The Pristine survey XIII: uncovering the very metal-poor tail of the thin disc

Fernández-Alvar, Emma; Kordopatis, Georges; Hill, Vanessa; Starkenburg, Else; Viswanathan, Akshara; Martin, Nicolas F.; Thomas, Guillaume F.; Navarro, Julio F.; Malhan, Khyati; Sestito, Federico; González Hernández, Jonay I.; Carlberg, Raymond G.
Bibliographical reference

Monthly Notices of the Royal Astronomical Society

Advertised on:
11
2021
Number of authors
12
IAC number of authors
2
Citations
22
Refereed citations
15
Description
We evaluate the rotational velocity of stars observed by the Pristine survey towards the Galactic anticentre spanning a wide range of metallicities from the extremely metal-poor regime ([Fe/H] < -3) to nearly solar metallicity. In the Galactic anticentre direction, the rotational velocity (Vϕ) is similar to the tangential velocity in the galactic longitude direction (Vℓ). This allows us to estimate Vϕ from Gaia early data release 3 (Gaia EDR3) proper motions for stars without radial velocity measurements. This substantially increases the sample of stars in the outer disc with estimated rotational velocities. Our stellar sample towards the anticentre is dominated by a kinematical thin disc with a mean rotation of ~-220 km s-1. However, our analysis reveals the presence of more stellar substructures. The most intriguing is a well-populated extension of the kinematical thin disc down to [Fe/H] ~ -2 . A scarcer fast-rotating population reaching the extremely metal-poor regime down to [Fe/H] ~ -3.5 is also detected but without statistical significance to unambiguously state whether this is the extremely metal-poor extension of the thin disc or the high-rotating tail of hotter structures (like the thick disc or the halo). In addition, a more slowly rotating kinematical thick disc component is also required to explain the observed Vℓ distribution at [Fe/H] > -1.5 . Furthermore, we detect signatures of a 'heated disc', the so-called Splash, at metallicities higher than ~-1.5. Finally, at [Fe/H] < -1.5 our anticentre sample is dominated by a kinematical halo with a net prograde motion.
Related projects
A view of our Milky Way galaxy with its close neighbors the Magellanic Clouds
Galaxy Evolution in the Local Group

Galaxy formation and evolution is a fundamental Astrophysical problem. Its study requires “travelling back in time”, for which there are two complementary approaches. One is to analyse galaxy properties as a function of red-shift. Our team focuses on the other approach, called “Galactic Archaeology”. It is based on the determination of galaxy

Matteo
Monelli
spectrum of mercury lamp
Chemical Abundances in Stars

Stellar spectroscopy allows us to determine the properties and chemical compositions of stars. From this information for stars of different ages in the Milky Way, it is possible to reconstruct the chemical evolution of the Galaxy, as well as the origin of the elements heavier than boron, created mainly in stellar interiors. It is also possible to

Carlos
Allende Prieto