To use or not to use synthetic stellar spectra in population synthesis models?

Coelho, P.; Bruzual, G.; Charlot, S.

doi:10.1093/mnras/stz3023

Cited by 38 publications

(39 citation statements)

References 107 publications

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“…The uncertainty of the age estimation comes from the uncertainty of the isochrone model and the metallicity assumption of the applied isochrone (Coelho et al 2020). The metallicity and α-enhancement of the real stellar population are not exactly the same as the assumed isochrone.…”

Section: Galaxy Agementioning

confidence: 99%

Chemical evolution of ultra-faint dwarf galaxies in the self-consistently calculated integrated galactic IMF theory

Yan

Jeřabková

Kroupa

2020

A&A

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The galaxy-wide stellar initial mass function (gwIMF) of a galaxy in dependence on its metallicity and star formation rate can be calculated by the integrated galactic IMF (IGIMF) theory. This theory has been applied in a study of the chemical evolution of the ultra-faint dwarf (UFD) satellite galaxies, but failed to reproduce the data. Here, we find that the IGIMF theory is naturally consistent with the data. We applied the time-evolving gwIMF, which was calculated at each time step. The number of type Ia supernova explosions that forms per unit stellar mass was renormalised according to the gwIMF. The chemical evolution of Boötes I, one of the best-observed UFD, was calculated. Our calculation suggests a mildly bottom-light and top-light gwIMF for Boötes I, and that this UFD has the same gas-consumption timescale as other dwarfs, but was quenched about 0.1 Gyr after formation. This is consistent with independent estimations, and it is similar to Dragonfly 44. The recovered best-fitting input parameters in this work are not covered in previous work, creating a discrepancy between our conclusions. In addition, a detailed discussion of the uncertainties is presented to address the dependence of the chemical evolution model results on the applied assumptions. This study demonstrates the power of the IGIMF theory in understanding star formation in extreme environments and shows that UDFs are a promising pathway to constrain the variation of the low-mass stellar IMF.

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Section: Galaxy Agementioning

confidence: 99%

Chemical evolution of ultra-faint dwarf galaxies in the self-consistently calculated integrated galactic IMF theory

Yan

Jeřabková

Kroupa

2020

A&A

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“…As described before, synthetic stellar libraries like the Munari et al (2005) library offer both a more extensive mapping of the HR diagram and better coverage in wavelength than empirical libraries. The impact of utilizing synthetic versus empirical stellar libraries, and libraries with limited versus full HR coverage on predicted properties, such as colours and magnitudes of SSPs, and age, metallicity, and reddening measures extracted from spectral fits, are investigated by Coelho, Bruzual & Charlot (2020). In the case of synthetic versus empirical, they find a null effect on the mean light-weighted ages, but find metallicity to be underestimated by ∼0.13, whereas in the case of limited versus full wavelength coverage, the ages are found to be underestimated while metallicity shows a little impact.…”

Section: The Stellar Spectral Librarymentioning

confidence: 99%

Stellar populations and physical properties of starbursts in the antennae galaxy from self-consistent modelling of MUSE spectra

Gunawardhana

Brinchmann

Weilbacher

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We have modelled the stellar and nebular continua and emission-line intensity ratios of massive stellar populations in the Antennae galaxy using high resolution and self-consistent libraries of model HII regions around central clusters of aging stars. The model libraries are constructed using the stellar population synthesis code, Starburst99, and photoionisation model, Cloudy. The Geneva and PARSEC stellar evolutionary models are plugged into Starburst99 to allow comparison between the two models. Using a spectrum-fitting methodology that allows the spectral features in the stellar and nebular continua (e.g. Wolf-Rayet features, Paschen jump), and emission-line diagnostics to constrain the models, we apply the libraries to the high-resolution MUSE spectra of the starbursting regions in the Antennae galaxy. Through this approach, we were able to model the continuum emission from Wolf-Rayet stars and extract stellar and gas metallicities, ages, electron temperatures and densities of starbursts by exploiting the full spectrum. From the application to the Antennae galaxy, we find that (1) the starbursts in the Antennae galaxy are characterised by stellar and gas metallicities of around solar, (2) the star-forming gas in starbursts in the Western loop of NGC 4038 appears to be more enriched, albeit slightly, than the rest of galaxy, (3) the youngest starbursts are found across the overlap region and over parts of the western-loop, though in comparison, the regions in the western-loop appear to be at a slightly later stage in star-formation than the overlap region, and (4) the results obtained from fitting the Geneva and Parsec models are largely consistent.

