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Author(s): L. Guzzo (corresponding author) [1, 2, 3, 4]; M. Pierleoni [3]; B. Meneux [5]; E. Branchini [6]; O. Le Fèvre [7]; C. Marinoni [8]; B. Garilli [5]; J. Blaizot [...]

We present a study of the intersection between the populations of star forming galaxies selected as either Lyman break galaxies (LBGs) or Lyman-alpha emitters (LAEs) in the redshift range 2.9 − 6.7 and within the same volume of universe sampled by the Multi-Unit Spectroscopic Explorer (MUSE) behind the Hubble Frontier Fields lensing cluster A2744. We define three samples of star-forming galaxies: LBG galaxies with an LAE counterpart (92 galaxies), LBG galaxies without an LAE counterpart (408 galaxies), and LAE galaxies without an LBG counterpart (46 galaxies). All these galaxies are intrinsically faint because of the lensing nature of the sample (M1500 ≥ −20.5). The fraction of LAEs among all selected star-forming galaxies increases with redshift up to z ∼ 6 and decreases for higher redshifts, in agreement with previous findings. The evolution of LAE/LBG populations with UV magnitude and Lyα luminosity shows that the LAE selection is able to identify intrinsically UV faint galaxies with M1500 ≥ −15 that are typically missed in the deepest lensing photometric surveys. The LBG population seems to fairly represent the total population of star-forming galaxies down to M1500 ∼ −15. Galaxies with M1500 < −17 tend to have SFRLyα < SFRuv, whereas the opposite trend is observed within our sample for faint galaxies with M1500 > −17, including galaxies only detected by their Lyα emission, with a large scatter. These trends, previously observed in other samples of star-forming galaxies at high-z, are seen here for very faint M1500 ∼ −15 galaxies; that is, much fainter than in previous studies. The present results show no clear evidence for an intrinsic difference between the properties of the two populations selected as LBG and/or LAE. The observed trends could be explained by a combination of several phenomena, like the existence of different star-formation regimes, the dust content, the relative distribution and morphology of dust and stars, or the stellar populations. [ABSTRACT FROM AUTHOR]

Context. Resonant lines are powerful probes of the interstellar and circumgalactic medium of galaxies. Their transfer in gas being a complex process, the interpretation of their observational signatures, either in absorption or in emission, is often not straightforward. Numerical radiative transfer simulations are needed to accurately describe the travel of resonant line photons in real and in frequency space, and to produce realistic mock observations. Aims. This paper introduces RASCAS, a new public 3D radiative transfer code developed to perform the propagation of any resonant line in numerical simulations of astrophysical objects. RASCAS was designed to be easily customisable and to process simulations of arbitrarily large sizes on large supercomputers. Methods. RASCAS performs radiative transfer on an adaptive mesh with an octree structure using the Monte Carlo technique. RASCAS features full MPI parallelisation, domain decomposition, adaptive load-balancing, and a standard peeling algorithm to construct mock observations. The radiative transport of resonant line photons through different mixes of species (e.g. Hi, Si ii, Mgii, Fe ii), including their interaction with dust, is implemented in a modular fashion to allow new transitions to be easily added to the code. Results. RASCAS is very accurate and efficient. It shows perfect scaling up to a minimum of a thousand cores. It has been fully tested against radiative transfer problems with analytic solutions and against various test cases proposed in the literature. Although it was designed to describe accurately the many scatterings of line photons, RASCAS may also be used to propagate photons at any wavelength (e.g. stellar continuum or fluorescent lines), or to cast millions of rays to integrate the optical depths of ionising photons, making it highly versatile. [ABSTRACT FROM AUTHOR]

We present an alternative approach to deriving second-order nonconformal hydrodynamics from the relativistic Boltzmann equation. We demonstrate how constitutive relations for shear and bulk stresses can be transformed into dynamical evolution equations, resulting in Israel-Stewart-like (ISL) hydrodynamics. To understand the far-from-equilibrium applicability of such ISL theories, we investigate the one-dimensional boost-invariant Boltzmann equation using special moments of the distribution function for a system with finite particle mass. Our analysis reveals that the mathematical structure of the ISL equations is akin to that of moment equations, enabling them to approximately replicate even the collisionless dynamics. We conclude that this particular feature is important in extending the applicability of ISL theories beyond the hydrodynamic regime.

