scholarly journals The quasar clustering and its evolution in a semi-analytic model based on ultra high-resolution N-body simulations

2015 ◽  
Vol 11 (S319) ◽  
pp. 61-61
Author(s):  
Taira Oogi ◽  
Motohiro Enoki ◽  
Tomoaki Ishiyama ◽  
Masakazu A. R. Kobayashi ◽  
Ryu Makiya ◽  
...  
Keyword(s):  
High Resolution ◽  
Qualitative Agreement ◽  
State Of The Art ◽  
High Mass ◽  
Analytic Model ◽  
Model Based ◽  
Major Merger ◽  
Low Mass ◽  
Halo Masses

AbstractWe investigate clustering properties of quasars using a new version of our semi-analytic model of galaxy and quasar formation with state-of-the-art cosmological N-body simulations (Ishiyama et al. 2015; Oogi et al. 2015). We assume that a major merger of galaxies triggers quasar activity. We find that the quasar bias does not depend significantly on the quasar luminosity, similar to observed trends. This result reflects the fact that quasars with a fixed luminosity have various Eddington ratios and thus have various host halo masses that primarily determine the quasar bias. The quasar bias increases with redshift, which is in qualitative agreement with observations. Our bias value is lower than the observed values at high redshifts, implying that we need some mechanisms that make quasars inactive in low-mass haloes and/or that make them more active in high-mass haloes.

scholarly journals Damped Ly α absorbers and atomic hydrogen in galaxies: the view of the GAEA model

2020 ◽  
Vol 497 (2) ◽  
pp. 2469-2485 ◽  
Author(s):  
Serafina Di Gioia ◽  
Stefano Cristiani ◽  
Gabriella De Lucia ◽  
Lizhi Xie
Keyword(s):  
State Of The Art ◽  
Mass Function ◽  
Distribution Model ◽  
Analytic Model ◽  
A Posteriori ◽  
The Galaxy ◽  
Low Mass ◽  
Halo Occupation Distribution ◽  
Metallicity Distribution ◽  
Good Agreement

ABSTRACT Using the GAEA semi-analytic model, we analyse the connection between Damped Ly α systems (DLAs) and H i in galaxies. Our state-of-the-art semi-analytic model is tuned to reproduce the local galaxy H i mass function, and that also reproduces other important galaxy properties, including the galaxy mass–gas metallicity relation. To produce catalogues of simulated DLAs we throw 105 random lines of sight in a composite simulated volume: dark matter haloes with log$(\frac{M_{200}}{ {\rm M}_{\odot }}) \ge 11.5$ are extracted from the Millennium Simulation, while for $9.2 \le \log (\frac{M_{200}}{ \mathrm{M}_{\odot }})\lt 11.5$ we use the Millennium II, and for $8 \le \log (\frac{M_{200}}{\mathrm{M}_{\odot }}) \lt 9.2$ a halo occupation distribution model. At 2 < z < 3, where observational data are more accurate, our fiducial model predicts the correct shape of the column density distribution function, but its normalization falls short of the observations, with the discrepancy increasing at higher redshift. The agreement with observations is significantly improved increasing both the H i masses and the disc radii of model galaxies by a factor of 2, as implemented ‘a posteriori’ in our 2M−2R model. In the redshift range of interest, haloes with $M_{200} \ge {10}^{11} \, \mathrm{M}_{\odot }$ give the major contribution to ΩDLA, and the typical DLA host halo mass is $\sim \!{10}^{11} \, \mathrm{M}_{\odot }$. The simulated DLA metallicity distribution is in relatively good agreement with observations, but our model predicts an excess of DLAs at low metallicities. Our results suggest possible improvements for the adopted modelling of the filtering mass and metal ejection in low-mass haloes.

scholarly journals The Cosmic Ballet III: halo spin evolution in the cosmic web

2021 ◽  
Author(s):  
Punyakoti Ganeshaiah Veena ◽  
Marius Cautun ◽  
Rien van de Weygaert ◽  
Elmo Tempel ◽  
Carlos S Frenk
Keyword(s):  
Initial Conditions ◽  
High Redshift ◽  
High Mass ◽  
Thin Filaments ◽  
Web Environment ◽  
Order Of Magnitude ◽  
Low Mass ◽  
Halo Masses ◽  
First Time ◽  
Environmental Dependence

