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Current models of galaxy evolution are constrained by the analysis of catalogs containing the flux and size of galaxies extracted from multiband deep fields carrying inevitable observational and extraction-related biases which can be highly correlated. In practice, taking all of these effects simultaneously into account is difficult, and derived models are inevitably biased. To address this issue, we use robust likelihood-free methods for the inference of luminosity function parameters, made possible via massive compression of multiband images using artificial neural networks. This technique makes the use of catalogs unnecessary when comparing observed and simulated multiband deep fields and constraining model parameters. A forward modeling approach generates galaxies of multiple types depending on luminosity function parameters and paints them on photometric multiband deep fields including both the instrumental and observational characteristics. The simulated and the observed images present the same selection effects and can therefore be properly compared. We train a fully-convolutional neural network to extract the most model-parameter-sensitive summary statistics out of these realistic simulations, shrinking down the dimensionality of the summary space. Finally, using the trained network to compress both observed and simulated deep fields, the model parameter values are constrained through Population Monte Carlo likelihood-free inference. Using synthetic photometric multiband deep fields similar to the CFHTLS and D1/D2 deep fields and massively compressing them through the convolutional neural network, we demonstrate the robustness, accuracy and consistency of this new catalog-free inference method. We are able to constrain the parameters of luminosity functions of different types of galaxies and our results are fully compatible with the classic catalog extraction approaches., Comment: 23 pages, 20 figures

Using the ligthcone from the cosmological hydrodynamical simulation Horizon-AGN, we produced a photometric catalogue over $0, Comment: 29 pages, 23 figures, 6 tables; submitted to MNRAS; Comments are welcome

The kinematic analysis of dark matter and hydrodynamical simulations suggests that the vorticity in large-scale structure is mostly confined to, and predominantly aligned with their filaments, with an excess of probability of 20 per cent to have the angle between vorticity and filaments direction lower than 60 degrees relative to random orientations. The cross sections of these filaments are typically partitioned into four quadrants with opposite vorticity sign, arising from multiple flows, originating from neighbouring walls. The spins of halos embedded within these filaments are consistently aligned with this vorticity for any halo mass, with a stronger alignment for the most massive structures up to an excess of probability of 165 per cent. On large scales, adiabatic/cooling hydrodynamical simulations display the same vorticity in the gas as in the dark matter. The global geometry of the flow within the cosmic web is therefore qualitatively consistent with a spin acquisition for smaller halos induced by this large-scale coherence, as argued in Codis et al. (2012). In effect, secondary anisotropic infall (originating from the vortex-rich filament within which these lower-mass halos form) dominates the angular momentum budget of these halos. The transition mass from alignment to orthogonality is related to the size of a given multi-flow region with a given polarity. This transition may be reconciled with the standard tidal torque theory if the latter is augmented so as to account for the larger scale anisotropic environment of walls and filaments., Comment: 17 pages, 19 figures, 3 tables. accepted for publication in MNRAS

The role of the cosmic web in shaping galaxy properties is investigated in the GAMA spectroscopic survey in the redshift range $0.03 \leq z \leq 0.25$. The stellar mass, $u - r$ dust corrected colour and specific star formation rate (sSFR) of galaxies are analysed as a function of their distances to the 3D cosmic web features, such as nodes, filaments and walls, as reconstructed by DisPerSE. Significant mass and type/colour gradients are found for the whole population, with more massive and/or passive galaxies being located closer to the filament and wall than their less massive and/or star-forming counterparts. Mass segregation persists among the star-forming population alone. The red fraction of galaxies increases when closing in on nodes, and on filaments regardless of the distance to nodes. Similarly, the star-forming population reddens (or lowers its sSFR) at fixed mass when closing in on filament, implying that some quenching takes place. Comparable trends are also found in the state-of-the-art hydrodynamical simulation Horizon-AGN. These results suggest that on top of stellar mass and large-scale density, the traceless component of the tides from the anisotropic large-scale environment also shapes galactic properties. An extension of excursion theory accounting for filamentary tides provides a qualitative explanation in terms of anisotropic assembly bias: at a given mass, the accretion rate varies with the orientation and distance to filaments. It also explains the absence of type/colour gradients in the data on smaller, non-linear scales., 26 pages, 18 figures, 7 tables, accepted for publication in MNRAS

We use Horizon-AGN, a hydrodynamical cosmological simulation, to explore the role of mergers in the evolution of massive (M > 10^10 MSun) galaxies around the epoch of peak cosmic star formation (13 are 'blue' (i.e. have significant associated star formation), the proportion of 'red' mergers increases rapidly at z, Comment: Submitted to MNRAS

International audience; Optimized nanomorphology in organic thin active layers is crucial for good performance in organic solar cells. However, the relation between morphology and electronic properties at nanoscale remains not completely understood. Here, we study the effect of film thickness and temperature annealing on the ordering of poly(3-hexylthiophene) chains when the polymer is blended with a columnar liquid crystalline molecule. Electronic absorption, atomic force microscopy measurements, and Raman spectroscopy show that morphology and chain ordering of the blend depend on the film thickness. We highlight the benefit of using a liquid crystal in organic blends, opening the way to use simple processing methods for the fabrication of organic electronic devices.

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 of billion years after the Big Bang. Contrary to local starforming galaxies, where dust re-emits a large part of the stellar ultraviolet (UV) light at infrared and sub-millimetre wavelengths, our self-consistent modelling of dust extinction predicts that a substantial fraction of UV photons should escape from primordial galaxies. Such a model allows us to compute reliably the number of high redshift objects as a function of luminosity, and yields galaxies whose UV luminosities closely match those measured in the deepest observational surveys available. This agreement is remarkably good considering our admittedly still simple modelling of the interstellar medium (ISM) physics. The luminosity functions (LF) of virtual UV luminous galaxies coincide with the existing data over the whole redshift range from 4 to 7, provided cosmological parameters are set to their currently favoured values. Despite their considerable emission at short wavelengths, we anticipate that the counterparts of the brightest UV galaxies will be detected by future sub-millimetre facilities like ALMA, Comment: 5 pages, 3 figures, submitted to MNRAS-let

