N-body simulations of open clusters and their destruction
(2026)- Abstract
- Stellar clusters are structures of stars that are bound together by their mutual gravitational forces. As a cluster evolves, it will lose stars as a consequence of internal and external effects. The external effect is the most important and affects the cluster via gravitational tidal forces that can strip stars away from the cluster. Stellar clusters are subject to gravitational scattering and tidal disruption by giant molecular clouds (GMCs) which can significantly affect their orbit and evolution.
This thesis investigates the impact that GMCs have on clusters, and how this affects their observed populations. We do this by using a combination of galactic models and N-body simulations.
In paper I, we investigate if the Sun could... (More) - Stellar clusters are structures of stars that are bound together by their mutual gravitational forces. As a cluster evolves, it will lose stars as a consequence of internal and external effects. The external effect is the most important and affects the cluster via gravitational tidal forces that can strip stars away from the cluster. Stellar clusters are subject to gravitational scattering and tidal disruption by giant molecular clouds (GMCs) which can significantly affect their orbit and evolution.
This thesis investigates the impact that GMCs have on clusters, and how this affects their observed populations. We do this by using a combination of galactic models and N-body simulations.
In paper I, we investigate if the Sun could have originated from the open cluster M67 which is currently located high above the disc of the Milky Way. The Sun is located in the Galactic disc so there is a clear dynamical discrepancy between the two objects. We show that it is possible, but unlikely, for the Sun to have been born in M67 if the Sun escapes the cluster at a young age, before M67 is
scattered to its current orbit by GMCs.
In paper II, we investigate how tidal disruption by GMCs affects the cluster population of the galaxy M51 over a period of the last 200 Myr. We do this by simulating 5000 unique clusters twice: with and without being affected by tidal forces from the GMCs. We are able to reproduce the majority of the observed population and find that low-mass clusters, that are located close to the galactic centre, are most likely to be disrupted. Clusters that are subject to GMC encounters are more rapidly destroyed and contain stars with higher kinetic energies.
In paper III, we perform a similar investigation as in paper II, but this time for a population of open clusters in the Solar Neighbourhood over the last 1 Gyr. We simulated 20692 clusters and find a good agreement with the observed population if we assume an initial cluster mass function that is truncated. High-mass clusters survive to 1 Gyr and are much less affected by GMCs. Lower-mass
clusters are strongly affected by GMCs, but also by their distance to the Galactic centre since the tidal field becomes stronger closer to the centre. Observations show an early disruption of clusters which indicate that they form less bound compared to the initial state of our simulated cluster population. We find that clusters that have had a GMC encounter within the last 20 Myr have tidal tails that are randomly orientated with respect to the direction of the Galactic centre. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/14bf4815-a331-4b70-878d-064c6820f370
- author
- Jörgensen, Timmi LU
- supervisor
-
- Ross Church LU
- Lennart Lindegren LU
- opponent
-
- Professor Goodwin, Simon Paul, University of Sheffield, Great Britain
- organization
- publishing date
- 2026
- type
- Thesis
- publication status
- published
- subject
- keywords
- Open clusters, Galactic dynamics, stellar dynamics, Numerical simulation
- pages
- 144 pages
- publisher
- Lund
- defense location
- Rydberg Hall, Department of Physics
- defense date
- 2026-03-06 09:00:00
- ISBN
- 978-91-8104-810-0
- 978-91-8104-811-7
- language
- English
- LU publication?
- yes
- id
- 14bf4815-a331-4b70-878d-064c6820f370
- date added to LUP
- 2026-02-09 14:47:13
- date last changed
- 2026-02-10 11:35:59
@phdthesis{14bf4815-a331-4b70-878d-064c6820f370,
abstract = {{Stellar clusters are structures of stars that are bound together by their mutual gravitational forces. As a cluster evolves, it will lose stars as a consequence of internal and external effects. The external effect is the most important and affects the cluster via gravitational tidal forces that can strip stars away from the cluster. Stellar clusters are subject to gravitational scattering and tidal disruption by giant molecular clouds (GMCs) which can significantly affect their orbit and evolution.<br/>This thesis investigates the impact that GMCs have on clusters, and how this affects their observed populations. We do this by using a combination of galactic models and N-body simulations.<br/>In paper I, we investigate if the Sun could have originated from the open cluster M67 which is currently located high above the disc of the Milky Way. The Sun is located in the Galactic disc so there is a clear dynamical discrepancy between the two objects. We show that it is possible, but unlikely, for the Sun to have been born in M67 if the Sun escapes the cluster at a young age, before M67 is<br/>scattered to its current orbit by GMCs.<br/>In paper II, we investigate how tidal disruption by GMCs affects the cluster population of the galaxy M51 over a period of the last 200 Myr. We do this by simulating 5000 unique clusters twice: with and without being affected by tidal forces from the GMCs. We are able to reproduce the majority of the observed population and find that low-mass clusters, that are located close to the galactic centre, are most likely to be disrupted. Clusters that are subject to GMC encounters are more rapidly destroyed and contain stars with higher kinetic energies.<br/>In paper III, we perform a similar investigation as in paper II, but this time for a population of open clusters in the Solar Neighbourhood over the last 1 Gyr. We simulated 20692 clusters and find a good agreement with the observed population if we assume an initial cluster mass function that is truncated. High-mass clusters survive to 1 Gyr and are much less affected by GMCs. Lower-mass<br/>clusters are strongly affected by GMCs, but also by their distance to the Galactic centre since the tidal field becomes stronger closer to the centre. Observations show an early disruption of clusters which indicate that they form less bound compared to the initial state of our simulated cluster population. We find that clusters that have had a GMC encounter within the last 20 Myr have tidal tails that are randomly orientated with respect to the direction of the Galactic centre.}},
author = {{Jörgensen, Timmi}},
isbn = {{978-91-8104-810-0}},
keywords = {{Open clusters; Galactic dynamics; stellar dynamics; Numerical simulation}},
language = {{eng}},
publisher = {{Lund}},
school = {{Lund University}},
title = {{N-body simulations of open clusters and their destruction}},
url = {{https://lup.lub.lu.se/search/files/241833877/Timmi_Grosen_J_rgensen_-_WEBB.pdf}},
year = {{2026}},
}