【报告人】郑征 （国家天文台）

【报告时间】2019年12月26日（星期四）10：00

【报告地点】物理学院B座9楼天象馆

【报告摘要】In the standard cosmological model, dark matter drives the structure formation of galaxies and constructs potential wells within which galaxies may form. The baryon fraction in dark halos can reach the Universal value (15.7%) in massive clusters and decreases rapidly as the mass of the system decreases. The formation of dwarf galaxies is sensitive both to baryonic processes and the properties of dark matter owing to the shallow potential wells in which they form. In dwarf galaxies in the Local Group, dark matter dominates the mass content even within their optical-light half-radii (Re ≈ 1 kpc). However, recently it has been argued that not all dwarf galaxies are dominated by dark matter. Here we report 19 dwarf galaxies that could consist mainly of baryons up to radii well beyond Re, at which point they are expected to be dominated by dark matter. Of these, 14 are isolated dwarf galaxies, free from the influence of nearby bright galaxies and high density environments. This result provides observational evidence that could challenge the formation theory of low-mass galaxies within the framework of standard cosmology.