Le 15 février 2013
À 10h30
Salle de Cours – Grande Coupole
Aurélie REMY
CEA Saclay
As galaxies evolve, their Interstellar Medium (ISM) becomes continually enriched with metals, and this metal enrichment influences the subsequent star formation. Dwarf galaxies in the local universe gives us insight into the enrichment process and star formation under ISM conditions that may provide clues to conditions in early universe metal-poor systems. This is the focus of The Dwarf Galaxy Survey (DGS) (P.I. Madden), a Herschel Guaranteed Time Key Program dedicated to surveying the gas and dust in 48 low-metallicity galaxies at Far Infrared (FIR) and submillimeter (submm) wavelengths. The FIR continuum is a powerful tracer of the chemical and physical conditions of the ISM of galaxies. The ISM of dwarfs galaxies poses a number of interesting puzzles in terms of the abundance of dust grains, the dust composition and even the FIR emission processes. Our new Herschel observations are designed to adress these questions in a systematic way and reveal different dust properties than that observed in more metal-rich environments. For example the overall dust temperature is found to be warmer in dwarfs. An excess submillimeter (submm) emission is often apparent near or beyond 400/500 µm rendering large uncertainties in the dust properties, even for something as fundamental as dust masses. We will present the first results of the analysis of the Herschel photometric data for our Dwarf Galaxies Survey. We present Herschel color-color diagrams and interpret these with the aid of 2 differents models : modified blackbodies and a full semi-empirical SED model. A systematic comparison of the dust properties from the Dwarf Galaxies Survey with the more metal-rich galaxies from the Herschel-KINGFISH sample will be performed. Star Formation Rates and Gas-to-Dust mass ratios as a function of metallicity will be discussed.