A 3.5-Gyr-old galaxy at redshift 1.55

Article Abstract:

The 53W091 galaxy present at a redshift (z) of 1.55 is a weak and red radio galaxy whose red color is due to the presence of old stars. Analysis of the galaxy's spectral data indicates that the stars were formed 3.5 Gyr years ago. The age of this galaxy is more than that of the Universe at z = 1.55 predicted by the Einstein-de Sitter cosmology model. The z during formation of 53W091 was probably 4. This shows that some galaxies were formed at redshifts greater than that of the recent formation period, which is based on studies of field galaxies.

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Significant primordial star formation at redshifts z approximately 3-4

Article Abstract:

The four problems related to understanding of high-redshift galaxies are resolved simultaneously if 10-30 percent of the stars in many galaxies at z approximately 3-4 are primordial unenriched by elements heavier than helium. Results imply that micromixing of metals within galaxies is inefficient on an approximately gigayear timescale.

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The star-formation history of the universe from the stellar populations of nearby galaxies

Article Abstract:

The formation and the evolution of the galaxial structure can determine the star-formation history of the Universe. The bigger the stellar mass of the galaxy, the earlier the stars were performed is determined.

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