2021/09/21 by C. Pappalardo, Pappalardo, Ciro
Chemistry · Physics and Astronomy · #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Spectroscopy and Laser Applications #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2109.10363
openalex publication_date 2021/09/21 · openalex created_date 2022/10/01 · openalex updated_date 2026/07/28
In this work, we investigate the reliability of spectral synthesis methods in\nthe estimation of the mean stellar age and metallicity, addressing the question\nof which signal-to-noise ratios (S/N) are needed to determine these quantities.\nTo address this problem we used simulated spectra containing stellar and\nnebular emission, reproducing the evolution of a galaxy for a constant and\nexponentially declining star formation law. The spectra have been degraded to\ndifferent S/N and analysed with three different spectral synthesis codes: FADO,\nSTARLIGHT, and STECKMAP assuming similar fitting set-ups and the same spectral\nbases. For S/N > 5 all tools considered show a large diversity in the results.\nFADO and STARLIGHT find median differences in light-weighted mean stellar ages\nof ~0.1 dex, while STECKMAP shows a higher value of ~0.2 dex. For S/N > 50 the\nmedian differences in FADO are ~0.03 dex (~7%), a factor 3 and 4 lower than the\n0.08 dex (~20%) and 0.11 dex (~30%) obtained from STARLIGHT and STECKMAP,\nrespectively. Our results indicate that phases of high specific star formation\nrate (sSFR) in galaxies require analysis tools that do not neglect the nebular\ncontinuum emission in the fitting process, since purely stellar models would\nhave strong problems in the estimation of star formation history, even in\npresence of high S/N spectra.\n The median values of these differences are of the order of 7% (FADO), 20%\n(STARLIGHT), and 30% (STECKMAP) for light-weighted quantities, and 20% (FADO),\n60% (STARLIGHT), and 20% (STECKMAP) for mass-weighted quantities. That implies\na severe overestimation of the mass-to-light ratio and stellar mass, even in\nthe presence of a mild contribution from the nebular continuum. Our work\nunderlines the importance of a self-consistent treatment of nebular emission,\nwhich is the only route towards a reliable determination of the assembly of any\nhigh-sSFR galaxy.\n