We study the time evolution of the density matrix of a high energy quark in the presence of a dense QCD background that is modeled as a stochastic Gaussian color field. At late times, we find that only the color singlet component of the quark’s reduced density matrix survives the in-medium evolution and that the density matrix becomes asymptotically diagonal in both transverse position and momentum spaces. In addition, we observe an accelerated entropy growth due to the larger phase space being explored by the quark and that the quantum and classical quark entropies converge at late times. We further observe that the quark state loses all memory of the initial condition. Combined with the fact that the reduced density matrix satisfies Boltzmann-diffusion transport, we conclude that the quark reduced density matrix can be interpreted as a classical phase space distribution.

We present an analysis of |${\rm H\,\rm{\small {I}}}$| Lyman  |$\alpha$| emission in deep VLT/MUSE observations of two highly magnified and extended galaxies at |$z=3.5$| and 4.03, including a newly discovered, almost complete Einstein ring. While these Lyman  |$\alpha$| haloes are intrinsically similar to the ones typically seen in other MUSE deep fields, the benefits of gravitational lensing allow us to construct exceptionally detailed maps of Lyman  |$\alpha$| line properties at sub-kpc scales. By combining all multiple images, we are able to observe complex structures in the Lyman  |$\alpha$| emission and uncover small (⁠|$\sim120$| km s−1 in Lyman  |$\alpha$| peak shift), but significant at |$ \gt $| 4  |$\sigma$|⁠ , systematic variations in the shape of the Lyman  |$\alpha$| line profile within each halo. Indeed, we observe a global trend for the line peak shift to become redder at large radii, together with a strong correlation between the peak wavelength and line width. This systematic intrahalo variation is markedly similar to the object-to-object variations obtained from the integrated properties of recent large samples. Regions of high surface brightness correspond to relatively small line shifts, which could indicate that Lyman  |$\alpha$| emission escapes preferentially from regions where the line profile has been less severely affected by scattering of Lyman  |$\alpha$| photons. [ABSTRACT FROM AUTHOR]

We simulate the flux emitted from galaxy haloes in order to quantify the brightness of the circumgalactic medium (CGM). We use dedicated zoom-in cosmological simulations with the hydrodynamical adaptive mesh refinement code ramses , which are evolved down to z  = 0 and reach a maximum spatial resolution of 380 h −1 pc and a gas mass resolution up to |$1.8\times 10^{5} \, h^{-1}\, \rm {M}_{\odot }$| in the densest regions. We compute the expected emission from the gas in the CGM using cloudy emissivity models for different lines (e.g. Lyα, C  iv , O  vi , C  vi , O  viii) considering UV background fluorescence, gravitational cooling and continuum emission. In the case of Lyα, we additionally consider the scattering of continuum photons. We compare our predictions to current observations and find them to be in good agreement at any redshift after adjusting the Lyα escape fraction. We combine our mock observations with instrument models for Faint Intergalactic Redshifted Emission Balloon-2 (FIREBall-2; UV balloon spectrograph) and HARMONI (visible and NIR IFU on the ELT) to predict CGM observations with either instrument and optimize target selections and observing strategies. Our results show that Lyα emission from the CGM at a redshift of 0.7 will be observable with FIREBall-2 for bright galaxies (NUV∼18 mag), while metal lines like O  vi and C  iv will remain challenging to detect. HARMONI is found to be well suited to study the CGM at different redshifts with various tracers. [ABSTRACT FROM AUTHOR]

GalICS 2.0 is a new semi-analytic code to model the formation and evolution of galaxies in a cosmological context. N-body simulations based on a Planck cosmology are used to construct halo merger trees, track subhaloes, compute spins and measure concentrations. The accretion of gas on to galaxies and the morphological evolution of galaxies are modelled with prescriptions derived from hydrodynamic simulations. Star formation and stellar feedback are described with phenomenological models (as in other semi-analytic codes). GalICS 2.0 computes rotation speeds from the gravitational potential of the dark matter, the disc and the central bulge. As the rotation speed depends not only on the virial velocity but also on the ratio of baryons to dark matter within a galaxy, our calculation predicts a different Tully–Fisher relation from models in which vrot ∞ vvir. This is why, GalICS 2.0 is able to reproduce the galaxy stellar mass function and the Tully–Fisher relation simultaneously. Our results are also in agreement with halo masses from weak lensing and satellite kinematics, gas fractions, the relation between star formation rate (SFR) and stellar mass, the evolution of the cosmic SFR density, bulge-to-disc ratios, disc sizes and the Faber–Jackson relation. [ABSTRACT FROM AUTHOR]

