Attack of the flying space whotsits

After two days, my screen is finally filled with orange stringy sausage thingies. Hurrah for science !

I've been re-examining an old data set, searching for hydrogen streams that may have gone unnoticed. Some known streams are very long indeed - these can't have been missed, because they'd be extremely obvious in the data. But shorter features could be hiding. Bright galaxies are a lot like bright light sources in ordinary photographs - they appear much larger than they actually are. One way to limit this is to plot contours, which show the structure much more clearly than intensity maps. As long as the galaxies aren't too bright, non-circular features in the contours generally show up much more easily than having to carefully try and adjust the contrast of a flux map.

The reason the galaxies look like these long cigar-like blobs is because the third dimension is velocity. We don't have great spatial resolution so generally the galaxies only appear as a circularish blob at any given velocity, occasionally just about resolved into something more interesting. But we have great velocity resolution. Because the galaxies are rotating, this means we detect them at many different velocity channels.

This method seems to be working pretty well : there are 2-3 nice examples of streams that are almost certainly real and maybe a dozen other weaker candidates. None of these would have shown up very clearly in standard maps. And I couldn't have made this figure back when the data first came in - I could have plotted the contours for all 93 galaxies here but it would probably have taken closer to two weeks rather than days.