Free and Open Source Software in Municipal Procurement:The Challenges and Benefits of Cooperation

The use of free and open source software by municipal governments is the exception rather than the rule. This is due to a variety of factors, including a failure of many municipal procurement policies to take into account the benefits of free software, free software vendors second-to-market status, and a lack of established free and open source software vendors in niche markets. With feasible policy shifts to improve city operations, including building upon open standards and engaging with free software communities, municipalities may be able to better leverage free and open source software to realize fully the advantages that stem from open software development

Jeans Instability of Palomar 5's Tidal Tail

Tidal tails composed of stars should be unstable to the Jeans instability and this can cause them to look like beads on a string. The Jeans wavelength and tail diameter determine the wavelength and growth rate of the fastest growing unstable mode. Consequently the distance along the tail to the first clump and spacing between clumps can be used to estimate the mass density in the tail and its longitudinal velocity dispersion. Clumps in the tidal tails of the globular cluster Palomar 5 could be due to Jeans instability. We find that their spacing is consistent with the fastest growing mode if the velocity dispersion in the tail is similar to that in the cluster itself. While all tidal tails should exhibit gravitational instability, we find that clusters or galaxies with low concentration parameters are most likely to exhibit short wavelength rapidly growing Jeans modes in their tidal tails.Comment: sumbmitted to MNRA