Describing protostellar disk structure in Ophiuchus

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Michel, Arnaud
Astronomy , Physics , Protostellar disks
Young forming stars host circumstellar disks of dust and gas. High-resolution, millimeter observations of disks at the protoplanetary stage reveal substructures such as gaps, rings, arcs, spirals, and cavities. These structures are often attributed to disturbances from young, newly formed planets or mechanisms conducive to planet formation. However, the formation mechanisms of the substructures are unconstrained, and only a few disks at the younger protostellar stage have known substructures to date. In this thesis, we present a detailed analysis of 1.3 and 0.87 mm observations of ten protostellar disks in the Ophiuchus star-forming region in a search for the origins of the substructure. Of the sample of ten, four disks have identified structure, three are smooth disks, and three are ambiguous. The structured disks have wide Gaussian-like rings (σR/Rdisk ∼ 0.26) above a smooth disk profile with low contrasts (C < 0.2) in comparison to protoplanetary disks where the rings are narrow and have a wide variety of contrasts (σR/Rdisk ∼ 0.08 and C ranges from 0 − 1). These structured protostellar disks are the brightest sources in the Ophiuchus sample, in agreement with trends observed for protoplanetary disks, and two show evidence of flaring, indicating large dust grains have not had time to fully settle onto the midplane of the disk. These observations indicate that structure in protostellar disks may be common. The presence of structure at the earliest stages suggests an early start for dust grain growth and, subsequently planet formation.
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