Clustered star formation as a natural explanation for the H alpha cut-off in disk galaxies

Article

关键词: INITIAL MASS FUNCTION;    EXTREME OUTER DISK;    SPIRAL GALAXIES;    FORMATION RATES;    GALACTIC DISKS;    FORMATION LAW;    GAS;    REGIONS;    CONTINUUM;    DENSITY;   

DOI  :  10.1038/nature07266

来源: SCIE

【 摘 要 】

The rate of star formation in a galaxy is often determined by the observation of emission in the H alpha line, which is related to the presence of short- lived massive stars. Disk galaxies show a strong cut- off in H alpha radiation at a certain galactocentric distance, which has led to the conclusion that star formation is suppressed in the outer regions of disk galaxies. This is seemingly in contradiction to recent observations(1) in the ultraviolet which imply that disk galaxies have star formation beyond the H alpha cut- off, and that the star-formation-rate surface density is linearly related to the underlying gas surface density, which is a shallower relationship than that derived from H alpha luminosities(2). In a galaxy- wide formulation, the clustered nature of star formation has recently led to the insight that the total galactic H alpha luminosity is nonlinearly related to the galaxy- wide star formation rate(3). Here we show that a local formulation of the concept of clustered star formation naturally leads to a steeper radial decrease in the H alpha surface luminosity than in the star-formation-rate surface density, in quantitative agreement with the observations, and that the observed H alpha cut- off arises naturally.

【 授权许可】

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