We present the stellar mass (M-*)-gas-phase metallicity relation (MZR) and its scatter at intermediate redshifts (0.5 <= z <= 0.7) for 1381 field galaxies collected from deep spectroscopic surveys. The star formation rate (SFR) and color at a given M-* of this magnitude-limited (R less than or similar to 24 AB) sample are representative of normal star-forming galaxies. For masses below 10(9) M-circle dot, our sample of 237 galaxies is similar to 10 times larger than those in previous studies beyond the local universe. This huge gain in sample size enables superior constraints on the MZR and its scatter in the low-mass regime. We find a power-law MZR at 10(8) M-circle dot < M-* < 10(11) M-circle dot: 12 + log (O/H) = (5.83 +/- 0.19)+(0.30 +/- 0.02) log (M-*/M-circle dot). At 10(9) M-circle dot < M-* < 10(10.5) M-circle dot, our MZR shows agreement with others measured at similar redshifts in the literature. Our power-law slope is, however, shallower than the extrapolation of the MZRs of others to masses below 10(9) M-circle dot. The SFR dependence of the MZR in our sample is weaker than that found for local galaxies (known as the fundamental metallicity relation). Compared to a variety of theoretical models, the slope of our MZR for low-mass galaxies agrees well with predictions incorporating supernova energy-driven winds. Being robust against currently uncertain metallicity calibrations, the scatter of the MZR serves as a powerful diagnostic of the stochastic history of gas accretion, gas recycling, and star formation of low-mass galaxies. Our major result is that the scatter of our MZR increases as M-* decreases. Our result implies that either the scatter of the baryonic accretion rate (sigma((M) over dot)) or the scatter of the M-*-M-halo relation (sigma(SHMR)) increases as M-* decreases. Moreover, our measure of scatter at z = 0.7 appears consistent with that found for local galaxies. This lack of redshift evolution constrains models of galaxy evolution to have both sigma((M) over dot) and sigma(SHMR) remain unchanged from z = 0.7 to z = 0.

We present new observations of the field containing the z = 3.786 protocluster PC 217.96+ 32.3. We confirm that it is one of the largest known and most overdense high-redshift structures. Such structures are rare even in the largest cosmological simulations. We used the Mayall/MOSAIC1.1 imaging camera to image a 1 degrees.2 x 0 degrees.6 area (approximate to 150 x 75 comoving Mpc) surrounding the protocluster's core and discovered 165 candidate Ly alpha emitting galaxies (LAEs) and 788 candidate Lyman Break galaxies (LBGs). There are at least two overdense regions traced by the LAEs, the largest of which shows an areal overdensity in its core (i. e., within a radius of 2.5 comoving Mpc) of 14 +/- 7 relative to the average LAE spatial density ((rho) over bar) in the imaged field. Further, (rho) over bar is twice that derived by other field LAE surveys. Spectroscopy with Keck/DEIMOS yielded redshifts for 164 galaxies (79 LAEs and 85 LBGs); 65 lie at a redshift of 3.785 +/- 0.010. The velocity dispersion of galaxies near the core is sigma = 350 +/- 40 km s(-1), a value robust to selection effects. The overdensities are likely to collapse into systems with present-day masses of > 10(15)M(circle dot) and > 6 x 10(14)M(circle dot) The low velocity dispersion may suggest a dynamically young protocluster. We find a weak trend between narrow-band (Ly alpha) luminosity and environmental density: the Ly alpha luminosity is enhanced on average by 1.35x within the protocluster core. There is no evidence that the Ly alpha equivalent width depends on environment. These suggest that star formation and/or active galactic nucleus (AGN) activity is enhanced in the higher-density regions of the structure. PC. 217.96+ 32.3 is a Coma cluster analog, witnessed in the process of formation.

The far-infrared fine-structure line [C II] at 1900.5 GHz is known to be one of the brightest cooling lines in local galaxies, and therefore it has been suggested to be an efficient tracer for star formation in very high redshift galaxies. However, recent results for galaxies at z > 6 have yielded numerous non-detections in star-forming galaxies, except for quasars and submillimetre galaxies. We report the results of ALMA observations of two lensed, star-forming galaxies at z = 6.029 and z = 6.703. The galaxy A383-5.1 (star formation rate [SFR] of 3.2 M-circle dot yr(-1) and magnification of mu = 11.4 +/- 1.9) shows a line detection with L-[C II] = 8.9 x 10(6) L-circle dot, making it the lowest L-[C II] detection at z > 6. For MS0451-H (SFR = 0.4 M-circle dot yr(-1) and mu = 100 +/- 20) we provide an upper limit of L-[C II] < 3 x 10(5) L-circle dot, which is 1 dex below the local SFR-L-[C II] relations. The results are consistent with predictions for low-metallicity galaxies at z > 6; however, other effects could also play a role in terms of decreasing L-[CII]. The detection of A383-5.1 is encouraging and suggests that detections are possible, but much fainter than initially predicted.

