A Study of Volatile Molecules in the Inner Preplanetary Disks Around Herbig AeBe Stars

University Of Notre Dame, Notre Dame IN

Investigators

Abstract

AST-0205881 PI Rettig To clarify the physical structure, gas and dust content, as well as the potential for planet formation around the poorly understood inner circumstellar disk regions of Herbig AeBe young emission line stars, the PI has begun a high resolution infrared (3-5mm) study of various molecules such as CO and H 3+ that are expected to be present. The near-infrared is a challenging spectral region to work, but this spectral region is optimal to explore CO as well as the symmetric hydrocarbons (e.g. CH 4 , C 2 H 6 , C 2 H 2 ) and H 3+ in material around hot young stars. For Herbig AeBe stars, it is not clear that primordial gas and dust can remain sufficiently long in the inner regions (1-50 AU) close to the star for planet formation to occur. The PI has already presented results for several such stars showing the detection of CO, CH 4 , and H3+ (the first detection of H 3+ emission outside the Solar System ever made). This research will use fundamental CO lines (4.7mm) to measure temperatures, column densities, and mass of CO in the inner disks around these stars. Observations of H 3+ may provide a more quantitative understanding of the chemical processing and the importance of energetic photo-processing in inner disks of these pre-main sequence stars. H 3+ is important as a direct probe of the ionization rate in preplanetary disks and is important in disk chemistry as nearly all ion-neutral reactions are initialized by this molecule. The detection of CO, CH 4 , and H 3+ are important to quantify the physical and chemical evolution of the inner disk and also constrain the gas dissipation rate and potential for planetary formation. Secondly, H 3+ is shown as a potential method to search for evidence of planet formation and/or disk evolution that will provide theorists an additional avenue to constrain disk and extra-solar planet formation.