Dominique Aubert

University of Strasbourg | UNISTRA · Observatoire astronomique

Dispersion measures (DM) of fast radio bursts (FRBs) probe the density of electrons in the intergalactic medium (IGM) along their lines-of-sight, including the average density versus distance to the source and its variations in direction. While previous study focused on low-redshift, FRBs are potentially detectable out to high redshift, where their...

We investigate the spatial offsets between dust and ultraviolet (UV) emission in high-redshift galaxies using the Cosmic Dawn III (CoDa III) simulation, a state-of-the-art fully coupled radiation-hydrodynamics cosmological simulation. Recent observations have revealed puzzling spatial disparities between ALMA dust continuum and UV emission as seen...

We present a new suite of late-end reionization simulations performed with aton-he, a revised version of the GPU-based radiative transfer code aton that includes helium. The simulations are able to reproduce the Lyα flux distribution of the E-XQR-30 sample of QSO absorption spectra at 5 ≲ z ≲ 6.2, and show that a large variety of reionization model...

When the first galaxies formed and starlight escaped into the intergalactic medium to reionize it, galaxy formation and reionization were both highly inhomogeneous in time and space, and fully-coupled by mutual feedback. To show how this imprinted the UV luminosity function (UVLF) of reionization-era galaxies, we use our large-scale, radiation-hydr...

During the Epoch of reionisation, the intergalactic medium is reionised by the UV radiation from the first generation of stars and galaxies. One tracer of the process is the 21 cm line of hydrogen that will be observed by the Square Kilometre Array (SKA) at low frequencies, thus imaging the distribution of ionised and neutral regions and their evol...

Context. In the next decade, radio telescopes, such as the Square Kilometer Array (SKA), will explore the Universe at high redshift, and particularly during the epoch of reionisation (EoR). The first structures emerged during this epoch, and their radiation reionised the previously cold and neutral gas of the Universe, creating ionised bubbles that...

In recent years, interstellar dust has become a crucial topic in the study of the high redshift Universe. Evidence points to the existence of large dust masses in massive star forming galaxies already during the Epoch of Reionization, potentially affecting the escape of ionising photons into the intergalactic medium. Moreover, correctly estimating...

We present the Sherwood-Relics simulations, a new suite of large cosmological hydrodynamical simulations aimed at modelling the intergalactic medium (IGM) during and after the cosmic reionization of hydrogen. The suite consists of over 200 simulations that cover a wide range of astrophysical and cosmological parameters. It also includes simulations...

In the next decade, radio telescopes like the Square Kilometer Array (SKA) will explore the Universe at high redshift, and particularly during the Epoch of Reionisation (EoR). The first structures emerged during this epoch, and their radiations have reionised the previously cold and neutral gas of the Universe creating ionised bubbles that percolat...

Recent determinations of the mean free path of ionising photons (mfp) in the intergalactic medium (IGM) at $\rm z=6$ are lower than many theoretical predictions. In order to gain insight, we investigate the evolution of the mfp in our new massive fully coupled radiation hydrodynamics cosmological simulation of reionization: Cosmic Dawn III (CoDa II...

Patchy cosmic reionization resulted in the ionizing UV background asynchronous rise across the Universe. The latter might have left imprints visible in present day observations. Several numerical simulation-based studies show correlations between reionization time and overdensities and object masses today. To remove the mass from the study, as it m...

Patchy cosmic reionization resulted in the ionizing UV background asynchronous rise across the Universe. The latter might have left imprints visible in present day observations. Several numerical simulation-based studies show correlations between reionization time and overdensities and object masses today. To remove the mass from the study, as it m...

We present the Sherwood-Relics simulations, a new suite of large cosmological hydrodynamical simulations aimed at modelling the intergalactic medium (IGM) during and after the cosmic reionization of hydrogen. The suite consists of over 200 simulations that cover a wide range of astrophysical and cosmological parameters. It also includes simulations...

In recent years, interstellar dust has become a crucial topic in the study of the high and very high redshift Universe. Evidence points to the existence of high dust masses in massive star forming galaxies already during the Epoch of Reionization, potentially affecting the escape of ionising photons into the intergalactic medium. Moreover, correctl...

Recent determinations of the mean free path of ionising photons (mfp) in the intergalactic medium (IGM) at $\rm z=6$ are lower than many theoretical predictions. In order to gain insight into this issue, we investigate the evolution of the mfp in our new massive fully coupled radiation hydrodynamics cosmological simulation of reionization: Cosmic D...

