I'm an Astronomer at the Institut d'Astrophysique de Paris. Previously, I was at the Institute for Astronomy, part of the Royal Observatory of Edinburgh and the University of Edinburgh. Prior to that, I studied at the University of Massachusetts at Amherst. I'm interested in how bodies move and interact in and around galaxies -- primarily our own Milky Way.

I study the nature of dark matter through its inferred and measured structure and properties. I also develop numerical techniques, including machine learning.

I can be reached at petersen@iap.fr or michael.petersen@roe.ac.uk.

Research Overview

Milky Way-Large Magellanic Cloud interation. Milky Way secular evolution, velocity fields in barred galaxies, structure formation in barred galaxies. Basis Function Expansions. Mock stellar catalogs. Dark matter halo dynamics. High precision n-body simulations. Numerical techniques.

If you are a student at IAP, the University of Edinburgh, or the University of Massachusetts (Amherst) and want to work on or discuss any of the above, please get in touch! I have a lot of projects at various levels that are just looking for the right researcher.

Science Theme 1: The Large Magellanic Cloud

Lately, I have been working on the observable effects of the Large Magellanic Cloud on the stellar halo of the Milky Way. With Jorge Peñarrubia, I made predictions for the observable (apparent) dipole signature in the halo resulting from the motion of the disc. We then detected the dipole signature in a sample of distant halo tracers. Click here for more details about the project and a selection of the press coverage.

Technical work: Basis Function Expansions

I have spent most of my scientific career using basis function expansions (BFE) to answer scientific questions (see above and below). This work has also necessitated advances in BFE technology, which resulted in a paper you can read here. For more details about the projects, see this dedicated page.

Science Theme 2: Barred Galaxies

Bars are the most ubiquitous non-axisymmetric structure observed in the local universe, observed in roughly two-thirds of local galaxies. My thesis focused on numerical simulations and analytic calculations to examine detailed physical processes related to the formation and evolution of bars.

One result to come of this work is the discovery of a trapped component in the dark matter halo that mimics the stellar bar, which we refer to as the shadow bar. Click on the image below for a more comprehensive look at the shadow bar work, or read the MNRAS paper.

The shadow bar has consequences for the structure of the dark matter halo at the solar circle.

The combination of the stellar and shadow bar drives non-axisymmetric structure in the dark matter halo--which has consequences for direct detection experiments on Earth. Click on the image below for a more comprehensive look at the implications for direct detection experiments, or read the PhysRevD paper.


While at the Royal Observatory Edinburgh, I contributed to organising various activities. See a dedicated overview page here.


Published work.


See what I'm up to on Github.


I'm also on Twitter.