropic random field is investigated. The problem of statistical simulation of realizations of random fields in threedimensional space is considered. The algorithm for the receiving of this realization has been formulated, which has been constructed on the base the mean-square approximation of random fields estimator. It has been constructed the statistical model for the Gaussian random fields in three-dimensional space, which has been given by its statistical characteristics.

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