In this article, the scientific life of D. Gogny is recounted by several collaborators. His strong involvement in researches related to various fields of physics (such as nuclear, atomic and plasma physics as well as electromagnetism) appears clearly, as well as the progresses made in the understanding of fundamental physics. [ABSTRACT FROM AUTHOR]

The VLT/Multi Unit Spectrograph Explorer (MUSE) integral-field spectrograph can detect Lyα emitters (LAE) in the redshift range 2.8≲z≲6.7 in a homogeneous way. Ongoing MUSE surveys will notably probe faint Lyα sources that are usually missed by current narrow-band surveys. We provide quantitative predictions for a typical wedding-cake observing strategy with MUSE based on mock catalogues generated with a semi-analytic model of galaxy formation coupled to numerical Lyα radiation transfer models in gas outflows.We expect ≈1500 bright LAEs (FLyα ≳ 10-17 erg s-1 -2) in a typical shallow field (SF) survey carried over ≈100 arcmin2 , and ≈2000 sources as faint as 10-18 erg s-1 cm-2 in a medium-deep field (MDF) survey over 10 arcmin2. In a typical deep field (DF) survey of 1 arcmin2 , we predict that ≈500 extremely faint LAEs (FLyα ≳ 4 × 10-19 erg s-1 -2) will be found. Our results suggest that faint Lyα sources contribute significantly to the cosmic Lyα luminosity and SFR budget. While the host haloes of bright LAEs at z ≈ 3 and 6 have descendants with median masses of 2 × 1012 and 5 × 1013 M≳, respectively, the faintest sources detectable by MUSE at these redshifts are predicted to reside in haloes which evolve into typical sub-L* and L* galaxy haloes at z = 0.We expect typical DF and MDF surveys to uncover the building blocks of Milky Way-like objects, even probing the bulk of the stellar mass content of LAEs located in their progenitor haloes at z ≈ 3. [ABSTRACT FROM AUTHOR]

A partially recrystallized sample of the Ni-based superalloy AD730 was taken from an intermediate stage of the ingot to billet conversion process and isothermally forged in a single stroke compression test at a sub-solvus temperature (1080 °C). The as-received material had a heterogeneous microstructure, containing a mixture of coarse and much finer recrystallized grains as well as unrecrystallized ones, and also heterogeneous γ′ precipitation. The recrystallization mechanisms occurring dynamically in the different grain populations were investigated via electron backscatter diffraction (EBSD). It was found that local microstructure could affect the operative recrystallization mechanism, with different mechanisms seen in the deformed and recrystallized regions, owing to their different precipitate distributions. Within a single deformed grain, three apparently distinct dynamic recrystallization (DRX) mechanisms were identified. The interaction of recrystallization with precipitates plays a central role in DRX. In certain cases precipitates may stimulate discontinuous DRX by providing recrystallization nuclei, alternatively they may impede and limit the growth of recrystallized grains, or in other cases still they promote continuous recrystallization. • Recrystallisation mechanisms of a heterogeneous starting microstructure are characterised. • Different local microstructures lead to different recrystallisation mechanisms operating. • Different interactions between precipitates and recrystallisation processes are described. • All precipitates in recrystallised regions result from dissolution and reprecipitation. [ABSTRACT FROM AUTHOR]

We review recent theoretical developments in the study of the structure of jets that are produced in ultra relativistic heavy ion collisions. The core of the review focusses on the dynamics of the parton cascade that is induced by the interactions of a fast parton crossing a quark-gluon plasma. We recall the basic mechanisms responsible for medium induced radiation, underline the rapid disappearance of coherence effects, and the ensuing probabilistic nature of the medium induced cascade. We discuss how large radiative corrections modify the classical picture of the gluon cascade, and how these can be absorbed in a renormalization of the jet quenching parameter . Then, we analyze the (wave)-turbulent transport of energy along the medium induced cascade, and point out the main characteristics of the angular structure of such a cascade. Finally, color decoherence of the in-cone jet structure is discussed. Modest contact with phenomenology is presented towards the end of the review. [ABSTRACT FROM AUTHOR]