We study the impact of galaxy-galaxy interactions on the FIR properties of galaxies and its evolution at 099%. However, the SFR and the SSFR decrease or do not change much as it approaches an early-type neighbor. The bifurcations of SFRs and SSFRs depending on the neighbor's morphology seem to occur at R_n~0.5r_vir,nei, which is supported by K-S and MC tests with a significance level of >98%. For all redshift bins, the SSFRs of late-type galaxies interacting with late-type neighbors are increased by factors of about 1.8+/-0.7 and 4.0+/-1.2 compared to those of non-interacting galaxies when the pair separation is smaller than 0.5r_vir,nei and 0.1r_vir,nei, respectively. The Tdust of both local and high-z late-type galaxies strongly interacting with late-type neighbors (i.e. R_n < 0.1r_vir,nei) appears to be higher than that of non-interacting galaxies with a significance level of 96-99%. However, Tdust of local late-type galaxies strongly interacting with early-type neighbors seems to be lower than or similar to that of non-interacting galaxies. Our results suggest that galaxy-galaxy interactions and mergers have been strongly affecting the SFR and the dust properties of star-forming galaxies over at least 8 billion years., Comment: 10 pages, 6 figures. To appear in A&A

For the first time the cross-correlation between type Ia supernova host galaxies and surrounding field galaxies is measured using the Supernova Legacy Survey sample. Over the z=0.2 to 0.9 redshift range we find that supernova hosts are correlated an average of 60% more strongly than similarly selected field galaxies over the 3-100 arcsec range and about a factor of 3 more strongly below 10 arcsec. The correlation errors are empirically established with a jackknife analysis of the four SNLS fields. The hosts are more correlated than the field at a significance of 99% in the fitted amplitude and slope, with the point-by-point difference of the two correlation functions having a reduced $\chi^2$ for 8 degrees of freedom of 4.3, which has a probability of random occurrence of less than 3x10^{-5}. The correlation angle is 1.5+/-0.5 arcsec, which deprojects to a fixed co-moving correlation length of approximately 6.5+/- 2/h mpc. Weighting the field galaxies with the mass and star formation rate supernova frequencies of the simple A+B model produces good agreement with the observed clustering. We conclude that these supernova clustering differences are primarily the expected outcome of the dependence of supernova rates on galaxy masses and stellar populations with their clustering environment., Comment: ApJ (Letts) accepted

The correlation between the large-scale distribution of galaxies and their spectroscopic properties at z=1.5 is investigated using the Horizon MareNostrum cosmological run. We have extracted a large sample of 10^5 galaxies from this large hydrodynamical simulation featuring standard galaxy formation physics. Spectral synthesis is applied to these single stellar populations to generate spectra and colours for all galaxies. We use the skeleton as a tracer of the cosmic web and study how our galaxy catalogue depends on the distance to the skeleton. We show that galaxies closer to the skeleton tend to be redder, but that the effect is mostly due to the proximity of large haloes at the nodes of the skeleton, rather than the filaments themselves. This effects translate into a bimodality in the colour distribution of our sample. The origin of this bimodality is investigated and seems to follow from the ram pressure stripping of satellite galaxies within the more massive clusters of the simulation. The virtual catalogues (spectroscopical properties of the MareNostrum galaxies at various redshifts) are available online at http://www.iap.fr/users/pichon/MareNostrum/catalogues, 18 pages, 27 figures, accepted for publication in MNRAS

We present the COSMOS2015 catalog which contains precise photometric redshifts and stellar masses for more than half a million objects over the 2deg$^{2}$ COSMOS field. Including new $YJHK_{\rm s}$ images from the UltraVISTA-DR2 survey, $Y$-band from Subaru/Hyper-Suprime-Cam and infrared data from the Spitzer Large Area Survey with the Hyper-Suprime-Cam Spitzer legacy program, this near-infrared-selected catalog is highly optimized for the study of galaxy evolution and environments in the early Universe. To maximise catalog completeness for bluer objects and at higher redshifts, objects have been detected on a $\chi^{2}$ sum of the $YJHK_{\rm s}$ and $z^{++}$ images. The catalog contains $\sim 6\times 10^5$ objects in the 1.5 deg$^{2}$ UltraVISTA-DR2 region, and $\sim 1.5\times 10^5$ objects are detected in the "ultra-deep stripes" (0.62 deg$^{2}$) at $K_{\rm s}\leq 24.7$ (3$\sigma$, 3", AB magnitude). Through a comparison with the zCOSMOS-bright spectroscopic redshifts, we measure a photometric redshift precision of $\sigma_{\Delta z/(1+z_s)}$ = 0.007 and a catastrophic failure fraction of $\eta=0.5$%. At $3, Comment: Accepted for publication in ApJ

We study the dust properties of galaxies in the redshift range 0.1 0.5 with L_IR>5x10^{10} L_\odot, appears to be 2-5 K colder than that of AKARI-selected local galaxies with similar luminosities; and the dispersion in T_dust for high-z galaxies increases with L_IR due to the existence of cold galaxies that are not seen among local galaxies. We show that this large dispersion of the L_IR-T_dust relation can bridge the gap between local star-forming galaxies and high-z submillimeter galaxies (SMGs). We also find that three SMGs with very low T_dust (

Aims. We use the deepest existing mid- and far-infrared observations (reaching ~3 mJy at 70 μ m) obtained with Spitzer in the Great Observatories Origins Deep Survey (GOODS) and Far Infrared Deep Extragalactic Legacy survey (FIDEL) fields to derive the evolution of the rest-frame 15 μ m, 35 μ m, and total infrared luminosity functions of galaxies spanning . We thereby quantify the fractional contribution of infrared luminous galaxies to the comoving star formation rate density over this redshift range. In comparison with previous studies, the present one takes advantage of deep 70 μ m observations that provide a more robust infrared luminosity indicator than 24 μ m affected by the emission of PAHs at high redshift (), and we use several independent fields to control cosmic variance.Methods. We used a new extraction technique based on the well-determined positions of galaxies at shorter wavelengths to extract the 24 and 70 μ m flux densities of galaxies. It is found that sources separated by a minimum of 0.5 FWHM are deblended by this technique, which facilitates multi-wavelength associations of counterparts. Using a combination of photometric and spectroscopic redshifts that exist for ~80% of the sources in our sample, we are able to estimate the rest-frame luminosities of galaxies at 15 μ m and 35 μ m. By complementing direct detections with a careful stacking analysis, we measured the mid- and far-infrared luminosity functions of galaxies over a factor ~100 in luminosity ( ) at . A stacking analysis was performed to validate the bolometric corrections and to compute comoving star-formation rate densities in three redshift bins , and, .Results. We find that the average infrared spectral energy distribution of galaxies over the last 2/3 of the cosmic time is consistent with that of local galaxies, although individual sources do present significant scatter. We also measured both the bright and faint ends of the infrared luminosity functions and find no evidence for a change in the slope of the double power law used to characterize the luminosity function. The redshift evolution of infrared luminous galaxies is consistent with pure luminosity evolution proportional to up to . We do not find evidence of differential evolution between LIRGs and ULIRGs up to , in contrast with previous claims. The comoving number density of infrared luminous galaxies has increased by a factor of 100 between . By , LIRGs produce half of the total comoving infrared luminosity density.

