For a wide range of non-axisymmetric phenomena in galaxies, like bars and spirals, the rate at which their pattern rotates regulates the morphology and dynamics of the galaxy and depends on its past evolutionary history. Measurements and modelling of pattern speeds can therefore put strong constraints on the mass distribution of galaxies as well as on their formation and evolution processes. In recent years, a growing body of theoretical studies and numerical simulations has been brought to bear on the implications of different pattern speeds in galaxies in general and in the Milky Way in particular. As far as measurements are concerned, considerable progress has been made in deriving bar pattern speeds via various methods for an increasing number of galaxies across different Hubble types, galaxy properties, and environments, whereas the pattern speeds of spirals have remained poorly constrained observationally. On the other hand, GAIA has made it possible to investigate in detail the bar and spiral pattern speeds of the Milky Way.

The aim of the Special Session is to bring together a number of junior and senior researchers working across observations, modelling, and simulations of disc galaxies to present data, share ideas, and propose future directions in a timely discussion about pattern speeds of bars and spirals. In particular, the goal is to foster exchange between these different communities by offering a timely program with talks and discussions in three 1.5-hour sessions focused onto the following key topics:

• Bar pattern speeds across the Hubble sequence: How rapidly do bars rotate? Are there differences across Hubble types, across galaxy properties, or across environments? Do different methods for measuring bar pattern speeds give consistent results? Which is the role of dark matter distribution and gas content in slowing down bars? Which are the implications of the observed rotation rates on bar formation and evolution? Is there evidence that pattern speeds were different in the past?



• Spiral pattern speeds across the Hubble sequence: What prospects are there for measuring spiral pattern speeds in galaxies? Do spirals rotate rigidly with a single fixed pattern speed, or do they wind up? How many spiral pattern speeds are likely to be present in each galaxy?



• Bar and spiral pattern speeds of the Milky Way: What are the pattern speeds of the bar/spirals Milky Way and how can they be measured? Has the bar slowdown been constant? What the initial bar pattern speed was? How the bar pattern speed affects the rest of the Milky Way? What are the dynamical and chemical imprints of spiral pattern speeds in the Milky Way?

Programme

This Special Session is scheduled for Monday, July 1st, 2024.

The Special Session will be divided into three blocks, each of them covering one of the main topics:

• Block 1 - Bar pattern speeds across the Hubble sequence: introduction talk (5 min), one review talk (25 min), four invited/contributed talks (15 min each), contributed posters.
• Block 2 - Spiral pattern speeds across the Hubble sequence: introduction talk (5 min), one review talk (25 min), four invited/contributed talks (15 min each), contributed posters.
• Block 3 - Bar and spiral pattern speeds of the Milky Way: introduction talk (5 min), one review talk (25 min), four invited/contributed talks (15 min each), contributed posters.

Invited speakers

• J. Alfonso L. AGUERRI (Instituto de Astrofisica de Canarias, Spain)
• Neige FRANKEL (University of Toronto, Canada)
• Mattia C. SORMANI (Università dell'Insubria, Italy)

Scientific organisers

• Chiara BUTTITTA (Osservatorio Astronomico di Capodimonte, Italy)
• Enrico Maria CORSINI (Co-chair) (Università di Padova, Italy)
• Virginia CUOMO (Universidad de Atacama, Chile)
• Victor P. DEBATTISTA (Co-chair) (University of Central Lancashire, UK)
• Elena D'ONGHIA (University of Wisconsin-Madison, USA)
• Soumavo GHOSH (Max-Planck-Institut fuer Astronomie, Germany)
• M. Isabel PÉREZ (Universidad de Granada, Spain)
• Juntai SHEN (Shanghai Jiao Tong University, China)

Contact

Enrico Maria Corsini (enricomaria.corsini @ unipd.it)