There is strong observational evidence indicating a time lag of order of some 100 Myr between the onset of starburst and AGN activity in galaxies. Dynamical time lags have been invoked to explain this. We extend this approach by introducing a viscous time lag the gas additionally needs to flow through the AGN's accretion disc before it reaches the central black hole. Our calculations reproduce the observed time lags and are in accordance with the observed correlation between black hole mass and stellar velocity dispersion.

We investigate black hole-host galaxy scaling relations in cosmological simulations with a self-consistent black hole growth and feedback model. Our sub-grid accretion model captures the key scalings governing angular momentum transport by gravitational torques from galactic scales down to parsec scales, while our kinetic feedback implementation enables the injection of outflows with properties chosen to match observed nuclear outflows (star formation-driven winds are not included to isolate the effects of black hole feedback). We show that 'quasar mode' feedback can have a large impact on the thermal properties of the intergalactic medium and the growth of galaxies and massive black holes for kinetic feedback efficiencies as low as 0.1 per cent relative to the bolometric luminosity. None the less, our simulations indicate that the black hole-host scaling relations are only weakly dependent on the effects of black hole feedback on galactic scales, since black hole feedback suppresses the growth of galaxies and massive black holes by a similar amount. In contrast, the rate at which gravitational torques feed the central black hole relative to the host galaxy star formation rate governs the slope and normalization of the black hole-host correlations. Our results suggest that a common gas supply regulated by gravitational torques is the primary driver of the observed co-evolution of black holes and galaxies.

We discovered a mistake in Eqs. (7) and (10) of Saglia et al. (2010, A&A, 524, A6), which propagates to Tables 8 and 9 and Fig. 25. We revise the tables, the figure and the affected statements in the paper. As a result, the reduction in the luminosity evolution due to the effects of the size and velocity dispersion evolution is smaller than claimed in Saglia et al. (2010).

Le principal objectif de ce travail est d'étudier les propriétés multi-longueurs d'onde d'un échantillon de galaxies pour mieux comprendre leur formation et leur évolution. J'ai utilisé les observations du Herschel en complément de données multi-longueurs d'onde dans le champ. J'ai réalisé une extraction des sources ponctuelles. Des catalogues de sources ont été générés en utilisant la méthode de l'ajustement de PSF. J'ai utilisé des catalogues SPIRE pour rechercher des candidats de galaxies SMG subissant les effets d'une lentille gravitationnelle. J'ai identifié 6 sources dans la liste principale et 55 sources dans une liste supplémentaire. En utilisant des ajustements de SEDs, j'ai ensuite estimé la distribution de redshifts de ces sources, et avons ensuite mené une analyse pour contraindre les propriétés des poussières. J'ai trouvé qu'il est très probable que ces sources soient des systèmes lensés. Mentionnons que parmi nos candidates, j'ai découvert une source rouge unique dont la SED en infrarouge lointain croît et qui semble être une galaxie sub-mm (SMG) fortement lensée à haut redshift. Ce genre de sources est rare et la plupart sont découvertes par hasard. J'ai soumis des propositions photométriques et spectroscopiques pour mesurer le redshift de cette source, en utilisant des observations continues avec IRAM-Nika2, NOEMA et SMA et des observations spectroscopiques avec le télescope de 30m de l'IRAM, NOEMA et GEMINI-nord. Les observations ont permis de mesurer le redshift de la lentille et de la galaxie lensée. Une autre observation sera exécutée avant la fin de l'année. Les résultats sont très prometteurs mais j'ai encore besoin de plus de données. / The main aim of this work is to study the multi-wavelength properties of a sample of galaxies to better understand their formation and evolution. I used the new observations from GALEX and \textit{Herschel} in combination with multi-wavelength data available in the field. I made point source catalogs extracted from the observations of GALEX, and \textit{Herschel} SPIRE and PACS bands using the method of the PSF fitting. Then I used Monte Carlo simulations to quantify the quality of the photometry process and the catalogs.Then I used SPIRE catalogs to search for candidate gravitationally lensed SMGs at high redshift. I identified 6 sources sources in a main list, and 55 sources in a supplementary list. Using SED fitting, performed with CIGALE code, I estimated the redshift distributions of these sources, and constrained their dust properties. I found that, it is very likely that we have gravitationally lensing systems. It should be mentioned that within our candidates we have discovered a unique red source with a rising Far-IR SED, which appears to be a strongly lensed submillimeter galaxies at z~5.2. This kind of sources are quite rare on the sky and are serendipitously discovered. I proposed some followup photometric and spectroscopy observation to measure the redshift of this sources, using for instance continuum observations with IRAM-Nika2, NOEMA, and SMA, and spectroscopic observation with IRAM 30m telescope, NOEMA, and GEMINI-North. The GEMINI-North observations succeeded in measuring the redshifts of the lens and of the lensed galaxy. One more will be executed at the end of this year. The results is quite promising, but more data are needed.