We present the most extensive and complete study of the properties for the largest sample (46 objects) of gamma-ray burst (GRB) host galaxies. The redshift interval and the mean redshift of the sample are 0, Comment: 33 pages, 18 figures, 11 tables, final version to appear in ApJ, January 20 issue. Figure 18 corrected

The XMM-Large Scale Structure survey field (XMM-LSS) is an extragalactic window surveyed in the X-ray with the XMM-Newton satellite. It has also been observed in the optical with the Canada-France Hawai Telescope (CFHTLS survey), and in the infrared with the Spitzer Space Telescope (SWIRE survey). These surveys have been carried out to study the structure and evolution of both baryonic and dark matter on cosmological scales. In two previous papers, we presented deep low frequency radio surveys of the XMM-LSS field, with limiting flux density levels of ~4 and ~1.5 mJy/beam at 325 and 610 MHz respectively (5 σ ). These radio surveys were motivated by the need to understand the various connections between the host galaxies of radio sources and their environments. In this paper, we identify optical counterparts to the low frequency radio sources, using the CFHTLS optical catalogue and images, that have an i -band limiting magnitude of $i_{\rm AB}\sim 25$. We use a likelihood ratio method and estimate that ~75% of the radio sources have a detected optical counterpart. Using the CFHTLS and SWIRE data, we derive photometric redshifts for the galaxies that are identified with a radio source, as well as for those that are not; we demonstrate the reliability of these photometric redshifts by deriving the stellar mass function for galaxies at different redshifts, and showing that it is consistent with previous determinations. We classify the radio sources as type-1 AGN, radio galaxies, or star-forming galaxies, and show that the radio luminosity function of the radio galaxies agrees with previous measurements.

In recent years, several authors have argued that low luminosity radio-loud active galactic nuclei (AGN) have a different mode of accretion, triggered by different physical mechanisms, than “normal” optically- or X-ray-selected AGN. The latter have a radiatively efficient nucleus (sometimes called “Quasar-mode”), which according to the unified scheme may be obscured from direct view at optical wavelengths, whereas essentially all of the energetic output of the low-luminosity radio-loud AGN is in their radio jets (“Radiomode”). In this paper, we independently study the internal and environmental properties of the optical hosts of the sample of ∼110 radio sources with redshifts 0.1 10 10.5−10.8 M� )i s that of massive elliptical galaxies, lying in galaxy groups or clusters, where the radio source is triggered by the cooling of the hot gas in their atmosphere. At these stellar masses, we find that the fraction of galaxies that host radio-loud AGN is essentially the same as that in the local Universe. The second population of radio sources have lower stellar masses, lie in large scale underdensities, and show excess mid-IR emission consistent with a hidden radiatively efficient active nucleus. The radio-loud fraction at these masses is increased relative to the local Universe. We argue that galaxy mergers and interactions may play an important role in triggering the AGN activity of this second population.

Fitting whole spectra at intermediate spectral resolution (R = 1000 -- 3000), to derive physical properties of stellar populations, appears as an optimized alternative to methods based on spectrophotometric indices: it uses all the redundant information contained in the signal. This paper addresses the validation of the method and it investigates the quality of the population models together with the reliability of the fitting procedures. We are using two algorithms: STECKMAP, a non-parametric regularized program and NBURSTS a parametric non-linear minimization. We compare three spectral synthesis models for single stellar populations: Pegase-HR, Galaxev (BC03) and Vazdekis/Miles, and we analyse spectra of Galactic clusters whose populations are known from studies of color-magnitude diagrams (CMD) and spectroscopy of individual stars. We find that: (1) The quality of the models critically depends on the stellar library they use. Pegase-HR and Vazdekis/Miles are consistent, while the comparison between Pegase-HR and BC03 shows some systematics reflecting the limitations of the stellar library (STELIB) used to generate the latter models; (2) The two fitting programs are consistent; (3) For globular clusters and M67 spectra, the method restitutes metallicities in agreement with spectroscopy of stars within 0.14 dex; (4) The spectroscopic ages are very sensitive to the presence of a blue horizontal branch (BHB) or of blue stragglers. A BHB morphology results in a young SSP-equivalent age. Fitting a free amount of blue stars in addition to the SSP model to mimic the BHB improves and stabilizes the fit and restores ages in agreement with CMDs studies. This method is potentially able to disentangle age or BHB effects in extragalactic clusters., Comment: accepted in MNRAS; Full version available at http://www-obs.univ-lyon1.fr/labo/perso/prugniel/mina/koleva.pdf

