Object of the Week, December 22 2013 -- Arp 219 (Collisional Ring)

UGC 2812 (Arp 219 = VV 495)

Eridanus

RA 03 39 53.3
DEC -02 06 47

Type: Galaxy Pair (Collisional Ring?)

Size: 0.8' x 0.7’

Mag: 14.0V (13.2 mag SB)

I was intrigued by this interacting system when I ran across it a few years ago in Madore, Nelson and Petrillo's 2009 "Atlas and Catalog of Collisional Ring Galaxies". Madore et al considered it a collisional ring (as seen in Arp's original image below) with a small "collider" (identified as C1 in the paper) to the upper right (southeast) in the image. The redshift-based distance of Arp 219 is ~470 million light-years, although the "collider" has no redshift data.

Arp placed this object in his category "Galaxies with adjacent loops". In addition to the main loop extending towards the companion, there is a huge, extremely low surface brightness outer arc or loop that can be partially seen in Arp's image extending to the lower right and out of the frame. The collider is actually inside this huge outer arc! A full resolution image of Arp 219 is available at NED here

Attachment 1000

How much of this action can be seen in amateur scopes? The main galaxy is visible in an 18" (and perhaps smaller) scope, in addition to nearby UGC 2814, a mag 14.3V galaxy 5' NE at roughly the same distance as Arp 219. The close companion, though, will probably require more aperture. But let us know!

Here's the view I had through Jimi's scope a couple of years back -- the collisional ring galaxy appeared fairly faint with a weakly concentrated "bar" elongated 3:1 or 7:2 WSW-ENE, ~40"x12". The well-defined bar is surrounded by a very low surface brightness halo, but a clearly brighter rim was not evident. The collider, PGC 200217 = 2MASXJ03395491-0207241 (B = 17.9), was visible 45" SE. It appeared extremely faint and small, round, 8" diameter. UGC 2814 lies 5.5' NE and is moderately bright, fairly small, round, 35" diameter, broad concentration with a brighter core. An isosceles triangle of mag 14-15 stars is close NE.


"GIVE IT A GO AND LET US KNOW"

My observation with my 22" scope taken from my Arp book.

22" f/4.1 reflector @ 184, 305, 327 and 458x

UGC 2812 – Low surface brightness round halo with diffuse edges. In the center is a bar-like bright core at
PA = 80º and 45” long. Halo is also 45” across. Adjacent loops not detected.

MAC 0339-0207 (PGC 200217 reference by Steve) required 458x to be seen as an extremely faint round even surface brightness patch. Sits 45” SE from the center of UGC 2812.

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