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Bachelor’s thesis projects
at the University Observatory
Bachelor’s thesis topics of the Extragalactic Astronomy Group
on machine learning, instrumental and observational (Wendelstein) projects,
stars and planets, galaxies, gravitational lensing and cosmology
can be found
→ here.
Please also check out the master’s thesis projects, and let us know which
would interest you, because they may in part be split and downgraded
to fit into a bachelor’s thesis.
1. Instrumentation and observational projects
Project 1.1:
Literaturstudie zu "Starshades" (26.4.2023)
(Frank Grupp, frank@grupp-astro.de))
Starshades sind - an Lotusblumen erinnernde - Strukturen die auf einem zweiten Satelliten in großer Entfernung zu einem einen Planeten beobachtenden Raumfahrzeug geflogen werden und mittels Beugung das Licht der "Sonne" des beobachteten Planeten abschatten. In der Arbeit soll der Stand der Technik zu Starshades zusammengefasst und die grundlegenden physikalischen Abhängigkeiten dargestellt und grafisch veranschaulicht werden.
2. Stars and planets
Planet formation models rely on understanding the initial phases of
dust grain evolution in molecular clouds.
The evolution occurs via collisional agglomeration, with the relative
grain motion driven by a combination of several mechanisms operating
in the clouds.
The coagulation model is currently oversimplified in that we assume
that dust grains stick together when they collide.
However, if the collision velocities are high enough, grains are
expected to fragment instead, leading to more complicated evolution
of the size distribution.
This thesis project would be to search the literature and implement a
dust fragmentation algorithm into our code, and explore the effect of
fragmentation on the evolution of the size distribution in molecular
clouds.
Cosmic rays entering molecular clouds are dominated by positively
charged protons.
At high cosmic ray fluxes (such as found near the Galactic center or in
starburst galaxies), their penetration may be limited by the electric
field generated by the build-up of net positive charge in the cloud.
This project could take one of two directions, depending on the
interest of the student.
A student interested in plasma physics and analytic work could
model the charge build-up in the linear regime, taking into account
a realistic model of the magnetic field geometry, and differing
transverse/longitudinal conductivities.
A student more interested in numerical work could assume a simple
field geometry, and simulate the nonlinear charge build-up in the
high CR flux regime.
The cosmic ray abundance in molecular clouds is modulated by the
presence of magnetic “pockets” –
local regions of low magnetic field in the cloud along a particular
field line, which develop naturally as a result of the motion of
magnetic field lines in a turbulent medium.
We have analyzed the statistics of the extent and depth of these
pockets, but many open questions remain concerning their shape and
dynamics.
We have MHD simulation data containing the geometry of the magnetic
field lines in a collapsing molecular cloud at different snapshots
in time.
The interested student could analyze this data and try to address
any of the questions suggested below, or one of his/her own choosing:
– As the pockets evolve in time, do they primarily grow/shrink,
or do they primarily move as solid bodies?
– There are indications that pockets are elongated along field
lines.
How true is this, and what is a typical pocket aspect ratio?
– Are different pockets simply connected with each other by the
field lines, or are there many disjoint magnetic pockets?
Diffusion of cosmic rays in molecular clouds arises as a result of
scattering off of small-scale irregularities in the magnetic field
that are excited by turbulence.
It is therefore crucial to have detailed understanding of the spectrum
of turbulence at small spatial scales in the ISM.
A student could review the existing literature on the turbulent
cascade in the ISM, and its application to cosmic ray diffusion.
As a particular application, there is interesting new research
suggesting that cosmic rays may be generated near young stars,
and then be transported to the protoplanetary disk along the local
magnetic field lines.
Turbulence in the disk is believed to be omnipresent due to the
magneto-rotational instability, which is in turn affected by the
cosmic rays through the local ionization rate.
Calculating the effect of this turbulence on the propagation of
cosmic rays would be an important work, as it is the first step to
a self-consistent model for the interplay between the MRI and the
cosmic rays.
Molecular clouds are surrounded by extended low-density gaseous
envelopes.
The interstellar UV field is the prime source of carbon ionization
in these regions, while the ionization of hydrogen only occurs due
to cosmic rays.
The analysis of chemical reactions triggered by cosmic rays suggests
a number of molecular ions form in the gas, whose direct observation
provides a powerful tool for constraining the rate of ionization by
cosmic rays and hence the models of their propagation in the envelopes.