We study the relationship between the local environment of galaxies and their star formation rate (SFR) in the Great Observatories Origins Deep Survey, GOODS, at z~1, from ultradeep imaging at 24 microns with the MIPS camera onboard Spitzer. We show that the star formation-density relation observed locally was reversed at z~1: the average SFR of an individual galaxy increased with local galaxy density when the universe was less than half its present age. Hierarchical galaxy formation models (simulated lightcones from the Millennium model) predicted such a reversal to occur only at only at earlier epochs (z>2) and at a lower level. We present a remarkable structure at z~1.016, containing X-ray traced galaxy concentrations, which will eventually merge into a Virgo-like cluster. This structure illustrates how the individual SFR of galaxies increases with density at the ~1-2 Mpc scale. The SFR of z~1 galaxies is found to correlate with stellar mass suggesting that mass plays a role in the observed star formation-density trend. However the specific SFR (=SFR/M*) decreases with stellar mass while it increases with galaxy density, which implies that the environment does directly affect the star formation activity of galaxies. Major mergers do not appear to be the unique or even major cause for this effect since nearly half (46%) of the luminous infrared galaxies (LIRGs) at z~1 present the HST-ACS morphology of spirals, while only a third present a clear signature of major mergers. The remaining galaxies are divided into compact (9%) and irregular (14%) galaxies. Moreover, the specific SFR of major mergers is only marginally stronger than that of spirals. Reproducing the SFR-density relation at z ~ 1 is a new challenge for models, requiring a correct balance between mergers and in-situ star formation at early epochs., Accepted for publication in Astronomy & Astrophysics, 17 pages, 29 figures (same as previous version except for a few typos). For a version of this paper with higher resolution figures, go to http://david.elbaz3.free.fr/papers.html

International audience; Bulk Heterojunction (BHJ) organic photovoltaic devices performances depend on the relative organization and physical properties of the electron-donor and -acceptor materials. In this paper, BHJs of poly(3-hexyl-thiophene) (P3HT) associated with an electron acceptor material, 1-(3-methoxycarbonyl)-propyl-1-phenyl[6,6]C6 (PCBM) or [Ni(4dodpedt)(2)], are studied in terms of morphology, ordering, and electrical properties. First, comparison between the two BHJs performed by Atomic Force Microscopy (AFM) and Raman characterizations shows that P3HT structuration is improved by blending with [Ni(4dodpedt)(2)]. Then, the relationship between charges trapping, electrical properties, and film morphology is investigated using conductive AFM and Kelvin Force Microscopy. Measurements in dark condition and under solar cell simulator provide complementary information on electrical phenomena in these organic nanostructures. Finally, time dependent measurement highlights the influence of charges stacking on conduction. Specifically, we demonstrate that charge accumulation initiated by illumination remains valid after switching off the light, and induces the modification in current versus voltage characteristic of P3HT: PCBM blend. Finally, we observe a current increasing which can be attributed to the energy barrier decreasing due to charges trapping in PCBM.

We propose a new method of pushing $Herschel$ to its faintest detection limits using universal trends in the redshift evolution of the far infrared over 24$\mu$m colours in the well-sampled GOODS-North field. An extension to other fields with less multi-wavelength information is presented. This method is applied here to raise the contribution of individually detected $Herschel$ sources to the cosmic infrared background (CIRB) by a factor 5 close to its peak at 250$\mu$m and more than 3 in the 350$\mu$m and 500$\mu$m bands. We produce realistic mock $Herschel$ images of the deep PACS and SPIRE images of the GOODS-North field from the GOODS-$Herschel$ Key Program and use them to quantify the confusion noise at the position of individual sources, i.e., estimate a "local confusion noise". Two methods are used to identify sources with reliable photometric accuracy extracted using 24$\mu$m prior positions. The clean index (CI), previously defined but validated here with simulations, which measures the presence of bright 24$\mu$m neighbours and the photometric accuracy index (PAI) directly extracted from the mock $Herschel$ images. After correction for completeness, thanks to our mock $Herschel$ images, individually detected sources make up as much as 54% and 60% of the CIRB in the PACS bands down to 1.1 mJy at 100$\mu$m and 2.2 mJy at 160$\mu$m and 55, 33, and 13% of the CIRB in the SPIRE bands down to 2.5, 5, and 9 mJy at 250$\mu$m, 350$\mu$m, and 500$\mu$m, respectively. The latter depths improve the detection limits of $Herschel$ by factors of 5 at 250$\mu$m, and 3 at 350$\mu$m and 500$\mu$m as compared to the standard confusion limit. Interestingly, the dominant contributors to the CIRB in all $Herschel$ bands appear to be distant siblings of the Milky Way ($z$$\sim$0.96 for $\lambda$$, Comment: 22 pages, 16 figures. Accepted for publication by Astronomy and Astrophysics

Long-duration gamma-ray bursts (LGRBs) are produced by the collapse of very massive stars. Due to the short lifetime of their progenitors, LGRBs pinpoint star-forming galaxies. We present here a multi-band search for the host galaxy of the long dark GRB 050219A within the enhanced Swift/XRT error circle. We used spectroscopic observations acquired with VLT/X-shooter to determine the redshift and star-formation rate of the putative host galaxy. We compared the results with the optical/IR spectral energy distribution obtained with different facilities. Surprisingly, the host galaxy is a old and quiescent early-type galaxy at z = 0.211 characterised by an unprecedentedly low specific star-formation rate. It is the first LGRB host to be also an early-type post-starburst galaxy. This is further evidence that GRBs can explode in all kind of galaxies, with the only requirement being an episode of star-formation., Comment: 11 pages, 10 figures, 3 tables; accepted for publication in Astronomy & Astrophysics

We have investigated the mass-metallicity (M-Z) relation using galaxies at 0.4, Comment: ApJ in press

The narrow K-z relation of powerful radio galaxies in the Hubble K diagram is often attributed to the stellar populations of massive elliptical galaxies. Extended over a large range of redshifts (0 4 implies that massive clouds were already formed at early epochs. We also find that the M_(bar,max) limit is similar to the critical mass M_crit of a self-gravitating cloud regulated by cooling (Rees & Ostriker, 1977; Silk, 1977). Moreover, the critical size r_crit = 75 Kpc is remarkably close to the typical diameter of Ly_alpha haloes surrounding distant radio galaxies. This confirms the validity of the method of baryonic mass determination based on the K-band luminosity. A puzzling question that remains to be answered is the short time-scale of mass-accumulation required to form such massive galaxies at z=4. We discuss the dispersion of the K-z relation and the link between the active nucleus and a large stellar mass.

