Over on this link, you’ll find a data-driven document (D3 FTW!) showing collaboration between the most authorship-intensive institutions in astronomy. The document is a chord diagram showing the strength of collaboration between research centres, based on co-authorship of papers.
I’ve included some screenshots here to give you the idea - the one above is for worldwide institutions between 2010 and July 2012.
This diagram is for UK institutions in 2011. Links between locations on the plot are not symmetric and are coloured to show the dominant partner. Strength of links are inversely proportional to the square root of author position so that the 1st authors counts for 1 point, 2nd author gets 1/√2, third get 1/√3 etc. This way I weight toward authors higher up on the list.
The data shown is for 125,000 geocoded papers from a total of 236,000 published by MNRAS, ApJ, AJ, A&A and PASP through to July 2012 (read about the mining here). 485,000 authorships are included, out of 820,000 in total. Data was geocoded based on author affiliation and grouped using the resultant lat/longs to 3 decimal places.
This plot, for worldwide institutions in 2011 is shown highlighting links between CEA Saclay and the other top publishing locations. You can play with many combinations of the data, displaying varying numbers of institutions from different parts of the world. Explore the data at http://files.orbitingfrog.com/ADSChord/.
[This is same data I used to create collaboration maps in this previous post, and can be found here on Google Fusion tables.]