The Interactive, Graphical Milky Way Concordance

Version 2.04

Conceived, compiled, and written by

Peter Barnes, Sydney University

STEP THREE: Producing plots.

The first script you must run is "gbox" (see the example below). This is because it sets up various counting, looping, and scale parameters which all the other scripts use. Now, you will note that this entire package plots in galactic coordinates. (RA,Dec coordinates of datafile entries are converted using the "ragal" script.) The main reason for this is that, since we are (or at least, I am) dealing with galactic objects, it is the natural coordinate system one should be using. Also, because of this, we are mostly at low latitudes, which means that spherical-to-planar projection effects are minimal, and for the purposes of this package were ignored. This makes plotting much simpler, and the scripts therefore only plot in a simple rectangular projection. Moreover, as a concordance of catalogue entries, large-scale geometric projection concerns were not deemed to be a priority for this release (but may be included in future releases). If you don't like this, you are free to develop an alternative that can deal not only with projection, but also with those nasty hexagesimal numerologies. Yuck!

To invoke any SM macros, you type the macro name and however many other input parameters the macro requires. This is listed next to the macro name if you have printed out a copy of cat.sm, or in the comment block after you type "re cat.sm" in SM. You can also find this out by typing "help <macroname>" in SM. For "gbox", you need 3 inputs: the low and high longitudes for the window you are interested in, and the latitude at the middle of the window. The reason for this is that the scale is then set by gbox to be equal-angle, based on the longitude extent and the size of the page. The way it is written now, the scale is set for landscape plots on a postscript printer (see the line in gbox which reads "define bmax (($lmax-$lmin)*0.3728)"). You will want to change the constant if you are producing portrait plots, or if you find your coordinates are not coming out square. So for example, "gbox 40 50 0" will define and plot a window 10° wide and ~7°.5 high centred on (l,b)=(45,0), as illustrated in the figure.

Once you have defined the window, you can plot any of the catalogues in any order, by simply typing the name of the appropriate script, followed by a single number (0, 1, or 2) which controls the label verbosity. In the file cat.sm, you will also see a few other scripts which are used as utilities by the catalogue scripts. Thus, "ragal" converts from (RA,Dec) to (l,b); "iras" plots the positions of Point Source Catalogue entries (if you have a file of such); "galrot" converts (l,V) to (R,d) assuming a rotation curve for the Galaxy; and "allcat <num>" simply executes all the (functioning) catalogue scripts in one go. Another type of script is "pbox", which plots where the Parkes 5 GHz survey maps lie, without actually plotting any source information.

Plots are sent to the printer in SM by changing (redefining) your device. Here are some sample plots to give you a feel for what the output should look like.

Go back to STEP ONE | Go back to STEP TWO

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If you find SM attractive and discover yourself writing more applications for this package which you think others may find useful, please send me a copy so I can distribute such scripts in future announcements.

Happy plotting!