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, Comment: 18 pages, 19 figures, accepted for publication in MNRAS, movies and pictures of the simulation can be found at this address http://horizon-AGN.projet-horizon.fr

Until recently, dust emission has been detected in very few host galaxies of gamma-ray bursts (GRBHs). With Herschel, we have now observed 17 GRBHs up to redshift z~3 and detected seven of them at infrared (IR) wavelengths. This relatively high detection rate (41%) may be due to the composition of our sample which at a median redshift of 1.1 is dominated by the hosts of dark GRBs. Although the numbers are small, statistics suggest that dark GRBs are more likely to be detected in the IR than their optically-bright counterparts. Combining our IR data with optical, near-infrared, and radio data from our own datasets and from the literature, we have constructed spectral energy distributions (SEDs) which span up to 6 orders of magnitude in wavelength. By fitting the SEDs, we have obtained stellar masses, dust masses, star-formation rate (SFR), and extinctions for our sample galaxies. We find that GRBHs are galaxies that tend to have a high specfic SFR (sSFR), and like other star-forming galaxies, their ratios of dust-to-stellar mass are well correlated with sSFR. We incorporate our Herschel sample into a larger compilation of GRBHs, and compare this combined sample to SFR-weighted median stellar masses of the widest, deepest galaxy survey to date. This is done in order to establish whether or not GRBs can be used as an unbiased tracer of cosmic comoving SFR density (SFRD) in the universe. In contrast with previous results, this comparison shows that GRBHs are medium-sized galaxies with relatively high sSFRs; stellar masses and sSFRs of GRBHs as a function of redshift are similar to what is expected for star-forming galaxy populations at similar redshifts. We conclude that there is no strong evidence that GRBs are biased tracers of SFRD; thus they should be able to reliably probe the SFRD to early epochs., 18 pages, 9 figures, accepted for publication in A&A. Revised to include Fig. 6, mistakenly omitted in original

We seek to derive star formation rates (SFR) and stellar masses (M_star) in distant galaxies and to quantify the main uncertainties affecting their measurement. We explore the impact of the assumptions made in their derivation with standard calibrations or through a fitting process, as well as the impact of the available data, focusing on the role of IR emission originating from dust. We build a sample of galaxies with z>1, all observed from the UV to the IR (rest frame). The data are fitted with the code CIGALE, which is also used to build and analyse a catalogue of mock galaxies. Models with different SFHs are introduced. We define different set of data, with or without a good sampling of the UV range, NIR, and thermal IR data. The impact of these different cases on the determination of M_star and SFR are analysed. Exponentially decreasing models with a redshift formation of the stellar population z ~8 cannot fit the data correctly. The other models fit the data correctly at the price of unrealistically young ages when the age of the single stellar population is taken to be a free parameter. The best fits are obtained with two stellar populations. As long as one measurement of the dust emission continuum is available, SFR are robustly estimated whatever the chosen model is, including standard recipes. M_star measurement is more subject to uncertainty, depending on the chosen model and the presence of NIR data, with an impact on the SFR-M_star scatter plot. Conversely, when thermal IR data from dust emission are missing, the uncertainty on SFR measurements largely exceeds that of stellar mass. Among all physical properties investigated here, the stellar ages are found to be the most difficult to constrain and this uncertainty acts as a second parameter in SFR measurements and as the most important parameter for M_star measurements., Comment: 14 pages, 14 figures, accepted for publication A&A

Gamma-ray bursts (GRBs) have been proposed as a tool for studying star formation in the Universe, so it is crucial to investigate whether their host galaxies and immediate environments are in any way special compared with other star-forming galaxies. Here we present spatially resolved maps of dust emission of the host galaxy of the closest known GRB 980425 at z=0.0085 using our new high-resolution observations from Herschel, Atacama Pathfinder Experiment (APEX), Atacama Large Millimeter Array (ALMA) and Australia Telescope Compact Array (ATCA). We modelled the spectral energy distributions of the host and of the star-forming region displaying the Wolf-Rayet signatures in the spectrum (WR region), located 800 pc from the GRB position. The host is characterised by low dust content and a high fraction of UV-visible star formation, similar to other dwarf galaxies. These galaxies are abundant in the local universe, so it is not surprising to find a GRB in one of them, assuming the correspondence between the GRB rate and star formation. The WR region contributes substantially to the host emission at the far-infrared, millimetre, and radio wavelengths and we propose that this is a consequence of its high gas density. If dense environments are also found close to the positions of other GRBs, then the ISM density should also be considered, along with metallicity, an important factor influencing whether a given stellar population can produce a GRB., Comment: Accepted by A&A. 14 pages, 7 figures, 2 tables. V2: minor updates to match the published version

An ergonomic situation analysis was performed in preparation for the introduction of new negative inspection and cutting workstations and the addition of several efficiency enhancements. This paper reviews the physical and neurosensorial demands on negative inspectors and cutters and explores whether a cause-and-effect relationship exists between equipment typically used and the discomforts and traumas that occur. It proposes work situation improvements in human posture, equipment, work surface, environmental arrangements, and work processes.

Using a mass-limited sample of 24um-detected, star-forming galaxies at 0.5, Comment: 6 pages, 4 figures, 1 table. ApJ Letters in press

We present the deepest far-IR observations obtained with Herschel and examine the 3-500um SEDs of galaxies at 03x10^10 Lsun kpc^-2) and a high specific SFR (i.e., SBs). The rest-frame, UV-2700A size of these distant SBs is typically half that of MS galaxies, supporting the correlation between star formation density and SB activity that is measured for the local sample. Locally, (U)LIRGs are systematically in the SB mode, whereas most distant (U)LIRGs form stars in the "normal" MS mode. This confusion between two modes of star formation is the cause of the so-called "mid-IR excess" population of galaxies found at z>1.5 by previous studies. MS galaxies have strong PAH emission line features, a broad far-IR bump resulting from a combination of dust temperatures (Tdust~15-50 K), and an effective Tdust~31 K, as derived from the peak wavelength of their IR SED. Galaxies in the SB regime instead exhibit weak PAH EW and a sharper far-IR bump with an effective Tdust~40 K. Finally, we present evidence that the mid-to-far IR emission of X-ray AGNs is predominantly produced by star formation and that candidate dusty AGNs with a power-law emission in the mid-IR systematically occur in compact, dusty SBs. After correcting for the effect of SBs on IR8, we identify new candidates for extremely obscured AGNs., Comment: Astronomy and Astrophysics, vol.533, A119 (version with updated figures 2 and 3). [26 pages, 25 figures]

