I'm an astronomer at the Royal Observatory Edinburgh, part of the University of Edinburgh. Previously, I was at the Institut d'Astrophysique de Paris. 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. To do so, I rely on the development of innovative numerical techniques.

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

Research Overview

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


If you are a student at 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: The Large Magellanic Cloud

I have worked 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.


I'm also interested in where the Large Magellanic Cloud came from and what we can learn about galaxy assembly from it. I hunted for some unique tracers in the leading arm in a recent paper, informed by simulations. We found some candidate stars at large distances from the centre; but we need more data.


A model of the LMC moving through the MW halo, as seen in a concentrated (top) and extended (bottom) tracer, in density (left) and tangential velocity (right).

Technical work: Basis Function Expansions, Multichannel Singular Spectrum Analysis

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 BFE projects, see this dedicated page.


One additional analysis tool I've been working on developing is Multichannel Singular Spectrum Analysis (MSSA). For more details about the MSSA projects, see this dedicated page.


Science Theme: 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 stellar bar (upper panels) and shadow bar (lower panels). Click to read more about the project!


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.


A mollweide projection of the dark matter density in the Milky Way on a spherical surface at the solar radius.

Activities

As a member of the Royal Observatory Edinburgh, I contribute to organising various activities. See a dedicated overview page here.



From a January 2016 Trip to Kitt Peak



ADS

Published work.

Github

See what I'm up to on Github.

ORCiD

0000-0003-1517-3935