Star Formation and ISM properties in the lowest metal-poor galaxies observed by Herschel

A remarkable result to date is our recent SHINING detection of the CII line with PACS in the ultrametalpoor galaxies: IZw18 and SBS0335052 (1/40th and 1/50 solar metallicity) giving us the best opportunity to study the star formation and ISM properties under the most extreme metalpoor conditions we have in our local universe conditionssimilar to primordial ISM at very high redshift. SBS0335052 and IZw18 are the most metalpoor galaxies that will ever beobserved by Herschel. In spite of similar metallicities, the 2 galaxies are very different in star formation rates and MIR and FIR luminosities, suggesting that metallicity is not the most important parameter controlling star formation activity. We ask here for complementary OI 63 mu m and OIII 88 mu m observations to be ableto interpret the CII detection in terms of ionised and neutral gas properties. These galaxies are not detected in CO and we believe that the CII is probing the molecular gas not traced by CO the .dark molecular gas. which could be a significant reservoir of fuel for the star formation in low metallicity galaxies. Our CII observations along with these followup lines, can provide a means to unveil this suspected reservoir of COfree molecular gas. The CII detection along with these 10.2h of observations requested in this proposa, will shed unique, new insight on extremely low metallicity conditions for star formation and also help provide a standard calibration for getting a handle at the molecular gas reservoir in the high redshift lowest metallicity galaxies which will be a focus for ALMA studies. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]