We discuss observational evidence that quasars play a key role in the formation of galaxies starting from the detailed study of the quasar HE0450-2958 and extending the discussion to a series of converging evidence that radio jets may trigger galaxy formation. The direct detection with VISIR at the ESO-VLT of the 7 kpc distant companion galaxy of HE0450-2958 allows us to spatially separate the sites of quasar and star formation activity in this composite system made of two ultra-luminous infrared galaxies (ULIRGs). No host galaxy has yet been detected for this quasar, but the companion galaxy stellar mass would bring HE0450-2958 in the local M(BH)-M(stellar bulge) relation if it were to merge with the QSO. This is bound to happen because of their close distance (7 kpc) and small relative velocity (~60-200 km/s). We conclude that we may be witnessing the building of the M(BH)-M(stellar bulge) relation, or at least of a major event in that process. The star formation rate (~340 Msun/yr), age (40-200 Myr) and stellar mass ([5-6]x10^10 Msun) are consistent with jet-induced formation of the companion galaxy. We suggest that HE0450-2958 may be fueled in fresh material by cold gas accretion from intergalactic filaments. We map the projected galaxy density surrounding the QSO as a potential tracer of intergalactic filaments and discuss a putative detection. Comparison to other systems suggests that inside-out formation of quasar host galaxies and jet-induced galaxy formation may be a common process. Two tests are proposed for this new paradigm: (1) the detection of offset molecular gas or dust emission with respect to the position of distant QSOs, (2) the delayed formation of host galaxies as a result of QSO activity, hence the two step building of the M(BH)/M(stellar bulge) ratio., 15 pages, 8 figures, accepted for publication in Astronomy and Astrophysics (with minor corrections)

[Abridged] This paper aims at providing new conservative constraints to the cosmic star-formation history from the empirical modeling of mid- and far-infrared data. We perform a non-parametric inversion of galaxy counts at 15, 24, 70, 160, and 850 microns simultaneously. It is a "blind" search (no redshift information is required) of all possible evolutions of the infrared luminosity function of galaxies, from which the evolution of the star-formation rate density and its uncertainties are derived. The cosmic infrared background (CIRB) measurements are used a posteriori to tighten the range of solutions. The inversion relies only on two hypotheses: (1) the luminosity function remains smooth both in redshift and luminosity, (2) a set of infrared spectral energy distributions (SEDs) of galaxies must be assumed. The range of star-formation histories that we derive is well constrained and consistent with redshift-based measurements from deep surveys. The redshift decompositions of the counts are also recovered successfully. Therefore, multi-wavelength counts and CIRB (both projected observations) alone seem to contain enough information to recover the cosmic star-formation history with quantifiable errors. A peak of the SFRD at z~2 is preferred, although higher redshifts are not excluded. We also find a good consistency between the observed evolution of the stellar mass density and the prediction from our model. Finally, the inability of the inversion to model perfectly and simultaneously all the multi-wavelength infrared counts (especially at 160 microns where an excess is seen around 20 mJ) implies either (i) the existence of a sub-population of colder galaxies, (ii) a larger dispersion of dust temperatures among local galaxies than expected, (iii) or a redshift evolution of the infrared SEDs of galaxies., 20 pages, 15 figures, 1 table. Accepted in A&A. The model is available at http://www.iap.fr/users/leborgne/irmodel09/index.html

A broad continuum excess in the near-infrared, peaking in the rest-frame at 2-5 micron, is detected in a spectroscopic sample of 88 galaxies at 0.5, Comment: 17 pages, 12 Figures, Accepted to ApJ

At redshifts around 0.1 the CFHT Legacy Survey Deep fields contain some 6x10^4 galaxies spanning the mass range from 10^5 to 10^12 Msun. We measure the stellar mass dependence of the two point correlation using angular measurements to largely bypass the errors, approximately 0.02 in the median, of the photometric redshifts. Inverting the power-law fits with Limber's equation we find that the auto-correlation length increases from a very low 0.4hMpc at 10^5.5 Msun to the conventional 4.5hMpc at 10^10.5 Msun. The power law fit to the correlation function has a slope which increases from gamma approximately 1.6 at high mass to gamma approximately 2.3 at low mass. The spatial cross-correlation of dwarf galaxies with more massive galaxies shows fairly similar trends, with a steeper radial dependence at low mass than predicted in numerical simulations of sub-halos within galaxy halos. To examine the issue of missing satellites we combine the cross-correlation measurements with our estimates of the low mass galaxy number density. We find on the average there are 60+/-20 dwarfs in sub-halos with M(total) > 10^7 Msun for a typical Local Group M(total)/M(stars)=30, corresponding to M/L_V approximately 100 for a galaxy with no recent star formation. The number of dwarfs per galaxy is about a factor of two larger than currently found for the Milky Way. Nevertheless, the average dwarf counts are about a factor of 30 below LCDM simulation results. The divergence from LCDM predictions is one of slope of the relation, approximately dN/dlnM approximately -0.5 rather than the predicted -0.9, not sudden onset at some characteristic scale. The dwarf galaxy star formation rates span the range from passive to bursting, which suggests that there are few completely dark halos., revised version submitted to Astrophysical Journal

Timmes, Brown & Truran found that metallicity variations could theoretically account for a 25% variation in the mass of 56Ni synthesized in Type Ia supernovae (SNe Ia), and thus account for a large fraction of the scatter in observed SN Ia luminosities. Higher-metallicity progenitors are more neutron-rich, producing more stable burning products relative to radioactive 56Ni. We develop a new method for estimating bolometric luminosity and 56Ni yield in SNe Ia and use it to test the theory with data from the Supernova Legacy Survey. We find that the average 56Ni yield does drop in SNe Ia from high metallicity environments, but the theory can only account for 7%--10% of the dispersion in SN Ia 56Ni mass, and thus luminosity. This is because the effect is dominant at metallicities significantly above solar, whereas we find that SN hosts have predominantly subsolar or only moderately above-solar metallicities. We also show that allowing for changes in O/Fe with the metallicity [Fe/H] does not have a major effect on the theoretical prediction of Timmes, Brown & Truran, so long as one is using the O/H as the independent variable. Age may have a greater effect than metallicity -- we find that the luminosity weighted age of the host galaxy is correlated with 56Ni yield, and thus more massive progenitors give rise to more luminous explosions. This is hard to understand if most SNe Ia explode when the primaries reach the Chandrasekhar mass. Finally, we test the findings of Gallagher et al., that the residuals of SNe Ia from the Hubble diagram are correlated with host galaxy metallicity, and we find no such correlation., ApJ, accepted, 34 pages, 11 figures, apologies for one column format -- necessary for the equations

