Archivi tag: Disk Galaxies

The Emergence of Disk Galaxies

Recent multi-wavelength observations suggest that the first sizable disk galaxies emerged at redshifts 2-3, when the Universe was most actively forming stars.  These disk galaxies look remarkably different than their local counterparts, being more turbulent, clumpier, and forming stars several orders of magnitude faster.  This focused, mid-sized workshop will bring together multi-wavelength observers and theorists interested in understanding what drives the observable properties of disk galaxies across cosmic time, how they transform from their progenitors at high redshifts into their descendants today, and what they tell us about star formation and feedback processes during Cosmic Noon.

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Dynamics of Disk Galaxies

Disk galaxies exhibit a variety of structures on various scales. On large scales, global spiral patters wind out from the central parts to almost the outer edge of an optical disk. Often, the inner ends of spiral arms are connected to a bar that extends to both sides of the nucleus. On small scales, interarm spurs, feathers, arm branchings and segments are in close geometrical association with spiral arms, while inner rings, dust-lane shocks, nuclear rings, and nuclear spirals are associated with bars. While a significant progress has been made over past sixty years in our understanding of these structures, there still remain many unsolved issues regarding the patterns in disks and other related processes, which are important to understand disk dynamics.

The main topics of the workshop to be addressed are:

– structures of disks, bulges, and bars
– formation and maintenance of patterns
– secular evolution of galaxies driven by bars/spiral arms
– substructure formation of bars/spiral arms
– dynamical modeling
– pattern speeds and pitch angle determinations
– gaseous component
– the Milky Way Galaxy

Structure and Dynamics of Disk Galaxies

This conference will focus on the formation and evolution of disk galaxies starting with a session dedicated to the Local Group and nearby galaxies which are critical objects for our understanding of the disk galaxy picture. This session will present a review of the properties of the disks of the Milky Way, M31, M33, and other nearby galaxies, their correlations with the bulge and halo components, and the effects of interactions with galaxy satellites.

Star formation in disks is a subject on which we can expect dramatic new results from multiwavelength observations from space-based and ground-based observatories (e.g. HST, ALMA, GALEX, Spitzer, Herschel, Chandra). By 2013, the Schmidt-Kennicutt law should have been explored on local (and not just disk-averaged) spatial scales throughout disks of a large sample of nearby galaxies. We should have constraints on disk growth timescales and radial dependence from measured star formation rates.

Studying the structure of galaxy disks is the starting point to address the formation of lenticular and spiral galaxies. Most nearby stellar disks are radially truncated in their outskirts. These outer edges could either trace the maximum angular momentum during the galaxy formation epoch or be associated with global star formation thresholds. New insights in the fields are expected from the analysis of structural properties of disks at high redshift from ongoing surveys which will unveil how disks evolve over time.

Accretion and merging events are keys in the formation of disks. Many authors have emphasized that quiescent accretion dominates the evolution of small galaxies, but more violent events like major mergers are more significant for large galaxies. This issue has been emphasized repeatedly by state of the art galaxy formation simulations, and much progress has been made as simulation resolution is improved and more realistic physics is included in those simulations.

Secular evolution is a subject that is making rapid progress in the observational and theoretical extragalactic astronomy. On the observational side, new results concerning the systematic properties of pseudobulges, such as stellar populations and star formation timescales are expected in a few years. On the theoretical side, we plan to cover different topics of this active research area, such as the pseudobulge formation out of bars, evolution of bars, and mechanisms responsible for the disk heating process.

In connection with the evolution of structural disk properties, there are a number of observables that will be coming to fruition in the next few years (stellar mass, rotation velocity, size, star formation rates, color gradients). Other important subtopics are bars at intermediate redshift, disks and environment (i.e., what happens to their star formation rates, sizes, colors when we throw them into groups/clusters). There is ample observational evidence for these processes at z<1, and some limited insights up to z=3. This session completes the archeological picture we are getting from disks in the Local Group.

One of the outstanding questions in galaxy formation and cosmology is that we do not understand how to make disk galaxies, especially pure disk galaxies, in a cold dark matter, hierarchically clustering Universe. This issue is related to two other hot topics of investigation of disk galaxy formation via numerical simulations, namely the angular momentum crisis and dark halo concentration crisis. These issues have grown sharper over time. They are some of the most interesting and pressing problems that we could address at this conference.

Some key questions we will address are:

How are galaxy properties linked to those of their dark halos?
What drives the formation of disks and bulges?
How do galaxies get their gas and process it into stars?
What are the links between central black hole formation, bulge formation and AGN?
How does secular evolution versus mergers drive spiral galaxy formation?
What do Local Group and nearby galaxies tell us about disk galaxy formation?