Galaxy pair NGC 5544/5

This color-composite CCD image shows the galaxy pair NGC 5544/5 (also known as Arp 299) in Bootes. This is one of the pairs we've used to trace the amount of dust in spiral galaxy disks, by taking advantage of the backlighting of a smooth and symmetric companion galaxy (see more details and HST images on this project. NGC 5544, the smooth face-on galaxy, is of early Hubble type - I make it SB(r)0/a, but Ron Buta likes SAB(r)a. I'd take his word with more weight at this level of detail. NGC 5544 has virtually no star formation, as seen in its lack of blue knots plus the fact that an ISO image at 12 microns just barely shows its nucleus. NGC 5545, in front. shows dust lanes silhouetted againsts the inner dusk of NGC 5544, from which we can derive the amount of obscuration - in this case, about 0.5 magnitude in blue light just inside the prominent arm, and about a magnitude in the arm. These are pretty typical values, the advantage being that using galaxy overlaps frees us of many of the assumptions about internal structure that are needed for such estimates from individual galaxies.

This color composite is from B and I images (with synthetic V) taken with a Tektronix 2048x2048 CCD at the prime focus of the 4-meter Mayall telescope of Kitt Peak National Observatory. North is at the top and east to the left, for direct comparison with a chart or eyepiece view. This presentation uses a logarithmic intensity transformation to preserve information across a wide dynamic range. This image shows a region 118 by 151 arcseconds.

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