Astro-Shed

Today’s image is a pair of interacting galaxies, NGC 3226 and NGC 3227, also known as APR 94. NGC 3227, the large central spiral is an SAB(s)a, while its companion, NGC 3226 is an E2 elliptical. There is also a string of galaxies to the right of the frame. The brightest one is NGC 3222.  This group is 2-3x the distance 3226/3227 pair and thus not associated with them.

NGC 3226/3227 was included in Halton Arp’s catalog of Peculiar Galaxies. Arp suggested that these two galaxies were interacting. The black and white image below better shows the spiral arm on the right side of NGC 3227. It seems to tangentially intersect with NGC 3226 and then extend off to the upper left of NGC 3227. So we can understand why Arp made this observation. However, median distance measurements from NASA’s Extragalactic Database (NED) show that these two galaxies are separated by 11 Mpc. This is equivalent to 35 Million light years! So is this just a chance alignment rather than a true interaction?

Researching this a little more, I came across a NASA Astronomy Picture of the Day (APOD) from 2013. Looking closely you can see more tidal trails on NGC 3227 proving there has been some interaction. https://apod.nasa.gov/apod/ap131009.html This may seem incredible based on the current separation distance. However, my theory is that we are seeing the galaxies moving apart after their interaction. The tidal tails may take a long time to be absorbed back into the typical spiral structure.

Let me know in the comments below if you believe these two galaxies have interacted. Alternatively, do you think they are currently interacting? Is their separation a lot less than what the current measurements show? Or, do you think it’s just a chance line of sight phenomenon? Perhaps NGC 3227 is being disturbed by a faint dwarf galaxy that we cannot see in the images?

The image was captured with a Celestron 8″ SCT x0.63, a ZWO ASI533MC Pro camera. 25×300 sec subs.