Abstract We explore the evolution of halo spins in the cosmic web using a very large sample of dark matter haloes in the ΛCDM Planck-Millennium N-body simulation. We use the nexus+ multiscale formalism to identify the hierarchy of filaments and sheets of the cosmic web at several redshifts. We find that at all times the magnitude of halo spins correlates with the web environment, being largest in filaments, and, for the first time, we show that it also correlates with filament thickness as well as the angle between spin-orientation and the spine of the host filament. For example, massive haloes in thick filaments spin faster than their counterparts in thin filaments, while for low-mass haloes the reverse is true. We also have studied the evolution of alignment between halo spin orientations and the preferential axes of filaments and sheets. The alignment varies with halo mass, with the spins of low-mass haloes being predominantly along the filament spine, while those of high-mass haloes being predominantly perpendicular to the filament spine. On average, for all halo masses, halo spins become more perpendicular to the filament spine at later times. At all redshifts, the spin alignment shows a considerable variation with filament thickness, with the halo mass corresponding to the transition from parallel to perpendicular alignment varying by more than one order of magnitude. The cosmic web environmental dependence of halo spin magnitude shows little evolution for z ≤ 2 and is likely a consequence of the correlations in the initial conditions or high redshift effects.

scholarly journals Additional fluorine abundance determinations in evolved stars

2019 ◽  
Vol 625 ◽  
pp. A40 ◽  
Author(s):  
C. Abia ◽  
S. Cristallo ◽  
K. Cunha ◽  
P. de Laverny ◽  
V. V. Smith
Keyword(s):  
High Resolution ◽  
State Of The Art ◽  
Carbon Star ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Evolved Stars ◽  
Current State ◽  
Model Predictions ◽  
Solar Metallicity ◽  
Low Mass

We present new fluorine abundance measurements for a sample of carbon-rich asymptotic giant branch (AGB) stars and two other metal-poor evolved stars of Ba/CH types. The abundances are derived from IR, K-band, high-resolution spectra obtained using GEMINI-S/Phoenix and TNG/Giano-b. Our sample includes an extragalactic AGB carbon star belonging to the Sagittarius dSph galaxy. The metallicity of our stars ranges from [Fe/H] = 0.0 down to − 1.4 dex. The new measurements, together with those previously derived in similar stars, show that normal (N-type) and SC-type AGB carbon stars of near solar metallicity present similar F enhancements, discarding previous hints that suggested that SC-type stars have larger enhancements. These mild F enhancements are compatible with current chemical-evolution models pointing out that AGB stars, although relevant, are not the main sources of this element in the solar neighbourhood. Larger [F/Fe] ratios are found for lower-metallicity stars. This is confirmed by theory. We highlight a tight relation between the [F/⟨s⟩] ratio and the average s-element enhancement [⟨s⟩/Fe] for stars with [Fe/H] > −0.5, which can be explained by the current state-of-the-art low-mass AGB models assuming an extended 13C pocket. For stars with [Fe/H] < −0.5, discrepancies between observations and model predictions still exist. We conclude that the mechanism of F production in AGB stars needs further scrutiny and that simultaneous F and s-element measurements in a larger number of metal-poor AGB stars are needed to better constrain the models.

scholarly journals Predicting fully self-consistent satellite richness, galaxy growth and starformation rates from the STastical sEmi-Empirical modeL steel.

