scholarly journals GALAH survey: chemically tagging the thick disk

2014 ◽  
Vol 67-68 ◽  
pp. 219-226 ◽  
Author(s):  
J. Bland-Hawthorn ◽  
S. Sharma ◽  
K. Freeman
Keyword(s):  
Thick Disk

On the connection between the thick disk and the galactic bar

2014 ◽  
Vol 67-68 ◽  
pp. 405-405
Author(s):  
A. Spagna ◽  
A. Curir ◽  
R. Drimmel ◽  
M.G. Lattanzi ◽  
P. Re Fiorentin ◽  
...  
Keyword(s):  
Thick Disk

scholarly journals The Age of Old Galactic Populations

1998 ◽  
Vol 11 (1) ◽  
pp. 560-561
Author(s):  
M. Grenon
Keyword(s):  
High Velocity ◽  
Radial Velocities ◽  
Thick Disk ◽  
Early Evolution ◽  
Galactic Bulge ◽  
Colour Class ◽  
The Galaxy ◽  
Nearby Stars

As a preparation to the HIPPARCOS mission, a large observing programme on NLTT stars (propermotion > 0.18 ″/yr) was started in Genevaphotometry. The original programme consists of 10047 stars brighter than mR = 11.5, or mR = 12.5 if of colour class m. Among them, 7813 targets could be included in the HIPPARCOS programme, selected according to their observability and internal priorities in favour of large parallaxe stars (photometric distances < 100 pc) and high-velocity stars. The bulk of new nearby, halo, mild-metal poor and SMR stars in the HIP Catalogue originates from this proposal (N° 139). No less than 208 new nearby stars with π ≥ 40 mas were discovered south of δ +10°, the closest has π(HIP)= 182 mas. Radial velocities were obtained with CORAVEL at OHP and ESO. Most aspects of the early evolution of the Galaxy may be addressed with this sample. Here we discuss, as examples, the ages of the thick disk and of the galactic bulge.

Kinematic and chemical signatures of the formation processes of the galactic thick disk

2010 ◽  
Vol 45 ◽  
pp. 437-440
Author(s):  
A. Spagna ◽  
A. Curir ◽  
M.G. Lattanzi ◽  
G. Murante ◽  
P. Re Fiorentin ◽  
...  
Keyword(s):  
Thick Disk ◽  
Formation Processes ◽  
Chemical Signatures

scholarly journals Thick Disk Planetary Nebulae

2006 ◽  
Vol 2 (S234) ◽  
pp. 363
Author(s):  
J.K. Baliga ◽  
D.C.V. Mallik
Keyword(s):  
Planetary Nebulae ◽  
Thick Disk

scholarly journals The merger that led to the formation of the Milky Way’s inner stellar halo and thick disk

Nature ◽  
2018 ◽  
Vol 563 (7729) ◽  
pp. 85-88 ◽  
Author(s):  
Amina Helmi ◽  
Carine Babusiaux ◽  
Helmer H. Koppelman ◽  
Davide Massari ◽  
Jovan Veljanoski ◽  
...  
Keyword(s):  
Thick Disk ◽  
Stellar Halo

scholarly journals Phylogeny of the Milky Way’s inner disk and bulge populations: Implications for gas accretion, (the lack of) inside-out thick disk formation, and quenching

2018 ◽  
Vol 618 ◽  
pp. A78 ◽  
Author(s):  
Misha Haywood ◽  
Paola Di Matteo ◽  
Matthew Lehnert ◽  
Owain Snaith ◽  
Francesca Fragkoudi ◽  
...  
Keyword(s):  
Star Formation ◽  
Accretion Rate ◽  
Large Fraction ◽  
Formation Rate ◽  
Thin Disk ◽  
Thick Disk ◽  
Star Formation History ◽  
Two Phase ◽  
Disk Formation ◽  
Gas Accretion

