Part 2 : Science !

It's all very well having a 3D view of what a galaxy cluster really looks like (sort of), but what if you want to do actual science ? Sadly we astronomers do not sit around all day gawking at pretty pictures like intergalactic voyeurs. What we actually do is to look for trends in data, to see how one quantity varies with another.

Of course there are plenty of plotting packages that can present data in 3D, but Blender has the advantage of being specifically designed to look at 3D data very easily. Moving the viewpoint, changing what is visible and how it is displayed are extremely easy. Sadly, the basic functions of any graphing tool - like displaying axes - are missing, so these have to be done manually.

Another key feature that's needed is to select and colour the galaxies according to any given parameter. This is done by a Python script that reads in the catalogue file from GOLDMine. Thus the user can, for instance, select all the early-type galaxies or all the spiral galaxies, or even all those that have been observed at 21cm but not detected, if they desire. This is all done through a GUI and doesn't require the user to edit code at all.

Maps of the Virgo Cluster in position-velocity space. Left :early-type galaxies. Right : late-type galaxies.

A slighly more advanced routine lets the user display galaxy properties by colour, rather than just selecting them as discrete variables. So, for example, if you want to look for a trend in galaxy morphology directly, rather than plotting any complicated morphology-density relation, you can do so.

Virgo galaxies coloured by morphology. Left - red-blue colour mapping. Right : HSV colour method

Another little script I developed lets the user get information on any galaxy they select, again from the GOLDMIne databse This lets the user instantly know the size, mass, colour etc. of any particular galaxy without recourse to the web. And if you want to see that galaxy in the optical, a couple of keystrokes loads the layer with pretty pictures.

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