CARTA is an extremely versatile tool for visualizing cubes. Here we provide some basics on how to explore ALFALFA grids using CARTA.

If you have obtained the data from the NRAO archive, you need to first update the headers to unlock all the utility of CARTA.

Load a grid into CARTA

Launch CARTA and select a (updated) grid to load in. In the bottom left panel, change the histogram scaling to be for the entire cube instead of per channel. Say "OK" when the warning pops up - it will only take a few seconds to recalculate.

You will then want to "grab" the "max" line of the histogram scaling and move it to the green highlighted section to get a reasonable scaling. You can also play with all the scaling parameters further to find your ideal image stretch.

Play through the cube

In the bottom right panel of CARTA, select the "Animator" tab. You can then click the arrow to play through the cube, or use the other controls to otherwise move through the cube.

Plot a spectrum

Draw a region

In order to plot a spectrum in CARTA, you first want to draw a region for which the spectrum will be calculated. Hover your mouse in the image window and click the third button from the left, which is a square. Clicking it once activates the ability to draw a region (rectangular by default), and clicking it a second time enables the selection of a region type. Rectangle or ellipse are both reasonable options.