NGC 3314 gets a counterpart

 Not that I’m about to change my avatar or anything, but I think this is one of the best pairs we observed from Kitt Peak. First pointed out in the Galaxy Zoo forum by GwydionM, this features a face-on spiral almost exactly in front of an edge-on spiral. Like NGC 3314, it gives a rare chance to see the dust content of a galaxy almost all the way from outer regions to the nucleus (limited there by the accuracy with which we can extrapolate the profile of the background galaxy inward). This also drives home a point which isn’t always obvious from pictures, and is especially insidious when looking at books where the pictures tend to be all about the same size. Similar-looking galaxies can span a wide range of sizes, even among spirals which don’t come as small and faint as spheroidal or irregular galaxies. We don’t yet have good redshifts for both; the Sloan data give the single value z=0.067 for what must be the blended light of both, probably meaning that they are at similar redshifts so the size comparison in this picture is pretty close to reality.  This image come from the first fruits of the next stage in processing our data, one which leaves them ready to analyze. To sample red light, we used an I filter rather similar to the SDSS i band. For the particular CCD we used, the skyglow that it sees causes a pattern of interference fringes from light reflecting within the chip. This can be calibrated and subtracted only using data on the night sky itself. We combined images where the target galaxies were at different places on the detector while rejecting objects that were at a certain pixel value only once (that is, things on the sky) to leave, ideally, only the interference pattern. I’m still tweaking until we decide that we’re close enough to that ideal…   SDSS 1145+35 color image                             If you look closely, you can spot the heavily reddened core of the background galaxy behind the spiral arm to the lower right of the foreground galaxy core, and note the darker absorption next  to those spiral arms. (I’ll be watching to see how this image shows up – this is the first time the regular Zookeepers let me have the keys to the blog, and I’m feeling my way around. It looked sort of odd in preview). 

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3 responses to “NGC 3314 gets a counterpart”

  1. Waveney says :

    I think the SDSS image for comparison is 587739304213938297 (Loaded Bills pdf list of images and searched for 0.067)

  2. Joseph K. H. Cheng says :

    Thank you very much, Bill, for explaining the detailed technical procedures which are beginning to form a coherent picture in my mind regarding the significance of cosmic dust and overlapping galaxies. Please keep the progress of the Kitt Peak observations coming.

  3. NGC3314 says :

    What an amateur this guy is at blogging! He tagged the image internally with the truncated coordinate name but neglected to actually mention that it’s SDSS 1145+35, which would have saved Waveney the trouble of searching.

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