We describe a compact cluster of massive red galaxies at z=1.51 discovered in one of the Gemini Deep Deep Survey (GDDS) fields. Deep imaging with the Near Infrared Camera and Multi Object Spectrometer (NICMOS) on the Hubble Space Telescope reveals a high density of galaxies with red optical to near-IR colors surrounding a galaxy with a spectroscopic redshift of 1.51. Mid-IR imaging with Infrared Array Camera (IRAC) on the Spitzer Space telescope shows that these galaxies have spectral energy distributions that peak between 3.6 and 4.5 microns. Fits to 12-band photometry reveal 12 or more galaxies with spectral shapes consistent with z = 1.51. Most are within ~170 co-moving kpc of the GDDS galaxy. Deep F814W images with the Advanced Camera for Surveys (ACS) on HST reveal that these galaxies are a mix of early-type galaxies, disk galaxies and close pairs. The total stellar mass enclosed within a sphere of 170 kpc in radius is > 8E+11 solar masses. The colors of the most massive galaxies are close to those expected from passive evolution of simple stellar populations (SSP) formed at much higher redshifts. We suggest that several of these galaxies will merge to form a single, very massive galaxy by the present day. This system may represent an example of a short-lived dense group or cluster core typical of the progenitors of massive clusters in the present day and suggests the red sequence was in place in over-dense regions at early times.

(ABRIDGED) We show that Type Ia supernovae (SNe Ia) are formed within both very young and old stellar populations, with observed rates that depend on the stellar mass and mean star-formation rates (SFRs) of their host galaxies. Models where the SN Ia rate depends solely on host galaxy stellar mass are ruled out with 99% confidence. Our analysis is based on 100 spectroscopically-confirmed SNe Ia, plus 24 photometrically-classified events, all from the Supernova Legacy Survey (SNLS) and distributed over 0.2, Comment: Accepted for publication in ApJ

We compare the rise times of nearby and distant Type Ia supernovae (SNe Ia) as a test for evolution using 73 high-redshift spectroscopically-confirmed SNe Ia from the first two years of the five year Supernova Legacy Survey (SNLS) and published observations of nearby SN. Because of the ``rolling'' search nature of the SNLS, our measurement is approximately 6 times more precise than previous studies, allowing for a more sensitive test of evolution between nearby and distant supernovae. Adopting a simple $t^2$ early-time model (as in previous studies), we find that the rest-frame $B$ rise times for a fiducial SN Ia at high and low redshift are consistent, with values $19.10^{+0.18}_{-0.17}({stat}) \pm 0.2 ({syst})$ and $19.58^{+0.22}_{-0.19}$ days, respectively; the statistical significance of this difference is only 1.4 \sg . The errors represent the uncertainty in the mean rather than any variation between individual SN. We also compare subsets of our high-redshift data set based on decline rate, host galaxy star formation rate, and redshift, finding no substantive evidence for any subsample dependence., Comment: Accepted for publication in AJ; minor changes (spelling and grammatical) to conform with published version

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 synthesis code currently providing the highest spectral resolution is Pegase-HR, which was made available by D. Le Borgne et al. in 2004. Based on an empirical stellar library, it provides synthetic spectra between 4000 and 6800 A at lambda/d(lambda)=10000 for any star formation history, with or without chemical evolution. Such a resolution is particularly useful for the study of low mass galaxies, massive star clusters, or other galaxy regions with low internal velocity dispersions. After a summary of the main features of Pegase-HR and comparisons with other population synthesis codes, this paper focuses on the inversion of optical galaxy spectra. We explore the limits of what information can or can not be recovered, based on theoretical principles and extensive simulations. First applications to extragalactic objects are shown., Comment: Inv. talk in "The Spectral Energy Distribution of Gas-Rich Galaxies: Confronting Models with Data", Heidelberg, 4-8 Oct. 2004, eds. C.C. Popescu and R.J. Tuffs, AIP Conf. Ser., in press

We examine the cosmic star formation rate (SFR) and its dependence on galaxy stellar mass over the redshift range 0.8 < z < 2 using data from the Gemini Deep Deep Survey (GDDS). The SFR in the most massive galaxies (M > 10^{10.8} M_sun) was six times higher at z = 2 than it is today. It drops steeply from z = 2, reaching the present day value at z ~ 1. In contrast, the SFR density of intermediate mass galaxies (10^{10.2} < M < 10^{10.8} M_sun) declines more slowly and may peak or plateau at z ~ 1.5. We use the characteristic growth time t_SFR = rho_M / rho_SFR to provide evidence of an associated transition in massive galaxies from a burst to a quiescent star formation mode at z ~ 2. Intermediate mass systems transit from burst to quiescent mode at z ~ 1, while the lowest mass objects undergo bursts throughout our redshift range. Our results show unambiguously that the formation era for galaxies was extended and proceeded from high to low mass systems. The most massive galaxies formed most of their stars in the first ~3 Gyr of cosmic history. Intermediate mass objects continued to form their dominant stellar mass for an additional ~2 Gyr, while the lowest mass systems have been forming over the whole cosmic epoch spanned by the GDDS. This view of galaxy formation clearly supports `downsizing' in the SFR where the most massive galaxies form first and galaxy formation proceeds from larger to smaller mass scales., Accepted for publication in ApJL

