Object of the Week Mar 18, 2012 - Arp 142 and his "Shred"

NGC 2936
09 37 44.2 +02 45 39
V = 13.1; Size 1.6'x0.9'; Surf Br = 13.3; PA = 35d

NGC 2937
09 37 45.0 +02 44 50
V = 13.7; Size 0.8'x0.4'; PA = 15d

PGC 1237172
09 37 41.2 +02 46 44
V = 16.4; Size 0.7'x0.2'; PA = 155d

In his 1966 "Atlas of Peculiar Galaxies", Halton Arp classified this highly disrupted system as "Material Emanating From Elliptical Galaxies", while Madore, Nelson and Petrillo include it as a Ring system in their 2009 "Atlas and Catalog of Collisional Ring Galaxies".

Although I had previously viewed the brighter 1' pair, NGC 2936 and NGC 2937, I was curious how the trio appeared in Jimi Lowrey's 48", and had an opportunity to take a close look last month, along with Jim Chandler and Jerry Morris.

NGC 2936 is a bright, disrupted galaxy with a highly irregular surface brightness and a curving shape with a faint tail. At 375x and 488x, the central region is extended E-W, roughly 30"x20", with a very small bright nucleus. A low surface brightness "tail" is attached on the west side of the bright central region. The relatively broad tail sweeps SSW for ~45", gradually dimming out due west of the center of NGC 2937. The tail significantly increases the overall dimensions of the galaxy to at least 1.2'x0.6'.

NGC 2937 appeared bright, fairly small, oval 3:2 SSW-NNE, ~0.5'x0.25', with a high surface brightness and a very small intense nucleus. The cores of 2936 and 2937 are separated by less than 1'.

Arp's "Shred" is PGC 1237172, a challenging galaxy attached to a 13th magnitude star just 1.3' NW of NGC 2936. At 488x, it appeared as a very faint, very low surface brightness streak, extending ~18"x5" NW-SE.

Madore labels PGC 1237172 as a "collider" with NGC 2936, but in a 1967 paper titled "Peculiar Galaxies and Radio Sources" (ApJ...148..321), Arp argues that this faint streak is an ejected "shred" or "jet" of NGC 2936 as its major axis is aligned perfectly with NGC 2936.

NGC 2936 and 2937 should present no problems in most scopes, but can you glimpse the "Shred"?

SDSS image
Attachment 132

"GIVE IT A GO AND LET US KNOW"

GOOD LUCK AND GREAT VIEWING!

Labeled ARP image
Attachment 127

Cool object Steve - but not only with big aperture

With my "good old" 16" I could pick up easily both NGC galaxies. NGC 2936 looks "banana shaped" with a peak on the north end. What I could not see was the "shred" but I will give a try with my 27". I hope I could report in some days, weather could be good.

Attachment 133
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Thanks Steve for posting this - I will make another run for the Shred the next time I'll make a run at dark skies.

Here are my observations from some time ago.

22" f/4 reflector @ 305, 377, 458 and 575x

NGC 2936 shows a high surface brightness 2:1 elongated patch with an irregular nucleus. The bright portion is about 30” long and PA = 90º. A spike is detected off the east end. It is about 20” long. A very faint flare comes off the west end pointing at PA 210º. It is about 45” long and 30” wide.

NGC 2937 is a high surface brightness 2:1 elliptical with somewhat well defined edges. PA = 10º and 30” long.

MAC 0937+0246 (Arp's Shred) was not detected.

Positive feedback with 27" Steve.
I tried the "shred" two days ago and could see it with 27" and 293x and NELM 6,5mag+
The shred was visible as a very faint 3:1 elongated streak. I could hold the streak steadily. The streak seems to be a little bit thicker than pictures showed. I big help was the 14vmag star next to the 13vmag starting star of the "shred". With both start I could check if the shred was not a star glow or another "star ghost"

Glad to hear you were successful with the shred! Anyone else give it a try?

Hey Steve,

The other night Anja and I got out and The Shred was on my to-do list. Last month we observed the shred in Jimis scope and I wanted to make sure I went after it in my 25".

s/2-3 t/3 SQM 21.40

I was really expecting it to be much more difficult than it was. The shred was visible about 50% of the time using my 7mm ortho (450x). The shred actually improved slightly using a 12.5 ortho becoming visible about 2/3rds of the time. The field comprised of a small double and a small triple with hints of Arp 142 at the top of the field. I wanted to see if Anja can confirm what I was seeing. Without coaching her I had asked her to tell me if any star "looked different". Without much difficulty, she freely mentioned that the left star of the double "looked like it had a small tail" I asked her to confirm the direction of the tail and she stated "away from the Arp".

I was quite proud she was able to see it!!