The following document lists the file abstract/SMADDEN_IRREGAL.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
Despite the fact that low metallicity dwarf irregular galaxies often have a paucity of observable CO, they exhibit star formation activity that can be as high as that found in starburst galaxies. Our recent Kuiper Airborne Observatory (KAO) observations, show that the 158 micron [CII] line is bright and extended in dwarf galaxies. The [CII] line intensities for the metal poor galaxies that we have detected with the KAO are 1x10^4 to 6x10^4 times the CO(1-0) line intensity. This effect is due to the decreased metallicity and dust content which results in reduced CO cores surrounded by larger photodissociation regions. These observations suggest that the CO(1-0) line may not be a good tracer of molecular gas in these galaxies since H2 may exhist in the [CII] zone. The KAO is only able to detect a very limited number of dwarf galaxies due to its relatively poor sensitivity. Thus, very few metal-poor low luminosity dwarf galaxies have been observed. We propose to extend our KAO sample to lower luminosity irregular galaxies of varying metallicities with ISO observations of [CII], [OI] and [NII]. Combined with CO, FIR continuum and 21 cm HI measurements, these observations will allow us to determine the physical conditions of the photodissociated gas in these galaxies. For the first time, we will be able to make a complete inventory of the gas reservoir in dwarf irregular galaxies where use of CO alone to infer H2 may significantly underestimate the molecular mass. The results of this study will help to address unresolved questions about the physical properties of clouds and star formation processes in irregular galaxies.