The interested student should analyze the available observational
data for different ions (such as H3+,
OH+, ArH+), in order to obtain a comprehensive
picture of how the cosmic-ray ionization varies in the envelopes.
Planetesimals are thought to form in gaseous disks surrounding young
stars, but the details are poorly understood.
An interesting possibility is that planetesimals actually only
form from scratch under special circumstances, and most stars simply
capture interstellar ones in their gaseous disk, which then trigger the
formation of further planetesimals from the solid material in the disk.
This project would be to estimate the number of such objects which
are captured in the disk of a forming star.
Depending on the interest of the student, this could be either
calculated using an analytical model of the time-dependent
gravitational potential well of the young star, or done numerically
by analyzing the gravitational potential of the gas in a simulation.
Small grains of solid material in space (dust) could be spun up as a
result of torques arising from the asymmetric grain structure and/or
the anisotropic radiation field.
It has been argued that the grains may spin so fast that they are
ripped apart by centrifugal force.
For this project, the student will study the associated literature
to develop an understanding of the size distribution and lifetime of
the grains that make up the interplanetary dust cloud.
They could then combine this information with existing models of the
grain disruption to determine whether centrifugal disruption plays
a role in shaping the dust population in our solar system.
In dense ISM regions, dust grains accrete a surface layer (mantle)
of ice.
The thickness of this mantle is regulated by a balance between
accretion from the surrounding gas, and removal as a result of
transient heating following the passage of high-energy charged
particles (cosmic rays) through the dust grain.
We have recently shown that the balance of these two processes depends
on the size of the grain, and the aim now is to explore the mantle
growth in different interstellar environments.
We are looking for a student to study the mantle growth in various
environments with the assistance of an existing code, and to
determine how the mantle thickness varies depending on the dust
size distribution.
Dense gas in star-forming regions is heated predominantly by cosmic
rays.
A significant part of the heating is due to secondary electrons –
the electrons which are produced when a primary cosmic-ray particle
knocks an electron off of a molecule in the gas.
We have recently calculated the energy spectrum of such electrons.
These electrons lose their energy in a variety of ways, some of which
heat the gas, and some the dust.
We are looking for a student who will use available models for
different energy loss processes to calculate what fraction of the
energy goes to gas heating.
Available data allow us to construct a model of the density
distribution of a filament of dense gas, located in a nearby
star-forming region.
These data also include measurements of the emission from two
different rotational levels of ammonia molecules, which could be used
to determine the gas temperature.
We are looking for a student to use the model of the gas density,
combined with a simple model of the spatial variability of the gas
temperature, and compare this to the measured ammonia emission.
This work would help us to test a recent theory that young stars act
as sources of cosmic rays which may heat the nearby gas.
3. Galaxies and AGN
All galaxies are magnetized. Where do galactic magnetic fields come
from, how are they maintained and how are they structured? These are
the questions we wish to answer. In this project we will develop
a model for the amplification of galactic magnetic fields based on
analytic calculations.
Project 3.2:
Propagation of cosmic rays in the Galaxy
(H. Lesch lesch@usm.lmu.de)
Cosmic rays represent a small but high-pressure part of the
interstellar medium. Through their pressure on the magnetic fields,
cosmic rays contribute considerably to the galactic dynamo. In this
project we will analyse the properties of Galactic cosmic rays and
their impact on gamma-ray emission.
How do we measure the age of a galaxy?
The Bachelor’s thesis project should summarize the methods that
have been developed to reach this goal and their uncertainties.
If there is enough time, one can also derive a spectroscopic age from
data available for a selected number of objects.
Three-dimensional galaxies are often modeled using the Schwarzschild
approach.
One computes stellar orbits in a given gravitational potential and
superposes them to reproduce the available dataset.
The modeling of two-dimensional objects like galaxies with stellar
disks poses some yet unsolved questions.
How well can one compute the gravitational potential using spherical
harmonics?
What is the optimal amount of regularization?
How well can one describe real galaxies?
During the thesis project answers to these questions will be tested
and implemented.
Project 3.5:
The masses of supermassive black holes at the centers of galaxies
(R. Saglia saglia@usm.lmu.de)
How do we measure the masses of supermassive black holes at the centers
of galaxies? What are their uncertainties? How much mass is hidden in
supermassive black holes? The results of the recent research should
be critically summarized and discussed.
