On the Formation of Galactic Thick Disks

Minchev, Ivan; Martig, Marie; Streich, David; Scannapieco, Cecilia; Jong, Roelof S. de; Steinmetz, Matthias

doi:10.1088/2041-8205/804/1/l9

Cited by 197 publications

(249 citation statements)

References 49 publications

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“…Our star-count models achieve a fitting of the relative proportions in different ways: for the range 6.0 < R < 7.5 kpc, the model of Jurić et al (2008; in which the thick disc is longer than the thin disc) seems more appropriate, however, the Bovy et al (2012b) model, which assumes a shorter scale length for the thick disc, is in better agreement for stars located at the largest radii. This disagreement could indicate a varying scale length or scale height with R for either or both of the discs, as recently suggested by Minchev et al (2015).…”

Section: Thin Disc Thick Discmentioning

confidence: 59%

TheGaia-ESO Survey: characterisation of the [α/Fe] sequences in the Milky Way discs

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Wyse

Gilmore

et al. 2015

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Context. High-resolution spectroscopic surveys of stars indicate that the Milky Way thin and thick discs follow different paths in the chemical space defined by [α/Fe] vs. [Fe/H], possibly suggesting different formation mechanisms for each of these structures. Aims. We investigate, using the Gaia-ESO Survey internal Data-Release 2, the properties of the double sequence of the Milky Way discs, which are defined chemically as the high-α and low-α populations. We discuss their compatibility with discs defined by other means, such as metallicity, kinematics, or positions. Methods. This investigation uses two different approaches: in velocity space, for stars located in the extended solar neighbourhood; and, in chemical space, for stars at different ranges of Galactocentric radii and heights from the Galactic mid-plane. The separation we find in velocity space allows us to investigate, using a novel approach, the extent of metallicity of each of the two chemical sequences, without making any assumption about the shape of their metallicity distribution functions. Then, using the separation in chemical space, adopting the magnesium abundance as a tracer of the α-elements, we characterise the spatial variation of the slopes of the [α/Fe]−[Fe/H] sequences for the thick and thin discs and the way in which the relative proportions of the two discs change across the Galaxy. Results. We find that the thick disc, defined as the stars tracing the high-α sequence, extends up to super-solar metallicities ([Fe/H] ≈ +0.2 dex), and the thin disc, defined as the stars tracing the low-α sequence, extends at least down to [Fe/H] ≈ −0.8 dex, with hints pointing towards even lower values. Radial and vertical gradients in α-abundances are found for the thin disc, with mild spatial variations in its [α/Fe]−[Fe/H] paths, whereas for the thick disc we do not detect any spatial variations of this kind. This is in agreement with results obtained recently from other high-resolution spectroscopic surveys. Conclusions. The small variations in the spatial [α/Fe]−[Fe/H] paths of the thin disc do not allow us to distinguish between formation models of this structure. On the other hand, the lack of radial gradients and [α/Fe]−[Fe/H] variations for the thick disc indicate that the mechanism responsible for the mixing of metals in the young Galaxy (e.g. radial stellar migration or turbulent gaseous disc) was more efficient before the (present) thin disc started forming.

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Section: Thin Disc Thick Discmentioning

confidence: 59%

TheGaia-ESO Survey: characterisation of the [α/Fe] sequences in the Milky Way discs

Kordopatis

Wyse

Gilmore

et al. 2015

A&A

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“…2 by Minchev et al 2016); -the age-[Fe/H] relation (Fig. 2 by Minchev et al 2016); -the flaring of mono-abundance populations (assuming similarity to mono-age populations) found by Bovy et al (2015) and predicted earlier by Minchev et al (2015), where Model 1 in the latter paper presents the same galaxy as the one used for the MCM13 chemodynamical model.…”

Section: Comparison With Observationsmentioning

confidence: 83%

“…Finally, a recently proposed thick disc formation mechanism is the superposition of coeval flaring disc subpopulation (Minchev et al 2015). Disc flaring can result from a number of different sources, the most effective most likely being the perturbative effect of mergers on the host disc.…”

