A Universal Stellar Initial Mass Function? A Critical Look at Variations

作者: Nate Bastian , Kevin R. Covey , Michael R. Meyer

DOI: 10.1146/ANNUREV-ASTRO-082708-101642

关键词: Log-normal distributionObservablePhysicsStar formationAstrophysicsInitial mass functionGlobular clusterGalaxyStarsSolar mass

摘要: Few topics in astronomy initiate such vigorous discussion as whether or not the initial mass function (IMF) of stars is universal, instead sensitive to conditions star formation. The distinction critical importance: IMF influences most observable properties stellar populations and galaxies, detecting variations could provide deep insights into process by which form. In this review, we take a look at case for variations, with view towards other explanations are sufficient given evidence. Studies field, local young clusters associations, old globular suggest that vast majority were drawn from "universal" IMF: power-law Salpeter index ($\Gamma=1.35$) above few solar masses, log normal shallower ($\Gamma \sim 0-0.25$) between tenths masses (ignoring effects unresolved binaries). shape universality stellar-substellar boundary still under investigation uncertainties remain large, but observations consistent declines < -0.5$) well below hydrogen burning limit. Observations resolved integrated galaxies also "universal IMF", suggesting no gross over much cosmic time. There indications "non-standard" IMFs specific extragalactic environments, clearly warrant further study. Nonetheless, there clear evidence varies strongly systematically after first generations stars.

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