Search Publications
DYNESTY: a dynamic nested sampling package for estimating Bayesian posteriors and evidences
Speagle, Joshua S.
We present DYNESTY, a public, open-source, PYTHON package to estimate Bayesian posteriors and evidences (marginal likelihoods) using the dynamic nested sampling methods developed by Higson et al. By adaptively allocating samples based on posterior structure, dynamic nested sampling has the benefits of Markov chain Monte Carlo (MCMC) algorithms tha…
Unresolved stellar companions with Gaia DR2 astrometry
Everall, Andrew; Brown, Anthony G. A.; Belokurov, Vasily +9 more
For stars with unresolved companions, motions of the centre of light and that of mass decouple, causing a single-source astrometric model to perform poorly. We show that such stars can be easily detected with the reduced χ2 statistic, or renormalized unit weight error (RUWE), provided as part of Gaia DR2. We convert RUWE into the amplit…
The milky way total mass profile as inferred from Gaia DR2
Grand, Robert J. J.; Gómez, Facundo A.; Fattahi, Azadeh +7 more
We determine the Milky Way (MW) mass profile inferred from fitting physically motivated models to the Gaia DR2 Galactic rotation curve and other data. Using various hydrodynamical simulations of MW-mass haloes, we show that the presence of baryons induces a contraction of the dark matter (DM) distribution in the inner regions, r ≲ 20 kpc. We provi…
The biggest splash
Grand, Robert J. J.; Fattahi, Azadeh; Belokurov, Vasily +4 more
Using a large sample of bright nearby stars with accurate Gaia Data Release 2 astrometry and auxiliary spectroscopy we map out the properties of the principle Galactic components such as the 'thin' and 'thick' discs and the halo. We confirm previous claims that in the Solar neighbourhood, there exists a large population of metal-rich ([Fe/H] > …
The lifecycle of molecular clouds in nearby star-forming disc galaxies
Henshaw, Jonathan D.; Kruijssen, J. M. Diederik; Longmore, Steven N. +29 more
It remains a major challenge to derive a theory of cloud-scale (≲100 pc) star formation and feedback, describing how galaxies convert gas into stars as a function of the galactic environment. Progress has been hampered by a lack of robust empirical constraints on the giant molecular cloud (GMC) lifecycle. We address this problem by systematically …
Kraken reveals itself - the merger history of the Milky Way reconstructed with the E-MOSAICS simulations
Kruijssen, J. M. Diederik; Chevance, Mélanie; Bonaca, Ana +6 more
Globular clusters (GCs) formed when the Milky Way experienced a phase of rapid assembly. We use the wealth of information contained in the Galactic GC population to quantify the properties of the satellite galaxies from which the Milky Way assembled. To achieve this, we train an artificial neural network on the E-MOSAICS cosmological simulations o…
A Volume-limited Sample of Cataclysmic Variables from Gaia DR2: Space Density and Population Properties
Knigge, C.; Hermes, J. J.; Gänsicke, B. T. +15 more
We present the first volume-limited sample of cataclysmic variables (CVs), selected using the accurate parallaxes provided by the second data release (DR2) of the European Space Agency Gaia space mission. The sample is composed of 42 CVs within 150 pc, including two new systems discovered using the Gaia data, and is $(77 \pm 10)$ per cent complete…
A new mass-loss rate prescription for red supergiants
Smith, Nathan; Gehrz, Robert D.; van Loon, Jacco Th +3 more
Evolutionary models have shown the substantial effect that strong mass-loss rates ( $\dot{M}$ s) can have on the fate of massive stars. Red supergiant (RSG) mass-loss is poorly understood theoretically, and so stellar models rely on purely empirical $\dot{M}$ -luminosity relations to calculate evolution. Empirical prescriptions usually scale with …
Reverse engineering the Milky Way
Forbes, Duncan A.
The ages, metallicities, alpha-elements, and integrals of motion of globular clusters (GCs) accreted by the Milky Way from disrupted satellites remain largely unchanged over time. Here we have used these conserved properties in combination to assign 76 GCs to five progenitor satellite galaxies - one of which we dub the Koala dwarf galaxy. We fit a…
Constraining the thermally pulsing asymptotic giant branch phase with resolved stellar populations in the Large Magellanic Cloud
Boyer, Martha L.; Girardi, Léo; de Grijs, Richard +18 more
Reliable models of the thermally pulsing asymptotic giant branch (TP-AGB) phase are of critical importance across astrophysics, including our interpretation of the spectral energy distribution of galaxies, cosmic dust production, and enrichment of the interstellar medium. With the aim of improving sets of stellar isochrones that include a detailed…