4. Cosmology, large-scale structure, and gravitational lensing
Project 4.1:
Distances to supernovae in various cosmological models
(J. Weller weller@usm.lmu.de)
The student will derive the correlation between distance and red shift
for different Friedmann Models. Boundary conditions to cosmological
parameters will be derived by comparison with supernova data. These
analyses are made with the aid of so-called Monte Carlo Markov chains.
If there is enough time, the analysis can be extended to models with
extra dimensions.
The size of a galaxy changes during its life.
Goal of the thesis is to summarize the results of the last years of
published research.
How do we measure the size of a galaxy?
What is the rate of change of the size of a galaxy with time?
Does it depend of the mass of the galaxy?
What are the mechanisms that drive the size change of galaxies?
Projects in the Astrophysics, Cosmology, and Artificial Intelligence Group
(Daniel Grün et al.)
Projects in the Physical Cosmology Group
(Jochen Weller et al.)
5. Computational and theoretical astrophysics
Research in the Computational Astrophysics Group (CAST) ranges from
the theoretical investigation of star and planet formation to studies
of processes on cosmological scales.
A variety of different, well-known numerical codes (such as Ramses,
Gadget, Sauron, Gandalf, Mocassin, and others) are used.
Primary investigations regard the formation, the structure, and
the evolution of protoplanetary disks, the formation of planetary
building blocks and planets, the relation between turbulence and phase
transitions in the multiphase interstellar medium (ISM), energetic
feedback processes, molecular cloud and star formation in galaxies, as
well as cosmological structure and galaxy formation and the interplay
between feedback processes, AGN, and galaxy evolution and their imprint
on the intergalactic medium (IGM) or the intercluster medium (ICM).
Thus, our group studies astrophysical processes on length scales
covering more than 14 orders of magnitude, from gigaparsec scales
of cosmological structures all the way down to sub-AU scales of dust
grains within protoplanetary disks.
It is now clear that small-scale processes like the condensation
of molecular clouds into stars, magnetic fields and the details of
heat transport as well as large-scale processes like gas infall from
the cosmic web into galaxies and environment are intimately coupled
and have to be investigated in a concerted effort.
The various past and ongoing projects within the CAST group cover
a link between the various scales and contribute to our understanding
of crucial aspects of the formation and evolution of stars and
protoplanetary disks, central black holes and AGNs, star-forming
regions and the ISM, galaxies and their IGM, galaxy clusters and the
ICM as well the large-scale structures in the universe.
They also also drive the continuous effort to develop and to apply
new numerical methods and the next generation of multi-scale codes
within the framework of numerical astrophysics.
Past and ongoing Bachelor’s and Master’s thesis projects
were always offered with respect to the individual strengths and
interests of the students and cover various areas in the field of
computational and theoretical astrophysics:
- Formation of large-scale cosmological structures (dark-matter
halos, galaxies, clusters of galaxies, role of black holes, magnetic
fields and non-thermal particles)
- Evolution and structure of the turbulent interstellar medium
(ISM physics, self-regulating star formation, formation of molecular
clouds, magnetic fields)
- Physics of galactic centers (active galactic nuclei, origin and
nature of the gas cloud G2 near the Galactic center)
- Formation of planets, stars, and stellar clusters (stars and
their influence on the surrounding protoplanetary disc, interstellar
matter, radiative transfer, dynamics of particles and planets in
protoplanetary disks)
- Application and development of numerical tools on parallel
CPUs and GPUs and visualization (particle-based
SPH/N-body, grid-based,
moving-mesh or meshless methods)
More detailed information on
ongoing and finished projects
as well as more detailed information on ongoing research can be
found on the web pages of the
Computational Astrophysics Group.
6. High-energy astrophysics
X-ray and gamma-ray observations have been instrumental in enabling
scientists to study some of the most extreme cosmic sources in the
Universe.
The utilisation of data obtained through X-ray and imaging atmospheric
Cherenkov telescopes facilitates the comprehension of physical
processes in these extreme environments and the tracing of their
evolution.
This provides opportunities to study processes at the frontier of
known physics.
The research undertaken by our group encompasses a broad spectrum
of enquiry into astrophysics and fundamental physics, including the
investigation of cosmic-ray acceleration processes and the quest to
comprehend the nature of Dark Matter.
Those interested in pursuing this field are invited to get in touch.
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