scholarly journals Correlations between triaxial shapes and formation history of dark matter haloes

2020 ◽  
Vol 500 (1) ◽  
pp. 1029-1037
Author(s):  
Erwin T Lau ◽  
Andrew P Hearin ◽  
Daisuke Nagai ◽  
Nico Cappelluti

ABSTRACT The shape of dark matter (DM) haloes plays a critical role in constraining cosmology with upcoming large-scale structure surveys. In this paper, we study the correlations between the triaxial shapes and formation histories in DM haloes in the MultiDark Planck 2 N-body cosmological simulation. We find that halo ellipticity is strongly correlated with halo properties that serve as proxies of halo formation history, such as halo concentration and the normalized peak-centroid offset. These correlations are nearly independent of the halo density peak height. We present a simple model for the correlation between halo ellipticity and concentration using conditional abundance matching, and provide fitting formulae for the multidimensional distributions of triaxial halo shape as a function of halo peak height. We apply our halo shape model to gauge the effects of halo ellipticity and orientation bias on the excess surface mass density profiles in cluster-sized haloes. Our model should be useful for exploring the impact of triaxial halo shape on cosmological constraints in upcoming weak lensing surveys of galaxy clusters.

2019 ◽  
Vol 622 ◽  
pp. A104 ◽  
Author(s):  
P. Simon ◽  
H. Saghiha ◽  
S. Hilbert ◽  
P. Schneider ◽  
C. Boever ◽  
...  

The matter environment of galaxies is connected to the physics of galaxy formation and evolution. In particular, the average matter distribution around galaxy pairs is a strong test for galaxy models. Utilising galaxy-galaxy-galaxy lensing as a direct probe, we map out the distribution of correlated surface mass-density around galaxy pairs in the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). We have compared, for the first time, these so-called excess mass maps to predictions provided by a recent semi-analytic model, which is implanted within the dark-matter Millennium Simulation. We analysed galaxies with stellar masses between 109 − 1011 M⊙ in two photometric redshift bins, for lens redshifts z ≲ 0.6. The projected separation of the galaxy pairs ranges between 170 − 300 h−1 kpc, thereby focusing on pairs inside groups and clusters. To allow us a better interpretation of the maps, we discuss the impact of chance pairs, that is galaxy pairs that appear close to each other in projection only. We have introduced an alternative correlation map that is less affected by projection effects but has a lower signal-to-noise ratio. Our tests with synthetic data demonstrate that the patterns observed in both types of maps are essentially produced by correlated pairs which are close in redshift (Δz ≲ 5 × 10−3). We also verify the excellent accuracy of the map estimators. In an application to the galaxy samples in the CFHTLenS, we obtain a 3σ − 6σ significant detection of the excess mass and an overall good agreement with the galaxy model predictions. There are, however, a few localised spots in the maps where the observational data disagrees with the model predictions on a ≈3.5σ confidence level. Although we have no strong indications for systematic errors in the maps, this disagreement may be related to the residual B-mode pattern observed in the average of all maps. Alternatively, misaligned galaxy pairs inside dark matter halos or lensing by a misaligned distribution of the intra-cluster gas might also cause the unanticipated bulge in the distribution of the excess mass between lens pairs.


2008 ◽  
Vol 4 (S254) ◽  
pp. 67-72 ◽  
Author(s):  
Shardha Jogee

AbstractHierarchical ΛCDM models provide a successful paradigm for the growth of dark matter on large scales, but they face important challenges in predicting how the baryonic components of galaxies evolve. I present constraints on two aspects of this evolution: (1) The interaction history of galaxies over the last 7 Gyr and the impact of interactions on their star formation properties, based on Jogeeet al. (2008a, b); (2) Constraints on the origin of bulges in hierarchical models and the challenge posed in accounting for galaxies with low bulge-to-total ratios, based on Weinzirl, Jogee, Khochar, Burkert, & Kormendy (2008, hereafter WJKBK08).


2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Partha Konar ◽  
Ananya Mukherjee ◽  
Abhijit Kumar Saha ◽  
Sudipta Show

Abstract We propose an appealing alternative scenario of leptogenesis assisted by dark sector which leads to the baryon asymmetry of the Universe satisfying all theoretical and experimental constraints. The dark sector carries a non minimal set up of singlet doublet fermionic dark matter extended with copies of a real singlet scalar field. A small Majorana mass term for the singlet dark fermion, in addition to the typical Dirac term, provides the more favourable dark matter of pseudo-Dirac type, capable of escaping the direct search. Such a construction also offers a formidable scope to radiative generation of active neutrino masses. In the presence of a (non)standard thermal history of the Universe, we perform the detailed dark matter phenomenology adopting the suitable benchmark scenarios, consistent with direct detection and neutrino oscillations data. Besides, we have demonstrated that the singlet scalars can go through CP-violating out of equilibrium decay, producing an ample amount of lepton asymmetry. Such an asymmetry then gets converted into the observed baryon asymmetry of the Universe through the non-perturbative sphaleron processes owing to the presence of the alternative cosmological background considered here. Unconventional thermal history of the Universe can thus aspire to lend a critical role both in the context of dark matter as well as in realizing baryogenesis.


