View Full Version : Arp 165 A weird faint fuzzy

2009-Jun-15, 06:04 PM
The reprieve from Arp galaxies was a brief one as I'm returning with one that does not involve a collision. Seems like most Arp galaxies I've featured of late involve ongoing collisions but this one does not. At least not of late. It may have interacted with another galaxy in the past that resulted in the distortions that got it onto Arp's list.

Arp 165/NGC2418 is very large galaxy some 240 million light years away. It is located on the eastern edge of Gemini. Arp 165 is classed as an elliptical peculiar galaxy. It has one low contrast blue arm against what otherwise is a galaxy that looks much like a typical elliptical, until you notice the odd tidal extension on the side opposite the blue arm. Arp classed it under "Galaxies (not classifiable as S(piral) or E(lliptical); with diffuse elements. This seems rather appropriate. It appears there has been very little study of this galaxy as I could find little on it. There are a couple small galaxies right near it (north) but I found no red shift data on them so can't tell if they are really companions or just apparent ones due to line of sight. One paper did call them companions but did so in a way that didn't indicate if the author considered them actual companions. In fact only one other galaxy in the entire field had any distance data I could find. That is CGCG 087-015, toward the upper right corner of my image at about the same distance as Arp 165. It is very blue but otherwise shows no sign of interacting with Arp 165. To the lower left of Arp 165 is a pair of galaxies that could be interacting, PGC 3090318/17 left to right. But without redshift data this is only a guess.

5 asteroids are in the image. Easiest to spot is (200477) 2000 YY5 at magnitude 18.8. It is the vertical trail south east of Arp 165. Below it and a bit to the west (right) is the short trail going up at 45 degrees about 2/3rds of the way from the above asteroid and the bottom of the image. It was made by (204503) 2005 CB37. It faded some half way through the exposure so appears split in two segments. It is listed at magnitude 19.7 so is quite faint. To its right and a bit down is the even fainter trail of magnitude 19.8 (98007) 2000 QR207 which left a horizontal trail. Northwest (up and right) of Arp 165 is (29519) 1997 YH13. For some reason (star maybe) it left a part of the red image so ends in a red spot. The trail is very short going down and right and is magnitude 18.9 though its slow motion makes it appear the brightest of all the asteroids in the image. In the Southwest corner (lower right is another very short trail. It is (125891) 2001 XL210 at magnitude 19.4. It appears brightest in the middle and goes up at about a 45 degree angle and it too ends with a red spot from the red frame. Except for that red it looks a lot like a S0 galaxy seen from the side.

Arp's image with the 200" Palomar telescope is at:
Seeing was poor on Palomar mountain when he took this image. So the above link is to the small version. Here's the large one but it shows no more detail, at least on my monitor.

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Image with far less compression (I had to really compress this one to fit without cropping it)


2009-Jun-16, 08:43 PM
Very nice image Rick, Very nice colors and very detailed distant galaxies. At the 7 o'clock position are those galaxies interacting?. I never get tired seeing these images that you produce of these Arp galaxies simply great!. Clear Skies my friend.

2009-Jun-16, 11:42 PM
If you mean PGC 3090318/17 I referred to I don't know as there's no red shift data on them that I could find. Other than those I didn't see any candidates for interaction.