Wednesday, February 13, 2013 - 4:15pm
"The far-infrared fine-structure lines in low-metallicity star-forming dwarf galaxies"
Abstract. The Herschel Space Observatory offers new insight on the ISM properties of dwarf galaxies. I will present Herschel/PACS spectroscopy results of the "Dwarf Galaxy Survey" (PI: S. Madden), which has targeted 50 nearby low-metallicity star-forming dwarf galaxies. The FIR fine-structure lines, namely [CII] 157mu, [OI] 63 and 145mu, [NII] 122mu, and [OIII] 88mu, are major coolants of the ISM and turn out to be bright in dwarf galaxies. Detected down to metallicities ~1/50 solar, they account for a few percent of LFIR. These lines are tracers of the multiphase ISM -- [OIII] and [NII] from the ionized gas, [OI] from the photodissociation regions -- and reveal the porous ISM structure of dwarf galaxies. However, if [CII] is usually the main FIR coolant in galaxies, its emission can have several origins, not only the PDR, but diffuse neutral/ionised clouds as well, which complicate our interpretation of C+ as a star formation tracer.