ATNF Daily Astronomy Picture

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28th of April 2015
Happy 25th Birthday to the Hubble Space Telescope
by Bärbel Koribalski (CASS)
The nearby dwarf galaxy ESO215-G?009 is unusual in many respects. It is highly obscured by foreground stars and dust of the Milky Way, making it diffult to measure its properties in optical images from ground-based telescopes. In contrast, its neutral hydrogen (HI) disk - measured with the Australia Telescope Compact Array (ATCA) as part of the Local Volume HI Survey (LVHIS) project - is huge, about 10 times larger than the stellar extent seen in the beautiful Hubble Space Telescope (HST) color-composite image shown above (Koribalski & Wang, in prep.). ESO215-G?009 also appears to be one of the most isolated galaxies known in the Local Volume, which may explain its very high HI mass to light ratio. While there is plenty of gas, a trigger for vigorous star formation appears to be missing.

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