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The conversion factor αCO from the observable CO(1-0) luminosity to the mass of molecular gas is known to vary between isolated galaxies and some mergers, but the underlying reasons are not clearly understood. Thus, the value(s) of αCO that are to be adopted remain highly uncertain. To provide better constraints, we applied the large velocity gradient method to a series of hydrodynamical simulatio
We present a cosmological zoom-in simulation of a Milky Way-like galaxy used to explore the formation and evolution of star clusters. We investigate in particular the origin of the bimodality observed in the colour and metallicity of globular clusters, and the environmental evolution through cosmic times in the form of tidal tensors. Our results self-consistently confirm previous findings that the
Very strong Sc i lines have recently been found in cool M giants in the Nuclear Star Cluster (NSC) in the Galactic center. Interpreting these as anomalously high scandium abundances in the Galactic center would imply a unique enhancement signature and chemical evolution history for NSCs, and a potential test for models of chemical enrichment in these objects. We present high resolution K-band spec
Chemical abundances for 15 elements (C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, and Ni) are presented for 83 stellar members of the 4 Gyr old solar-metallicity open cluster M67. The sample contains stars spanning a wide range of evolutionary phases, from G dwarfs to red clump stars. The abundances were derived from near-IR (λ1.5-1.7 μm) high-resolution spectra (R ,F= ,F22,500) from the SD
The solar neighbourhood contains disc stars that have recently crossed spiral arms in the Galaxy. We propose that boundaries in local velocity distributions separate stars that have recently crossed and been more strongly perturbed by a particular arm from those that haven't. Ridges in the stellar velocity distributions constructed from the second Gaia data release trace orbits that could have tou
We explore the connections between stellar age, chemistry, and kinematics across a Galactocentric distance of 7.5 < R(kpc) < 9.0, using a sample of ~12 000 intermediate-mass (FGK) turn-offstars observed with the RAdial Velocity Experiment (RAVE) survey. The kinematics of this sample are determined using radial velocity measurements from RAVE, and parallax and proper motion measurements from the T
We characterize the selection function of RAdial Velocity Experiment (RAVE) using 2 Micron All Sky Survey (2MASS) as our underlying population, which we assume represents all stars that could have potentially been observed.We evaluate the completeness fraction as a function of position, magnitude and colour in two ways: first, on a field-by-field basis, and second, in equal-size areas on the sky.
Recently, seven Earth-sized planets were discovered around the M-dwarf star TRAPPIST-1. Thanks to transit-timing variations, the masses and therefore the bulk densities of the planets have been constrained, suggesting that all TRAPPIST-1 planets are consistent with water mass fractions on the order of 10%. These water fractions, as well as the similar planet masses within the system, constitute st
Aims. The central region of a circumstellar disk is difficult to resolve in global numerical simulations of collapsing cloud cores, but its effect on the evolution of the entire disk can be significant. Methods. We used numerical hydrodynamics simulations to model the long-term evolution of self-gravitating and viscous circumstellar disks in the thin-disk limit. Simulations start from the gravitat
Context. Although there have been numerous studies of chemical abundances in the Galactic bulge, the central two degrees have been relatively unexplored due to the heavy and variable interstellar extinction, extreme stellar crowding, and the presence of complex foreground disk stellar populations. Aims. In this paper we discuss the metallicity distribution function, vertical and radial gradients,
Context. In the advent of new infrared high-resolution spectrometers, accurate and precise atomic data in the infrared are urgently needed. Identifications, wavelengths, strengths, broadening, and hyper-fine splitting parameters of stellar lines in the near-infrared are in many cases not accurate enough to model observed spectra, and in other cases, these parameters do not even exist. Some stellar
Observed FeO/MgO ratios in the Moon and Earth are inconsistent with simulations done with a single homogeneous silicate layer. In this paper we use a newly developed equation of state to perform smoothed particle hydrodynamics simulations on the lunar-forming impact, testing the effect of a primordial magma ocean on Earth. This is investigated using the impact parameters of both the canonical case
In our solar system, terrestrial planets and meteoritical matter exhibit various bulk compositions. To understand this variety of compositions, formation mechanisms of meteorites are usually investigated via a thermodynamic approach that neglects the processes of transport throughout the protosolar nebula. Here, we investigate the role played by rocklines (condensation/sublimation lines of refract
The Neptunian satellite system is unusual, comprising Triton, a large (∼2700 km) moon on a close-in, circular, yet retrograde orbit, flanked by Nereid, the largest irregular satellite (∼300 km) on a highly eccentric orbit. Capture origins have been previously suggested for both moons. Here we explore an alternative in situ formation model where the two satellites accreted in the circum-Neptunian d
The CHaracterising ExOPlanet Satellite (CHEOPS) was selected on October 19, 2012, as the first small mission (S-mission) in the ESA Science Programme and successfully launched on December 18, 2019, as a secondary passenger on a Soyuz-Fregat rocket from Kourou, French Guiana. CHEOPS is a partnership between ESA and Switzerland with important contributions by ten additional ESA Member States. CHEOPS
