|Galaxy Tricolor Images - 100" DuPont
Telescope, Las Campanas Observatory
Barry, Olga, Bryan and Ryan
These images were taken by Dr. Barry Madore and Dr. Olga Pevanova at
the Las Campanas Observatory.
The data were reduced by Olga and Ryan Quadri, who is working with Dr. Bryan Penprase at Pomona College on his Harvey Mudd College senior thesis.
The reduction process includes flat fielding and flux calibration in IRAF, cosmic ray removal and continuum substraction in IDL, and a final tricolor image
was created for each of the three galaxies NGC 1313, NGC 300 and NGC 7793 based on the flux calibrated images. Each image name includes the band which
was used in the RGB images in the order of the R, G, and B channel.
The goal is to determine the inner structure of the galaxies, using
the nebular diagnostics of the lines of H-alpha, H-beta, OIII (502; 437
and 497), SII (674) and
OII (374). The line ratios of H-alpha/H-beta are sensitive to the extinction within the galaxy, OIII(502)/OIII(437) is sensitive to the temperature of the region,
SII(674)/H-alpha traces supernova shock waves, OIII(502)/H-beta is sensitive to the excitation within the nebulae, and (OIII(502)+OIII(497))/H-beta gives information
on the metallicity of the regions.
The line images shown in the pages below show the morphology of the
three galaxies in these various diagnostics. In some of the images, continuum
images are superimposed
on top of the nebular diagnostics to show the drastically different form of the galaxy HII regions, where most of the emission from these emission lines arises.
The reduction process involved existing routines in IRAF and new IDL
programs which shift the images, scale continuum images for subtraction
of stars, and provide
the final tricolor images. All of this work is part of an ongoing collaboration between Dr. Bryan Penprase, Ryan Quadri of Claremont and Dr. Barry Madore of Carnegie
NGC 300 Images
NGC 1313 Images
NGC 7793 Images