Photometric redshifts are estimated on the basis of template scenarios with the help of the code ZPEG, an extension of the galaxy evolution model PEGASE.2 and available on the PEGASE web site. The spectral energy distribution (SED) templates are computed for nine spectral types including starburst, irregular, spiral and elliptical. Dust, extinction and metal effects are coherently taken into account, depending on evolution scenarios. The sensitivity of results to adding near-infrared colors and IGM absorption is analyzed. A comparison with results of other models without evolution measures the evolution factor which systematically increases the estimated photometric redshift values by $��z$ > 0.2 for z > 1.5. Moreover we systematically check that the evolution scenarios match observational standard templates of nearby galaxies, implying an age constraint of the stellar population at z=0 for each type. The respect of this constraint makes it possible to significantly improve the accuracy of photometric redshifts by decreasing the well-known degeneracy problem. The method is applied to the HDF-N sample. From fits on SED templates by a $��^2$-minimization procedure, not only is the photometric redshift derived but also the corresponding spectral type and the formation redshift $z_for$ when stars first formed. Early epochs of galaxy formation z > 5 are found from this new method and results are compared to faint galaxy count interpretations. The new tool is available at: http://www.iap.fr/pegase, 10 pages, 10 postscript figures, 2 tables; accepted for publication in Astronomy & Astrophysics; to compute redshifts see http://www.iap.fr/pegase/

Promoting physical activity is an imperative for public Health. Inactivity is a risk factor of coronary artery disease. The aim of this study is to determine the feasibility of a physical activity behavior change, maintained 12 month after an intervention. Aims (1) Increase weekly exercise training volume, (2) decrease BMI and abdominal circumference. Method Eighty overweight subjects without involvement in regular physical activity were included, age 57 years ± 6.5. Professionally active: 55%, hypertension: 89%, dyslipidemia: 67%, diabetes mellitus: 71%, smoker: 25%, history of depression: 27%, stress: 30%, BMI: 33.2 ± 5.8; abdominal circumference 111 ± 14.4 cm. After a medical exam with motivation counselling and exercise test, a program of 10 sessions is prescribed. Level of exercise is individually adapted. Each session begin with 2.5 hours of exercise (callisthenic, cycling and muscle resistance) followed by relaxation session, walk, cooking lessons, information. Individual smoking and psychological counselling. At the end of the program, an individual goal of “weekly exercise training volume” is determined by the participant with the help of the physiotherapist. To reinforce patient s efforts, 4 phone calls were added plus one recall session at 12 months (training, physician and physiotherapy counselling). Results at 12 months Seventeen dropout (move for retire 6, move 2, illness5, unknown 4) and 63 completed the program. On the basis of this population who answered at the recall, 76% maintained their initial goal. The BMI decreased of 1.3 kg/m 2 and waist circumference decreased of 2 cm (from 111 ± 14.4 to 109 ± 22). Conclusion Multidisciplinary team of a rehab centre can motivate successfully sedentary overweight individuals to change of lifestyle in prevention of a cardiovascular disease.

Long duration gamma-ray bursts (GRBs) allow us to explore the distant Universe, and are potentially the most effective tracer of the most distant objects. Our current knowledge of the properties of GRB host galaxies at redshifts >5 is very scarce. We propose to improve this situation by obtaining more observations of high-redshift hosts to better understand their properties and help enable us to use GRBs as probes of the high-redshift universe. We performed very deep photometric observations of three high-redshift GRB host galaxies, GRB 080913 at z =6.7, GRB 060927 at z =5.5 and GRB 060522 at z =5.1. In addition, we completed deep spectroscopic observations of the GRB080913 host galaxy with X-Shooter at the VLT to search for Ly-alpha emission. For the sake of the discussion, we use published results on another high-redshift GRB host, GRB 050904 at z = 6.3. The sample of GRB host galaxies studied in this paper consists of four out of the five spectroscopically confirmed GRBs at z>5. Despite our presented observations being the deepest ever reported of high-redshift GRB host galaxies, we do not detect any of the hosts, neither in photometry nor in spectroscopy in the case of GRB 080913. These observations indicate that the GRB host galaxies seem to evolve with time and to have lower SFRs at z >5 than they have at z5, our observations are not sufficiently sensitive to allow us to infer further conclusions on whether this specific population is representative of the general one. The characterization of high-redshift GRB host galaxies is a very challenging endeavor requiring a lot of telescope time, but is necessary to improve our understanding of the high-redshift universe., Accepted to A&A

We derive the evolution of the infrared (IR) luminosity function (LF) over the last 4/5ths of cosmic time, using deep 24um and 70um imaging of the GOODS North and South fields. We use an extraction technique based on prior source positions at shorter wavelengths to build the 24 and 70um source catalogs. The majority (93%) of the sources have a spectroscopic (39%) or a photometric redshift (54%) and, in our redshift range of interest (i.e., 1.3, Comment: 19 pages, 14 figures. Accepted for publication in A&A. Online catalog at CDS soon

The Herschel Space Observatory enables us to accurately measure the bolometric output of starburst galaxies and active galactic nuclei (AGN) by directly sampling the peak of their far-infrared (IR) emission. Here we examine whether the spectral energy distribution (SED) and dust temperature of galaxies have strongly evolved since z~2.5. We use Herschel deep extragalactic surveys from 100 to 500um to compute total IR luminosities in galaxies down to the faintest levels, using PACS and SPIRE in the GOODS-North field (PEP and HerMES key programs). We show that measurements in the SPIRE bands can be used below the statistical confusion limit if information at higher spatial resolution is used to identify isolated galaxies whose flux is not boosted by bright neighbors. Below z~1.5, mid-IR extrapolations are correct for star-forming galaxies with a dispersion of only 40% (0.15dex), therefore similar to z~0 galaxies. This narrow distribution is puzzling when considering the range of physical processes that could have affected the SED of these galaxies. Extrapolations from only one of the 160um, 250um or 350um bands alone tend to overestimate the total IR luminosity. This may be explained by the lack of far-IR constraints around and above ~150um (rest-frame) on local templates. We also note that the dust temperature of luminous IR galaxies around z~1 is mildly colder by 10-15% than their local analogs and up to 20% for ULIRGs at z~1.6. Above z=1.5, distant galaxies are found to exhibit a substantially larger mid- over far-IR ratio, which could either result from stronger broad emission lines or warm dust continuum heated by a hidden AGN. Two thirds of the AGNs identified in the field with a measured redshift exhibit the same behavior as purely star-forming galaxies. Hence a large fraction of AGNs harbor star formation at very high SFR and in conditions similar to purely star-forming galaxies., Astronomy and Astrophysics, Herschel Special Issue, in press as a Letter; 5 pages