Gaia DR2 has revealed substructures in the phase space distribution of stars in the Milky Way. In particular, ridge like structures can be seen in the (R,V_phi) plane and asymmetric arches in (V_R, V_phi) plane. We show that the ridges are also clearly present when the (R,V_phi) plane is mapped by , ,, <|z|>,[Fe/H] and [alpha/Fe]. The last three maps suggest that stars along the ridges lie preferentially close to the Galactic midplane (|z|<0.2 kpc), and, have metallicity and alpha elemental abundance similar to that of the Sun.

Paper PDF: 

Linking_ridges__arches_and_vertical_waves_in_the_kinematics_of_the_Milky_Way.pdf

The Galactic Archaeology with HERMES (GALAH) survey is a large scale, magnitude limited, southern stellar spectroscopic survey providing spectra, stellar parameters and chemical abundances for stars located in different components of the Galaxy. Random selection, based only on object's brightness and its celestial coordinates, implies that a representative set of peculiar stellar types are observed.

Here we focus on carbon enhanced stars which can be identified by peculiar features present in their GALAH spectra.

Paper PDF: 

GALAH_carbon_enhanced_R2.pdf

Late-type stars deplete their atmospheric lithium abundance on the main sequence in a way that depends on mass, metallicity, age and possibly other parameters (rotation rate, activity. presence of binary companion or planets). There are still many unanswered questions about the evolution of this unique element in the Galaxy and in the stars themselves; it is unclear which parameters and physical mechanisms that govern Li depletion and if Galactic enrichment has proceeded differently in different stellar populations.

Paper PDF: 

MN_Letter_Lithium.pdf

One of the main goals of the Galah survey is to find stellar siblings in the Galactic disk and associate them to a common parent cluster by means of chemistry and dynamics. The success of such chemical tagging hinges critically on our ability to determine the abundances of late-type dwarf and giant stars with high precision, but also to assess whether their present-day abundance patterns truly reflect their original compositions.

Paper PDF: 

Gao_M67.pdf

We present a study using the second data release of the GALAH survey of stellar parameters and elemental abundances of 15 pairs of stars identified by Oh et al. They identified these pairs as potentially co-moving pairs using proper motions and parallaxes from Gaia DR1. We find that 11 very wide (>1 pc) pairs of stars do in fact have similar Galactic orbits, while a further four claimed co-moving pairs are not truly co-orbiting.

Paper PDF: 

sty3042.pdf

One of the main motivations for the GALAH survey is to measure abundances of many elements in sufficiently large number of stars that some of them can be identified as stars that were born in the same cluster but all indications of this fact have been lost, except for the chemical fingerprint. Chemical tagging can reveal the connection between such stars, but state of the art observations and analytical methods will be needed to actually perform this task.

Paper PDF: 

Chemtag_short.pdf

The overlap between the spectroscopic Galactic Archaeology with HERMES (GALAH) survey and Gaia provides a high-dimensional chemodynamical space of unprecedented size. We present a first analysis of a subset of this overlap, of 7066 dwarf, turn-off, and sub-giant stars. These stars have spectra from the GALAH survey and high parallax precision from the Gaia DR1 Tycho-Gaia Astrometric Solution. We investigate correlations between chemical compositions, ages, and kinematics for this sample.

Paper PDF: 

Buder_AandA_2019_624_A19_GALAH_TGAS.pdf

Around one percent of evolved stars are surprisingly rich in lithium, and the fraction rises with rising metallicity. Lithium is destroyed by proton capture at relatively low temperature, and in standard stellar evolution models it is depleted significantly in post-main-sequence evolution. A number of mechanisms have been proposed as the source of lithium in giant stars, based on their rareness and their tendency to be found near the red clump and the "bump" in the red giant branch luminosity function.

Paper PDF: 

Lithium_team_200428.pdf

The emergence of the first sources of light at redshifts of z˜10-30 signaled the transition from the simple initial state of the Universe to one of increasing complexity. Recent progress in our understanding of the formation of the first stars and galaxies, starting with cosmological initial conditions, primordial gas cooling, and subsequent collapse and fragmentation are reviewed. The important open question of how the pristine gas was enriched with heavy chemical elements in the wake of the first supernovae is emphasized.

We present tentative evidence for the existence of a dissolved star cluster at [Fe/H] = -2.7 in the Sextans dwarf spheroidal galaxy. We use the technique of chemical tagging to identify stars that are highly clustered in a multi-dimensional chemical abundance space ( {C}-space). In a sample of six stars, three, possibly four, stars are identified as potential cluster stars.