Related papers: HII region variability and pre-main-sequence evolu…
We examine the effects of ionization, radiation pressure and main sequence winds from massive stars on self-gravitating, clumpy molecular clouds, thereby modeling the formation and pre-supernova feedback of massive star clusters. We find…
Aims. Filamentary structures of early type stars are found to be a common feature of the Magellanic Clouds formed at an age of about 0.9-2*10^8 yr. As we go to younger ages these large structures appear fragmented and sooner or later form…
The nebular properties (electronic density, extinction, age, O/H abundances) of HII regions found along the bars of the sample of barred spiral galaxies studied by Martin & Friedli (1997) are examined. From line ratio diagnostic diagrams,…
We present results from a large volume simulation of Hydrogen reionization. We combine 3d radiative transfer calculations and an N-body simulation, describing structure formation in the intergalactic medium, to detail the growth of HII…
We investigate the formation by accretion of massive primordial protostars in the range 10 to 300 Msun. The high accretion rate used in the models (4.4 x 10^{-3} Msun/yr) causes the structure and evolution to differ significantly from those…
Massive stars have a strong impact on their surroundings, in particular when they produce a core-collapse supernova at the end of their evolution. In these proceedings, we review the general evolution of massive stars and their properties…
Spatially resolved studies of star forming regions show that the assumption of spherical geometry is not realistic in most cases, with a major complication posed by the gas being ionised by multiple non-centrally located stars or star…
We investigate the pulsational properties of Pre--Main-Sequence (PMS) stars by means of linear and nonlinear calculations. The equilibrium models were taken from models evolved from the protostellar birthline to the ZAMS for masses in the…
We have observed the W75 N massive star forming region in SiO(J=2-1 & J=1-0) at 3" - 5" resolution and in 6 cm, 2 cm, and 7 mm continuum emission at 1.4" - 0.2" resolution. The abundance ratio of [SiO]/[H2] is roughly 5-7 x 10^-11 which is…
Direct collapse of supermassive stars is a possible pathway to form supermassive black hole seeds at high redshifts. Whereas previous three-dimensional (3D) simulations demonstrate that supermassive stars form via rapid mass accretion,…
The location of HII regions, which indicates the locus of present star formation in galaxies, is analyzed for a large collection of 110 irregular galaxies (Irr) imaged in H$\alpha$ and nearby continuum. The analysis is primarily by visual…
We review the structural properties of giant extragalactic HII regions and HII galaxies based on two dimensional hydrodynamic calculations, and propose an evolutionary sequence that accounts for their observed detailed structure. The model…
Both observations and direct numerical simulations are discordant with predictions of conventional stellar evolution codes for the latest stages of a massive star's life prior to core collapse. We suggest that the problem lies in the…
Theoretical models and observations suggest that the abundances of molecular ions in protoplanetary disks should be highly sensitive to the variable ionization conditions set by the young central star. We present a search for temporal flux…
Observations show that star formation is an inefficient and slow process. This result can be attributed to the injection of energy and momentum by stars that prevents free-fall collapse of molecular clouds. The mechanism of this stellar…
Radiative feedback is among the most important consequences of clustered star formation inside molecular clouds. At the onset of star formation, radiation from massive stars heats the surrounding gas, which suppresses the formation of many…
We present an SPH parameter study of the dynamical effect of photoionization from O--type stars on star--forming clouds of a range of masses and sizes during the time window before supernovae explode. Our model clouds all have the same…
The study of physical and chemical properties of massive protostars is critical to better understand the evolutionary sequence which leads to the formation of high-mass stars. IRAS 18151-1208 is a nearby massive region (d = 3kpc, L ~ 20000…
We present semi-analytic models of the epoch of reionization focusing on the differences between continuous and bursty star formation (SF). Our model utilizes physically motivated analytic fits to 1D radiative transfer simulations of HII…
Massive protostars launch accretion-powered, magnetically-collimated outflows, which play crucial roles in the dynamics and diagnostics of the star formation process. Here we calculate the shock heating and resulting free-free radio…