P\'egase.3: A code for modeling the UV-to-IR/submm spectral and chemical evolution of galaxies with dust

A code computing consistently the evolution of stars, gas and dust, as well as the energy they radiate, is required to derive reliably the history of galaxies by fitting synthetic SEDs to multiwavelength observations. The new code P\'egase.3 described in this paper extends to the far-IR/submm the UV-to-near-IR modeling provided by previous versions of P\'egase. It first computes the properties of single stellar populations at various metallicities. It then follows the evolution of the stellar light of a galaxy and the abundances of the main metals in the ISM, assuming some scenario of mass assembly and star formation. It simultaneously calculates the masses of the various grain families, the optical depth of the galaxy and the attenuation of the SED through the diffuse ISM in spiral and spheroidal galaxies, using grids of radiative transfer precomputed with Monte Carlo simulations taking scattering into account. The code determines the mean radiation field and the temperature probability distribution of stochastically heated individual grains. It then sums up their spectra to yield the overall emission by dust in the diffuse ISM. The nebular emission of the galaxy is also computed, and a simple modeling of the effects of dust on the SED of star-forming regions is implemented. The main outputs are UV-to-submm SEDs of galaxies from their birth up to 20 Gyr, colors, masses of galactic components, ISM abundances of metallic elements and dust species, supernova rates. The temperatures and spectra of individual grains are also available. The paper discusses several of these outputs for a scenario representative of Milky Way-like spirals. P\'egase.3 is fully documented and its Fortran 95 source files are public. The code should be especially useful for cosmological simulations and to interpret future mid- and far-IR data, whether obtained by JWST, LSST, Euclid or e-ELT.Comment: 15 pages. In press in A&A. Source files of the code available at http://www.iap.fr/users/fioc/Pegase/Pegase.3/ (and http://www.iap.fr/pegase/); documentation at arXiv:1902.0219

Photometric redshifts from evolutionary synthesis with PEGASE: the code ZPEG and the z=0 age constraint

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 $\Delta z$ > 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 $\chi^2$-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/pegaseComment: 10 pages, 10 postscript figures, 2 tables; accepted for publication in Astronomy & Astrophysics; to compute redshifts see http://www.iap.fr/pegase

Relation noyau actif et histoire de la formation d'étoiles dans les radio galaxies distantes

Les radio galaxies sont les candidats préférentiels pour comprendre la formation et l'évolution des galaxies sur une grande échelle de temps. Observées jusqu'à z>5 en raison de leur brillance, elles sont abritées par des galaxies elliptiques géantes. L'émission radio révèle la présence d'un trou noir supermassif. Un tore de poussière entourant le noyau actif de galaxie (AGN) agit comme un coronographe naturel permettant alors l'étude de la galaxie hôte. L'objectif de cette thèse est de déterminer l'évolution de la composante stellaire en présence d'un AGN. La décomposition est faite à partir de la distribution spectrale d'énergie (SED) de l'UV au submillimétrique en utilisant le code d'évolution de galaxies PEGASE.3 et un code d' AGN, les deux modélisant l'émission de la poussière par transfert radiatif.En premier lieu, nous présentons le projet HeRGE, 70 radio galaxies observées avec Herschel, qui permet de mesurer leurs luminosités totales infrarouges, comparables à celles des ULIRG. Une décomposition de la luminosité infrarouge entre l'émission AGN et un modèle de starburst est proposée pour l'ensemble de l'échantillon. Ces luminosités élevées sont interprétées en termes de taux d'accrétion et de formation d'étoiles, favorisant la croissance du trou noir par rapport à la galaxie hôte.En second lieu, l'orientation du jet par rapport au tore est contrainte à partir de l'infrarouge moyen et du rapport des émissions radio des lobes (isotrope, 500MHz) et du coeur (anisotrope, 20GHz). Ces observations en accord avec le modèle d'unification permettent d'évaluer le facteur d'absorption Av, l'inclinaison du tore et de contraindre le facteur de Lorentz.Une sélection de 12 radio galaxies observées de l'UV au sub-mm est analysée avec PEGASE.3 et un modèle d'AGN. Une seule composante stellaire est insuffisante. Seules deux composantes (une évoluée et massive, et une jeune issue d'un starburst) permettent un ajustement significatif de la SED complète. La composante évoluée est très massive (environ 10^12 msun) formée sur une courte période de temps (5 and are commonly associated with the massive early-type galaxies observed in the local universe. While the radio emission reveals the presence of a supermassive black hole, a dusty parsec-scale torus acts like a natural coronograph, making it easier to study the properties of the host galaxy. The aim of this PhD thesis is to characterise the nature and evolution of the stellar population and the relationship between the stellar population and the active galactic nucleus (AGN). To reach our scientific goals, we use the galaxy evolution code, PEGASE, combined with a AGN model which both consider the radiative transfer of the UV, optical, and IR photons through dust. To begin, we present the HeRGE project consisting of 70 radio galaxies which have been observed with Herschel. These IR observations allow us to calculate the total infrared luminosities and reveal that our sample belongs to the ULIRG regime. We decompose the infrared SED into an AGN and starburst components using observational templates. Converted into accretion and star formation rate, their relative luminosities indicate that the black holes are growing proportionally faster than are the host galaxies.In addition, we constrain the configuration of the jet and torus by combining the results from mid-infrared spectral energy distribution (SED), and the radio emission from the lobes (isotropic at 500MHz) and the core (anisotropic at 20GHz). In agreement with the unified scheme, these observations allow us to estimate the absorption Av, the inclination of the torus, and provides a constraint on the Lorentz factor for the radio jet.A subsample of 12 radio galaxies observed from the UV to sub-mm is also analysed with PEGASE.3 and an AGN torus model. While one stellar component is clearly insufficient to fit the observations, two stellar components are necessary to successfully reproduce the SED (one evolved and massive, about 10^12 msun, formed over a reasonably short time, <1Gyr at high redshift; and a much younger component, <40Myr, that is also less massive, about 10^11 msun. Such a star formation history suggests rapid growth at high redshift of longer duration followed much by another period of rapid, stochastic growth.These results put strong constraints on galaxy formation models. Unfortunately, the crudeness of some of our data and theoretical understanding the IR emission from AGN, means that the relation of the galaxy to its AGN is still not well constrained. Additional observations at optical through millimeter wavelengths are needed to extend our findings.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF