Polycyclic Aromatic Hydrocarbons with SPICA

¹ Centro de Astrobiologίa (CSIC/INTA), Madrid, Spain
² Université de Toulouse ; UPS ; CESR ; 9 ave colonel Roche, F-31028 Toulouse cedex 9, France
³ CNRS; UMR 5187; 31028 Toulouse, France
⁴ INAF Cagliari, Italy
⁵ Leiden Observatory, University of Leiden, Leiden, The Netherlands

Abstract

Thanks to high sensitivity, high angular resolution and broad spectral coverage, SPICA will offer a unique opportunity to better characterize the nature of polycyclic aromatic hydrocarbons (PAHs) and very small grains (VSGs), to better use them as probes of astrophysical environments. The angular resolution will enable to probe the chemical frontiers in the evolution process from VSGs to neutral PAHs, to ionized PAHs and to "Grand-PAHs" in photodissotiation regions and HII regions, as a function of G₀ /n (UV radiation field / density). High sensitivity will favor the detection of the far-IR skeletal emission bands of PAHs, which provide specific fingerprints and could lead to the identification of individual PAHs. This overall characterization will allow to use PAH and VSG populations as tracers of physical conditions in spatially resolved protoplanetary disks and nearby galaxies (using mid-IR instruments), and in high redshift galaxies (using the far-IR instrument), thanks to the broad spectral coverage SPICA provides. Based on our previous experience with ISO and Spitzer we discuss how these goals can be reached.