We explore the properties of high-redshift Lyman alpha emitters (LAEs), and their link with the Lyman-break galaxy (LBG) population, using a semi-analytic model of galaxy formation g that takes into account resonant scattering of Lyα photons in gas outflows. We can reasonably 2L reproduce the abundances of LAEs and LBGs from z ≈ 3 to 7, as well as most UV luminosity functions (LFs) of LAEs. The stronger dust attenuation for (resonant) Lyα photons compared t to UV continuum photons in bright LBGs provides a natural interpretation to the increase of 11 the LAE fraction in LBG samples, XLAE, towards fainter magnitudes. The redshift evolution of XLAE seems however very sensitive to UV magnitudes limits and equivalent width (EW) cuts. In spite of the apparent good match between the statistical properties predicted by the model and the observations, we find that the tail of the Lyα EW distribution (EW ≳ 100 Å) U cannot be explained by our model, and we need to invoke additional mechanisms. We find that 3 LAEs and LBGs span a very similar dynamical range, but bright LAEs are times rarer than LBGs in massive haloes. Moreover, massive haloes mainly contain weak LAEs in our model, a which might introduce a bias towards low-mass haloes in surveys which select sources with high-EW cuts. Overall, our results are consistent with the idea that LAEs and LBGs make a very similar galaxy population. Their apparent differences seem mainly due to EW selections, UV detection limits, and a decreasing Lyα to UV escape fraction ratio in high star formation rate galaxies. [ABSTRACT FROM AUTHOR]

We study the angular broadening of a medium-induced QCD cascade. We derive the equation that governs the evolution of the average transverse momentum squared of the gluons in the cascade as a function of the medium length, and we solve this equation analytically. Two regimes are identified. For a medium of a not too large size, and for not too soft gluons, the transverse momentum grows with the size of the medium according to standard momentum broadening. The other regime, visible for a medium of a sufficiently large size and very soft gluons, is a regime dominated by multiple branchings: there, the average transverse momentum saturates to a value that is independent of the size of the medium. This structure of the in-medium QCD cascade is, at least qualitatively, compatible with the recent LHC data on dijet asymmetry. [ABSTRACT FROM AUTHOR]

We observed Hubble Deep Field South with the new panoramic integral-field spectrograph MUSE that we built and have just commissioned at the VLT. The data cube resulting from 27 h of integration covers one arcmin2 field of view at an unprecedented depth with a 1σ emission-line surface brightness limit of 1 × 10-19 erg s-1 cm-2 arcsec-2, and contains ~90?000 spectra. We present the combined and calibrated data cube, and we performed a first-pass analysis of the sources detected in the Hubble Deep Field South imaging. We measured the redshifts of 189 sources up to a magnitude I814?=?29.5, increasing the number of known spectroscopic redshifts in this field by more than an order of magnitude. We also discovered 26 Lyα emitting galaxies that are not detected in the HST WFPC2 deep broad-band images. The intermediate spectral resolution of 2.3 Å allows us to separate resolved asymmetric Lyα emitters, [O?ii]3727 emitters, and C?iii]1908 emitters, and the broad instantaneous wavelength range of 4500 Å helps to identify single emission lines, such as [O?iii]5007, Hβ, and Hα, over a very wide redshift range. We also show how the three-dimensional information of MUSE helps to resolve sources that are confused at ground-based image quality. Overall, secure identifications are provided for 83% of the 227 emission line sources detected in the MUSE data cube and for 32% of the 586 sources identified in the HST catalogue. The overall redshift distribution is fairly flat to z = 6.3, with a reduction between z = 1.5 to 2.9, in the well-known redshift desert. The field of view of MUSE also allowed us to detect 17 groups within the field. We checked that the number counts of [O?ii]3727 and Lyα emitters are roughly consistent with predictions from the literature. Using two examples, we demonstrate that MUSE is able to provide exquisite spatially resolved spectroscopic information on the intermediate-redshift galaxies present in the field. This unique data set can be used for a wide range of follow-up studies. We release the data cube, the associated products, and the source catalogue with redshifts, spectra, and emission-line fluxes. [ABSTRACT FROM AUTHOR]

