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A ‘Universal’ Density Profile for the Outer Stellar Halos of Galaxies

Published online by Cambridge University Press:  21 March 2017

Rhea-Silvia Remus ,
Andreas Burkert  and
Klaus Dolag
Rhea-Silvia Remus
Affiliation:
Universitäts-Sternwarte München, LMU, Scheinerstr. 1, D-81679 München, Germany
Andreas Burkert
Affiliation:
Universitäts-Sternwarte München, LMU, Scheinerstr. 1, D-81679 München, Germany MPI for Extraterrestrial Physics, Giessenbachstrasse 1, D-85748 Garching, Germany
Klaus Dolag
Affiliation:
Universitäts-Sternwarte München, LMU, Scheinerstr. 1, D-81679 München, Germany MPI for Astrophysics, Karl-Schwarzschild Strasse 1, D-85748 Garching, Germany email: [email protected]
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Abstract

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The outer stellar halos of galaxies contain vital information about the formation history of galaxies, since the relaxation timescales in the outskirts are long enough to keep the memory, while the information about individual formation events in the central parts has long been lost due to mixing, star formation and relaxation. To unveil some of the information encoded in these faint outer halo regions, we study the stellar outskirts of galaxies selected from a fully hydrodynamical high-resolution cosmological simulation, called Magneticum. We find that the density profiles of the outer stellar halos of galaxies over a broad mass range can be well described by an Einasto profile. For a fixed total mass range, the free parameters of the Einasto fits are closely correlated. Galaxies which had more (dry) merger events tend to have lesser curved outer stellar halos, however, we find no indication that the amount of curvature is correlated with galaxy morphology. The Einasto-like shape of the outer stellar halo densities can also explain the observed differences between the Milky Way and Andromeda outer stellar halos.

Keywords

galaxies: halosstructureGalaxy: structure
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 11 , Symposium S321: Formation and Evolution of Galaxy Outskirts , March 2016 , pp. 84 - 86
Copyright
Copyright © International Astronomical Union 2017 

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