2019 ◽  
Author(s):  
Philip J Grylls ◽  
F Shankar ◽  
J Leja ◽  
N Menci ◽  
B Moster ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Empirical Model ◽  
State Of The Art ◽  
Theoretical Models ◽  
Stellar Mass ◽  
High Mass ◽  
Self Consistent ◽  
Halo Masses ◽  
Semi Empirical

Abstract Observational systematics complicate comparisons with theoretical models limiting understanding of galaxy evolution. In particular, different empirical determinations of the stellar mass function imply distinct mappings between the galaxy and halo masses, leading to diverse galaxy evolutionary tracks. Using our state-of-the-art STatistical sEmi-Empirical modeL, steel, we show fully self-consistent models capable of generating galaxy growth histories that simultaneously and closely agree with the latest data on satellite richness and star-formation rates at multiple redshifts and environments. Central galaxy histories are generated using the central halo mass tracks from state-of-the-art statistical dark matter accretion histories coupled to abundance matching routines. We show that too flat high-mass slopes in the input stellar-mass-halo-mass relations as predicted by previous works, imply non-physical stellar mass growth histories weaker than those implied by satellite accretion alone. Our best-fit models reproduce the satellite distributions at the largest masses and highest redshifts probed, the latest data on star formation rates and its bi-modality in the local Universe, and the correct fraction of ellipticals. Our results are important to predict robust and self-consistent stellar-mass-halo-mass relations and to generate reliable galaxy mock catalogues for the next generations of extra-galactic surveys such as Euclid and LSST.

scholarly journals Kinematic unrest of low mass galaxy groups

2020 ◽  
Vol 635 ◽  
pp. A36 ◽  
Author(s):  
G. Gozaliasl ◽  
A. Finoguenov ◽  
H. G. Khosroshahi ◽  
C. Laigle ◽  
C. C. Kirkpatrick ◽  
...  
Keyword(s):  
Velocity Dispersion ◽  
Group Velocity Dispersion ◽  
High Mass ◽  
New Members ◽  
Galaxy Groups ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
Low Mass ◽  
Analysis Of Dynamics ◽  
Halo Masses

In an effort to better understand the formation of galaxy groups, we examine the kinematics of a large sample of spectroscopically confirmed X-ray galaxy groups in the Cosmic Evolution Survey with a high sampling of galaxy group members up to z = 1. We compare our results with predictions from the cosmological hydrodynamical simulation of HORIZON-AGN. Using a phase-space analysis of dynamics of groups with halo masses of M200c ∼ 1012.6 − 1014.50 M⊙, we show that the brightest group galaxies (BGG) in low mass galaxy groups (M200c <  2 × 1013 M⊙) have larger proper motions relative to the group velocity dispersion than high mass groups. The dispersion in the ratio of the BGG proper velocity to the velocity dispersion of the group, σBGG/σgroup, is on average 1.48 ± 0.13 for low mass groups and 1.01 ± 0.09 for high mass groups. A comparative analysis of the HORIZON-AGN simulation reveals a similar increase in the spread of peculiar velocities of BGGs with decreasing group mass, though consistency in the amplitude, shape, and mode of the BGG peculiar velocity distribution is only achieved for high mass groups. The groups hosting a BGG with a large peculiar velocity are more likely to be offset from the Lx − σv relation; this is probably because the peculiar motion of the BGG is influenced by the accretion of new members.

SEM-Based Nanoprobing on 40, 32 and 28 nm CMOS Devices Challenges for Semiconductor Failure Analysis

2013 ◽  
Author(s):  
Erik Paul ◽  
Holger Herzog ◽  
Sören Jansen ◽  
Christian Hobert ◽  
Eckhard Langer
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Scanning Electron Microscope ◽  
Failure Analysis ◽  
Case Studies ◽  
State Of The Art ◽  
Root Cause ◽  
Highly Efficient ◽  
Technology Nodes ◽  
Scanning Electron

Abstract This paper presents an effective device-level failure analysis (FA) method which uses a high-resolution low-kV Scanning Electron Microscope (SEM) in combination with an integrated state-of-the-art nanomanipulator to locate and characterize single defects in failing CMOS devices. The presented case studies utilize several FA-techniques in combination with SEM-based nanoprobing for nanometer node technologies and demonstrate how these methods are used to investigate the root cause of IC device failures. The methodology represents a highly-efficient physical failure analysis flow for 28nm and larger technology nodes.

A Factor Analytic Model of College Studen Development

NASPA Journal ◽  
1999 ◽  
Vol 36 (4) ◽  
Author(s):  
Ellen Lavelle ◽  
Bill Rickford
Keyword(s):  
Higher Education ◽  
College Student ◽  
Student Development ◽  
Perspective Taking ◽  
College Student Development ◽  
Analytic Model ◽  
Model Based ◽  
Factor Analytic Model ◽  
Factor Analytic ◽  
Self Discovery

Models of college student development have demonstrated an insensitivity to the differences that exist among various students, although such differences are very important in a world where student bodies in higher education are increasingly diverse. The authors present a model based on The Dakota Inventory of Student Orientations, which may be useful for program developmen that fosters reflection, self discovery, perspective-taking, and collaboration among students with varying orientations towards learning.

scholarly journals Multiple objects tracking in the UAV system based on hierarchical deep high-resolution network

2021 ◽  
Author(s):  
Wei Huang ◽  
Xiaoshu Zhou ◽  
Mingchao Dong ◽  
Huaiyu Xu
Keyword(s):  
High Resolution ◽  
Object Tracking ◽  
High Performance ◽  
State Of The Art ◽  
Class Imbalance ◽  
Unified Framework ◽  
Multiple Objects ◽  
Tracking Process ◽  
Objects Tracking ◽  
Different Types

AbstractRobust and high-performance visual multi-object tracking is a big challenge in computer vision, especially in a drone scenario. In this paper, an online Multi-Object Tracking (MOT) approach in the UAV system is proposed to handle small target detections and class imbalance challenges, which integrates the merits of deep high-resolution representation network and data association method in a unified framework. Specifically, while applying tracking-by-detection architecture to our tracking framework, a Hierarchical Deep High-resolution network (HDHNet) is proposed, which encourages the model to handle different types and scales of targets, and extract more effective and comprehensive features during online learning. After that, the extracted features are fed into different prediction networks for interesting targets recognition. Besides, an adjustable fusion loss function is proposed by combining focal loss and GIoU loss to solve the problems of class imbalance and hard samples. During the tracking process, these detection results are applied to an improved DeepSORT MOT algorithm in each frame, which is available to make full use of the target appearance features to match one by one on a practical basis. The experimental results on the VisDrone2019 MOT benchmark show that the proposed UAV MOT system achieves the highest accuracy and the best robustness compared with state-of-the-art methods.

scholarly journals On the emergent system mass function: the contest between accretion and fragmentation

2020 ◽  
Vol 500 (2) ◽  
pp. 1697-1707
Author(s):  
Paul C Clark ◽  
Anthony P Whitworth
Keyword(s):  
Star Formation ◽  
Standard Deviation ◽  
Mass Distribution ◽  
Power Law ◽  
Accretion Rate ◽  
Mass Function ◽  
High Mass ◽  
New Model ◽  
System Formation ◽  
Low Mass

ABSTRACT We propose a new model for the evolution of a star cluster’s system mass function (SMF). The model involves both turbulent fragmentation and competitive accretion. Turbulent fragmentation creates low-mass seed proto-systems (i.e. single and multiple protostars). Some of these low-mass seed proto-systems then grow by competitive accretion to produce the high-mass power-law tail of the SMF. Turbulent fragmentation is relatively inefficient, in the sense that the creation of low-mass seed proto-systems only consumes a fraction, ${\sim }23{{\ \rm per\ cent}}$ (at most ${\sim }50{{\ \rm per\ cent}}$), of the mass available for star formation. The remaining mass is consumed by competitive accretion. Provided the accretion rate on to a proto-system is approximately proportional to its mass (dm/dt ∝ m), the SMF develops a power-law tail at high masses with the Salpeter slope (∼−2.3). If the rate of supply of mass accelerates, the rate of proto-system formation also accelerates, as appears to be observed in many clusters. However, even if the rate of supply of mass decreases, or ceases and then resumes, the SMF evolves homologously, retaining the same overall shape, and the high-mass power-law tail simply extends to ever higher masses until the supply of gas runs out completely. The Chabrier SMF can be reproduced very accurately if the seed proto-systems have an approximately lognormal mass distribution with median mass ${\sim } 0.11 \, {\rm M}_{\odot }$ and logarithmic standard deviation $\sigma _{\log _{10}({M/M}_\odot)}\sim 0.47$).

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