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Post Info TOPIC: Dwarf Galaxy IZw18


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RE: Dwarf Galaxy IZw18
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IZw18: the galaxy that reveals the universe's history

The first galaxies were formed some 13.3 billion years ago, mainly composed of hydrogen and helium, the primary elements that emerged from the Big Bang. Their study to date has been technically very challenging due to their great distance from us, but the observation of analogous galaxies in our vicinity has turned out to be an excellent shortcut.
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IZw18.kmz
Google Sky File

-- Edited by Blobrana at 15:29, 2008-01-12

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Title: Dust in the Extremely Metal-Poor Blue Compact Dwarf Galaxy IZw18: The Spitzer Mid-Infrared View
Authors: Yanling Wu, V.Charmandaris, L.K.Hunt, J.Bernard-Salas, B.R.Brandl, J.A.Marshall, Vianney Lebouteiller, J.R.Houck

 IZw18, a blue compact dwarf (BCD) galaxy with the 2nd lowest metallicity measured in a star-forming object, has been observed with all three instruments on board the Spitzer Space Telescope. We present the deepest 5-36 micron mid-infrared (mid-IR) spectrum of this galaxy as yet obtained, as well as 3.6 to 70 micron imaging results. As with SBS0335-052E, another BCD with similar metallicity, IZw18 shows no detectable emission from polycyclic aromatic hydrocarbons (PAHs). However, the continuum emission, from 15 to 70 micron, of IZw18 has a much steeper slope, more characteristic of a typical starburst galaxy of solar abundance. The neon abundance as measured from the infrared fine-structure lines is ~1/23 Z_sun, and the sulphur abundance is ~ 1/35 Z_sun, generally consistent with the nebular oxygen abundance of 1/30 Z_sun derived from optical lines. This suggests that the extinction to the infrared emitting regions of this galaxy is low, also in agreement with the optical Balmer line ratios.

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