The geometry and dynamical role of stellar wind bubbles in photoionized H ii regions

ABSTRACT Winds from young massive stars contribute a large amount of energy to their host molecular clouds. This has consequences for the dynamics and observable structure of star-forming clouds. In this paper, we present radiative magnetohydrodynamic simulations of turbulent molecular clouds that form individual stars of 30, 60, and 120 solar masses emitting winds and ultraviolet radiation following realistic stellar evolution tracks. We find that winds contribute to the total radial momentum carried by the expanding nebula around the star at 10 per cent of the level of photoionization feedback, and have only a small effect on the radial expansion of the nebula. Radiation pressure is largely negligible in the systems studied here. The 3D geometry and evolution of wind bubbles is highly aspherical and chaotic, characterized by fast-moving ‘chimneys’ and thermally driven ‘plumes’. These plumes can sometimes become disconnected from the stellar source due to dense gas flows in the cloud. Our results compare favourably with the findings of relevant simulations, analytic models and observations in the literature while demonstrating the need for full 3D simulations including stellar winds. However, more targeted simulations are needed to better understand results from observational studies.

Properties of ISM in two star-forming regions

The Hi-GAL provides an opportunity to make a complete and unbiased view of the continuum emission in the Galactic plane in five bands: 70, 160, 250, 350, and 500 μm. Our research focuses on two of star-forming regions. The first one is the molecular cloud, which includes G45.12+0.13 and G45.07+0.13 UCHII regions. Using the Modified blackbody fitting on Herschel images obtained in four bands: 160, 250, 350, and 500 μm, we determined the distribution of N(H2) hydrogen column density and Td dust temperature. The maps of N(H2) and Td show that UCHII regions clearly stand out against the general background of the molecular cloud with a relatively low density (from 1.0 x 1023 to 3.0 x 1023 cm-2) and significantly higher temperature (up to 100 K), what is fully consistent with the basic concept of UCHII regions about the presence of a hot, high mass stellar source and stellar wind, which leads to the blowing out of matter. The second one is the elongated star-forming region, which includes five stellar subgroups around IRAS 05184+3635, 05177+3636, 05168+3634, 05162+3639 and 05156+3643 sources. Here, on the contrary, the N(H2) is noticeably higher (from 1.0 x 1023 to 5.0 x 1023 cm-2) than in the surrounding molecular cloud and the Td does not exceed 25 K.

Interaction of solid bodies with atmospheres of protoplanets

During the early stages of planet formation accretion of small bodies add mass to the planet and deposit their energy kinetic energy. Caused by frictional heating and/or large stagnation pressures within the dense and extended atmospheres most of the in-falling bodies get destroyed by melting or break-up before they impact on the planet’s surface. The energy is added to the atmospheric layers rather than heating the planet directly. These processes can significantly alter the physical properties of protoplanets before they are exposed with their primordial atmospheres to the early stellar source when the protoplanetary disk becomes evaporated.

The rapid evolution of dust content in galaxies over the last five billion years

The Herschel-ATLAS (H-ATLAS) will provide an unrivalled sample of galaxies, probing the normal star-forming submillimetre population of galaxies for the first time. Here, we exploit the Science Demonstration Phase (SDP) data to model the evolution of the interstellar content of galaxies in recent history. The most massive H-ATLAS galaxies show a large increase in the dust content five billion years ago compared to the present epoch. These observations are difficult to explain using standard dust models, one possibility could be contributions from a non-stellar source of dust e.g. grain growth in dense clouds; this would imply that less than 10% of dust would be condensed in stellar atmospheres. Alternatively, an initial mass function which becomes top heavy at high star formation rate densities could also explain this discrepancy.

Uniqueness and evolutionary status of MWC 349A

MWC349A, which had remained an ordinary member of the MWC catalog for a few decades, is now known as: (1) the brightest stellar source of radio continuum; (2) the only known high-gain natural maser in hydrogen recombination lines; and (3) the only strictly proven natural high-gain laser (in IR hydrogen recombination lines). These phenomena seem to occur in the circumstellar disk seen almost edge-on. They help us understand the structure and kinematics of the disk. The evolutionary status of MWC 349A is still debated: a young HAeBe star with a pre-planetary disk or an old B[e] star or even a protoplanetary nebula? We discuss new observational data obtained at the Maria Mitchell Observatory and elsewhere which may cast light on this issue.