CPROPS_V is a modified version of the CPROPS package by Rosolowsky & Leroy for decomposing emission in spectral line data cubes. It outputs three additional parameters into the PROPS structure:
The gradient is determined by fitting a plane to the first moment map of the cloud. Only pixels within the cloud mask are used in calculating the first moment. The fitting is a weighted least-squared fit by default (with weights given by inverse square uncertainties in the 1st moment), unless the /ROBUST keyword is given, in which case an unweighted robust fit is performed. The fitting is done using the routines planefit.pro and rob_mapfit.pro, written by Freudenreich, so these routines must be in your IDL_PATH. Note that the robust method requires additional routines in the Freudenreich library (click here to download a tar file). As with the original CPROPS, CPROPS_V relies upon the IDL Astronomy Library.
- vgrad: velocity gradient in km/s/pc
- vgradpa: position angle of the velocity gradient, measured CCW from the +x axis
- vresid: RMS residual velocity after removing the gradient
Uncertainties in vgrad and vgradpa are currently not calculated; this is still in the works.
In addition, CPROPS_V implements a variety of additional options I've found useful. This includes four new flags, /ALL_NEIGHBORS (to relax the criterion for pixels to be adjacent), /EXTRAPLOG (to output a data table showing the extrapolation of cloud properties), /ROBUST (to use a robust method for fitting the cloud velocity gradients), and /ZERO2NAN (replace all zeroes with blank values). The actual differences in code from the standard CPROPS distribution are documented below.
- fits2props.pro: Implement the /ALL_NEIGHBORS, /EXTRAPLOG, /ROBUST, and /ZERO2NAN flags. Output information about /PHYSICAL parameters to screen. Fixed a typo (specpfriends -> specfriends).
- cloudalyze.pro: Calculates velocity gradient for each cloud. Gets passed the /ROBUST and /EXTRAPLOG keywords, for robust velocity gradient fitting and for exporting log of extrapolated values. Calculates bootstrapped uncertainties for mommajpix and momminpix.
- reject_region.pro: gets passed the all_neighbors keyword, which is passed on to assign2.pro.
- vel_gradient.pro: new routine for doing the gradient fitting.
Last update by Tony Wong on 2 Jul 2012