Search Publications
Estimating Distances from Parallaxes
Bailer-Jones, Coryn A. L.
Astrometric surveys such as Gaia and LSST will measure parallaxes for hundreds of millions of stars. Yet they will not measure a single distance. Rather, a distance must be estimated from a parallax. In this didactic article, I show that doing this is not trivial once the fractional parallax error is larger than about 20%, which will be the case f…
The Tycho-Gaia astrometric solution . How to get 2.5 million parallaxes with less than one year of Gaia data
Michalik, Daniel; Lindegren, Lennart; Hobbs, David
Context. The first release of astrometric data from Gaia will contain the mean stellar positions and magnitudes from the first year of observations, and proper motions from the combination of Gaia data with Hipparcos prior information (HTPM).
Aims: We study the potential of using the positions from the Tycho-2 Catalogue as additional informat…
Gaia FGK benchmark stars: Effective temperatures and surface gravities
Gustafsson, B.; Soubiran, C.; Heiter, U. +3 more
Context. In the era of large Galactic stellar surveys, carefully calibrating and validating the data sets has become an important and integral part of the data analysis. Moreover, new generations of stellar atmosphere models and spectral line formation computations need to be subjected to benchmark tests to assess any progress in predicting stella…
Gaia FGK benchmark stars: abundances of α and iron-peak elements
Gilmore, G.; Montes, D.; Recio-Blanco, A. +26 more
Context. In the current era of large spectroscopic surveys of the Milky Way, reference stars for calibrating astrophysical parameters and chemical abundances are of paramount importance.
Aims: We determine elemental abundances of Mg, Si, Ca, Sc, Ti, V, Cr, Mn, Co, and Ni for our predefined set of Gaia FGK benchmark stars.
Methods: By ana…
Dependency of Dynamical Ejections of O Stars on the Masses of Very Young Star Clusters
Kroupa, Pavel; Pflamm-Altenburg, Jan; Oh, Seungkyung
Massive stars can be efficiently ejected from their birth star clusters through encounters with other massive stars. We study how the dynamical ejection fraction of O star systems varies with the masses of very young star clusters, {{M}ecl}, by means of direct N-body calculations. We include diverse initial conditions by varying the hal…
Properties of dark subhaloes from gaps in tidal streams
Erkal, Denis; Belokurov, Vasily
Cold or warm, the dark matter substructure spectrum must extend to objects with masses as low as 107 M⊙, according to the most recent Lyman α measurements. Around a Milky Way-like galaxy, more than a thousand of these subhaloes will not be able to form stars but are dense enough to survive even deep down in the potential well…
New Near-infrared Period-Luminosity-Metallicity Relations for RR Lyrae Stars and the Outlook for Gaia
Luri, X.; Clementini, G.; Ripepi, V. +6 more
We present results of the analysis of 70 RR Lyrae stars located in the bar of the Large Magellanic Cloud (LMC). Combining the spectroscopically determined metallicity of these stars from the literature with precise periods from the OGLE III catalog and multi-epoch Ks photometry from the VISTA survey of the Magellanic Clouds system, we d…
Detecting stars, galaxies, and asteroids with Gaia
de Bruijne, J. H. J.; Hestroffer, D.; Krone-Martins, A. +3 more
Context. Gaia is Europe's space astrometry mission, aiming to make a three-dimensional map of 1000 million stars in our Milky Way to unravel its kinematical, dynamical, and chemical structure and evolution.
Aims: We present a study of Gaia's detection capability of objects, in particular non-saturated stars, double stars, unresolved external …
Detecting dark matter substructures around the Milky Way with Gaia
Feldmann, Robert; Spolyar, Douglas
Cold dark matter (CDM) theory, a pillar of modern cosmology and astrophysics, predicts the existence of a large number of starless dark matter haloes surrounding the Milky Way (MW). However, clear observational evidence of these `dark' substructures remains elusive. Here, we present a detection method based on the small, but detectable, velocity c…
Action-space Clustering of Tidal Streams to Infer the Galactic Potential
Hogg, David W.; Helmi, Amina; Sanderson, Robyn E.
We present a new method for constraining the Milky Way halo gravitational potential by simultaneously fitting multiple tidal streams. This method requires three-dimensional positions and velocities for all stars to be fit, but does not require identification of any specific stream or determination of stream membership for any star. We exploit the …