Semi-analytical models (SAMs) are currently the best way to understand the formation of galaxies within the cosmic dark-matter structures. They are able to give a statistical view of the variety of the evolutionary histories of galaxies in terms of star formation and stellar mass assembly. While they reproduce the local stellar mass functions, correlation functions, and luminosity functions fairly well, they fail to match observations at high redshift (z ≥ 3) in most cases, particularly in the low-mass range. The inconsistency between models and CDM observations indicates that the history of gas accretion in galaxies, within their host dark-matter halo, and the transformation of gas into stars, are not followed well. We briefly present a new version of the GalICS semi-analytical model. With this new model, we explore the impact of classical mechanisms, such as supernova feedback or photoionization, on the evolution of the stellar mass assembly and the star formation rate. Even with strong efficiency, these two processes cannot explain the observed stellar mass function and star formation rate distribution or the stellar mass versus dark matter halo mass relation. We thus introduce an ad hoc modification of the standard paradigm, based on the presence of a no-star-forming gas component, and a concentration of the star-forming gas in galaxy discs. The main idea behind the existence of the no-star-forming gas reservoir is that only a fraction of the total gas mass in a galaxy is available to form stars. The reservoir generates a delay between the accretion of the gas and the star formation process. This new model is in much better agreement with the observations of the stellar mass function in the low-mass range than the previous models and agrees quite well with a large set of observations, including the redshift evolution of the specific star formation rate. However, it predicts a large amount of no-star-forming baryonic gas, potentially larger than observed, even if its nature has still to be examined in the context of the missing baryon problem. Outputs from all models are available at the CDS. [ABSTRACT FROM AUTHOR]

A large-scale hydrodynamical cosmological simulation, Horizon-AGN, is used to investigate the alignment between the spin of galaxies and the cosmic filaments above redshift 1.2. The analysis of more than 150 000 galaxies per time step in the redshift range 1.2 < z < 1.8 with morphological diversity shows that the spin of low-mass blue galaxies is preferentially aligned with their neighbouring filaments, while high-mass red galaxies tend to have a perpendicular spin. The reorientation of the spin of massive galaxies is provided by galaxy mergers, which are significant in their mass build-up. We find that the stellar mass transition from alignment to misalignment happens around 3 × 1010 M⊙. Galaxies form in the vorticity-rich neighbourhood of filaments, and migrate towards the nodes of the cosmic web as they convert their orbital angular momentum into spin. The signature of this process can be traced to the properties of galaxies, as measured relative to the cosmic web. We argue that a strong source of feedback such as active galactic nuclei is mandatory to quench in situ star formation in massive galaxies and promote various morphologies. It allows mergers to play their key role by reducing post-merger gas inflows and, therefore, keeping spins misaligned with cosmic filaments. [ABSTRACT FROM PUBLISHER]

We study the average properties of the gluon cascade generated by an energetic parton propagating through a quark-gluon plasma. We focus on the soft, medium-induced emissions which control the energy transport at large angles with respect to the leading parton. We show that the effect of multiple branchings is important. In contrast with what happens in a usual QCD cascade in vacuum, medium-induced branchings are quasidemocratic, with offspring gluons carrying sizable fractions of the energy of their parent gluon. This results in an efficient mechanism for the transport of energy toward the medium, which is akin to wave turbulence with a scaling spectrum ∼1/√ω. We argue that the turbulent flow may be responsible for the excess energy carried by very soft quanta, as revealed by the analysis of the dijet asymmetry observed in Pb-Pb collisions at the LHC. [ABSTRACT FROM AUTHOR]

