Related papers: Precise Asteroseismic Ages for the Helmi Streams

Aims. HD166734 is an eccentric eclipsing binary system composed of two supergiant O-type stars, orbiting with a 34.5-day period. In this rare configuration for such stars, the two objects mainly evolve independently, following single-star…

We present new Atacama Large Millimeter/Submillimeter Array (ALMA) observations of the [CII] 158 $\mu$m transition and the dust continuum in HZ4, a typical star-forming galaxy when the Universe was only $\sim1$ Gyr old ($z\approx5.5$). Our…

I present the preliminary results of a program to measure the star formation history in the halo of the Andromeda galaxy. Using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope, we obtained the deepest optical images of…

With the observations of an unprecedented number of oscillating subgiant stars expected from NASA's TESS mission, the asteroseismic characterization of subgiant stars will be a vital task for stellar population studies and for testing our…

Taking advantage of the ultra-deep near-infrared imaging obtained with the Hubble Space Telescope on the Hubble Ultra Deep Field, we detect and explore for the first time the properties of the stellar haloes of two Milky Way-like galaxies…

The inner Galactic halo is a complex graveyard of the Milky Way's earliest accretion events, where severe orbital phase-mixing challenges traditional dynamical stream-finding techniques. We present a purely data-driven, 12-dimensional…

The stellar population of the Milky Way bulge is thoroughly studied, with a plethora of measurements from virtually the full suite of instruments available to astronomers. It is thus perhaps surprising that alongside well-established…

We use the very high resolution, fully cosmological simulations from the Aquarius project, coupled to a semi-analytical model of galaxy formation, to study the phase-space distribution of halo stars in "solar neighbourhood"-like volumes. We…

Accretion flows onto massive stars must transfer mass so quickly that they are themselves gravitationally unstable, forming dense clumps and filaments. These density perturbations interact with young massive stars, emitting ionizing…

The Giant Stellar Stream (GSS) is a prominent tidal feature in the halo of the Andromeda Galaxy (M31), representing the ongoing destruction of a satellite galaxy. In this paper, we investigate the formation of the GSS through detailed…

The isotope abundances provide powerful diagnostics of the chemical enrichment in our Galaxy. The star HD 140283 is one of the best-studied very metal-poor dwarf stars. It is very old, and the chemical abundance in this star is a good…

Old Globular Clusters (GCs) in the Milky Way have ages of about 13 Gyr, placing their formation time in the reionization epoch. We propose a novel scenario for the formation of these systems based on the merger of two or more atomic cooling…

The cold dark matter picture predicts an abundance of substructure within the Galactic halo. However, most substructures host no stars and can only be detected indirectly. Stellar streams present a promising probe of this dark substructure.…

The Milky Way's stellar halo, which extends to $>100$ kpc, encodes the evolutionary history of our Galaxy. However, most studies of the halo to date have been limited to within a few kpc of the Sun. Here, we characterize differences between…

We present wide and deep photometry of the northwest part of the halo of the Andromeda galaxy (M31) using Hyper Suprime-Cam on the Subaru Telescope. The survey covers 9.2 deg$^{2}$ field in the $g$, $i$, and $NB515$ bands and shows a clear…

Using photometry from Data Release 10 of the northern footprint of the Sloan Digital Sky Survey, we detect two new stellar streams with lengths of between $25\arcdeg$ and $50\arcdeg$. The streams, which we designate Hermus and Hyllus, are…

Tidal interactions between massive galaxies and their satellites are fundamental processes in a Universe with L-Cold Dark Matter cosmology, redistributing material into faint features that preserve records of past galactic interactions.…

We derive age constraints for 1639 red giants in the APOKASC sample for which seismic parameters from Kepler, as well as effective temperatures, metallicities and [alpha/Fe] values from APOGEE DR12 are available. We investigate the relation…

Recent years have seen the discovery of an ever growing number of stellar debris streams and clouds. These structures are typically detected as extended and often curvilinear overdensities of metal-poor stars that stand out from the…

(Abridged) We use HIFI maps of the 987 GHz H2O 2(02)-1(11) emission to measure the sizes and shapes of 19 high-mass protostellar envelopes. To identify infall, we use HIFI spectra of the optically thin C18O 9-8 and H2O-18 1(11)-0(00) lines.…