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The Local Theory of the Cosmic Skeleton
D. Pogosyan, C. Pichon, C. Gay +4
The local theory of the critical lines of 2D and 3D Gaussian fields that underline the cosmic structures is presented. In the context of cosmological matter distribution the subset…
Phase-space structures I: A comparison of 6D density estimators
M. Maciejewski, S. Colombi, C. Alard +2
This paper reviews and analyses methods used to identify neighbours in 6D space and estimate the corresponding phase-space density. It compares SPH methods to 6D Delaunay tessellat…
The fully connected N-dimensional skeleton: probing the evolution of the cosmic web
T. Sousbie, S. Colombi, C. Pichon
A method to compute the full hierarchy of the critical subsets of a density field is presented. It is based on a watershed technique and uses a probability propagation scheme to im…
Cold streams in early massive hot haloes as the main mode of galaxy formation
A. Dekel, Y. Birnboim, G. Engel +7
The massive galaxies in the young universe, ten billion years ago, formed stars at surprising intensities. Although this is commonly attributed to violent mergers, the properties o…
Full-Sky Weak Lensing Simulation with 70 Billion Particles
Romain Teyssier, Sandrine Pires, Simon Prunet +7
We have performed a 70 billion dark-matter particles N-body simulation in a 2 Gpc periodic box, using the concordance, cosmological model as favored by the latest WMAP3 re…
Initial Conditions for Large Cosmological Simulations
S. Prunet, C. Pichon, D. Aubert +3
This technical paper describes a software package that was designed to produce initial conditions for large cosmological simulations in the context of the Horizon collaboration. Th…
Numerical investigation of lenses with substructures using the perturbative method
Sébastien Peirani, Christophe Alard, Christophe Pichon +2
We present a statistical study of the effects induced by substructures on the deflection potential of dark matter halos in the strong lensing regime. This investigation is based on…
On the Onset of Stochasticity in CDM Cosmological Simulations
Jerome Thiebaut, Christophe Pichon, Thierry Sousbie +2
The onset of stochasticity is measured in CDM cosmological simulations using a set of classical observables. It is quantified as the local derivative of the logarithm of the dis…
Bimodal gas accretion in the Horizon-MareNostrum galaxy formation simulation
P. Ocvirk, C. Pichon, R. Teyssier
(abridged) The physics of diffuse gas accretion and the properties of the cold and hot modes of accretion onto proto-galaxies between z=2 and z=5.4 is investigated using the large…
Recovering the topology of the IGM at z~2
S. Caucci, S. Colombi, C. Pichon +3
We investigate how well the 3D density field of neutral hydrogen in the Intergalactic Medium (IGM) can be reconstructed using the Lyman-alpha absorptions observed along lines of si…
The three dimensional skeleton: tracing the filamentary structure of the universe
T. Sousbie, C. Pichon, S. Colombi +2
The skeleton formalism aims at extracting and quantifying the filamentary structure of the universe is generalized to 3D density fields; a numerical method for computating a local…
Lattice Melting and Rotation in Perpetually Pulsating Equilibria
C. Pichon, D. Lynden-Bell, J. Pichon +1
Systems whose potential energies consists of pieces that scale as r^-2 together with pieces that scale as r^2, show no violent relaxation to Virial equilibrium but may pulsate at c…
Transverse and longitudinal correlation functions in the Intergalactic Medium from 32 close pairs of high-redshift quasars
F. Coppolani, P. Petitjean, F. Stoehr +6
We present the transverse flux correlation function of the Lyman-alpha forest in quasar absorption spectra at z~2.1 from VLT-FORS and VLT-UVES observations of a total of 32 pairs o…
The 3D skeleton of the SDSS
Thierry Sousbie, Christophe Pichon, Hélène Courtois +2
The length of the three-dimensional filaments observed in the fourth public data-release of the SDSS is measured using the {\em local skeleton} method. It consists in defining the…
The correlation of the Lyman-alpha forest and metals in close pairs of hight-redshift quasars
F. Coppolani, P. Petitjean, F. Stoehr +6
We derive the transverse flux correlation function in the Lyman-alpha forest at z~2.1 from VLT-FORS observations of a total of 32 pairs of quasars. The shape and correlation length…
STEllar Content and Kinematics from high resolution galactic spectra via Maximum A Posteriori
P. Ocvirk, C. Pichon, A. Lancon +1
We introduce STECKMAP (STEllar Content and Kinematics via Maximum A Posteriori), a method to recover the kinematical properties of a galaxy simultaneously with its stellar content…
Stellar Content from high resolution galactic spectra via Maximum A Posteriori
P. Ocvirk, C. Pichon, A. Lancon +1
This paper describes STECMAP (STEllar Content via Maximum A Posteriori), a flexible, non-parametric inversion method for the interpretation of the integrated light spectra of galax…
The Sources of Intergalactic Metals
E. Scannapieco, C. Pichon, B. Aracil +5
We study the clustering properties of metals in the intergalactic medium (IGM) as traced by 619 CIV, 81 SiIV, N >= 10^12 cm^-2 and 316 MgII, and 82 FeII N >= 10^11.5 cm^-2 absorpti…
Modelling and interpreting optical spectra of galaxies at R=10000
Ariane Lancon, Pierre Ocvirk, Damien Le Borgne +5
One way to extract more information from the integrated light of galaxies is to improve the spectral resolution at which observations and analysis are carried out. The population s…
The origin and implications of dark matter anisotropic cosmic infall on ~L* haloes
Dominique Aubert, Christophe Pichon, Stephane Colombi
We measure the anisotropy of dark matter flows on small scales in the near environment of haloes using a large set of simulations. We rely on two different approaches to quantify t…
Stellar populations and their kinematics from high and medium resolution spectra: mixed inversions
P. Ocvirk, C. Pichon, A. Lancon
We present inversion techniques aiming at recovering the stellar content (age, metallicity, extinction) and kinematics of a stellar population from its absorption line spectrum. Th…
The Clustering of Intergalactic Metals
Christophe Pichon, Evan Scannapieco, Bastien Aracil +4
We measure the spatial clustering of metals in the intergalactic medium from z = 1.7 to 3.0, as traced by 643 CIV and 104 SiIV N >= 10^12 cm^-2 absorption systems in 19 high signal…
Metals in the Intergalactic Medium
Bastien Aracil, Patrick Petitjean, Christophe Pichon +1
We use high spectral resolution (R=45000) and high signal-to-noise ratio (S/N \~ 35-70 per pixel) spectra of 19 high-redshift (2.1<z_em<3.2) quasars to investigate the metal conten…
On the kinematic deconvolution of the local neighbourhood luminosity function
C. Pichon, A. Siebert O. Bienayme
A method for inverting the statistical star counts equation, including proper motions, is presented; in order to break the degeneracy in that equation it uses the supplementary con…