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# Journal-club Postdoc

« A Comprehensive Comparative Test of Seven Wildly-Used Spectral Synthesis Models Against Multi-Band Photometry of Young Massive Star Clusters »

Aida Wofford

Spectral synthesis models of massive-star populations are crucial to characterise star formation at all cosmic epochs. Recently, three independent groups released massive-star evolution models including various updates, from the details of the input physics, to the effects of rotation, to those of interacting binaries. We test spectral synthesis models based on seven different flavors of massive-star evolution against near-ultraviolet to near-infrared photometry of eight young massive clusters in galaxies, NGC 1566 and NGC 5253, which have published metallicities matching the two values for which all seven flavors of models are available. The photometry is from the \textit{Hubble Space Telescope} Treasury program, LEGUS, and the archive. The high angular resolution, extensive cluster inventory and inclusion of a near-ultraviolet band make the LEGUS dataset excellent for this study. We account for both stellar and nebular emission in the models and try two different prescriptions for attenuation by dust. From Bayesian fits to the observations, we find cluster reddenings, masses and ages in the ranges $(0.05\pm0.02-0.54\pm0.13)$ mag, $(1.8\pm0.3-10\pm5)\times10^4\,M_\odot$ and $(1.6\pm0.4-40\pm27.7)$\,Myr, which are characterised by typically small standard deviations derived for individual clusters using different models ($\sim0.03\,$mag, $\sim10^4\,M_\odot$ and $\sim1\,$Myr), although maximum differences are typically 0.09 mag in $E(B-V)$, a factor of 2.8 in mass, and a factor of 2.5 in age. In terms of best fit, the observations are slightly better reproduced by models with interacting binaries and least well reproduced by models with single rotating stars.
Our study provides a first quantitative estimate of the accuracies and uncertainties of the most recent spectral evolution models of massive-star populations, demonstrates the good progress of models in fitting high-quality observations, and highlights the needs for using a larger cluster sample and testing more extensively the model parameter space.
mardi 15 décembre 2015 - 11:00
Salle des séminaires Évry Schatzman, Institut d'Astrophysique
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