Saturday, October 20, 2012

Galacticus v0.9.1 released

After just over one year of development, v0.9.1 of Galacticus is now released! That means that v0.9.1 is now considered "stable" and will receive only bug fixes (not any new features). It also means that v0.9.0 is now considered obsolete and will no longer be supported.

Most of the work on Galacticus v0.9.1 has been to improve robustness, resulting in a much more stable code. However, there are some new features too:
  • Several new "simplified" implementations of galaxy physics have been added. These are designed to allow Galacticus to run simplistic models, perhaps for comparison to other semi-analytic models, or to explore the importance of including more detailed physics. They also typically result in shorter run times (at the cost of reduced realism). These new additions include:
    • a galactic structure solver in which radii scale linearly with angular momentum;
    • an even simpler galactic structure solver which simply fixes radii of galaxies to the virial radius times the spin parameter (multiplied by a user-specified coefficient);
    •  simple "power-law" scaling algorithms for cooling rates, feedback in disks and star formation timescales in disks;
  • New algorithms have been added to solve the Press-Schechter excursion set problem, allowing for modelling of non-CDM cosmologies (for further details see the previous blog post);
  • The reionization epoch (used to cut off accretion into low mass halos) can now be specified via the optical depth to reionization instead of specifying the redshift directly;
  • The script has some new features:
    • Allows for generic analysis scripts to be run on each completed models;
    • Models can be run on a Condor cluster.
  • Merger trees constructed within Galacticus can now be exported into either Galacticus' native file format or the IRATE format.
  • AGN luminosities can now be computed in any filter, using SEDs which depend on the black hole bolometric luminosity, and including the effects of absorption at X-ray wavelengths;
  • The black hole/AGN feedback model has been improved to allow "radio-mode" feedback to occur only when the halo is in the "hot-mode" regime, and to allow energy injected into the hot halo to drive mass out of the halo if the input power exceeds the cooling rate;
  • The Wetzel & White (2010) satellite merger timescale algorithm is now available;
  • It is now possible to construct lightcones:
    • Includes a script which grabs all merger trees in a lightcone from the Millennium Database;
    • New output and output filtering options allow for only galaxies within the lightcone to be output and for their positions to be translated to lightcone coordinates.
Development now moves to v0.9.2 of Galacticus which has an entirely re-written internal class structure for nodes and galaxies. This makes it very easy to add new components and extend existing ones, and does away with the need to write significant amounts of boilerplate for each new component. Other plans for v0.9.2 include doing away with several of the assumptions which are forced on N-body merger trees to allow handling of fly-by encounters, further optimizations, and improvements to the physics in several areas.

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