During the EoR, the first stars and galaxies appear while creating ionized bubbles that will eventually percolate near z=6. These ionized bubbles and percolation process are nowadays under a lot of scrutiny since observations of the HI gas will be carried on in the next decade with e.g. the SKA radiotelescope. Studies of the EoR are performed on se...

The decline in abundance of Lyman-α (Lyα) emitting galaxies at z ≳ 6 is a powerful and commonly used probe to constrain the progress of cosmic reionization. We use the CoDaII simulation, which is a radiation hydrodynamic simulation featuring a box of ∼94 comoving Mpc side length, to compute the Lyα transmission properties of the intergalactic mediu...

The high redshift Lyman-α forest, in particular the Gunn-Peterson trough, is the most unambiguous signature of the neutral to ionized transition of the intergalactic medium (IGM) taking place during the Epoch of Reionization (EoR). Recent studies have shown that reproducing the observed Lyman-α opacity distributions after overlap required a non-mon...

Our understanding of the intergalactic medium at redshifts z = 5–6 has improved considerably in the last few years due to the discovery of quasars with z > 6 that enable Lyman-α forest studies at these redshifts. A realisation from this has been that hydrogen reionization could end much later than previously thought, so that large “islands” of cold...

A late end to reionisation at redshift z ≃ 5.3 is consistent with observed spatial variations in the Lyα forest transmission and the deficit of Lyα emitting galaxies around extended Lyα absorption troughs at z = 5.5. In this model, large islands of neutral hydrogen should persist in the diffuse intergalactic medium (IGM) until z ≃ 6. We use a novel...

A late end to reionisation at redshift $z\simeq 5.3$ is consistent with observed spatial variations in the Ly$\alpha$ forest transmission and the deficit of Ly$\alpha$ emitting galaxies around extended Ly$\alpha$ absorption troughs at $z=5.5$. In this model, large islands of neutral hydrogen should persist in the diffuse intergalactic medium (IGM)...

The high redshift Lyman-alpha forest, in particular the Gunn-Peterson trough, is the most unambiguous signature of the neutral to ionized transition of the intergalactic medium (IGM) taking place during the Epoch of Reionization (EoR). Recent studies, e.g. Kulkarni et al. (2019a) and Keating et al. (2019), showed that reproducing the observed Lyman...

The process of heating and reionization of the Universe at high redshift links small scale structures/galaxy formation and large scale inter-galactic medium properties. Even if the first one is difficult to observe, an observation window is opening on the second one, with the promising development of current and future radio telescopes. They will p...

Our understanding of the intergalactic medium at redshifts $z=5$-$6$ has improved considerably in the last few years due to the discovery of quasars with $z>6$ that enable Lyman-$\alpha$ forest studies at these redshifts. A realisation from this has been that hydrogen reionization could end much later than previously thought, so that large "islands...

We present an analysis of the evolution of the Lyman-series forest into the epoch of reionization using cosmological radiative transfer simulations in a scenario where reionization ends late. We explore models with different mid-points of reionization and gas temperatures. We find that once the simulations have been calibrated to match the mean flu...

Cosmic Dawn II yields the first statistically meaningful determination of the relative contribution to reionization by galaxies of different halo mass, from a fully coupled radiation-hydrodynamics simulation of the epoch of reionization large enough (∼100 Mpc) to model global reionization while resolving the formation of all galactic haloes above $...

Cosmic Dawn II (CoDa II) is a new, fully coupled radiation-hydrodynamics simulation of cosmic reionization and galaxy formation and their mutual impact, to redshift z < 6. With 40963 particles and cells in a 94 Mpc box, it is large enough to model global reionization and its feedback on galaxy formation while resolving all haloes above 108 M⊙. Usin...

The decline in abundance of Lyman-$\alpha$ (Ly$\alpha$) emitting galaxies at $z \gtrsim 6$ is a powerful and commonly used probe to constrain the progress of cosmic reionization. We use the CoDaII simulation, which is a radiation hydrodynamic simulation featuring a box of $\sim 94$ comoving Mpc side length, to compute the Ly$\alpha$ transmission pr...

Cosmic Dawn ("CoDa") II yields the first statistically-meaningful determination of the relative contribution to reionization by galaxies of different halo mass, from a fully-coupled radiation-hydrodynamics simulation of the epoch of reionization large enough ($\sim 100$ Mpc) to model global reionization while resolving the formation of all galactic...

A long (110 cMpc h−1) and deep absorption trough in the Ly α forest has been observed extending down to redshift 5.5 in the spectrum of ULAS J0148+0600. Although no Ly α transmission is detected, Ly β spikes are present which has led to claims that the gas along this trough must be ionized. Using high-resolution cosmological radiative transfer simu...

We present an analysis of the evolution of the Lyman-series forest into the epoch of reionization using cosmological radiative transfer simulations in a scenario where reionization ends late. We explore models with different midpoints of reionization and gas temperatures. We find that once the simulations have been calibrated to match the mean flux...

We present a deep learning model trained to emulate the radiative transfer during the epoch of cosmological reionization. CRADLE (Cosmological Reionization And Deep LEarning) is an auto-encoder convolutional neural network that uses 2D maps of the star number density and the gas density field at z = 6 as inputs and that predicts 3D maps of the time...

A long (110 cMpc/$h$) and deep absorption trough in the Ly$\alpha$ forest has been observed extending down to redshift 5.5 in the spectrum of ULAS J0148+0600. Although no Ly$\alpha$ transmission is detected, Ly$\beta$ spikes are present which has led to claims that the gas along this trough must be ionized. Using high resolution cosmological radiat...

We present a deep learning model trained to emulate the radiative transfer during the epoch of cosmological reionization. CRADLE (Cosmological Reionization And Deep LEarning) is an autoencoder convolutional neural network that uses two-dimensional maps of the star number density and the gas density field at z=6 as inputs and that predicts 3D maps o...

High-redshift QSO spectra show large spatial fluctuations in the Ly-alpha opacity of the intergalactic medium on surprisingly large scales at z>~5.5. We present a radiative transfer simulation of cosmic reionization driven by galaxies that reproduces this large scatter and the rapid evolution of the Ly-alpha opacity distribution at 5<z<6. The simul...

High-redshift quasi-stellar object (QSO) spectra show large spatial fluctuations in the Ly α opacity of the intergalactic medium on surprisingly large scales at |$z$| ≳ 5.5. We present a radiative transfer simulation of cosmic reionization driven by galaxies that reproduces this large scatter and the rapid evolution of the Ly α opacity distribution...

Cosmic Dawn II (CoDa II) is a new, fully-coupled radiation-hydrodynamics simulation of cosmic reionization and galaxy formation and their mutual impact, to redshift z < 6. With $4096^3$ particles and cells in a 94 Mpc box, it is large enough to model global reionization and its feedback on galaxy formation while resolving all haloes above $10^8$ M$...

Photoheating associated with reionization suppressed star formation in low-mass galaxies. Reionization was inhomogeneous, however, affecting different regions at different times. To establish the causal connection between reionization and suppression, we must take this local variation into account. We analyze the results of CoDa ('Cosmic Dawn') I,...

High-redshift QSO spectra show large spatial fluctuations in the Ly$\alpha$ opacity of the intergalactic medium on surprisingly large scales at $z\gtrsim 5.5$. We present a radiative transfer simulation of cosmic reionization driven by galaxies that reproduces this large scatter and the rapid evolution of the Ly$\alpha$ opacity distribution at $5<z...

Photoheating associated with reionization suppressed star formation in low-mass galaxies. Reionization was inhomogeneous, however, affecting different regions at different times. To establish the causal connection between reionization and suppression, we must take this local variation into account. We analyze the results of CoDa (`Cosmic Dawn') I,...

Context . The reduced speed of light approximation is used in a variety of simulations of the epoch of reionization and galaxy formation. Its popularity stems from its ability to drastically reduce the computing cost of a simulation by allowing the use of larger and therefore fewer timesteps to reach a solution. This approximation is physically mot...

Context . Coupled radiative-hydrodynamics simulations of the epoch of reionization aim to reproduce the propagation of ionization fronts during the transition before the overlap of HII regions. Many of these simulations use moment-based methods to track radiative transfer processes using explicit solvers and are therefore subject to strict stabilit...

Today's galaxies experienced cosmic reionization at different times in different locations. For the first time, reionization ($50\%$ ionized) redshifts, $z_R$, at the location of their progenitors are derived from new, fully-coupled radiation-hydrodynamics simulation of galaxy formation and reionization at $z > 6$, matched to N-body simulation to z...

We study the inhomogeneity of the reionization process by comparing the reionization times of z = 0 galaxies as a function of their mass. For this purpose, we combine the results of the CODA-I AMR radiative hydrodynamics simulation of the Reionization with the halo merger trees of a pure dark matter tree-code z = 0 simulation evolved from the same...

