Daily Image
04-11-2014
A Dwarf in Detail
| Submitter: | Erwin de Blok |
| Description: | A few months ago the AG organised a workshop on making pretty pictures from astronomical data. This workshop was given by Jayanne English from the University of Manitoba and who used to be part of the Hubble Heritage team, famous for its colourful Hubble telescope pictures. As a result of this workshop, Erwin de Blok from ASTRON used his multi-wavelength data, along with other archival data, of nearby Local Group dwarf galaxy to make false-colour image shown here. The optical background is made of a combination of B, V and R images from the Local Group Survey by Massey et al (2007, AJ, 133, 2392). The blue stars have been enhanced using near-UV data from GALEX (Hunter et al 2010, AJ, 139, 447). The red emission shows the H alpha distribution as published in de Blok et al (2006, AJ, 131, 363), and finally the distribution of the neutral hydrogen (HI) is taken from Australia Telescope Compact Array observations described in de Blok et al (2000, ApJ, 537, L95). Note how the bluest (youngest) stars can be found near holes in the HI. The origin of the large hole in the bottom-left (south east) is not clear. It could be caused by star formation, but there is no clear evidence for a remnant population. Alternatively, NGC 6822 could be interacting with an even smaller dwarf (visible as the cloud in the top-right), with the hole (and the tail that can be seen going off towards the bottom left) being the result of a tidal interaction. NGC 6822 is only 0.5 Mpc away from us and is the closest gas-rich dwarf galaxy outside the Large and Small Magellanic clouds. The image measures about 0.7 by 0.7 degrees - NGC 6822 therefore has an apparent size about that of the moon! |
| Copyright: | Erwin de Blok |
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