Reconstructing the star formation history of the Milky Way disc(s) from chemical abundances

Snaith, Owain; Haywood, M.; Matteo, P. Di; Lehnert, M. D.; Combes, F.; Katz, David; Gómez, A.

doi:10.1051/0004-6361/201424281

Cited by 161 publications

(303 citation statements)

References 103 publications

(317 reference statements)

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“…1. The stars below the separating line are considered either as metal-poor thin disk objects (see discussion on these objects in Haywood 2008 andHaywood et al 2013 for the status of these objects, and Snaith et al 2014Snaith et al , 2015 for a description of their chemical evolution), or as accreted stars, following the study by Nissen & Schuster (2010). The colors (indicated in the legend) and size (larger implies older) of the symbols indicate the age of the stars.…”

Section: Datamentioning

confidence: 99%

“…We used a closed-box model, which is discussed at length in Snaith et al (2014Snaith et al ( , 2015. We note that the effects described here are expected to be of similar or even higher amplitudes than with standard infall models.…”

Section: The Model and Chemical Tracksmentioning

confidence: 99%

“…Recent results (Ness et al 2013a,b;Di Matteo et al 2014 have confirmed the view that the Milky Way (MW) is also a pure disk galaxy (Shen et al 2010;Kunder et al 2012), i.e., it has no substantial classical bulge. Furthermore, measurements of its SFH have shown that during the peak of star formation in the universe, the MW was a star-bursting galaxy and was forming its thick disk (Snaith et al , 2015Lehnert et al 2014). The structural parameters of this population, with a short scale length (Bensby et al 2011;Cheng et al 2012a;Bovy et al 2012) suggest that it constitutes most of the mass in the MW's central region (Ness et al 2013a,b;Di Matteo et al 2014Haywood et al, in prep.…”

Section: Introductionmentioning

confidence: 99%

“…Hence, these scenarios leave no room for a substantial component of intermediate metallicity in the MW. This credo has been questioned by a new scheme presented in Haywood et al (2013), Snaith et al (2014Snaith et al ( , 2015, and Haywood (2014a,b).…”

Section: Introductionmentioning

confidence: 99%

“…Because of the coupling assumed between accretion and SFR in these models, a natural signature of such a scheme would therefore be that SFHs vary with distance from the Galactic center. Direct measurement of the star formation history outside the solar vicinity is not feasible currently; however, we know that a given SFH leaves specific signatures on the radial and temporal dependence of the chemical abundances in stars Snaith et al 2014Snaith et al , 2015. Since thick disk stars observed in the solar vicinity were born over a A&A 579, A5 (2015) wide range of galactocentric distances (see Sect.…”

Section: Introductionmentioning

confidence: 99%

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Clues to the formation of the Milky Way’s thick disk

Haywood

Matteo

Snaith

et al. 2015

A&A

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We analyze the chemical properties of a set of solar vicinity stars, and show that the small dispersion in abundances of α-elements at all ages provides evidence that the star formation history (SFH) has been uniform throughout the thick disk. In the context of longtimescale infall models, we suggest that this result points either to a limited dependence of the gas accretion on the Galactic radius in the inner disk (R < 10 kpc) or to a decoupling of the accretion history and SFH due to other processes governing the interstellar medium in the early disk, suggesting that infall cannot be a determining parameter of the chemical evolution at these epochs. We argue that these results and other recent observational constraints -namely the lack of radial metallicity gradient and the non-evolving scale length of the thick disk -are better explained if the early disk is viewed as a pre-assembled gaseous system, with most of the gas settled before significant star formation took place -formally the equivalent of a closed-box model. In either case, these results point to a weak or non-existent inside-out formation history in the thick disk or in the first 3-5 Gyr of the formation of the Galaxy. We argue, however, that the growing importance of an external disk whose chemical properties are distinct from those of the inner disk would give the impression of an inside-out growth process when seen through snapshots at different epochs. The progressive, continuous process usually invoked may not have actually existed in the Milky Way.

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Section: Datamentioning

confidence: 99%

Section: The Model and Chemical Tracksmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Clues to the formation of the Milky Way’s thick disk

Haywood

Matteo

Snaith

et al. 2015

A&A

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Our Galaxy, the Milky Way

Matteo

2021

Galaxies

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Clues on the Milky Way disc formation from population synthesis simulations

et al. 2016

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In recent years the stellar populations of the Milky Way have been investigated from large scale surveys in different ways, from pure star count analysis to detailed studies based on spectroscopic surveys. While in the former case the data can constrain the scale height and scale length thanks to completeness, they suffer from high correlation between these two values. On the other hand, spectroscopic surveys suffer from complex selection functions which hardly allow to derive accurate density distributions. The scale length in particular has been difficult to be constrained, resulting in discrepant values in the literature. Here, we investigate the thick disc characteristics by comparing model simulations with large scale data sets. The simulations are done from the population synthesis model of Besançon. We explore the parameters of the thick disc (shape, local density, age, metallicity) using a Monte Carlo Markov Chain method to constrain the model free parameters . Correlations between parameters are limited due to the vast spatial coverage of the used surveys (SDSS + 2MASS). We show that the thick disc was created during a long phase of formation, starting about 12 Gyr ago and finishing about 10 Gyr ago, during which gravitational contraction occurred, both vertically and radially. Moreover, in its early phase the thick disc was flaring in the outskirts. We conclude that the thick disc has been created prior to the thin disc during a gravitational collapse phase, slowed down by turbulence related to a high star formation rate, as explained for example in Bournaud et al. (2009) or Lehnert et al. (2009. Our result does not favor a formation from an initial thin disc thickened later by merger events or by secular evolution of the thin disc. We then study the in-plane distribution of stars in the thin disc from 2MASS and show that the thin disc scale length varies as a function of age, indicating an inside out formation. Moreover, we investigate the warp and flare and demonstrate that the warp amplitude is changing with time and the node angle is slightly precessing. Finally, we show comparisons between the new model and spectroscopic surveys. The new model allows to correctly simulate the kinematics, the metallicity, and α-abundance distributions in the solar neighbourhood as well as in the bulge region.

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Reconstructing the star formation history of the Milky Way disc(s) from chemical abundances

Cited by 161 publications

References 103 publications

Clues to the formation of the Milky Way’s thick disk

Clues to the formation of the Milky Way’s thick disk

Our Galaxy, the Milky Way

Clues on the Milky Way disc formation from population synthesis simulations

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