The Destructive Birth of Massive Stars and Massive Star Clusters
Anna Rosen (UCSC)
Massive stars play an essential role in the Universe. They are rare, yet the energy and momentum they inject with their intense radiation fields and stellar winds into the interstellar medium (ISM) dwarfs the contribution by their vastly more numerous low-mass cousins. These mechanisms can halt accretion onto massive stars and limit star formation in massive star clusters (MSCs), which can host thousands of massive stars. For stellar winds, I discuss how we can use observations to constrain a range of kinetic energy loss channels for the shock-heated gas from stellar winds in MSCs. I demonstrate that the kinetic energy injected by stellar winds in MSCs is not a significant contributor to stellar feedback for young MSCs. I argue instead that radiation pressure is likely the dominant feedback mechanism in massive star and MSC formation. Therefore detailed simulation of their formation requires an accurate treatment of radiation. For this purpose, I have developed a new, highly accurate hybrid radiation algorithm that properly treats the absorption of the direct radiation field from stars and the re-emission and processing by interstellar dust. With this new method, I performed a suite of three-dimensional radiation-hydrodynamic simulations of the formation of massive stars and MSCs. For individual massive stellar systems, I find that mass is channeled to the massive stellar system via gravitational and Rayleigh-Taylor instabilities. I will also present a simulation of the formation of a MSC from the collapse of a dense, turbulent, magnetized million solar mass molecular cloud. I find that the influence of the magnetic pressure and radiative feedback slows down star formation. These early results suggest that the combined effect of turbulence, magnetic pressure, and radiative feedback from massive stars is responsible for the observed low star formation efficiencies in molecular clouds.
Characterizing Dust Attenuation in Local Star Forming Galaxies
Andrew Battisti (UMass)
The presence of dust in galaxies can significantly alter their observed spectral energy distribution. If not properly accounted for, this effect can lead to incorrect values of derived physical quantities such as the star formation rate, stellar mass, and photometric redshift. Virtually all studies of star forming galaxies, both local and distant, make use the attenuation curve derived from a small sample of local starburst galaxies to correct for the effects of dust. However, it is not clear how reasonable the general application of this curve is for more typical star forming galaxies. In this talk, I will present results from a study utilizing ~10000 local (z<0.1) star forming galaxies to identify the extent to which attenuation varies as a function of galactic physical properties.