Author(s):  
Luigi Rizzi

This chapter illustrates the technical notion of ‘explanatory adequacy’ in the context of the other forms of empirical adequacy envisaged in the history of generative grammar: an analysis of a linguistic phenomenon is said to meet ‘explanatory adequacy’ when it comes with a reasonable account of how the phenomenon is acquired by the language learner. It discusses the relevance of arguments from the poverty of the stimulus, which bear on the complexity of the task that every language learner successfully accomplishes, and therefore define critical cases for evaluating the explanatory adequacy of a linguistic analysis. After illustrating the impact that parametric models had on the possibility of achieving explanatory adequacy on a large scale, the chapter addresses the role that explanatory adequacy plays in the context of the Minimalist Program, and the interplay that the concept has with the further explanation ‘beyond explanatory adequacy’ that minimalist analysis seeks.


Author(s):  
D.V. Budianskyi

The characteristic features of I. Kavaleridze’s drama is considered in the article. It is noted that there are signs of the artist’s individuality, attraction to expressionist forms, artistic techniques characteristic for the art of sculpture: symbolism, monumentality, hyperbole. I. Kavaleridze was well versed in the drama laws, understood the specifics of the stage events construction, had a large arsenal of literary means, thanks to which the characters’ monologues and dialogues were extremely expressive and colorful. In his work, he implemented original solutions that were ahead of time. Therefore, many of the artist’s ideas and achievements received due recognition only after his death. I. Kavaleridze’s creative heritage covers a wide range of both purely artistic and general philosophical problems. Among them the formation of the era of modernism and its features in the Ukrainian art of the early XX century, the impact of revolutionary ideas on the work of the 1920s, the role of spiritual leaders of the Ukrainian people T. Shevchenko and G. Skovoroda in the formation of national consciousness, political and ideological pressure on figurative art language and the formation of a socialist-realist canon, etc. The analysis of the productions of I. Kavalerizde’s plays “The First Furrow” and “Gregory and Paraskeva” on the stage of the Mykhailo Shchepkin Sumy Theater of Drama and Musical Comedy in 1970-1972. The article notes that these plays were staged in Sumy for the first time in the history of Ukrainian theater. The premiere of “The First Furrow” (the play was called “Old Men”) took place on March 19, 1970. The figure of the national genius Hryhoriy Skov oroda was als o embodied for the first time on t he stage in Sumy in th e play “Hryhoriy and Paraskeva”. It premiered on October 21, 1972. I. Rybchynsky, Honored Artist of the USSR, performed the production. Creating generalized historical outlines of people’s life, features of life at that time, depicting psychological portraits of people in various, sometimes-dramatic collisions, in the productions of I. Kavaleridze’s plays on the Sumy stage the emphasis was on universal values such as virtue, love. The main character was the Ukrainian people, who nurtured such large-scale historical figures, gave them strength and wisdom for great achievements. Based on publications in periodicals of that time, memoirs of Ukrainian directors, the peculiarities of the director’s interpretation, stenographic and musical design of these plays on the Sumy stage are considered. Considerable attention is paid to the analysis of acting works in I. Kavaleridze’s plays. In particular, the peculiarities of the actor’s embodiment of the image of the national genius Hryhoriy Skovoroda on the stage are presented. It is noted that I. Kavaleridze’s plays, created in a difficult political, social and ideological context, are rightly considered to be highly artistic works of Ukrainian drama. Their staging was carried out on various theatrical stages, including Mykhailo Shchepkin Sumy Theater of Drama and Musical Comedy is an important page of national theatrical art.


1999 ◽  
Vol 190 ◽  
pp. 470-472
Author(s):  
Eva K. Grebel ◽  
Wolfgang Brandner

A new age calibration of Cepheids and supergiants is used to study the large-scale recent star formation history of the LMC and the SMC. We find evidence for migration of star formation along the LMC bar as well as for the existence of long-lived (≈ 200 Myr) extended star-forming features.


