NGC 1365 - The Transformation

The Idea

The idea behind this exercise is to use the galaxy NGC 1365 as a strong barred spiral galaxy. However, NGC 1365 is distinctly not round from our viewpoint. The assumption is that we see NGC 1365 at an angle instead of face-on. One can get a fair approximation of what it would look like if seen face-on by distorting an image from oblong to round.

Here is the transformed image

What I did

Scanned image of NGC 1365 from David Malin's book

Cropped image to center on the galactic center

Rotated image by 35 degrees to get long axis of galaxy vertical

Stretched image horizontally by a factor of 1.7 and cropped to about 2400 x 2400 pixels

The parameters of the transformation are the amount of rotation and the amount of stretch. The amount of rotation was done purely by eye. Rotations every 5 degrees were compared and the best one chosen. The amount of stretch was based first on the ratio of D_25 to d_25 as listed in the Tully catalog (1.82) and then adjusted by eye. A value of 1.82 produces too long and prominent of a bar, so a smaller stretch has been adopted.