Deprojection of galaxy images

[bijusaha-astro]

I have FITS files of galaxies collected from SDSS. Most of them are not face-on so, I want to to deproject the galaxy to a face-on orientation. I came across a paper Davis et. al., 2012 which mentioned that for deprojecting, we have to rotate the galaxy based on position angle and magnify based upon the ellipticity. The rotation can be done with IRAF command IMLINTRAN. But, I am unable to obtain the PA and the ellipticity estimates.

I employed the photutils.isophote.Ellipse class and after creating an instance with my data, I called the fit_image module, so that I can obtain the position angle and ellipticity estimate (after which, I can easily rotate and magnify to obtain the deprojected image). But while running the fit_image module, I have beenfacing a issue called "WARNING: No meaningful fit was possible. [photutils.isophote.ellipse]".

Is there a way to resolve this or understand why is it occuring.

I attach the FITS image. Please have a look. I assume, that the galaxy is predominantly spiral (with no elliptical feature) is making the isophote algorithm fail. If so, how to fit elliptical isophotes and find position angle for such galaxies?

As an alternative, is there some other way in photutils itself that can help in deprojecting the galaxy to a face-on orientation? It would be very helpful.

[larrybradley]

@bijusaha-astro The isophote tools are designed to fit elliptical isophotes. If the data is not described by elliptical isophotes (e.g. a sprial galaxy), then the fit is going to be bad and/or fail. You could try fitting only in the bulge region of your galaxy (using the maxsma keyword).

Your image of NGC1042 looks nearly face on (and nearly "circular"), so getting a good value of PA and ellipticity will be difficult. Perhaps look around in the literature.