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On the Formation of Galaxy Halos: Comparing NGC 5128 and the Local Group Members

W. E. Harris·G. L. H. Harris
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Abstract

The metallicity distribution function (MDF) for the old red-giant stars in the halo of NGC 5128, the nearest giant elliptical galaxy, is virtually identical with the MDF for the old-disk stars in the LMC and also strongly resembles the halo MDF in M31. These galaxies all have high mean halo metallicities ( ~ -0.4$) with very small proportions of low-metallicity stars. These observations reinforce the view that metal-rich halos are quite normal for large galaxies of all types. Such systems are unlikely to have built up by accretion of pre-existing, gas-free small satellite galaxies, unless these satellites had an extremely shallow mass distribution (d log N / d log M > -1). We suggest that the halo of NGC 5128 is more likely to have assembled from hierarchical merging of gas-rich lumps in which the bulk of star formation took place during or after the merger stage.

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W. E. Harris, G. L. H. Harris. 2001-08-14. On the Formation of Galaxy Halos: Comparing NGC 5128 and the Local Group Members. https://doi.org/10.1086/323928

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