The ESA Gaia astrometric mission and deep photometric surveys have revolutionized our knowledge of the Milky Way. There are many ongoing efforts to search these data for substructure to find evidence of individual accretion events that built up the Milky Way and its halo. One of these newly identified features, called Nyx, was announced as an accreted stellar stream traveling in the plane of the disk.

Paper PDF: 

Nix_on_Nyx.pdf

Open clusters are unique tools to study the chemical distribution of elements along the Galactic disk and its evolution with time. Thanks to precise astrometry and parallaxes from Gaia DR2, it is possible to identify the stars observed by GALAH (and by other spectroscopic surveys) that are members of these stellar associations. Once the cluster members are identified, radial velocities and chemical abundances from spectroscopy will allow us to characterise the Galactic cluster population as a function of kinematic, space, time and chemical abundances.

Paper PDF: 

GALAH_OCs_1910.pdf

Due to its proximity the Orion star forming region is often used as a proxy to study processes related to star formation and observe young stars in the environment they were born in. Orion is getting additional attention within the Gaia DR2, as distance measurements are now good enough that a three dimensional structure of the complex can be explored.

Paper PDF: 

Orion_chemistry-5.pdf

We present lithium abundances for 105 dwarf stars in the halo of the Milky Way that were accreted as part of the Gaia-Enceladus-Sausage (GES). We use these stars to investigate the ``cosmological lithium problem'' --- the observed discrepancy between the amount of lithium in old, metal-poor dwarf stars in our Galaxy, and the amount of lithium predicted to have been produced during the Big Bang. In particular, we investigate whether the formation environment of stars plays a role in the lithium abundance and scatter of the Spite Plateau.

Paper PDF: 

The_GALAH_Survey__Accreted_dwarf_stars_show_the_Lithium_Spite_Plateau-4.pdf

The paper will present extensive grids of non-LTE departure coefficients for ~13 different elements, the first paper of its kind. These grids were used for GALAH DR3. The results of the paper will however be based on a separate, line-by-line re-analysis of a subset of GALAH DR3 (~50000 stars), in LTE and in non-LTE. This will demonstrate the importance of taking departures from LTE into account in spectroscopic studies, when it comes to studying the mean Galactic chemical evolution and its dispersion.

Paper PDF: 

paper.pdf

Gaia DR2 has revealed numerous substructures in velocity space and in the R-Vphi plane for stars within a few kpc of the solar position. Some of these substructures trace ridges of constant energy, others trace ridges of constant angular momentum. In addition, GALAH has identified that more than 40% of local stars have super solar metallicities, and their origin in the solar neighbourhood has long been a mystery.

This represents our efforts to derive detailed abundances from LAMOST spectra using the cannon. We used GALAH as a source of training data, and we obtained access to the GALAH spectra in order to make chi^2 cuts on our training set different from those flagged in the GALAH dr2 catalog. A pdf of our latest draft (nearly ready for submission) is attached. Apologies for not circulating it sooner.

abstract: Large stellar surveys are revealing the chemodynamical structure of the Galaxy across a vast spatial extent.

Paper PDF: 

The_Milky_Way_s_enrichment_across_five_nucleosynthetic_channels_from_4_million_LAMOST_spectra.pdf

The ensemble of chemical element abundance measurements for stars, along with precision distances and orbit properties, provides high-dimensional data to study the evolution of the Milky Way. With this third data release of the Galactic Archaeology with HERMES (GALAH) survey, we publish 678\,423 spectra for 588\,571 mostly nearby stars (81.2\% of stars are within $<$ 2 kpc), observed with the HERMES spectrograph at the Anglo-Australian Telescope.

Paper PDF: 

2011.02505.pdf

Using kinematics from Gaia and the large elemental abundance space of the second data release of the GALAH survey, we identify two new members of the Fimbulthul stellar stream, and chemically tag them to massive, multi-metallic globular cluster ω Centauri. Recent analysis of the second data release of Gaia had revealed the Fimbulthul stellar stream in the halo of the Milky Way. It had been proposed that the stream is associated with the ω Centauri, but this proposition relied exclusively upon the kinematics and metallicities of the stars to make the association. In this work, we find our two new members of the stream to be metal-poor stars that are enhanced in sodium and aluminium, typical of second population globular cluster stars, but not otherwise seen in field stars. Furthermore, the stars share the s-process abundance pattern seen in ω Centauri, which is rare in field stars. Apart from one star within 1.5 deg of ω Centauri, we find no other stars observed by GALAH spatially near ω Centauri or the Fimbulthul stream that could be kinematically and chemically linked to the cluster. Chemically tagging stars in the Fimbulthul stream to ω Centauri confirms the earlier work, and further links this tidal feature in the Milky Way halo to ω Centauri.

Paper PDF: 

1911.01548.pdf

The latest Gaia data release enables us to accurately identify stars that are more luminous than would be expected on the basis of their spectral type and distance. During an investigation of the 329 best Solar twin candidates uncovered among the spectra acquired by the GALAH survey, we identified 64 such over-luminous stars. In order to investigate their exact composition, we developed a data-driven methodology that can generate a synthetic photometric signature and spectrum of a single star.

Paper PDF: 

GALAH_triple_sun-like.pdf