L'objectif de mon travail de thèse a consisté à tenter de comprendre quels sont les mécanismes principaux à l'origine de la formation d'étoiles dans les galaxies au cours des derniers dix milliards d'années. Alors qu'il avait été proposé dans le passé que le rôle des fusions de galaxies était dominant pour expliquer l'allumage de la formation d'étoiles dans les galaxies lointaines formant leurs étoiles à de très grands taux, des études plus récentes ont au contraire mis en évidence des lois d'échelles reliant le taux de formation d'étoiles des galaxies à leur masse stellaire ou masse de gaz. La faible dispersion de ces lois semblait être en contradiction avec l'idée d'épisodes stochastiques violents de formation stellaire liés à des interactions, mais plutôt en accord avec une nouvelle vision de l'histoire des galaxies où celles-ci sont nourries de manière continue en gaz intergalactique.Nous nous sommes particulièrement intéressés à l'une de ces lois d'échelles, la relation entre le taux de formation d'étoiles (SFR) et la masse stellaire des galaxies, appelées communément la séquence principale des galaxies à formation d'étoiles. Nous avons étudié cette séquence principale, SFR-M*, en fonction de la morphologie et d'autres paramètres physiques comme le rayon, la couleur, la clumpiness. Le but étant de comprendre l'origine de la dispersion de cette relation en lien avec les processus physiques responsables de cette séquence afin d'identifier le mode principal de formation d'étoile gouvernant cette séquence. Ce travail a nécessité une approche multi-longueurs d'ondes ainsi que l'utilisation de simulations de profils de galaxies pour distinguer les différents types morphologiques de galaxies impliqués dans la séquence principale.

We investigate the star formation history (SFH) and chemical evolution of isolated analogs of Local Group (LG) ultrafaint dwarf galaxies (UFDs; stellar mass range of 10(2)M(circle dot) < M-*< 10(5) M-circle dot) and gas-rich, low-mass dwarfs (Leo P analogs; stellar mass range of 10(5)M(circle dot) < M-*< 10(6) M-circle dot). We perform a suite of cosmological hydrodynamic zoom-in simulations to follow their evolution from the era of the first generation of stars down to z=0. We confirm that reionization, combined with supernova (SN) feedback, is primarily responsible for the truncated star formation in UFDs. Specifically, halos with a virial mass of M-vir less than or similar to 2 x 10(9) M-circle dot form greater than or similar to 90% of stars prior to reionization. Our work further demonstrates the importance of Population. III stars, with their intrinsically high [C/Fe] yields and the associated external metal enrichment, in producing low-metallicity stars ([Fe/H] less than or similar to -4) and carbon-enhanced metal-poor (CEMP) stars. We find that UFDs are composite systems, assembled from multiple progenitor halos, some of which hosted only Population. II stars formed in environments externally enriched by SNe in neighboring halos, naturally producing extremely low metallicity Population II stars. We illustrate how the simulated chemical enrichment may be used to constrain the SFHs of true observed UFDs. We find that Leo P analogs can form in halos with M-vir similar to 4 x 10(9) M-circle dot 9 (z = 0). Such systems are less affected byreionization and continue to form stars until z = 0, causing higher-metallicity tails. Finally, we predict the existence of extremely low metallicity stars in LG UFD galaxies that preserve the pure chemical signatures of Population III nucleosynthesis.

The ubiquity of Lyman alpha (Ly alpha) emission in a sample of four bright [O III]- strong star-forming galaxies with redshifts above seven has led to the suggestion that such luminous sources represent a distinct population compared with their fainter, more numerous counterparts. The presence of Lya emission within the reionization era could indicate that these sources created early ionized bubbles due to their unusually strong radiation, possibly because of the presence of active galactic nuclei. To test this hypothesis, we secured long integration spectra with XSHOOTER on the VLT for three z similar or equal to 7 sources selected to have similar luminosities and prominent excess fluxes in the IRAC 3.6 or 4.5 mu m band, usually attributed to strong [O III] emission. We secured additional spectroscopy for one of these galaxies at z = 7.15 using MOSFIRE at the Keck telescope. For the most well-studied source in our sample with the strongest IRAC excess, we detect significant nebular emission from He II and N V indicative of a non-thermal source. For the other two sources at z = 6.81 and z = 6.85, for which no previous optical/near-infrared spectroscopy was available, Ly alpha is seen in one and C III] emission in the other. Although based on a modest sample, our results further support the hypothesis that the phenomenon of intense [O III] emission is associated preferentially with sources lying in early ionized bubbles. However, even though one of our sources at z = 7.15 suggests the presence of non-thermal radiation, such ionized bubbles may not uniquely arise in this manner. We discuss the unique advantages of extending such challenging diagnostic studies with JWST.