By day, I study pathologic tissues under the microscope. By night, I train my CCD camera to record pathologic galaxies in my telescope! And I find the “shell” or “ring” galaxies the oddest of these dysmorphic galaxies! Ken Crawford’s rendition of a “Shell Galaxy” NGC 7600 in Astronomy Picture of the Day (APOD) Dec. 23, 2011 is great. Bob Franke’s deep image of NGC 3226-7 is strange indeed. But my personal favorite, introduced to me by Joe Mize, is Arp 227 in Pisces (page 190 in “The Arp Atlas of Peculiar Galaxies”)! To me, this pair of shell galaxies is the quintessential pathologic galaxy venue. This group, at a distance of about 100 million light-years, includes NGC 474 (largest), NGC 470 with its blue spiral arms and hydrogen-alpha knots and NGC 467 to the upper left next to 7th magnitude K0 star HD 7991. The wide arcs or “shells” may be the result of tidal gravitational mutual encounters or could be the result of merged collided galaxies producing a effect analogous to ripples on a pond (to quote Leshin APOD). These rings are extremely faint and you will find few color images of this on the internet (sane people don’t try this)! The above color image is a 20-hour exposure LRGB with both luminance and chrominance data binned 2X2 with the 14.5-inch RCOS and Apogee camera taken in October 2011. Half of my red color data had to be discarded because of a large gradient. Not sure where that came from. Perhaps Sandy Goodstein was walking around my observatory with a red flashlight! There are also multiple faint, possibly related, smaller galaxies around NGC 467 in my color image which show detail morphology. My luminance is 15 hours long and an inverted image shows the extent of the shells. Notice something shining flared rays emanating from the lower left corner. Couldn’t figure out what that was! Working this faint, every photon counts! The CFHT (Mauna Kea, Hawaii) image (link below) has the best-defined and deepest shells of any image I have found. There sure is a lot of interest in galaxy evolution lately and the Atlas3D Project website about the subject is worth visiting (link below) if only to compare the “Hubble Tuning Fork” concept of galaxy evolution to the current “Comb”! I am pleasantly surprised that the Chiefland skies quite easily supported this kind of deep galaxy excavation!
http://apod.nasa.gov/apod/ap071008.html – 2007 APOD color NGC 474
http://apod.nasa.gov/apod/ap110226.html – Stephen Leshin color NGC 474
http://apod.nasa.gov/apod/ap110726.html – DEEEP CFHT monochrome version of NGC 474
http://bf-astro.com/ngc3227/ngc3227.htm – Bob Franke’s NGC 3226-7
http://apod.nasa.gov/apod/ap111223.html – Ken Crawford’s NGC 7600
http://www-astro.physics.ox.ac.uk/atlas3d/ – ATLAS3D website