EMMA is a cosmological simulation code aimed at investigating the reionization epoch. It handles simultaneously collisionless and gas dynamics, as well as radiative transfer physics using a moment-based description with the M1 approximation. Field quantities are stored and computed on an adaptive three-dimensional mesh and the spatial resolution ca...

Cosmic reionization by starlight from early galaxies affected their evolution, thereby impacting reionization, itself. Star formation suppression, for example, may explain the observed underabundance of Local Group dwarfs relative to N-body predictions for Cold Dark Matter. Reionization modelling requires simulating volumes large enough ~(100 Mpc)^...

EMMA is a cosmological simulation code aimed at investigating the reionization epoch. It handles simultaneously collisionless and gas dynamics, as well as radiative transfer physics using a moment-based description with the M1 approximation. Field quantities are stored and computed on an adaptive 3D mesh and the spatial resolution can be dynamicall...

We calibrate here cosmological radiative transfer simulations with aton/ramses with a range of measurements of the Ly α opacity from Quasi-Stellar Objects (QSO) absorption spectra. We find the Ly α opacity to be very sensitive to the exact timing of hydrogen reionization. Models reproducing the measured evolution of the mean photoionization rate an...

We use high-resolution simulations of the formation of the local group, post-processed by a radiative transfer code for UV photons, to investigate the reionization of the satellite populations of an isolated Milky Way-M31 galaxy pair in a variety of scenarios. We use an improved version of ATON which includes a simple recipe for radiative feedback....

We constrain the initial stage of the reionization process around progenitors of galaxies, such as the extent of the initial HII region before its fusion with the UV background and the duration of its propagation. We use a set of reionisation simulations with different resolutions and ionizing source recipes. A catalog of the HII regions properties...

The imprint of baryonic acoustic oscillations in the structure of the intergalactic gas is in principle detectable during the epoch of reionization, at z>6. Using large scale cosmological simulations post-processed to take in account the impact of radiative transfer, we assess the redshift evolution of the 21 cm signal at the BAO scale, evolution t...

Cosmological simulations of reionization are analyzed in order to assess the reionization history of individual galaxies. A catalog of the evolution of the HII region properties is calculated with a merger tree of HII regions. It is assumed that a galaxy experiences a reionization in isolation until its related HII region merge with another one equ...

We present the results of a set of numerical simulations aimed at studying reionization at the galactic scale. We use a high-resolution realization of the formation of the Milky Way (MW)-M31 system to simulate the reionization of the Local Group. The reionization calculation was performed with the post-processing radiative transfer code ATON and th...

We present a new implementation of radiation hydrodynamics (RHD) in the adaptive mesh refinement (AMR) code RAMSES. The multi-group radiative transfer (RT) is performed on the AMR grid with a first-order Godunov method using the M1 closure for the Eddington tensor, and is coupled to the hydrodynamics via non-equilibrium thermochemistry of hydrogen...

We describe a new methodology to analyze the reionization process in numerical simulations: The evo- lution of the reionization is investigated by focusing on the merger histories of individual HII regions. From the merger tree of ionized patches, one can track the individual evolution of the regions such as e.g. their size, or investigate the prop...

We describe a new methodology to analyze the reionization process in numerical simulations: the chronology and the geometry of reionization is investigated by means of merger histories of individual HII regions. From the merger tree of ionized patches, one can track the individual evolution of the regions properties such as e.g. their size, or the...

We present a new semi-analytical model of the population of satellite galaxies of the Milky Way, aimed at estimating the effect of the geometry of reionization at galaxy scale on the properties of the satellites. In this model reionization can be either: (A) externally-driven and uniform, or (B) internally-driven, by the most massive progenitor of...

We describe a methodology to analyse the reionisation in numerical simulations. We particularly focus on the merger history of HII regions during the process. For this purpose, we identified the HII regions using a friend-of-friend algorithm and then derived the merger tree of these regions. By investigating the properties of evolving ionised regio...

We present a new semi-analytical model of the population of satellite galaxies of the Milky Way, aimed at estimating the effect of the geometry of reionization at galaxy scale on the properties of the satellites. In this model reionization can be either: (A) externally-driven and uniform, or (B) internally-driven, by the most massive progenitor of...

We present a new semi-analytical model of the population of satellite galaxies of the Milky Way, aimed at estimating the effect of the geometry of reionization at galaxy scale on the properties of the satellites. In this model, reionization can be either (A) externally driven and uniform, or (B) internally driven by the most massive progenitor of t...

