Polycyclic aromatic hydrocarbons in disks around young solar-type stars

Geers, V.C. (2007)

Doctoral Thesis

In this thesis we study the dust around solar-type young stars. In particular, we focus on one specific species of dust, namely the Polycyclic Aromatic Hydrocarbons (PAHs), a family of large molecules, or small grains, that are widely observed in nearby star-forming regions. We address the following questions. What happens to PAHs in the embedded phase of a forming star? Are PAHs present in low-mass young star systems? Does the PAH emission originate from the envelope or from the disk? What do they tell us about disk structure and evolution and grain growth? What can we say about the evolution of PAHs during star formation and their typical size? We present mid-infrared spectroscopy and imaging surveys combined with 3D radiative transfer models to constrain the presence and location of PAH emission toward embedded young stellar objects and circumstellar disks around young solar-type stars. PAHs are detected toward a small fraction (11-14%) of young solar-type stars with disks and toward a minority of embedded objects (<3%), with derived abundances of 10-100 times lower than standard interstellar values. A new class of disks with weak mid-IR continuum emission and very strong PAH features is found.

• Stars: Pre-main sequence
• Stars: planetary systems: protoplanetary disks
• Circumstellar matter
• Astrochemistry
• ISM: molecules

• All authors: Geers, V.C.
• Supervisor: Dishoeck, E.F. van
• Qualification: Doctor (dr.)
• Awarding Institution: Leiden Observatory, Faculty of Science, Leiden University
• Date: 2007-10-23
• Court: LEI Universiteit Leiden