Related papers: OB associations and their origins
OB associations are low-density groups of young stars that are dispersing from their birth environment into the Galactic field. They are important for understanding the star formation process, early stellar evolution, the properties and…
Low-density and unbound stellar groups, OB associations have been historically delineated through their bright and massive members. They have been analysed for decades, but the arrival of Hipparcos, and more recently of Gaia led to a change…
The formation and evolution of young star clusters and OB associations is fundamental to our understanding of the star formation process, the conditions faced by young binary and planetary systems, and the formation of long-lived open and…
Historically, it has often been asserted that most stars form in compact clusters. In this scenario, present-day gravitationally-unbound OB associations are the result of the expansion of initially gravitationally-bound star clusters.…
In this review I discuss different theories of the formation of OB associations in the Milky Way, and provide the observational evidences in support of them. In fact, the second release of Gaia astrometric data (April 2018) is…
Low-mass stars 0.1 ~< M ~< 1 Msun) in OB associations are key to addressing some of the most fundamental problems in star formation. The low-mass stellar populations of OB associations provide a snapshot of the fossil star-formation record…
Open clusters and associations are groups of young stars, respectively bound and unbound, that share the same origin and disperse over time into the galactic field. As such, their formation and evolution are the key to understand the origin…
The OB associations, which are fossil star formation regions, retain the end-products of the star formation process in an open, unobscured environment. Observations of the low mass stars in OB associations provide a far clearer picture of…
We present 3-dimensional kinematical observations of the massive OB association Cygnus OB2 to identify the mechanisms responsible for disrupting young star clusters. The picture revealed by these observations is of a highly-substructured,…
OB associations are primordial tracers of star formation and Galactic structure. Originally defined about 80 years ago, their historical membership lists have been superseded thanks to the precise astrometry from ESA's \textit{Gaia}'s…
OB associations play an important role in Galactic evolution, though their origins and dynamics remain poorly studied, with only a small number of systems analysed in detail. In this paper we revisit the existence and membership of the…
Nearby associations of stars which are coeval are important benchmark laboratories because they provide robust measurements of stellar ages. The study of such coeval groups makes it possible to better understand star formation by studying…
We investigate the formation of star clusters in an unbound GMC, where the supporting kinetic energy is twice as large as the cloud's self-gravity. This cloud manages to form a series of star clusters and disperse, all within roughly 2…
We present the first results of a comprehensive census of the stellar content of the nearby OB associations based on Hipparcos positions, proper motions and parallaxes for 12842 candidate member stars distributed over 21 fields on the sky.…
The concept that stars form in the modern era began some 60 years ago with the key observation of expanding OB associations. Now we see that these associations are an intermediate scale in a cascade of hierarchical structures that begins on…
OB associations, birthplaces of the most luminous stars, are key objects for understanding the formation of high-mass stars and their effects on their environments. The aim of this work is to explore the structure and kinematics of the…
The formation of massive stars is one of the major unsolved problems in stellar astrophysics. However, only few if any of these are found as single stars, on average massive stars have more than one companion. Many of them are born in dense…
[abridged] Unbound young stellar systems, the loose ensembles of physically related young bright stars, trace the typical regions of recent star formation in galaxies. Their morphologies vary from small associations of stars to enormous…
It is often stated that star clusters are the fundamental units of star formation and that most (if not all) stars form in dense stellar clusters. In this monolithic formation scenario, low density OB associations are formed from the…
The observable characteristics and subsequent evolution of young stellar populations is dominated by their massive stars. As our understanding of those massive stars and the factors affecting their evolution improves, so our interpretation…