2019 ◽  
Vol 5 (4) ◽  
pp. 695-702 ◽  
Author(s):  
Julien Morency-Laflamme ◽  
Theodore McLauchlin

Abstract Does ethnic stacking in the armed forces help prevent military defection? Recent research, particularly in Africa and the Middle East, suggests so; by favoring in-groups, regimes can keep in-group soldiers loyal. In-group loyalty comes at the cost of antagonizing members of out-groups, but many regimes gladly run that risk. In this research note, we provide the first large-scale evidence on the impact of ethnic stacking on the incidence of military defection during uprisings from below, using data on fifty-seven popular uprisings in Africa since formal independence. We find clear evidence for the downside: ethnic stacking is associated with more frequent defection if out-group members are still dominant in the armed forces. We find more limited support for the hypothesized payoff. Ethnic stacking may reduce the risk of defection, but only in regimes without a recent history of coup attempts. Future research should therefore trace the solidification of ethnic stacking over time.


2019 ◽  
Vol 489 (1) ◽  
pp. 459-469 ◽  
Author(s):  
Tereasa G Brainerd ◽  
Masaya Yamamoto

ABSTRACT We investigate the locations of satellite galaxies in the z = 0 redshift slice of the hydrodynamical Illustris-1 simulation. As expected from previous work, the satellites are distributed anisotropically in the plane of the sky, with a preference for being located near the major axes of their hosts. Due to misalignment of mass and light within the hosts, the degree of anisotropy is considerably less when satellite locations are measured with respect to the hosts’ stellar surface mass density than when they are measured with respect to the hosts’ dark matter surface mass density. When measured with respect to the hosts’ dark matter surface mass density, the mean satellite location depends strongly on host stellar mass and luminosity, with the satellites of the faintest, least massive hosts showing the greatest anisotropy. When measured with respect to the hosts’ stellar surface mass density, the mean satellite location is essentially independent of host stellar mass and luminosity. In addition, the satellite locations are largely insensitive to the amount of stellar mass used to define the hosts’ stellar surface mass density, as long as at least 50–70 per cent of the hosts’ total stellar mass is used. The satellite locations are dependent upon the stellar masses of the satellites, with the most massive satellites having the most anisotropic distributions.


2020 ◽  
Vol 493 (3) ◽  
pp. 4551-4569 ◽  
Author(s):  
Danail Obreschkow ◽  
Pascal J Elahi ◽  
Claudia del P Lagos ◽  
Rhys J J Poulton ◽  
Aaron D Ludlow

ABSTRACT Linking the properties of galaxies to the assembly history of their dark matter haloes is a central aim of galaxy evolution theory. This paper introduces a dimensionless parameter s ∈ [0, 1], the ‘tree entropy’, to parametrize the geometry of a halo’s entire mass assembly hierarchy, building on a generalization of Shannon’s information entropy. By construction, the minimum entropy (s = 0) corresponds to smoothly assembled haloes without any mergers. In contrast, the highest entropy (s = 1) represents haloes grown purely by equal-mass binary mergers. Using simulated merger trees extracted from the cosmological N-body simulation SURFS, we compute the natural distribution of s, a skewed bell curve peaking near s = 0.4. This distribution exhibits weak dependences on halo mass M and redshift z, which can be reduced to a single dependence on the relative peak height δc/σ(M, z) in the matter perturbation field. By exploring the correlations between s and global galaxy properties generated by the SHARK semi-analytic model, we find that s contains a significant amount of information on the morphology of galaxies – in fact more information than the spin, concentration, and assembly time of the halo. Therefore, the tree entropy provides an information-rich link between galaxies and their dark matter haloes.


2012 ◽  
Vol 8 (S295) ◽  
pp. 300-303
Author(s):  
Rosa González Delgado ◽  
Enrique Pérez ◽  
Roberto Cid Fernandes ◽  
Rubén García-Benito ◽  
André de Amorim ◽  
...  

AbstractThe Calar Alto Legacy Integral Field Area (CALIFA) project is an ongoing 3D spectroscopic survey of 600 nearby galaxies of all kinds. This pioneer survey is providing valuable clues on how galaxies form and evolve. Processed through spectral synthesis techniques, CALIFA datacubes allow us to, for the first time, spatially resolve the star formation history of galaxies spread across the color-magnitude diagram. The richness of this approach is already evident from the results obtained for the first ~ 1/6 of the sample. Here we show how the different galactic spatial sub-components (“bulge” and “disk”) grow their stellar mass over time. We explore the results stacking galaxies in mass bins, finding that, except at the lowest masses, galaxies grow inside-out, and that the growth rate depends on a galaxy's mass. The growth rate of inner and outer regions differ maximally at intermediate masses. We also find a good correlation between the age radial gradient and the stellar mass density, suggesting that the local density is a main driver of galaxy evolution.


Sign in / Sign up

Export Citation Format

Share Document