Simulations of galaxy evolution aim to capture our current understanding as well as to make predictions for testing by future experiments. Simulations and observations are often compared in an indirect fashion: physical quantities are estimated from the observational data and compared to models. However, many applications can benefit from a more direct approach, where the observing process is also simulated, so that the models are seen fully from the observer's perspective. To facilitate this, we have developed the Millennium Run Observatory (MRObs), a theoretical virtual observatory which uses virtual telescopes to 'observe' semianalytic galaxy formation simulations based on the suite of Millennium Run (MR) dark matter simulations. The MRObs produces data that can be processed and analysed using the standard observational software packages developed for real observations. At present, we produce images in 40 filters covering the rest-frame ultraviolet to infrared for two stellar population synthesis models, for three different models of absorption by the intergalactic medium, and in two cosmologies (Wilkinson Microwave Anisotropy Probe year 1 and 7). Galaxy distributions for a large number of mock light cones can be 'observed' using models of major ground- and space-based telescopes. The data include light cone catalogues linked to structural properties of galaxies, pre-observation model images, mock telescope images and Source Extractor products that can all be traced back to the higher level dark matter, semi-analytic galaxy and light cone catalogues available in the MR data base. Here, we describe our methods and announce a first public release of simulated observations that emulate a large number of extragalactic surveys [e.g. Sloan Digital Sky Survey, Canada-France-Hawaii Telescope Legacy Survey (CFHT-LS), Great Observatories Origins Deep Survey (GOODS), GOODS/Early Release Science (ERS), Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) and Hubble Ultra Deep Field (HUDF)]. The MRObs browser, an online tool, further facilitates exploration of the simulated data. We demonstrate the benefits of a direct approach through a number of example applications: (1) deep galaxy number counts in the CANDELS survey; (2) observed properties of galaxy clusters; (3) structural parameters of galaxies; and (4) identification of dropout galaxies. The MRObs enhances the range of questions that can be asked of semianalytic models, allowing observers and theorists to work towards each other with virtually complete freedom of where to meet. [ABSTRACT FROM AUTHOR]

Aims. Our aim is to perform the same colour-density analysis on galaxy mock samples as was carried out on a 5 h-1 Mpc scale using the VIMOS-VLT Deep Survey (VVDS), and to compare the results from these mock samples with observed data. This allows us to test galaxy evolution in the model and to understand the relation between the studied environment and the underlying dark matter distribution. Methods. We used galaxy mock catalogues with the same flux limits as the VVDS-Deep (IAB ⩽ 24) survey (Cmocks), constructed using a semi-analytic model for galaxy evolution applied to the Millennium Simulation. From each Cmock, we extracted a subsample of galaxies mimicking the VVDS observational strategy (Omocks). We then computed the B-band luminosity function LF and the colour-density relation in the mock samples using the same methods as employed for the VVDS data. Results. We find that the B-band LF in mock samples roughly agrees with the observed LF, but at 0.2 < z < 0.8 the faint-end slope of the model LF is steeper than the observed one. Computing the LF for early- and late-type galaxies separately, we show that mock samples have an excess of faint early-type galaxies and of bright late-type galaxies compared with the data. We find that the colour-density relation in Omocks agrees excellently with that in Cmocks. This suggests that the VVDS observational strategy does not introduce any severe bias to the observed colour-density relation. At z ∼ 0.7, the colour-density relation in mock samples agrees qualitatively with observations, with red galaxies residing preferentially in high densities. However, the strength of the colour-density relation in mock samples does not vary within 0.2 < z < 1.5, while the observed relation flattens with increasing redshift and possibly inverts at z ∼ 1.3. We argue that the lack of evolution in the colour-density relation in the model cannot be due only to inaccurate prescriptions for the evolution of satellite galaxies, but indicates that the treatment of the central galaxies has also to be revised. Conclusions. The reversal of the colour-density relation can be explained by wet mergers between young galaxies, producing a starburst event. This should be seen on group scales, where mergers are frequent, with possibly some residual trend on larger scales. This residual is found in observations at z = 1.5 on a scale of ∼5 h-1 Mpc, but not in the model, suggesting that the treatment of physical processes influencing both satellites and central galaxies in models should be revised. A detailed analysis would be desirable on small scales as well, which requires flux limits fainter than those of the VVDS data. [ABSTRACT FROM AUTHOR]

