THE LONG-TERM EVOLUTION OF THE GALACTIC DISK TRACED BY DISSOLVING STAR CLUSTERS

By Joss Bland-Hawthorn, Mark R. Krumholz, Kenneth C. Freeman. 2010

120 citations recorded by the source corpus.

The Galactic disk retains vast amount of information about how it came to be and how it evolved over cosmic time. However, we know very little about the secular processes associated with disk evolution. One major uncertainty is the extent to which stars migrate radially through the disk, thereby washing out signatures of their past (e.g., birth sites). Recent theoretical work finds that such “blurring” of the disk can be important if spiral arms are transient phenomena. Here we describe an experiment to determine the importance of diffusion from the Solar circle with cosmic time. Consider a star cluster that has been placed into a differentially rotating, stellar fluid. We show that all clusters up to ∼104 M☉ in mass, and a significant fraction of those up to ∼105 M☉, are expected to be chemically homogeneous, and that clusters of this size can be assigned a unique “chemical tag” by measuring the abundances of ≲10 independent element groups, with better age and orbit determinations allowing fewer abundance measurements. The star cluster therefore acts like a “tracer dye,” and the present-day distribution of its stars provides a strong constraint on the rate of radial diffusion or migration in the Galactic disk. A star cluster of particular interest for this application is the “Solar family”—the stars that were born with the Sun. If we were able to identify a significant fraction of these, we could determine whether the Sun was born at its present radius or much further in. We show all-sky projections for the Solar family under different dynamical scenarios and identify the most advantageous fields on the sky for the experiment. Sellwood & Binney have argued for strong radial transport driven by transient spiral perturbations: in principle, we could measure the strength of this migration directly. In searching for the Solar family, we would also identify many thousands of other chemically homogeneous groups, providing a wealth of additional information. We discuss this prospect in the context of the upcoming HERMES high-resolution million-star survey.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

Yule-Simpson’s paradox in Galactic Archaeology (2019, methodology): “Galactic Archaeologists use the observed stellar kinematics, chemical abundances, and derived ages as fossil records to recover the chemo-dynamical history of the Milky Way (Freeman & Bland-Hawthorn 2002; Bland-Hawthorn et al. 2010; Rix & Bovy 2013; Binney 2013; Minchev 2016; Hogg et al. 2016).”
A NEW MECHANISM FOR RADIAL MIGRATION IN GALACTIC DISKS: SPIRAL–BAR RESONANCE OVERLAP (2009, background): “Therefore, in the next couple of years we may be in a position to directly measure the spread of open clusters across the Galaxy as a function of age, thus providing direct constraints on the amount of mixing in the Milky Way (Bland-Hawthorn et al. 2010).”
The GALAH survey: observational overview and Gaia DR1 companion (2016, background): “From theoretical explorations of clustered star formation (e.g., Bland-Hawthorn et al. 2010a; Feng & Krumholz 2014), we expect there to be stars from a large number of unique star-forming events (“initial star-forming groups”) mixed throughout both the thin and thick disks.”
The GALAH Survey: Second Data Release (2018, background): “The overarching goal of the GALAH survey is to acquire highresolution spectra of a million stars for chemical tagging, in order to investigate the assembly history of the Galaxy (Freeman & BlandHawthorn 2002; De Silva et al. 2009; Bland-Hawthorn et al. 2010).”
Radial migration in disc galaxies — I. Transient spiral structure and dynamics (2011, background): “Schönrich & Binney (2009a,b) included a probabilistic prescription of radial migration in a chemical evolution modelconstrained by Milky Way observables and found that, similarlyto R08b, the MDF is broadened and the AMR flattened as a result of migration.”
The Milky Way’s stellar disk (2013, background): “This leaves ‘age’ and ‘chemical abundances’ [ −−→ X/H] as lifelong tags to mark sub-populations (Bland-Hawthorn et al. 2010), and disk sub-components have long been defined that way (Fuhrmann 2011).”
PLATO as it is: a legacy mission for Galactic archaeology (2017, unknown): “In particular, observing how individual star clusters have spread out is the most direct measure of radial migration with cosmic time (Bland-Hawthorn et al. 2010).”
On the fraction of star formation occurring in bound stellar clusters (2012, background): “Alternatively, it has been argued that the collapse time-scale increases weakly with the GMC mass (Bland-Hawthorn et al. 2010).”
The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, background): “If even a few disrupted stellar systems with different ages can be recovered, we can learn about the role of secular evolution and stellar migration over cosmic time from their dispersal across the disk (Bland-Hawthorn et al. 2010).”
STARS, GAS, AND DARK MATTER IN THE SOLAR NEIGHBORHOOD (2015, background): “The stars in the solar neighborhood have been formed in a huge number of events and environments during the lifetime of the local disk (e.g., Bland-Hawthorn et al. 2010), so cluster-tocluster variations should not affect our analysis.”
Constraining the Milky Way assembly history with Galactic Archaeology (2016, methodology): “Probably one of the best ways of quantifying radial migration in the Milky Way is using the technique of chemical tagging (Bland-Hawthorn et al., 2010), where stars born in the same cluster (now dispersed) are expected to appear as a clump in the multi-dimensional chemical space.”
Evolution of galactic discs: multiple patterns, radial migration, and disc outskirts (2012, background): “…l constraints on the migration mechanism at work in the MW is “chemical tagging” (Freeman and Bland-Hawthorn, 2002) with, e.g., the HERMES survey, which will allow us to directly measure the spread of evaporated open clusters across the Galaxy as a function of age (Bland-Hawthorn et al., 2010).”