Spitzer Space Telescope - Archive Research Proposal #50752


PAH emission from Herbig AeBe stars: Do hydrocarbons in proto-planetary disks
have a unique aroma?

Principal Investigator: Luke Keller
           Institution: Ithaca College

     Technical Contact: Luke Keller, Ithaca College

Co-Investigators: 
Greg Sloan, Cornell University                                        

Science Category: circumstellar/debris disks 
Dollars Approved: 25000 

Abstract:
Over half of the intermediate-mass young stellar objects in the Galaxy (e.g.
Herbig AeBe stars or HAeBe) have high-contrast emission in the mid-infrared
spectral features of polycyclic aromatic hydrocarbons (PAHs) above the continuum
produced by thermal emission from dust in the circumstellar disks. We have
examined the PAH emission in detail for a sample of 19 HAeBe stars observed with
the Spitzer IRS as part of the IRS Disks GTO program. Even with this relatively
small sample, we have identified some trends that, should they survive in a
larger sample of HAeBe stars, will allow us to infer large-scale disk geometry
(both inner and outer) and the degree of photo-processing of organic molecular
material in HAeBe disks. The bottom line of our work thus far is that HAeBe
apparently have distinctive PAH spectra among the many other astronomical
environments that are characterized by strong PAH emission. We therefore propose
to apply our spectral analysis methods to an additional 57 HAeBe observed with
the IRS and currently (or soon to be) available in the Spitzer archive. Our
total sample of 76 HAeBe stars will allow closer scrutiny of the trends that we
have identified in our empirical study and will also be the subject of a
detailed disk modeling effort that will include the PAH emission.