(Updated: 3/12/2001)

Plotting DensePak/Hydra data

This page will describe in detail how to plot data of a single DensePak field. If you want to plot Hydra data, please read the note at the bottom of the page first.

Measure the properties you are interested in, e.g. using splot in IRAF.
Create a table with fiber positions (given in arcseconds) and the values you want to plot. Sky fibers and broken fibers should not be listed in the table. Fibers with no detection can be given the value "0" to produce open circles later in the plot.
Table of fiber positions
Sample table (dpexample.rslt)
Look at your DensePak data to find the minimum and maximum value (e.g. min=150, max=300) and the number of lines in your table (e.g. 86 in dpexample.rslt).
Copy the IDL program fibers.pro into the same directory where your DensePak data are.
If you haven't done so yet, copy the following lines into your .Xresources file in your home directory.
```
        ! IDL backing store
        idl.retain: 2
        idl.gr_visual: PseudoColor
        idl.gr_depth: 8
     
```
You have to restart your computer, so that it reads the changes in your .Xresources file. This can be done either by logging out and back in or by typing the command
```
        xrdb -merge .Xresources
     
```
under UNIX.
Start IDL (in the same directory where your DensePak data are) by typing idl under UNIX.

Create a square graphic window by typing

        IDL>window,xsize=600,ysize=600

Start the program by typing fibers. The program prompts you for the name of the data file, the number of lines, the minimum and maximum value and a title for the plot. E.g.:

        IDL>fibers
        Enter name of data file: dpexample.rslt
        Enter number of lines: 86
        Enter minimum value for color bar: 150
        Enter maximum value for color bar: 300
        Enter plot title: NGC4449 - vel. (km/s)

Note:

If you forgot to create a window first (s. 7.), the colorbar doesn't work properly and your plot is stretched in x (Example). Simply create the window (window,xsize=600,ysize=600), run the program again, and it will plot your data with the correct colorbar and dimensions.
The colorbar uses white as the color for the maxium value. This is dumb when printed onto white paper. I didn't try to fix this. Just use a somewhat higher value as maximum for the colorbar, so that the maximum value in your data is shifted into the red colors.

If your data values contain "0", you have to edit both the program and your data table, because right now "0" is considered to be a non-detection. Chose a value which is well below your minimum data value, e.g. -20. Replace all non-detection zeros in your data table with -20. To edit the program, replace the expressions

`if z(0) eq 0`	with	`if z(0) eq -20`	(in line 57) and
`if z(i) eq 0`	with	`if z(i) eq -20`	(in line 68).

Then, compile the program again by typing .r fibers and run it again by typing fibers.

Sometimes it is difficult to fit the line profiles in your DensePak spectra by single fits. The program fibers.pro can handle two measurements/fits for each fiber by plotting the second value as a smaller circle inside the normal fiber circle. If you want the program to do that, you have to edit your data table. Insert the positions and the second measurements of fibers for which you have two measurements right after the corresponding first measurements of these fibers. E.g.:
```
              -6.23 -17.92    196.082
              -2.08 -17.92    211.979
              -2.08 -17.92    230.702
               2.08 -17.92    191.194
               6.23 -17.92    201.861
              10.38 -17.92    201.724
              10.38 -17.92    219.534
              14.54 -17.92    209.101
           
```

Your plot will look similar to one of these:

Note: The background will be white and the axes black when printed onto paper.

To make a postscript file of your plot (e.g. n4449.ps), type the following commands in IDL:

        IDL>set_plot,'ps'
        IDL>device,file='n4449.ps',bits=8,/color,xsize=5,ysize=5,xoffset=1.5,$
        IDL>yoffset=5,/inches
        IDL>fibers
        Enter name of data file: dpexample.rslt
        Enter number of lines: 86
        Enter minimum value for color bar: 150
        Enter maximum value for color bar: 300
        Enter plot title: NGC4449 - vel. (km/s)
        IDL>device,/close
        IDL>set_plot,'x'

i.e. you have to run the program again to write the plot into the postscript file. You can change the size and position of the plot on your paper by changing the numbers in xsize=5,ysize=5,xoffset=1.5,yoffset=5 above.

To exit IDL, type exit.

Note: It is possible to modify the program fibers.pro to plot several DensePak fields in one graph (Example, IDL program) or to plot Hydra data (Example, IDL program). To be able to do so, you have to change the size of your graphic window and the size of your postscript file accordingly. You also have to change the position of the plots and their axis ranges in the program fibers.pro. For Hydra data, the size of the fiber field may be too big to plot properly scaled fibers, i.e. you may want to increase the radius of the fibers in Hydra field plots (see Example where the fibers have diameters of 30").
There are many possible fiber setups and therefore many plotting possibilities. It is impossible to cover them all with instructions on how to plot them. But I hope that this step by step guide for plotting a single DensePak field will help you to create the plots you need for your data.

Special thanks to Matt Haffner for helping me write the program fibers.pro.