We show that the bulge and the disk of the Milky Way (MW) at R ≲ 7 kpc are well described by a unique chemical evolution and a two-phase star formation history (SFH). We argue that the populations within this inner disk, not the entire disk, are the same, and that the outer Lindblad resonance (OLR) of the bar plays a key role in explaining this uniformity. In our model of a two-phase SFH, the metallicity, [α/Fe] and [α/H] distributions, and age-metallicity relation are all compatible with the observations of both the inner disk and bulge. The dip at [Fe/H] ∼ 0 dex seen in the metallicity distributions of the bulge and inner disk reflects the quenching episode in the SFH of the inner MW at age ∼8 Gyr, and the common evolution of the bulge and inner disk stars. Our results for the inner region of the MW, R ≲ 7 kpc, are consistent with a rapid build-up of a large fraction of its total baryonic mass within a few billion years. We show that at z ≤ 1.5, when the MW was starting to quench, transitioning between the end of the α-enhanced thick disk formation to the start of the thin disk, and yet was still gas rich, the gas accretion rate could not have been significant. The [α/Fe] abundance ratio before and after this quenching phase would be different, which is not observed. The decrease in the accretion rate and gas fraction at z ≤ 2 was necessary to stabilize the disk allowing the transition from thick to thin disks, and for beginning the secular phase of the MW’s evolution. This possibly permitted a stellar bar to develop which we hypothesize is responsible for quenching the star formation. The present analysis suggests that MW history, and in particular at the transition from the thick to the thin disk – the epoch of the quenching – must have been driven by a decrease of the star formation efficiency. We argue that the decline in the intensity of gas accretion, the formation of the bar, and the quenching of the star formation rate (SFR) at the same epoch may be causally connected thus explaining their temporal coincidence. Assuming that about 20% of the gas reservoir in which metals are diluted is molecular, we show that our model is well positioned on the Schmidt-Kennicutt relation at all times.

Magnetically Driven Jets from Accretion Disks. III. 2.5‐dimensional Nonsteady Simulations for Thick Disk Case

1998 ◽  
Vol 508 (1) ◽  
pp. 186-199 ◽  
Author(s):  
Takahiro Kudoh ◽  
Ryoji Matsumoto ◽  
Kazunari Shibata
Keyword(s):  
Accretion Disks ◽  
Thick Disk

scholarly journals The AMBRE project: The thick thin disk and thin thick disk of the Milky Way

2017 ◽  
Vol 608 ◽  
pp. L1 ◽  
Author(s):  
M. R. Hayden ◽  
A. Recio-Blanco ◽  
P. de Laverny ◽  
S. Mikolaitis ◽  
C. C. Worley
Keyword(s):  
Vertical Velocity ◽  
Velocity Dispersion ◽  
Stellar Populations ◽  
Thin Disk ◽  
Thick Disk ◽  
Solar Neighborhood ◽  
Chemical Enrichment ◽  
History Of ◽  
External Galaxies ◽  
Subgiant Stars

We analyze 494 main sequence turnoff and subgiant stars from the AMBRE:HARPS survey. These stars have accurate astrometric information from Gaia DR1, providing reliable age estimates with relative uncertainties of ±1 or 2 Gyr and allowing precise orbital determinations. The sample is split based on chemistry into a low-[Mg/Fe] sequence, which are often identified as thin disk stellar populations, and high-[Mg/Fe] sequence, which are often associated with thick disk stellar populations. We find that the high-[Mg/Fe] chemical sequence has extended star formation for several Gyr and is coeval with the oldest stars of the low-[Mg/Fe] chemical sequence: both the low- and high-[Mg/Fe] sequences were forming stars at the same time. We find that the high-[Mg/Fe] stellar populations are only vertically extended for the oldest, most-metal poor and highest [Mg/Fe] stars. When comparing vertical velocity dispersion for the low- and high-[Mg/Fe] sequences, the high-[Mg/Fe] sequence has lower vertical velocity dispersion than the low-[Mg/Fe] sequence for stars of similar age. This means that identifying either group as thin or thick disk based on chemistry is misleading. The stars belonging to the high-[Mg/Fe] sequence have perigalacticons that originate in the inner disk, while the perigalacticons of stars on the low-[Mg/Fe] sequence are generally around the solar neighborhood. From the orbital properties of the stars, the high-[Mg/Fe] and low-[Mg/Fe] sequences are most likely a reflection of the chemical enrichment history of the inner and outer disk populations, respectively; radial mixing causes both populations to be observed in situ at the solar position. Based on these results, we emphasize that it is important to be clear in defining what populations are being referenced when using the terms thin and thick disk, and that ideally the term thick disk should be reserved for purely geometric definitions to avoid confusion and be consistent with definitions in external galaxies.

scholarly journals Search for streams in thick disk and halo of the Milky Way

2016 ◽  
Vol 771 ◽  
pp. 012032
Author(s):  
Dian Puspita Triani ◽  
M Ikbal Arifyanto
Keyword(s):  
Milky Way ◽  
Thick Disk
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