Star formation in galaxies: the role of spiral arms

Abstract

Studying star formation in spiral arms tells us not only about the evolution of star formation, and molecular clouds, but can also tell us about the nature of spiral structure in galaxies. I will address both these topics using the results of recent simulations and observations. Galactic scale simulations are beginning to examine in detail the evolution of GMCs as they form in spiral arms, and then disperse by stellar feedback or shear. The overall timescale for this process appears comparable to the crossing time of the GMCs, a few Myrs for $10^5$ M${}_{\odot }$ clouds, 20 Myr or so for more massive GMCs. Both simulations and observations show that the massive clouds are found in the spiral arms, likely as a result of cloud-cloud collisions. Simulations including stars should also tell us about the stellar age distribution in GMCs, and across spiral arms. More generally, recent work on spiral galaxies suggests that the dynamics of gas flows in spiral arms are different in longlived and transient spiral arms, resulting in different age patterns in the stars. Such results could be used to help establish the main driver of spiral structure in the Milky Way (Toomre instabilities, the bar, or nearby companion galaxies) in conjunction with future surveys.

7 pages, 3 figures, invited review, to appear in Proceedings of the IAU Symposium No. 298, "Setting the scene for Gaia and LAMOST"

References in corpus (9)

• Star Formation in Disk Galaxies. I. Formation and Evolution of Giant Molecular Clouds via Gravitational Instability and Cloud Collisions
• The Birth of Molecular Clouds: Formation of Atomic Precursors in Colliding Flows
• The Exciting Lives of Giant Molecular Clouds
• Dynamics of Non-Steady Spiral Arms in Disk Galaxies
• GMC formation by agglomeration and self gravity
• Star formation in Galactic spiral arms and the inter-arm regions
• Shocks, cooling and the origin of star formation rates in spiral galaxies
• Giant Molecular clouds: what are they made from, and how do they get there?
• Kiloparsec-Scale Simulations of Star Formation in Disk Galaxies. I. The unmagnetized and zero-feedback limit

Cited by in corpus (2)

• Galaxy Zoo Builder: Morphological Dependence of Spiral Galaxy Pitch Angle
• Differences in star formation activity between tidally triggered and isolated bars: a case study of NGC 4303 and NGC 3627