Welcome to the Homepage
of the Theory Group

Research Areas

The theory group at the Department of Astronomy (DdeA) exists since 2009. It started with the arrival of Dr. Michael Fellhauer in late 2008, the first theoretical astronomer at the DdeA, and his first student Paulina Assmann, starting her PhD in numerical simulations of the formation of dwarf spheroidal galaxies (dSph), in 2009. Today, the theory group consists of two professors (Dr. Dominik Schleicher started in March 2015), two post-docs and nine students. The theory group works mainly in the field of numerical simulations in stellar dynamics and hydrodynamics.

In the 7 years of existence the theory group published more than 45 articles in refereed journals and saw the finalisation of 1 PhD, 3 Magister and 4 titulo theses. We acquired 7 FONDECYT projects (3 regular, 4 postdoctorado) and are part of CATA. We have established national and international working collaborations with groups all over the world (e.g. Germany, UK, China,...). The students have presented successfully their work in many national and international conferences.

News: An extensive catalogue of early-type galaxies in the nearby universe

We present a catalogue of 1715 early-type galaxies from the literature, spanning the luminosity range from faint dwarf spheroidal galaxies to giant elliptical galaxies. The aim of this catalogue is to be one of the most comprehensive and publicly available collections of data on early-type galaxies. The emphasis in this catalogue lies on dwarf elliptical galaxies, for which some samples with detailed data have been published recently. For almost all of the early-type galaxies included in it, this catalogue contains data on their locations, distances, redshifts, half-light radii, the masses of their stellar populations and apparent magnitudes in various passbands. Data on metallicity and various colours are available for a majority of the galaxies presented here, including many of the rather faint early-type galaxies in the Local group. The data on magnitudes, colours, metallicities and masses of the stellar populations is supplemented with entries that are based on fits to data from simple stellar population models and existing data from observations. Also, some simple transformations have been applied to the data on magnitudes, colours and metallicities in this catalog, in order to increase the homogeneity of this data. Estimates on the Sersic profiles, internal velocity dispersions, maximum rotational velocities, dynamical masses and ages are listed for several hundreds of the galaxies in this catalogue. Finally, each quantity listed in this catalogue is accompanied with information on its source, so that users of this catalogue can easily exclude data that they do not consider as reliable enough for their purposes.
The catalogue files can be downloaded here.

The Theory Group in Concepcion was hosting the MODEST 15 - "Modelling (and Observing) Dense Stellar Systems" - international conference at the University of Concepcion, March 2nd-6th, 2015.

In particular we are interested in:

  • Sub-group: D. Schleicher

  • Formation of the first stars in the Universe
    including primordial and metal poor stars. Our goal is to understand the role of chemistry and cooling during the fragmentation process, and the typical stellar mass as a function of metallicity.
  • Formation of the first supermassive black holes
    with a particular focus on the direct collapse scenario. We explore the circumstances that can lead to the direct collapse of a massive gas cloud with no or very little fragmentation. A particular focus concerns the role of the ambient radiation background as well as the viscous heating in self-gravitating disks.
  • Modeling astrochemistry in 3D simulations
    Chemistry and cooling play a central role in many astrophysical applications, and there modeling is therefore important to understand fragmentation and the stability of self-gravitating disks. We are therefore participating in the development of the astrochemistry package KROME (http://www.kromepackage.org/ ) to include chemistry in 3D simulations.
  • The origin of magnetic fields
    Magnetic fields are ubiquitos in the Universe, and the observed synchrotron fluxes from high redshift galaxies suggest their formation at early times in the Universe. We explore in particular the role of the small-scale dynamo for the amplification of magnetic fields, and how it contributes to establish the far-infrared - radio correlation.
  • Variability in Close Binary Systems
    We are interested in the modeling of hydrodynamical and magneto-hydrodynamical processes in compact binary systems. The latter includes the formation of accretion disks due to Roche lobe overflow or stellar winds, as well as dynamo action due to the rapid rotation in compact binaries. Such processes may give rise to the observed eclipsing time variations in Post-Common-Envelope Binaries (PCEBs) and potentially explain the long period in Double Periodic Variables (DPVs). We also explore whether the observed eclipsing time variations of the PCEBs can be interpreted as planets.

