Studies of Dense Cores with ALMA

Dense cores are the simplest star-forming sites that we know, but despite their simplicity, they still hold a number of mysteries that limit our understanding of how solar-type stars form. ALMA promises to revolutionize our knowledge of every stage in the life of a core, from the pre-stellar phase to the final disruption by the newly born star. This contribution presents a brief review of the evolution of dense cores and illustrates particular questions that will greatly benefit from the increase in resolution and sensitivity expected from ALMAComment: 6 pages, 2 figures, to appear in Astrophysics and Space Science, special issue of "Science with ALMA: a new era for Astrophysics" conference, ed. Dr. Bachille

Plasma Diagnostics of the Interstellar Medium with Radio Astronomy

Contains fulltext : 119335.pdf (preprint version ) (Open Access

The hydrodynamic evolution of circumstellar gas around massive stars. Pt. 2 The impact of the time sequence O star #-># RSG #-># WR star

We investigate the interaction of a 35 M_sun star with its circumstellar medium over the entire stellar life time, combining an implicit hydrodynamic code for the calculation of the massive stellar evolution, and an explicit hydrodynamic code for the treatment of the circumstellar gas. The final supernova phase is not included. The 35 M_sun stellar model has three well defined evolutionary phases: main sequence, red supergiant and Wolf-Rayet stage. It provides a realistic test for the three-wind model of Wolf-Rayet bubbles. We find the velocity of the red supergiant wind to be a key parameter affecting the formation and detectability of a ring nebula in the Wolf-Rayet stage. We investigate systematic differences of wind shells and nebulae around post-RSG WR stars compared to those of post-LBV WR stars. The Wolf-Rayet star WR 136 is located on our evolutionary track in the HR diagram, and the computed circumstellar gas distribution at the time our stellar hits the position of WR 136 is in good agreement with its observed nebula NGC 6888. The ring nebula Sh 308 around WR 6 can be explained when the RSG wind has higher velocity than in the case of NGC 6888. Our results support the interpretation of the HII regions SH 303 and Sh 304 as parts of the fossil swept-up main sequence shell surrounding Sh 308, in accord with the three-wind model. (orig.)Available from TIB Hannover: RR 4697(903) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman