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Galaxies flowing in the oriented saddle frame of the cosmic web
Kraljic, K,Pichon, C,Dubois, Y,Codis, S,Cadiou, C,Devriendt, J,Musso, M,Welker, C,Arnouts, S,Hwang, H S,Laigle, C,Peirani, S,Slyz, A,Treyer, M,Vibert, D Oxford University Press 2019 Monthly notices of the Royal Astronomical Society Vol.483 No.3
COSMOS2015 photometric redshifts probe the impact of filaments on galaxy properties
Laigle, C,Pichon, C,Arnouts, S,McCracken, H J,Dubois, Y,Devriendt, J,Slyz, A,Le Borgne, D,Benoit-Lé,vy, A,Hwang, Ho Seong,Ilbert, O,Kraljic, K,Malavasi, N,Park, Changbom,Vibert, D Oxford University Press 2018 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.474 No.4
<P>The variation of galaxy stellar masses and colour types with the distance to projected cosmic filaments are quantified using the precise photometric redshifts of the COSMOS2015 catalogue extracted from Cosmological Evolution Survey (COSMOS) field (2 deg(2)). Realistic mock catalogues are also extracted from the lightcone of the cosmological hydrodynamical simulation HORIZON-AGN. They show that the photometric redshift accuracy of the observed catalogue (sigma(z) < 0.015 at M-* > 10(10)M(circle dot) and z < 0.9) is sufficient to provide two-dimensional (2D) filaments that closely match their projected three-dimensional (3D) counterparts. Transverse stellar mass gradients are measured in projected slices of thickness 75 Mpc between 0.5 < z < 0.9, showing that the most massive galaxies are statistically closer to their neighbouring filament. At fixed stellar mass, passive galaxies are also found closer to their filament, while active star-forming galaxies statistically lie further away. The contributions of nodes and local density are removed from these gradients to highlight the specific role played by the geometry of the filaments. We find that the measured signal does persist after this removal, clearly demonstrating that proximity to a filament is not equivalent to proximity to an overdensity. These findings are in agreement with gradients measured in both 2D and 3D in the HORIZON-AGN simulation and those observed in the spectroscopic surveys VIPERS and GAMA (which both rely on the identification of 3D filaments). They are consistent with a picture in which the influence of the geometry of the large-scale environment drives anisotropic tides that impact the assembly history of galaxies, and hence their observed properties.</P>
Fouvry, J.-B.,Pichon, C.,Chavanis, P.-H. Springer-Verlag 2018 Astronomy and astrophysics Vol.609 No.-
<P>A discrete self-gravitating quasi-Keplerian razor-thin axisymmetric stellar disc orbiting a massive black hole sees its orbital structure diffuse on secular timescales as a result of a self-induced resonant relaxation. In the absence of collective effects, such a process is described by the recently derived inhomogeneous multi-mass degenerate Landau equation. Relying on Gauss’ method, we computed the associated drift and diffusion coefficients to characterise the properties of the resonant relaxation of razor-thin discs. For a disc-like configuration in our Galactic centre, we showed how this secular diffusion induces an adiabatic distortion of orbits and estimate the typical timescale of resonant relaxation. When considering a disc composed of multiple masses similarly distributed, we have illustrated how the population of lighter stars will gain eccentricity, driving it closer to the central black hole, provided the distribution function increases with angular momentum. The kinetic equation recovers as well the quenching of the resonant diffusion of a test star in the vicinity of the black hole (the “Schwarzschild barrier”) as a result of the divergence of the relativistic precessions. The dual stochastic Langevin formulation yields consistent results and offers a versatile framework in which to incorporate other stochastic processes. </P>
New Fitting Formula for Cosmic Nonlinear Density Distribution
Shin, Jihye,Kim, Juhan,Pichon, Christophe,Jeong, Donghui,Park, Changbom American Astronomical Society 2017 The Astrophysical journal Vol.843 No.1
<P>We have measured the probability distribution function (PDF) of a cosmic matter density field from a suite of N-body simulations. We propose the generalized normal distribution of version 2 (N-v2) as an alternative fitting formula to the well-known log-normal distribution. We find that N-v2 provides a significantly better fit than that of the log-normal distribution for all smoothing radii (2, 5, 10, 25 [Mpc h(-1)]) that we studied. The improvement is substantial in the underdense regions. The development of non-Gaussianities in the cosmic matter density field is captured by continuous evolution of the skewness and shift parameters of the N-v2 distribution. We present the redshift evolution of these parameters for aforementioned smoothing radii and various background cosmology models. All the PDFs measured from large and high-resolution N-body simulations that we use in this study can be obtained from the web site https://astro.kias.re.kr/jhshin.</P>
Uhlemann, C,Pajer, E,Pichon, C,Nishimichi, T,Codis, S,Bernardeau, F Oxford University Press 2018 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.474 No.3
<P>Non-Gaussianities of dynamical origin are disentangled from primordial ones using the formalism of large deviation statistics with spherical collapse dynamics. This is achieved by relying on accurate analytical predictions for the one-point probability distribution function and the two-point clustering of spherically averaged cosmic densities (sphere bias). Sphere bias extends the idea of halo bias to intermediate density environments and voids as underdense regions. In the presence of primordial non-Gaussianity, sphere bias displays a strong scale dependence relevant for both high- and low-density regions, which is predicted analytically. The statistics of densities in spheres are built to model primordial non-Gaussianity via an initial skewness with a scale dependence that depends on the bispectrum of the underlying model. The analytical formulas with the measured non-linear dark matter variance as input are successfully tested against numerical simulations. For local non-Gaussianity with a range from f(NL) = -100 to + 100, they are found to agree within 2 per cent or better for densities rho is an element of [0.5, 3] in spheres of radius 15 Mpc h(-1) down to z = 0.35. The validity of the large deviation statistics formalism is thereby established for all observationally relevant local-type departures from perfectly Gaussian initial conditions. The corresponding estimators for the amplitude of the non-linear variance sigma(8) and primordial skewness fNL are validated using a fiducial joint maximum likelihood experiment. The influence of observational effects and the prospects for a future detection of primordial non-Gaussianity from joint one-and two-point densities-in-spheres statistics are discussed.</P>
Galaxy evolution in the metric of the cosmic web
Kraljic, K.,Arnouts, S.,Pichon, C.,Laigle, C.,de la Torre, S.,Vibert, D.,Cadiou, C.,Dubois, Y.,Treyer, M.,Schimd, C.,Codis, S.,de Lapparent, V.,Devriendt, J.,Hwang, H. S.,Le Borgne, D.,Malavasi, N.,Mi Oxford University Press 2018 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.474 No.1