The Globular Star Clusters of the Andromeda Galaxy by Charli M Sakari

Author:Charli M Sakari
Language: eng
Format: epub
ISBN: 9781643277509
Publisher: IOP Publishing
Published: 2019-12-19T00:00:00+00:00

M31 has more intermediate-metallicity and metal-poor GCs: although they seem to be distributed spherically around the center of M31, a significant number of these more metal-poor GCs (with ) look to be rotating with the main galaxy. There is also a net metallicity gradient in the GC sample (though the median GC metallicity is lower than the median metallicity of the field stars). These findings seem to suggest that a non-negligible number of the GCs in the inner halo either formed in the body of M31 (the in situ scenario) or formed in 1-2 massive dwarf galaxies that were later accreted but happened to be rotating around M31 with the field stars. The [Ca/Fe] abundances (and, in a handful of cases, the ages) of the majority of these GCs also indicate that they had to have formed in a fairly massive galaxy.

The Milky Way does not have a similar dominant population of rotating metal-poor GCs. This could mean that M31 experienced higher rates of star formation early on, creating more massive metal-poor and intermediate-metallicity GCs that have survived to the present day; or it could mean that M31 has accreted more massive satellites. Indeed, the presence of the GSS strongly suggests that M31 is in the process of accreting a satellite about the mass of the LMC. This massive galaxy likely brought in many of the GCs in the inner region, or triggered high rates of star formation in M31.17

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