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We report results from near-infrared imaging of IZw18, the most metal-poorgalaxy in the local universe with NICMOS on board the Hubble Space Telescope(HST). Observations were obtained in the broad F205W filter ($\sim$ K) and inthe medium-wide bands F171M and F180M, the latter which cover strong molecularabsorption features in cool stars. The new data, together with previouslyobtained HST/NICMOS images in the F110W ($\sim$ J) and F160W ($\sim$ H)filters, provide a census of the cool stellar population in this chemicallyunevolved galaxy. We find that stars as old as $\sim 1$ Gyr are required toexplain the observed colour-magnitude diagrams. Combining broad and medium-wideband photometry, we have classified the observed stars. The observed stellarpopulations, to the depth of our data, are dominated by luminous red supergiantstars. However, an intermediate-age component is also present. We haveidentified carbon star candidates, and show that they dominate the stellarcontent for intermediate mass and age. We show that low metallicityintermediate-age stars have, for a given colour, a F110W ($\sim$ J-band) excesscompared to local carbon stars. The carbon stars identified in IZw18 are themost distant (more than 10 Mpc) resolved examples yet discovered.Comment: Accepted for publication in A&

A new infrared view of evolved stars in IZw 18