  • Sub-group: M. Fellhauer

  • The Formation and Survival of Young Embedded Star Clusters:
    We see that star formation happens not uniformly distributed but clustered in form of loose associations up to massive SC complexes (clusters of SC). The geometry of a young star forming region is usually not spherically symmetric as assumed in previous models but rather hierarchical in form of clumps and filaments. Our group models these more realistic initial conditions and investigates which effects govern the dynamics and which parameters are to use if one wants to determine the chance of survival (gas expulsion) of these SCs. With our simple models we can run hundreds of simulations and can obtain statistically relevant results.
    project page
  • The Formation and Evolution of dSph Galaxies:
    We investigate a new scenario for the formation of these faint dwarf galaxies. They are known to show features like distorted isophotes, off-centre nuclei or secondary density peaks. In our model we place dissolving star clusters (as we know: all stars form in SCs) inside the central area of a dark matter (DM) halo. The stars of the dissolving SCs are forming the faint luminous component of the dSph galaxy. Due to the fact that we are dealing with very low densities inside a very massive DM halo, our models reproduce all the features seen in faint dSph galaxies. In terms of the evolution we have developed a new method to search for a best matching progenitor and successfully applied this method for the ultra-faint dSph galaxies Hercules and Segue 1.
    project page
  • The Formation and Evolution of Tidal Tails:
    All objects (SCs and dSphs) orbiting the Milky Way (MW) are forming tidal tails. These tails align with time along the orbit and so it would be possible to deduce the orbit of the object from the location of the tails. Furthermore, these tails sometimes show density enhancements. In principle, having a large sample of tails, it should be possible to deduce the shape and strength of the MW potential from them. One needs a understanding of how certain parts of the MW (disc, bulge, halo) influence the tails and their over-densities. We are investigating how tails and their densities form in different environments and on different orbits and how they trace the Galactic potential.
  • Ultra-Compact Dwarf Galaxies (UCDs) and Faint Fuzzies (FFs):
    Our group has developed a model to explain the formation of UCDs and FFs via the merging of SCs inside of SC complexes. We are also involved in studies about their stellar populations and if they exhibit variations in their initial mass function (IMF), i.e. a top or bottom heavy IMF.
  • The Effects of Modified Newtonian Dynamics (MOND):
    We are working on a study to investigate if the dynamics of spherical galaxies can be explained by MOND. We are gathering one of the largest samples of galaxy data to assess the dynamics of the galaxies. Our group has developed a new hybrid N-body-SPH code which can model MOND in stellar dynamics (RayMOND based on RAMSES). With this code we are able to simulate galaxy interactions in MOND and compare the results to regular LCDM models.
  • Harassment and Ram-Pressure Stripping:
    We are studying the transformation of dwarf galaxies under the influence of ram-pressure and harassment in a cluster environment or in group environments (pre-porcessing. We produced models for disc galaxies, dwarf ellipticals and tidal dwarf galaxies without DM. We investigated the fate of globular cluster systems in these environments as well.
  • Stellar Populations in Dense Stellar Systems:
    We try to find evidence if the unusual high mass-to-light ratios of some dense systems like UCDs can be explained by top or bottom heavy initial mass functions?
Project pages are still under construction or missing. Please, stay tuned...

Available Thesis Projects


The theory group - April 2016.

Members of the Team

Dr. Michael Fellhauer

  • associate professor
  • PhD in astronomy, Ruprecht-Karls University, Heidelberg, Germany
  • Old Dwarfs and Young Clusters
  • projects:
  • FONDECYT regular No. 1130521
  • Basal CATA (associate member)
  • Homepage

Dr. Dominik Schleicher

  • assistant professor
  • PhD in astronomy, Ruprecht-Karls University, Heidelberg, Germany
  • first stars, BHs and galaxies
  • Homepage

Dr. Joerg Dabringhausen

  • postdoc
  • PhD in astronomy, University of Bonn, Germany
  • Top-heavy IMFs in ultra-compact dwarf galaxies
  • MONDian dynamics to explain properties of dwarf galaxies
  • projects:
  • FONDECYT postdoctorado No. 3140146

Dr. Paulina Assmann

  • postdoc
  • PhD in astronomy, UdeC (supervisor: M. Fellhauer)
  • Formation of Dwarf Spheroidal galaxies
  • massive remnants in dense stellar systems (influence of GR)
  • projects:
  • China-Chile postdoc

Raul Esteban Dominguez Figueroa

  • Magister student
  • titulo in astronomy (supervisor: M. Fellhauer), UdeC
  • The importance of the IMF and mass-segregation in young star clusters

Alex Rodrigo Alarcon Jara

  • Magister student
  • licenciatura in astronomy, UdeC
  • incorporating the SFH into the models of merging star clusters

Jocelyn Nicole Hazeldine Lefenda

  • Magister student
  • licenciatura in astronomy, UdeC
  • formation of dwarf galaxies

Catalina Andrea Aravena Nunez

  • Magister student
  • licenciatura in astronomy, UdeC
  • formation of dwarf galaxies

Fernanda Cecilia Urrutia Zapata

  • Magister student
  • licenciatura in astronomy, UdeC
  • formation of dwarf galaxies

Diego Rolando Matus Carillo

  • tesis de titulo
  • licenciatura in astronomy, UdeC
  • modelling Canes Venaticii I

Bastian Alejandro Reinoso Reinoso

  • tesis de titulo
  • licenciatura in astronomy, UdeC
  • tidal tails in logarithmic haloes

Alberto Antonio Letelier Finot

  • tesis de titulo
  • licenciatura in astronomy, UdeC
  • modelling Coma Berenice

Marcelo Andres Figueroa Guerra

  • titulo student
  • licenciatura in astronomy, UdeC

Former Members


Pictures of the University

Faculty for Physics and Mathematics; the University of Concepcion from above; the central place of the university, new astronomy building

Text of Press Releases

Catalogue of Elliptical Galaxies; 05-2016
Hercules; 10-2014
X-mas tree; (explanation) 12-2013
Aurigas Wheel; 04-2012
X-mas tree; (detection) 10-2011

Publications

2016

2015

2014

2013

2012

2011

2010

2009

MODEST 15

The Theory Group in Concepcion was hosting the

MODEST 15

 - "Modelling (and Observing) Dense Stellar Systems" -
international conference at the University of Concepcion

March 2nd-6th, 2015.
MODEST 15