Practical Works (TP4)

EPFL’s GalSpec lab offers students access to cutting-edge research in modern astrophysics and galaxy evolution via practical work assignments, semester and master thesis works, aiming to address basic, unsolved questions in galaxy evolution, and push forward innovative simulations and spectral modelling methods to increase our understanding of the Universe.

Pre-knowledge in Astrophysics (i.e. having attended some Astrophysics courses at EPFL) is certainly beneficial, applications from other disciplines are welcome – if you wish to participate in a project, please contact directly Michaela Hirschmann ([email protected]).

Note that most of the Master Thesis projects can be adapted to be TP-IV practical works. 

Supervisors: M. Hirschmann (Faculty), R. Tress (PostDoc)

Type of Project: Master project (can be adapted for TP-IV)

Project description: Understanding the interstellar medium of barred galaxies via next-generation, idealised simulations

The PHANGS survey [1] is observing nearby galaxies at unprecedented high resolution with different revolutionary telescopes, such as ALMA and JWST, to study their complex interstellar medium in great detail. Many of those galaxies are barred disc galaxies. These barred structures are responsible in efficiently driving copious gas towards the centre, inducing complex gas motions, extreme star formation and potentially fuelling the a central active galactic nucleus. To robustly understand and interpret these observations, at GalSpec, we conduct high-resolution, idealised magnetohydrodynamic simulations of such galaxies. In this context, the student would work on the generation of a model of the background stellar and dark matter potential in which the gas evolves, stars form and explode etc (by developing own python routines). This can be done by constructing an analytic fixed background potential in a similar way as in [2]. The IR photometric data of these observed galaxies (which is a proxy for the old stellar component) can be fitted with a disc component, a bulge component, and an exponential bar component. Parameters can then be adjusted with simple isothermal simulations of the gas in such a background potential by comparing to the observed galaxy morphology. These results will be used to conduct a variety of novel, idealised MHD simulation of “PHANGS”-like galaxies to provide a novel, interpretative framework for the observed PHANGS galaxies.




Supervisors: M.  Hirschmann (Faculty), M. Farcy (PostDoc)

Type of Project: Master project (can be adapted for TP-IV)

Project descriptionWhich physical process(es) can suppress star formation in galaxies at cosmic dawn?

Recent observations have discovered an increasingly large population of massive, quiescent galaxies as early as z>4, which has now been spectroscopically confirmed by first data from the James Webb Space Telescope. The origin of the suppression of star formation already less then 2 million years after the Big Bang remains an unsolved puzzle, and is debated to be related to specific physical processes such as merger events and star bursts, Supernovae explosions, AGN feedback etc. Interestingly, modern, state-of-the-art cosmological simulation largely fail to reproduce the observed number densities of quiescent, massive galaxies. This failure may be related to uncertain sub-grid models adopted, but also to the definition of quiescent galaxies in observations. The proposed project will be based on cosmological simulations of high-redshift galaxies, and aims to explore how different tracers and definitions of quiescence change the comparison of simulations to novel JWST observations of massive quiescent galaxies at z>4. Results will be used for the development of improved feedback models and the conduction of new cosmological simulations. The student will learn to work with modern cosmological simulations, and gain experience in using and developing python packages.

Supervisors: M.  Hirschmann (Faculty), Adele Plat (PostDoc)

Type of Project: Master project (can be adapted for TP-IV)

Project description: Origin of extreme emission-line galaxies at cosmic dawn

New observations with the James Webb Space Telescope have unveiled a population of very high-redshift galaxies with extremely elevated emission-line ratios (e.g. in [OIII]/Hb or [OIII]/[OII] originating from ionised gas in galaxies) compared to that of present-day galaxies. The physical origin of these elevated line ratios is highly debated and could be linked to different extreme conditions of the interstellar medium and various ionisation conditions in galaxies at earliest cosmic epochs. With observations alone, however, it can be very difficult to robustly address this puzzle, i.e. to disentangle the influence of different ISM and radiation properties on line emission. Thus, this project aims at *theoretically* exploring which ISM and ionisation properties are able to cause extreme emission-line galaxies at earliest cosmic epochs, consistent with the new JWST observations. For that, novel emission-line catalogues of simulated galaxies (based on different cosmological simulations) will be employed and compared. Results will be important for the further development and improvement of emission-line modelling of simulated galaxies. The student will learn to work with modern cosmological simulations, photo-ionisation models, and gain experience in using and developing python packages.

Supervisors: M. Hirschmann (Faculty)

Type of Project: Master project (can be adapted for TP-IV)

Project description: Are new JWST observations of massive galaxies at z>10 questioning our LambdaCDM cosmological model?

Thanks to the new, revolutionary James Webb Space Telescope, galaxies have been discovered to form earlier in cosmic history and are likely more massive than previously thought and predicted by state-of-the-art cosmological simulations assuming a LambdaCDM cosmogony. A number of potential solutions to resolve this tension have been discussed in literature, such as less efficient stellar feedback/UV radiation background, higher star formation efficiency, existence of massive (PopIII) stars producing more UV photons, no significant dust attenuation etc, but hardly any quantitive study has been conducted so far testing these scenarios. In this context, the student would take advantage of a modern galaxy formation model applied to merger trees from a large dark-matter-only simulation to explore the impact of different stellar feedback and star formation models on number counts of UV-bright galaxies at z > 10 and the related UV luminosity function, confronted to new JWST data. These model developments will be used to create novel mock galaxy catalogues for high-redshift galaxy populations to provide an interpretative framework for current and future high-redshift galaxy surveys, such as with JWST.