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AST 393S





SPH Simulation of Clustered Star Formation with Dust and Gas Energetics

Andrea Urban, University of Texas at Austin

Forming stars affect their environment in many ways and one of the earliest effects is the heating of the dust and, indirectly, the gas by radiation. The heating of the gas will raise the Jeans Mass and affect nearby star formation, possibly inhibiting the growth of low mass stars. We investigate this process in our SPH simulation, which includes gravity, particle splitting, sink particles, and a new technique for modeling dust and gas energetics. The dust and gas energetics are powered by the accretion luminosity of young stellar objects which heats the surrounding dust to high temperatures. At high densities, the hot dust heats the gas through collisions. At lower densities, the heated gas is able to cool via rotational molecular lines, primarily from CO. At very low densities, the gas may also be heated by cosmic rays. We consider these effects in our simulation of a clustered star forming region. We discuss our methodology and preliminary results.



Molecular dynamics simulation of formation of poly aromatic hydrocarbon dust

Atsushi Ito, Nagoya University, Japan

The dust molecules which consist of tens of atoms were observed in interstellar space. Especially poly aromatic hydrocarbon (PAH) was detected from IR Spitzer observation. It is thought that PAH differs from a silicate dust and an amorphous ice dust and has a two dimension structure. However, the origin of PAH is not understood well. We tried PAH formation due to the self organization of carbon and hydrogen atoms using molecular dynamics (MD) simulation. In the MD simulation, hydrocarbon molecules grew via chain structure and octopus structure to PAH. As the ratio of the number of hydrogen atoms to that of carbon atoms increases, the size of the created PAH becomes smaller.



A census of starless cores and deeply embedded protostars with Spitzer and Bolocam: Perseus, Serpens, and Ophiuchus

Melissa Enoch, Caltech

I will describe results from an unbiased census of prestellar cores and deeply embedded protostars in Perseus, Serpens, and Ophiuchus, completed by combining large-scale 1.1 mm surveys and Spitzer c2d maps. I discuss the properties of the youngest objects in each cloud, and implications for the core formation process, the origin of the stellar initial mass function (IMF), and protostellar evolution.

The shape of the combined starless core mass distribution is consistent with recent measurements of the IMF, providing further evidence that the IMF is directly linked to the core formation process. A relatively short starless core lifetime suggests that core formation is a fairly dynamic process, in contrast to the quasi-static evolution typically associated with a magnetically dominated scenario. Focusing on protostellar evolution, I find that protostars spend 1-2e5 years in the Class 0 phase, similar to the Class I timescale. A population of low luminosity Class I sources argues for episodic accretion during the Class I phase, with approximately 25% of sources in a quiescent state. Lastly, I describe recent follow-up results with CARMA, and discuss how higher resolution millimeter observations may change these results.



Chemistry of the high-mass starforming complex NGC 7538 IRS 9: Preliminary results from TEXES

John Barentine, University of Texas at Austin

The formation of high-mass stars is generally well understood but challenges remain in explaining the details; the chemical evolution of high mass young stellar objects in particular is an active area of research. I will present high-resolution TEXES molecular spectra of NGC 7538 IRS9, a typical high-mass YSO, obtained in October 2007 at Gemini North. The molecular transitions we observed probe regions of different physical conditions and the high spectral resolution of TEXES allows detailed study of velocity structures delineated by the molecules. We also wish to compare our results with similar data already in hand on the nearby object NGC 7538 IRS 1, which appears to be in a more advanced formation state than IRS 9, forming the basis for future work.


20 August 2007
Astronomy Program · The University of Texas at Austin · Austin, Texas 78712
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