Related papers: Completing the Massive Star Population: Striking I…
We investigate the effect of the cluster environment on the star formation properties of galaxies in 8 nearby Abell clusters. Star formation properties are determined for individual galaxies using the equivalent width of H alpha plus [NII]…
Star clusters are ideal tracers of star formation activity in systems outside the volume that can be studied using individual, resolved stars. These unresolved clusters span orders of magnitude in brightness and mass, and their formation is…
Nearby companions alter the evolution of massive stars in binary systems. Using a sample of Galactic massive stars in nearby young clusters, we simultaneously measure all intrinsic binary characteristics relevant to quantify the frequency…
Stars in open clusters are powerful probes of the intervening Galactic magnetic field, via background starlight polarimetry, because they provide constraints on the magnetic field distances. We use 2MASS photometric data for a sample of 31…
Massive stars (those larger than 8 solar masses at formation) have radiative envelopes that cannot sustain a dynamo, the mechanism that produces magnetic fields in lower-mass stars. Despite this, approximately 7\% of massive stars have…
We investigate the hypothesis that stars form in aggregates of binary systems and that the dynamical evolution of these aggregates leads to the observed properties of binary stars in the Galactic field. We assume that the initial…
In the outskirts of nearby spiral galaxies, star formation is observed in extremely low gas surface densities. Star formation in these regions, where the interstellar medium is dominated by diffuse atomic hydrogen, is difficult to explain…
The discovery around the turn of the millenium of a population of very massive (M$_\star$ > 2$\times$10$^6$ M$_\odot$) compact stellar systems (CSS) with physical properties (radius, velocity dispersion, stellar mass etc.) that are…
The evolution of massive stars is the basis of several astrophysical investigations, from predicting gravitational-wave event rates to studying star-formation and stellar populations in clusters. However, uncertainties in massive star…
Massive stars blow powerful winds and eventually explode as supernovae. By doing so, they inject energy and momentum in the circumstellar medium, which is pushed away from the star and piles up to form a dense and expanding shell of gas.…
The evolution of young compact star clusters is studied using N-body simulations in which both stellar evolution and physical collisions between stars are taken into account. The initial conditions are chosen to represent R136, a compact…
We present the galaxy stellar mass function (MF) and its evolution in clusters from z~0.8 to the current epoch, based on the WIde-field Nearby Galaxy-cluster Survey (WINGS) (0.04<z<0.07), and the ESO Distant Cluster Survey (EDisCS) (0.4<z…
The characteristic mass M_c and slope Gamma of the IMF are reviewed for clusters, field regions, galaxies, and regions formed during cosmological times. Local star formation has a somewhat uniform M_c and Gamma. Statistical variations in…
Aims: We investigate the build-up of stellar mass through star formation in field galaxies, galaxy groups, and clusters in order to better understand the physical processes regulating star formation in different haloes. Methods: In order to…
A sample of 97 galactic field Be stars were studied by taking into account the effects induced by the fast rotation on their fundamental parameters. All program stars were observed in the BCD spectrophotometric system in order to minimize…
High-mass stars are notable for several reasons: they are characterized by strong winds, which inject momentum and enriched material into their surroundings, and die spectacularly as supernovae, leaving behind compact remnants and heavy…
The birth of stars and the formation of galaxies are cornerstones of modern astrophysics. While much is known about how galaxies globally and their stars individually form and evolve, one fundamental property that affects both remains…
Stars, and collections of stars, encode rich signatures of stellar physics and galaxy evolution. With properties influenced by both their environment and intrinsic nature, stars retain information about astrophysical phenomena that are not…
Most if not all stars form in star clusters. Thus the distribution of star clusters preserves the information on the star formation history of a galaxy. Massive clusters form only during episodes of high star formation activity whereas…
In this review, I present the case for how massive stars may form through stellar collisions. This mechanism requires very high stellar densities, up to 4 orders of magnitude higher than are observed in the cores of dense young clusters. In…