NGC 7714/5 (Arp 284)

At optical (red) wavelengths, the peculiar galaxy NGC 7714/5 looks like this:

NGC 7714 is to the right (west) and NGC 7715 to the east. The galaxies are separated by 2 arcminutes (25 kiloparsecs). Note the stellar bridge between the galaxies and the tidal tails extending from both galaxies. Also notice that NGC 7714 has a partial ring. This image was obtained by Beverly Smith with the 2.1m telescope at McDonald Observatory in collaboration with Rick Pogge (Ohio State University).

The distribution of interstellar atomic hydrogen in this system looks like this:

These data were obtained with the Very Large Array, part of the National Radio Astronomy Observatory. This map has 12 arcsecond resolution. The gas distribution is color-coded, with the highest column density red and lowest blue. The yellow contours are optical data from the Digitalized Palomar Observatory Sky Survey, smoothed to 12 arcseconds resolution. Notice the complete loop of gas to the northwest of NGC 7714. Also notice that the gas in the bridge and eastern tail is shifted to the north relative to the stars (From Smith, Struck, and Pogge 1997, Astrophysical Journal, 483, 754).

For some narrowband optical images of this system obtained by Rick Pogge, look at the Ohio State Picture Gallery.

To see a mpeg movie of a simulation of the NGC 7714 and NGC 7715 encounter, click here (from Smith and Wallin 1992, Astrophysical Journal, vol. 393, p. 544). In this model, the smaller galaxy has a mass of 1/3 that of the larger galaxy and the impact parameter is 0.85 times the radius of the larger disk. Compare the final frame with the McDonald optical image shown above. Notice that the ring, the bridge, and the tails are successfully reproduced. This model only contains stars.