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Register a new userThe Pegase.3 code of spectrochemical evolution of galaxies: documentation and complements
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Pegase.3 is a Fortran 95 code modeling the spectral evolution of galaxies from the far-ultraviolet to submillimeter wavelengths. It also follows the chemical evolution of their stars, gas and dust. For a given scenario (a set of parameters defining the history of mass assembly, the star formation law, the initial mass function...), Pegase.3 consistently computes the following: * the star formation, infall, outflow and supernova rates from 0 to 20 Gyr; * the stellar metallicity, the abundances of main elements in the gas and the composition of dust; * the unattenuated stellar spectral energy distribution (SED); * the nebular SED, using nebular continua and emission lines precomputed with code Cloudy (Ferland et al. 2017); * the attenuation in star-forming clouds and the diffuse interstellar medium, by absorption and scattering on dust grains, of the stellar and nebular SEDs. For this, the code uses grids of the transmittance for spiral and spheroidal galaxies. We precomputed these grids through Monte Carlo simulations of radiative transfer based on the method of virtual interactions; * the re-emission by grains of the light they absorbed, taking into account stochastic heating. The main innovation compared to Pegase.2 is the modeling of dust emission and its evolution. The computation of nebular emission has also been entirely upgraded to take into account metallicity effects and infrared lines. Other major differences are that complex scenarios of evolution (derived for instance from cosmological simulations), with several episodes of star formation, infall or outflow, may now be implemented, and that the detailed evolution of the most important elements -- not only the overall metallicity -- is followed.
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We provide here the documentation of the new version of the spectral evolution model PEGASE. PEGASE computes synthetic spectra of galaxies in the UV to near-IR range from 0 to 20 Gyr, for a given stellar IMF and evolutionary scenario (star formation law, infall, galactic winds). The radiation emitted by stars from the main sequence to the pre-supernova or white dwarf stage is calculated, as well as the extinction by dust. A simple modeling of the nebular emission (continuum and lines) is also proposed. PEGASE may be used to model starbursts as well as old galaxies. The main improvements of PEGASE.2 relative to PEGASE.1 (Fioc & Rocca-Volmerange 1997) are the following: (1)The stellar evolutionary tracks of the Padova group for metallicities between 0.0001 and 0.1 have been included; (2)The evolution of the metallicity of the interstellar medium (ISM) due to SNII, SNIa and AGB stars is followed. Stars are formed with the same metallicity as the ISM (instead of a solar metallicity in PEGASE.1), providing thus a metallicity-consistent model; (3)Lejeune et al.s library of stellar spectra is used; (4)The extinction by dust is computed for geometries corresponding to disk and spheroidal galaxies using a radiative transfer code taking into account the scattering. The main outputs (as a function of time) are spectra, colors and magnitudes in various photometric systems, luminosities, type II and Ia supernovae rates, line intensities and equivalent widths, amount and metallicity of stars and gas, mass locked in stellar remnants, optical depth and total dust emission. The corresponding article (Fioc & Rocca-Volmerange 2000) will be submitted soon. A detailed modeling of the spectrum of the dust emission and of HII regions (Moy, Rocca-Volmerange & Fioc 2000) will be included in futu
Aspects ([asp{epsilon}], ASsociation PositionnellE/ProbabilistE de CaTalogues de Sources in French) is a Fortran 95 code for the cross-identification of astrophysical sources. Its source files are freely available. Given the coordinates and positional uncertainties of all the sources in two catalogs K and K, Aspects computes the probability that an object in K and one in K are the same or that they have no counterpart. Three exclusive assumptions are considered: (1) Several-to-one associations: a K-source has at most one counterpart in K, but a K-source may have several counterparts in K; (2) One-to-several associations: the same with K and K swapped; (3) One-to-one associations: a K-source has at most one counterpart in K and vice versa. To compute the probabilities of association, Aspects needs the a priori (i.e. ignoring positions) probability that an object has a counterpart. The code obtains estimates of this quantity by maximizing the likelihood to observe all the sources at their effective positions under each assumption. The likelihood may also be used to determine the most appropriate model, given the data, or to estimate the typical positional uncertainty if unknown.
We present PEGASE-HR, a new stellar population synthesis program generating high resolution spectra (R=10 000) over the optical range lambda=400--680 nm. It links the spectro-photometric model of galaxy evolution PEGASE.2 (Fioc & Rocca-Volmerange 1997) to an updated version of the ELODIE library of stellar spectra observed with the 193 cm telescope at the Observatoire de Haute-Provence (Prugniel & Soubiran 2001a). The ELODIE star set gives a fairly complete coverage of the Hertzprung-Russell (HR) diagram and makes it possible to synthesize populations in the range [Fe/H]=-2 to +0.4. This code is an exceptional tool for exploring signatures of metallicity, age, and kinematics. We focus on a detailed study of the sensitivity to age and metallicity of the high-resolution stellar absorption lines and of the classical metallic indices proposed until now to solve the age-metallicity degeneracy. Validity tests on several stellar lines are performed by comparing our predictions for Lick indices to the models of other groups. The comparison with the lower resolution library BaSeL (Lejeune et al. 1997) confirms the quality of the ELODIE library when used for simple stellar populations (SSPs) from 10 Myr to 20 Gyr. Predictions for the evolved populations of globular clusters and elliptical galaxies are given and compared to observational data. Two new high-resolution indices are proposed around the Hgamma line. They should prove useful in the analysis of spectra from the new generation of telescopes and spectrographs.
Upcoming HI surveys will deliver large datasets, and automated processing using the full 3-D information (two positional dimensions and one spectral dimension) to find and characterize HI objects is imperative. In this context, visualization is an essential tool for enabling qualitative and quantitative human control on an automated source finding and analysis pipeline. We discuss how Visual Analytics, the combination of automated data processing and human reasoning, creativity and intuition, supported by interactive visualization, enables flexible and fast interaction with the 3-D data, helping the astronomer to deal with the analysis of complex sources. 3-D visualization, coupled to modeling, provides additional capabilities helping the discovery and analysis of subtle structures in the 3-D domain. The requirements for a fully interactive visualization tool are: coupled 1-D/2-D/3-D visualization, quantitative and comparative capabilities, combined with supervised semi-automated analysis. Moreover, the source code must have the following characteristics for enabling collaborative work: open, modular, well documented, and well maintained. We review four state of-the-art, 3-D visualization packages assessing their capabilities and feasibility for use in the case of 3-D astronomical data.
Star forming galaxies represent a small yet sizable fraction of the X-ray sky (1%-20%, depending on the flux). X-ray surveys allow to derive their luminosity function and evolution, free from uncertainties due to absorption. However, much care must be put in the selection criteria to build samples clean from contamination by AGN. Here we review the possibilities offered by the proposed WFXT mission for their study. We analyze the expected luminosity and redshift distributions of star forming galaxies in the proposed WFXT surveys. We discuss the impact of such a mission on the knowledge of the cosmic star formation history, and provide a few suggestions.
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