AA/2016/28986  FADO                                     (Gomes & Papaderos 2017)
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Fitting Analysis using Differential Evolution Optimization (FADO): Spectral
population synthesis through genetic optimization under self-consistency
boundary conditions
      Gomes J.M. & Papaderos P.
      <Astron. Astrophys. Ser. ??, ?? (2017)>
      =2017A&A..??..??
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ADC_Keywords: Galaxies ; Galaxies:spectra ; optical ; Interstellar_Medium ;
              Equivalent_widths
Keywords: Galaxies: evolution - Galaxies: star formation - Galaxies: starburst - 
          Galaxies: stellar content - Galaxies: fundamental parameters - 
          Methods: numerical

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Abstract:
    The goal of population spectral synthesis (PSS; also referred to as
    inverse, semi-empirical evolutionary- or fossil record approach) is to
    decipher from the spectrum of a galaxy the mass, age and metallicity of
    its constituent stellar populations. This technique, which is the reverse
    of but complementary to evolutionary synthesis, has been established as
    fundamental tool in extragalactic research. It has been extensively
    applied to large spectroscopic data sets, notably the SDSS, leading to
    important insights into the galaxy assembly history. However, despite
    significant improvements over the past decade, all current PSS codes
    suffer from two major deficiencies that inhibit us from gaining sharp
    insights into the star-formation history (SFH) of galaxies and potentially
    introduce substantial biases in studies of their physical properties
    (e.g., stellar mass, mass-weighted stellar age and specific star formation
    rate). These are i) the neglect of nebular emission in spectral fits,
    consequently, ii) the lack of a mechanism that ensures consistency between
    the best-fitting SFH and the observed nebular emission characteristics of
    a star-forming (SF) galaxy (e.g., hydrogen Balmer-line luminosities and
    equivalent widths-EWs, shape of the continuum in the region around the
    Balmer and Paschen jump).  In this article, we present FADO (Fitting
    Analysis using Differential evolution Optimization) -- a conceptually
    novel, publicly available PSS tool with the distinctive capability of
    permitting identification of the SFH that reproduces the observed nebular
    characteristics of a SF galaxy. This so-far unique self-consistency
    concept allows us to significantly alleviate degeneracies in current
    spectral synthesis, thereby opening a new avenue to the exploration of the
    assembly history of galaxies. The innovative character of FADO is further
    augmented by its mathematical foundation: FADO is the first PSS code
    employing genetic differential evolution optimization. This, in
    conjunction with various other currently unique elements in its
    mathematical concept and numerical realization (e.g., mid-analysis
    optimization of the spectral library using artificial intelligence, test
    for convergence through a procedure inspired by Markov chain Monte Carlo
    techniques, quasi-parallelization embedded within a modular architecture)
    results in key improvements with respect to computational efficiency and
    uniqueness of the best-fitting SFHs. Furthermore, FADO incorporates within
    a single code the entire chain of pre-processing, modeling,
    post-processing, storage and graphical representation of the relevant
    output from PSS, including emission-line measurements and estimates of
    uncertainties for all primary and secondary products from spectral
    synthesis (e.g., mass contributions of individual stellar populations,
    mass- and luminosity-weighted stellar ages and metallicities). This
    integrated concept greatly simplifies and accelerates a lengthy sequence
    of individual time-consuming steps that are generally involved in PSS
    modeling, further enhancing the overall efficiency of the code and
    inviting to its automated application to large spectroscopic data sets.
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Description:
    FADO comes from the Latin word "fatum" that means fate or destiny. It is
    also a well known genre of Portuguese music, and by choosing this acronym
    for this spectral synthesis tool we would like to pay tribute to Portugal.
    The main goal of FADO is to explore the star-formation and chemical
    enrichment history (the "Fado") of galaxies based on two hitherto unique
    elements in spectral fitting models: a) self-consistency between the
    best-fitting star formation history (SFH) and the nebular characteristics
    of a galaxy (e.g., hydrogen Balmer-line luminosities and equivalent
    widths; shape of the nebular continuum, including the Balmer and Paschen
    discontinuity) and b) genetic optimization and artificial intelligence
    algorithms.

    This document is part of the FADO v.1 distribution package, which contains
    two different ascii files, ReadMe and Read_F, and one tarball archive
    FADOv1.tar.gz. FADOv1.tar.gz contains the binary (executable) compiled in
    both OpenSuSE 13.2 64bit LINUX (FADO) and MAC OS X (FADO_MACOSX). The
    former is compatible with most LINUX distributions, while the latter was
    only tested for Yosemite 10.10.3. It contains the configuration files for
    running FADO: FADO.config and PLOT.config, as well as the "Simple Stellar
    Population" (SSP) base library with the base file list Base.BC03.L, the
    FADO v.1 short manual Read_F and this file (in the ReadMe directory) and,
    for testing purposes, three characteristic de-redshifted spectra from
    SDSS-DR7 in ascii format, corresponding to a star-forming (spec1.txt),
    composite (spec2.txt) and LINER (spec3.txt) galaxy. Auxiliary files needed
    for execution of FADO (.HIfbound_em.ascii, .HeII_fbound.ascii,
    .HeIfboundem.ascii, grfont.dat and grfont.txt) are also included in the
    tarball. By decompressing the tarball the following six directories are
    created: input, output, plots, ReadMe, SSPs and tables (see below for a
    brief explanation).
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File Summary:
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  FileName      Lrecl  Records   Explanations
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ReadMe             80        .   This file
Read_F            195        .   FADO v.1 ReadMe
FADOv1.tar.gz      --       15   FADO v.1 tarball
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**********************************
Description of file: FADOv1.tar.gz

If you list the files after decompressing you should get:

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   SIZE (bytes)      FILES                 | Description
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7234080              FADO                  | FADO binary (executable) LINUX
   6664              FADO.config           | FADO config file for the fitting
7003036              FADO_MACOSX           | FADO binary (executable) MAC OS X
  66020              grfont.dat            | FONTS for PGPLOT
 557436              grfont.txt            | FONTS for PGPLOT
 324993              .HeIfboundem.ascii    | Auxiliary file for running FADO
  44222              .HeII_fbound.ascii    | Auxiliary file for running FADO
  21286              .HIfbound_em.ascii    | Auxiliary file for running FADO
   4096              input*                | Directory with 3 SDSS-DR7 spectra
   4096              output                | Empty directory for output
   2815              PLOT.config           | FADO plotting configuration file
   4096              plots                 | Empty directory for plots
   4096              ReadMe                | Short manual Read_F and ReadMe
  12288              SSPs                  | SSPs and base file Base.BC03.L
   4096              tables                | Empty directory for tables
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* Three characteristic SDSS DR7 spectra are two-column ascii format,
  corresponding to wavelenghts and fluxes and one ascii table (List) with the
  name and luminosity distance in Mpc.

Byte-by-byte Description of the three SDSS-DR7 spectra: spec1.txt, spec2.txt
                                                      & spec3.txt 
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   Bytes  Format    Units                Label         Explanations
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   1 - 5  F4.1      Å                    Wavelength    ---
   11-21  F6.1      1e-17 erg/(s*cm**2)  Fluxes        ---
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Byte-by-byte Description of the file: List
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   Bytes  Format    Units                Label         Explanations
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   1 - 8  A9        ---                  Spectrum      ---
   10-15  F3.2      Mpc                  Distance      ---
   17-20  F1.2        Å                  Resolution    FWHM
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Acknowledgements: jean @ astro.up.pt and papaderos @ astro.up.pt
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(End)                                                        [CDS]   25-Mar-2017