Aims. This paper is the first in a series investigating Lyman-alpha (hereafter Lyα) radiation transfer through hydrodynamical simulations of galaxy formation. Its aim is to assess the impact of interstellar medium (ISM) physics on Lyα radiation transfer and to quantify how galaxy orientation alters observational signatures with respect to the line of sight. Methods. We compare the results of Lyα radiation transfer calculations through the ISM of a couple of idealized galaxy simulations in a dark matter halo of ∼1010 Mʘ. In the first one, G1, this ISM is modeled using physics typical of large-scale cosmological hydrodynamics simulations of galaxy formation, where gas is prevented from radiatively cooling below 104 K. In the second one, G2, gas is allowed to radiate away more of its internal energy via metal lines and consequently fragments into dense star-forming clouds. Results. First, as expected, the small-scale structuration of the ISM plays a determinant role in shaping a galaxy's Lyα properties. The artificially warm, hence smooth, ISM of G1 yields an escape fraction of ∼50% at the Lyα line center, and produces symmetrical double-peak profiles. In contrast, in G2, most young stars are embedded in thick star-forming clouds, and the result is a ∼10 times lower escape fraction. G2 also displays a stronger outflowing velocity field, which favors the escape of red-shifted photons, resulting in an asymmetric Lyα line. Second, the Lyα properties of G2 strongly depend on the inclination at which it is observed: From edge-on to face-on, the line goes from a double-peak profile with an equivalent width (EW) of ∼-5 Å to a 15 times more luminous, red-shifted asymmetric line with EW ∼ 90 Å. Conclusions. The remarkable discrepancy in the Lyα properties we derived for two ISM models raises a fundamental question. In effect, it demonstrates that Lyα radiation transfer calculations can only lead to realistic properties in simulations where galaxies are resolved into giant molecular clouds. Such a stringent requirement translates into severe constraints both in terms of ISMphysics modeling and numerical resolution, putting these calculations beyond the reach of current large-scale cosmological simulations. Finally, we find inclination effects to be much stronger for Lyα photons than for continuum radiation. This could potentially introduce severe biases in the selection function of narrow-band Lyα emitter surveys and in their interpretation, and we predict that these surveys could indeed miss a significant fraction of the high-z galaxy population. [ABSTRACT FROM AUTHOR]

ABSTRACT We investigate the observability of cold accretion streams at redshift 3 via Lyα emission and the feasibility of cold accretion as the main driver of Lyα blobs (LABs). We run cosmological zoom simulations focusing on three haloes spanning almost two orders of magnitude in mass, roughly from 1011 to . We use a version of the ramses code that includes radiative transfer of ultraviolet (UV) photons, and we employ a refinement strategy that allows us to resolve accretion streams in their natural environment to an unprecedented level. For the first time in a simulation, we self-consistently model self-shielding in the cold streams from the cosmological UV background, which enables us to predict their temperatures, ionization states and Lyα luminosities with improved accuracy. We find the efficiency of gravitational heating in cold streams in a halo to be around 10-20 per cent throughout most of the halo but reaching much higher values close to the centre. As a result, most of the Lyα luminosity comes from gas which is concentrated at the central 20 per cent of the halo radius, leading to Lyα emission which is not extended. In more massive haloes, of , cold accretion is complex and disrupted, and gravitational heating does not happen as a steady process. Ignoring the factors of Lyα scattering, local UV enhancement and supernovae feedback, the cold 'messy' accretion alone in these massive haloes can produce LABs that largely agree with observations in terms of morphology, extent and luminosity. Our simulations slightly and systematically overpredict LAB abundances, perhaps hinting that the interplay of these ignored factors may have a negative net effect on extent and luminosity. We predict that a factor of a few increase in sensitivity from current observational limits should unambiguously reveal continuum-free accretion streams around massive galaxies at z= 3. [ABSTRACT FROM AUTHOR]

ABSTRACT We investigate the observability of cold accretion streams at redshift 3 via Lyα emission and the feasibility of cold accretion as the main driver of Lyα blobs (LABs). We run cosmological zoom simulations focusing on three haloes spanning almost two orders of magnitude in mass, roughly from 1011 to . We use a version of the ramses code that includes radiative transfer of ultraviolet (UV) photons, and we employ a refinement strategy that allows us to resolve accretion streams in their natural environment to an unprecedented level. For the first time in a simulation, we self-consistently model self-shielding in the cold streams from the cosmological UV background, which enables us to predict their temperatures, ionization states and Lyα luminosities with improved accuracy. We find the efficiency of gravitational heating in cold streams in a halo to be around 10-20 per cent throughout most of the halo but reaching much higher values close to the centre. As a result, most of the Lyα luminosity comes from gas which is concentrated at the central 20 per cent of the halo radius, leading to Lyα emission which is not extended. In more massive haloes, of , cold accretion is complex and disrupted, and gravitational heating does not happen as a steady process. Ignoring the factors of Lyα scattering, local UV enhancement and supernovae feedback, the cold 'messy' accretion alone in these massive haloes can produce LABs that largely agree with observations in terms of morphology, extent and luminosity. Our simulations slightly and systematically overpredict LAB abundances, perhaps hinting that the interplay of these ignored factors may have a negative net effect on extent and luminosity. We predict that a factor of a few increase in sensitivity from current observational limits should unambiguously reveal continuum-free accretion streams around massive galaxies at z= 3. [ABSTRACT FROM AUTHOR]