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“…For example, empirical spectra may show emission or absorption features that evidently exist in nature, but are omitted from theoretical models because their origin is unknown and cannot be identified. A recent analysis of the effects of library limitations on galaxy spectral fitting was presented by Coelho et al [122].…”

Section: Improved Atmospheresmentioning

confidence: 99%

Applications of Stellar Population Synthesis in the Distant Universe

Stanway

2020

Galaxies

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Comparison with artificial galaxy models is essential for translating the incomplete and low signal-to-noise data we can obtain on astrophysical stellar populations to physical interpretations which describe their composition, physical properties, histories and internal conditions. In particular, this is true for distant galaxies, whose unresolved light embeds clues to their formation and evolution as well as their impact on their wider environs. Stellar population synthesis models are now used as the foundation of analysis at all redshifts, but are not without their problems. Here we review the use of stellar population synthesis models, with a focus on applications in the distant Universe.Galaxies 2020, 8, 6 2 of 32 astronomical observations, usually over a wider wavelength range or with a higher signal-to-noise, to break.In the photon-starved regime occupied by observations of the earliest galaxies to radiate through the Universe, this presents a problem: often it simply is not possible to find an independent diagnostic which will distinguish between models, and obtainable signal-to-noise may be limited by instrumental and background noise rather than by the source. In this situation, the interpretation offered by a single population synthesis model is often accepted without close scrutiny, with a deep faith placed on the calibration of those models in the relatively local Universe. In the past, for observations of galaxies at z < 2, this faith has been well founded. The stellar populations which can be resolved in detail and probed in the Milky Way and the Local Group are typical of galaxies at these redshifts in both age and metallicity. However as the observational frontier is pushed back to ever higher redshifts, it is clear that the typical star formation densities and environments are very different, as are the stellar metallicities [10, and references therein]. This has prompted a reevaluation of the stellar population synthesis models in use at these redshifts, and their calibration in hitherto unconsidered regimes [11].This review discusses both our current state of understanding of galaxies in the distant Universe, and how that understanding is informed by the stellar population synthesis models we use. Key examples and uncertainties are highlighted, and a holistic approach, in which all possible diagnostic indicators of a stellar population are considered, is advocated. Galaxies in the Distant Universe The First StarsThe definition of the distant Universe varies, but in the context of galaxy formation and evolution it applies primarily to the interval between the formation of the first stars ('cosmic dawn') which ended the cosmic Dark Ages at around z ∼ 7 − 15, and the coincident peaks of the volume-averaged star formation rate density history and AGN activity at z ∼ 2 ('cosmic noon'). Over this ∼2.5 Gyr interval, the first galaxies were not only born, but also evolved significantly [e.g. 12,13], such that galaxy populations at z > 5 are typically younger, more highly ionizing, less massive and less...

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To use or not to use synthetic stellar spectra in population synthesis models?

Cited by 38 publications

References 107 publications

Chemical evolution of ultra-faint dwarf galaxies in the self-consistently calculated integrated galactic IMF theory

Chemical evolution of ultra-faint dwarf galaxies in the self-consistently calculated integrated galactic IMF theory

Stellar populations and physical properties of starbursts in the antennae galaxy from self-consistent modelling of MUSE spectra

Applications of Stellar Population Synthesis in the Distant Universe

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