Morphologically Complex Protostellar Envelopes: Structure and Kinematics.

Star Formation;Protostars;Molecular Lines;Radiative Transfer;Proto-planetary Disks;Astronomy;Science;Astronomy and Astrophysics

Tobin, John J.Looney, Leslie ;

University of Michigan

关键词: Star Formation;    Protostars;    Molecular Lines;    Radiative Transfer;    Proto-planetary Disks;    Astronomy;    Science;    Astronomy and Astrophysics;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/89794/jjtobin_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

I present an in-depth study of protostars and their surrounding envelopes of dense gas and dust,using a multitude of observational methods to reveal new details of the star formation process.I use mid-infrared imaging from the textit{Spitzer Space Telescope}, combined with photometryspanning the near-infrared to millimeter wavelengths, to construct a model of the L1527 protostellar system. I modeled both the spectral energy distribution and resolved scattered light images to determine physical properties of the protostellar system.The nature of the apparent central point source in the textit{Spitzer} images was uncertainuntil high-resolution L-band imaging from the Gemini observatory resolved thepoint source into a disk in scattered light, having a radius of 200 AU. Protostellar envelopes are also often found to cast shadows againstthe 8 micron Galactic background in textit{Spitzer} imaging, enabling direct probes of envelope structure. The shadow images show that the dense envelopes around twenty-two Class 0protostars are generally morphologically complex from 0.1 pc scales down to $sim$1000 AU; they areoften filamentary, and frequently non-axisymmetric. The observed envelopestructure indicates a likely origin in turbulent cloud structure rather than a quasi-static/equilibriumformation. The complex envelope structure also may indicate an increased likelihoodof fragmentation during collapse, forming close binaries.To further characterize these envelopes, I have observed them in the dense moleculargas tracers nthp and nht, both of which closely follow the 8 micron extinctionmorphology. The magnitude of the velocity gradients and envelope complexity on $sim$10000 AUscales indicates that the velocity structure may reflect large-scale infall in addition to the often assumed rotation.Comparisons with three-dimensional filamentary and symmetric rotating collapse models reinforcethe interpretation of velocities reflecting large-scale infall, showing that the structure of the envelope must be considered when interpreting the velocity field. To more definitively probe rotation, the kinematic structure on sub-1000 AU scales must be studied, where rotationwill certainly be a more prominent component of the velocity field.