VOSS 2020



The centres of galaxies are superb laboratories for studying the interplay between stellar dynamics, hydrodynamics, star formation, stellar feedback, and supermassive black holes. New technological developments, such as high-resolution integral field spectrographs with adaptive optics, are enabling us to study these regions with an unprecedented level of detail and breadth of scope, and the amount of information gathered has grown dramatically in the past few years. This is bringing transformational advances in extragalactic astronomy, but the richness of the data and the complexity of the subject can be potentially confusing, while progress in the field require a solid understanding of fundamental physical concepts with respect to the structure, dynamics and stellar population content of these components.

This course of lectures and hands-on projects will provide young researchers with a thorough preparation for understanding the
observed properties of galaxy centres and the theory behind them.
We will introduce students to what current observations tell us about the central components of galaxies, how these relate to galaxy scaling relations such as those of supermassive black holes, and the state-of- the-art techniques used for morphological analysis and 3D spectroscopy as applied to the central regions of galaxies. We will then interpret the observed phenomena in terms of dynamical theories of galaxy formation and evolution. We will start by basing students’ intuitions on analytical approaches that often provide useful insights. We will then proceed to orbital analyses and KAM theory, a key conceptual tool for barred galaxies. This will enable us to explain much of the observed features and a substantial part of the behavior of N-body simulations. With this preparation in hand, we will be able to present and interpret results of N-body simulations, and to relate them back to the observed nature of galaxy centres.


  • Observations of the central regions of galaxies: properties of bulges and bars, supermassive black holes and their scaling relations
  • Modern techniques in galaxy image decomposition: overview of different approaches, studying the structural properties of bars and bulges via image fits
  • Integral field spectroscopy: summary of current surveys and instrumentation, state-of-art integrated stellar-population analysis
  • Essentials of galactic dynamics: galaxies as collisionless systems, orbits and integrals of motion in galaxy potentials, stability analysis of stellar disks
  • Theory of bars: resonances in spiral galaxies, Lagrange points in barred galaxies, peanut-shaped bars, weakly dissipative dynamics
  • Dynamics of bars and bulges in N-body models: constructing models of bulges and disks, formation of bulges, coevolution of bulges and central supermassive black holes, formation of bars, gravitational interaction between bars and bulges
  • Theory of multiple central components: formation and evolution of double bars, dynamics of nuclear rings and spirals

List of the Faculty

Witold MACIEJEWSKI (Chair)
Witold MACIEJEWSKI (Chair)Liverpool John Moores University, UK
Expertise in orbitai dynamics and hydrodynamics. VOSS
1993 alumnus. Senior Lecturer at Liverpool John Moores
University. He developed a theory of nuclear spiral shocks
in galaxies, and found regular orbits that support nested
bars. He enjoys working at the interface of theory and
observations, especially on the interpretation of
kinematics derived from integral-field and interferometry
data. He has published more than fifty refereed papers
and popular science articles. (He taught both
undergraduate and graduate courses, in physics and in
astronomy, in Poland, in the United States and in the
United Kingdom.)
Peter Erwin
Peter ErwinMPE, Germany
Expertise in observational galaxy morphology, including bars,
double bars, classical bulges and pseudobulges of various kinds,
nuclear star clusters, and measurements of supermassive black
holes. Currently based at the Max-Planck-lnstitute for Extraterrestrial
 Physics, he has published over 75 refereed papers. Author of Imfit, a
popular software suite for modeling and decomposing galaxy
images. Leader of the Composite Bulges Survey, an HST-based
collaboration focused on defining the local
reference for understanding the morphological, kinematic, and
stellar-population components of disk galaxy centers.
Isabel Pérez
Isabel PérezUniversidad de Granada, Spain
Expertise on stellar populations, observational studies of ionised gas
and stars in disc galaxies, particularly in barred galaxies. Professor at
the University of Granada. Active member of the international
collaborations: CALIFA,TIMER, SIGNALS/SITELLE, and WEAVE/Apertif
focused on the exploitation of state-of-art integral field
spectrographs around the world to study galaxy evolution. More
than fifty refereed papers on the subject. She has supervised
numerous graduate and undegraduate students. She teaches,
physics and astrophysics, at the undergraduate and graduate level
since 2006. Apart from an active research career she has being
strongly involved in outreach activities. She participates in several
projects of teaching innovation at the University of Granada and a
European project for inclusion at schools using astronomy. She is an
active collaborator in the local media to disseminate science and
promote science at schools.
Daniel Pfenniger
Daniel PfennigerUniversité de Genève, Switzerland
Expert in the gravitational dynamics of galaxies, in particular
barred galaxies, peanut-shaped bars, bulges, double bars,
and galaxy secular evolution. The methods used have mainly
combined mathematical tools to various types of numerical
simulations, as traditional analytical methods are unable to
describe the central role of chaos to the evolution of
complex systems such as galaxies. Also has contributed to
several topics of theoretical astrophysics, such as baryonic
dark matter as cold interstellar gas, chemistry in the early
universe, gravitating gas subject to a phase transition, warm
dark matter, and the role of quantum physics in
cosmologenic neutrinos. Teaching researcher and professor
since 1990 at the Departmenet of Astronomy at University of
Geneva, after a postdoctoral stay at the Institute for
Advanced Study, Princeton, USA.
Kanak Saha
Kanak SahaIUCAA, India
Faculty member at the Inter-University Centre for Astronomy and
Astrophysics (IUCAA), India. Expertise on the dynamics of galaxies;
worked extensively on the formation and evolution of bars and
bulges using N-body simulations. Other research activities include
high redshift galaxies, UV astronomy using our Indian satellite
AstroSat. He has published more than 30 refereed papers and
organisers of several schools and workshops in Astronomy and
Astrophysics in Indian universities.
Richard D'SOUZA, SJ (Dean)
Richard D'SOUZA, SJ (Dean)Vatican Observatory
Guy CONSOLMAGNO, SJ Director Vatican Observatory

Specola Vaticana
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