ABSTRACT We present a new model for high redshift Lyman α emitters (LAEs) in the cosmological context which takes into account the resonant scattering of Lyα photons through expanding gas. The GALICS semi-analytic model provides us with the physical properties of a large sample of high redshift galaxies. We implement, in post-processing, a gas outflow model for each galaxy based on simple scaling arguments. The coupling with a library of numerical experiments of Lyα transfer through expanding (or static) dusty shells of gas allows us to derive the Lyα escape fraction and profile of each galaxy. Results obtained with this new approach are compared with simpler models often used in the literature. The predicted distribution of Lyα photons escape fraction shows that galaxies with a low star formation rate (SFR) have a fesc of the order of unity, suggesting that, for those objects, Lyα may be used to trace the SFR assuming a given conversion law. In galaxies forming stars intensely, the escape fraction spans the whole range from 0 to 1. The model is able to get a good match to the ultraviolet (UV) and Lyα luminosity function data at 3 < z < 5. We find that we are in good agreement with both the bright Lyα data and the faint LAE population observed by Rauch et al. at z= 3 whereas a simpler constant Lyα escape fraction model fails to do so. Most of the Lyα profiles of our LAEs are redshifted by the diffusion in the expanding gas which suppresses intergalactic medium absorption and scattering. The bulk of the observed Lyα equivalent width (EW) distribution is recovered by our model, but we fail to obtain the very large values sometimes detected. Our predictions for stellar masses and UV luminosity functions of LAEs show a satisfactory agreement with observational estimates. The UV-brightest galaxies are found to show only low Lyα EWs in our model, as it is reported by many observations of high redshift LAEs. We interpret this effect as the joint consequence of old stellar populations hosted by UV-bright galaxies, and high H i column densities that we predict for these objects, which quench preferentially resonant Lyα photons via dust extinction. [ABSTRACT FROM AUTHOR]

ABSTRACT We present for the first time predictions for ultraviolet (UV) line emission of intergalactic and circumgalactic gas from Adaptive Mesh Resolution (AMR) large-scale structure simulations at redshifts 0.3 < z < 1.2, with a specific emphasis on its observability with current and near-future UV instrumentation. In the three UV transitions of interest (Lyα, O vi and C iv), there is a clear bimodality in the type of emitting objects: the overwhelming majority of the flux stems from discrete, compact sources, while a much larger fraction of the volume is filled by more tenuous gas. We characterize both object types with regard to their number densities, physical sizes and shapes, brightnesses and luminosities, velocity structures, masses, temperatures, ionization states, and metal content. Degrading our AMR grids to characteristic resolutions offered by available (such as FIREBall) or foreseeable instrumentation allows us to assess which inferences can be drawn from currently possible observations, and to set foundations to prepare observing strategies for future missions. In general, the faint emission of the intergalactic medium (IGM) and filamentary structure remains beyond the capabilities of instruments with only short-duration exposure potential (i.e. stratospheric balloons), even for the most optimistic assumption for Lyα, while the yet fainter metal line transitions (O vi and C iv) for these structures will actually remain challenging for long-duration exposures (i.e. space-based telescopes), mostly due to their low metallicities pushing them more than three orders of magnitudes in brightness below the Lyα radiation. For the bright, circumgalactic medium, the situation is much more promising, and it is foreseeable that in the near future we will not only just detect such sources, but also the combination of all three lines in addition to velocity information will yield valuable insight into the physical processes at hand, illuminating (and discriminating between) important mechanisms during the formation of galaxies and their backreaction on to the IGM from whence they formed. [ABSTRACT FROM AUTHOR]

We present the implementation of the Blaizot-Méndez-Wschebor approximation scheme of the nonperturbative renormalization group we present in detail, which allows for the computation of the full-momentum dependence of correlation functions. We discuss its significance and its relation with other schemes, in particular, the derivative expansion. Quantitative results are presented for the test ground of scalar O(N) theories. Besides critical exponents, which are zero-momentum quantities, we compute the two-point function at criticality in the whole momentum range in three dimensions and, in the high-temperature phase, the universal structure factor. In all cases, we find very good agreement with the best existing results. [ABSTRACT FROM AUTHOR]