Section: The Galactic Thick Discmentioning

confidence: 99%

“…Other sources of disc flaring include misaligned gas infall (Scannapieco et al 2009) and reorientation of the disc rotation axis . Minchev et al (2015) studied the formation of thick discs using two suites of simulations of galactic disc formation, one of which we present here. This is a full cosmological zoom-in hydro simulation, using initial conditions from one of the Aquarius Project haloes (Scannapieco et al 2009;Springel et al 2008).…”

Section: Migration Suppresses Disc Flaring When Infalling Satellites mentioning

confidence: 99%

“…Age gradients are predicted for both the (morphologically defined) thin and thick discs. Adapted from Minchev et al (2015). lation.…”

Section: Migration Suppresses Disc Flaring When Infalling Satellites mentioning

confidence: 99%

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Constraining the Milky Way assembly history with Galactic Archaeology

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The aim of Galactic Archaeology is to recover the evolutionary history of the Milky Way from its present day kinematical and chemical state. Because stars move away from their birth sites, the current dynamical information alone is not sufficient for this task. The chemical composition of stellar atmospheres, on the other hand, is largely preserved over the stellar lifetime and, together with accurate ages, can be used to recover the birthplaces of stars currently found at the same Galactic radius. In addition to the availability of large stellar samples with accurate 6D kinematics and chemical abundance measurements, this requires detailed modeling with both dynamical and chemical evolution taken into account. An important first step is to understand the variety of dynamical processes that can take place in the Milky Way, including the perturbative effects of both internal (bar and spiral structure) and external (infalling satellites) agents. We discuss here (1) how to constrain the Galactic bar, spiral structure, and merging satellites by their effect on the local and global disc phase-space, (2) the effect of multiple patterns on the disc dynamics, and (3) the importance of radial migration and merger perturbations for the formation of the Galactic thick disc. Finally, we discuss the construction of Milky Way chemo-dynamical models and relate to observations.

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The Apache Point Observatory Galactic Evolution Experiment (APOGEE) and its successor, APOGEE‐2

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2016

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The Apache Point Observatory Galactic Evolution Experiment (APOGEE) of Sloan Digital Sky Survey III (SDSS-III) has produced a large catalog of high resolution (R = 22 500), high quality (S/N > 100), infrared (H-band) spectra for stars throughout all stellar populations of the Milky Way, including in regions veiled by significant dust opacity. APOGEE's half million spectra collected on > 163 000 unique stars, with time series information via repeat visits to each star, are being applied to numerous problems in stellar populations, Galactic astronomy, and stellar astrophysics. From among the early results of the APOGEE project -which span from measurements of Galactic dynamics, to multi-element chemical maps of the disk and bulge, new views of the interstellar medium, explorations of stellar companions, the chemistry of star clusters, and the discovery of rare stellar species -I highlight a few results that demonstrate APOGEE's unique ability to sample and characterize the Galactic disk and bulge. Plans are now under way for an even more ambitious successor to APOGEE: the six-year, dual-hemisphere APOGEE-2 project. Both phases of APOGEE feature a strong focus on targets having asteroseismological measurements from either Kepler or CoRoT, from which it is possible to derive relatively precise stellar ages. The combined APOGEE and APOGEE-2 databases of stellar chemistry, dynamics and ages constitute an unusually comprehensive, systematic and homogeneous resource for constraining models of Galactic evolution.

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On the Formation of Galactic Thick Disks

Cited by 197 publications

References 49 publications

TheGaia-ESO Survey: characterisation of the [α/Fe] sequences in the Milky Way discs

TheGaia-ESO Survey: characterisation of the [α/Fe] sequences in the Milky Way discs

Constraining the Milky Way assembly history with Galactic Archaeology

The Apache Point Observatory Galactic Evolution Experiment (APOGEE) and its successor, APOGEE‐2

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