This is 'cmhog', revision 2 (cmhog2). A PPM code to simulate the 2D gas flow in a barred galaxy. It is based on the code Piner, Stone and Teuben published in their 1995 (ApJ 449, 508) article. This code was derived from Jim Stone's CMHOG code, see e.g. http://www.astro.princeton.edu/~jstone/cmhog.html Although the code stands alone, it is useful to have the MIRIAD, and especially, NEMO package around. See hydro.tex in the documentation tree for suggestions how to use the code with these utilities. Some of the tools may be reproduced in $NEMO/src/image/hdf/cmhog, although we attempt to keep the two synchronized April 2002 Peter Teuben --- Updates: September 2002: piner94.src can now initialize an internal grid for testing $pgrid $ is needed in cmhogin. a potential on a grid can now be read in, and gas (TODO) April 2003: piner94.src : added vhalo,rhalo to /pgrid/ May 2011: - Kim et al. (2011) paper report a sign error in the bar component of the azimuthal force. Equally so, the bar was placed along the X axis, not the Y axis as was intended. This unfortuitous combination of errors made the hydro flow look just about right.... a true conspiracy! - gfortran needs $end at the end of each line in the 'cmhogin' file. This luckily also works with g77. - we keep two variables, hardcoded, that can be tweeked back to the pre-2011 version of the code: signerr = 1 (in galaxy.src) balongy = .FALSE. (in piner94.src) Known problems: - numeric grid potential from barred potential not stable enough (could this also be related to the azimuthal force issue?)