We present a new semi-analytical model of the population of satellite galaxies of the Milky Way, aimed at estimating the effect of the spatial structure of reionisation at galaxy scale on the properties of the satellites. In this model reionisation can be either: (A) externally-driven and uniform, or (B) internally-driven, by the most massive proge...

We present a set of cosmological simulations with radiative transfer in order to model the reionization history of the universe from z = 18 down to z = 6. Galaxy formation and the associated star formation are followed self-consistently with gas and dark matter dynamics using the RAMSES code, while radiative transfer is performed as a post-processi...

Graphics Processing Units (GPUs) offer a new way to accelerate numerical calculations by means of on-board massive parallelisation. We discuss two examples of GPU implementation relevant for cosmological simulations, an N-Body Particle-mesh solver and a radiative transfer code. The latter has also been ported on multi-GPU clusters. The range of acc...

We present a set of cosmological simulations with radiative transfer in order to model the reionization history of the Universe. Galaxy formation and the associated star formation are followed self-consistently with gas and dark matter dynamics using the RAMSES code, while radiative transfer is performed as a post-processing step using a moment-bas...

The largest galaxies acquire their mass early on, when the Universe is still youthful. Cold streams violently feed these young galaxies a vast amount of fresh gas, resulting in very efficient star formation. Using a well resolved hydrodynamical simulation of galaxy formation, we demonstrate that these mammoth galaxies are already in place a couple...

We present a particle-mesh N-body integrator running on GPU using CUDA. Relying on a grid-based description of the gravitational potential, it can simulate the evolution of self-interacting ‘stars’ in order to model e.g. galaxies. All the steps of the application have been ported on the GPU , namely 1/ an histogramming algorithm with CUDPP, 2/ of t...

The popular model of hierarchical structure formation in a universe dominated by cold dark matter, while quite successful in matching the observed large-scale density distribution, is currently facing a "small-scale crisis". For instance, the predicted abundance of satellites (or substructures) is more than an order of magnitude larger than the num...

We have performed a 70 billion dark-matter particles N-body simulation in a 2 $h^{-1}$ Gpc periodic box, using the concordance, cosmological model as favored by the latest WMAP3 results. We have computed a full-sky convergence map with a resolution of $\Delta \theta \simeq 0.74$ arcmin$^{2}$, spanning 4 orders of magnitude in angular dynamical rang...

We present a statistical study of the effects induced by substructures on the deflection potential of dark matter haloes in the strong lensing regime. This investigation is based on the pertubative solution around the Einstein radius in which all the information on the deflection potential is specified by only a pair of 1D functions on this ring. U...

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. These tools generalize E. Bertschinger's Grafic1 software to distributed parallel architectures and offer a flexible alternative to the Grafic2 software for ``zoom'' initia...

A radiative transfer scheme is presented, based on a moment description of the equation of radiative transfer and the so-called ‘M1 closure model’ for the Eddington tensor. This model features a strictly hyperbolic transport step for radiation: it has been implemented using standard Godunov-like techniques in a new code called aton. Coupled to simp...

In a series of three papers, the dynamical interplay between environments and dark matter haloes is investigated, while focusing on the dynamical flows through the virtual virial sphere. It relies on both cosmological simulations, to constrain the environments, and an extension to the classical matrix method to derive the responses of the halo. A c...

We present a numerical technique to compute the gravitational lensing induced by simulated haloes. It relies on a 2D-Tree domain decomposition in the lens plane combined with a description of N-Body particles as extended clouds with a non-singular density. This technique is made fully adaptive by the use of a density-dependent smoothing which allow...

A new description of the halo's dynamics is introduced. The response of haloes interacting with the accretion and the tidal field is described analytically in the non-linear and secular regime via a perturbative approach. It relates the dynamical properties of a population of such objects to the statistics of their environment. The latter are deduc...

We investigate statistically the dynamical consequences of cosmological fluxes of matter and related moments on progenitors of today's dark matter haloes. These haloes are described as open collisionless systems which do not undergo strong interactions anymore. Their dynamics is described via canonical perturbation theory which accounts for two typ...

We measure the anisotropy of dark matter flows on small scales (∼500 kpc) in the near environment of haloes using a large set of simulations. We rely on two different approaches to quantify the anisotropy of the cosmic infall: we measure the flows at the virial radius of the haloes while describing the infalling matter via fluxes through a spherica...

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-to-noise (40-80) and high resolution (R = 45000) quasar spectra. The number densities and two-point correlation functions of both these species are largely constant with...