Object of the Week March 29, 2015 - Arp 270 (NGC 3395/3396) in Leo Minor

Object of the Week March 29, 2015 - Arp 270 (NGC 3395/3396) in Leo Minor
Bonus nearby galaxy triplet; NGC 3413, NGC 3424, NGC 3430, also IC 2604 and IC 2608 nearby.

NGC 3395 = Arp 270, UGC 5931, MCG 6-24-17, PGC 32424
R.A.: 10h49m50.1s
Dec.: +32°58'59" (2000)
Size: 1.6'x 0.9'
Mag: 12.40 B

NGC 3396 = Arp 270, UGC 5935, MCG 6-24-18, PGC 32434
R.A.: Right next to NGC 3395 :>)

Here is a SkyTools chart, with DSS overlay, of the area discussed here...

Attachment 1580

... and the circle on the chart is 1/2 degree in diameter, for scale.

NGC 3395 and NGC 3396, both discovered by Herschel on December 7th, 1785 (along with the other NGC objects discussed here), form an outstanding pair of apparently interacting galaxies, well-placed this time of year in Leo Minor. Each is listed at mag 12.4, but due to their respective surface brightnesses, NGC 3395 appears slightly brighter. Together they represent object #270 in Dr. Arp's Catalogue of Peculiar Galaxies, their category being "double galaxies with connected arms".

From this web page http://www.kopernik.org/images/archive/n3395.htm I learned that NGC 3395 and NGC 3396 are a pair of closely interacting galaxies that appear to be in contact. Both are in the IRAS catalog of infrared sources, and this indicates massive star formation. However, neither galaxy is a particularly bright infrared object, and thus they have probably not actually collided. One current theory would suggest that these two are in the process of merging into a single elliptical galaxy. These guys are both at a distance of perhaps 85 million light years, and have the same redshift.

NGC 3395, the larger and brighter of the 2 galaxies, is classified by NED as a SAB(rs)cd pec, a Mixed Barred Non-barred Spiral, mixed Inner Ring S-shaped, peculiar, Luminosity Class III (whatever that is supposed to mean), and is noted to have a starburst nucleus. At its southern end, using my 25" dob, I could just make out the end of an arm sticking out to the west, and this little wayward arm actually carries its own designation, IC 2605! The core of this galaxy was brighter, but not distinct, to me.

http://ned.ipac.caltech.edu/img/2011...:z:bbl2011.gif

NGC 3396 is classified as a IBm pec, which works out to be a Barred Irregular, peculiar, although I couldn't make out any structure at all, except for the bright and defined core. This pair of galaxies didn't appear to quite touch each other, but my observation was made under conditions that were only average in quality. Here is a nice photo, but it shows a lot more detail than I could manage...

http://astronomerica.awardspace.com/.../NGC3395-6.php

Close to Arp 270 are (5) other galaxies. IC 2604 (mag 14.7 B) and IC 2608 (mag 15.5 B) lie 14 arcminutes SSW and 14 arcminutes SSE of Arp 270, forming a nearly perfect isosceles triangle with ARP 270 at the northern tip. These little guys were very dim, and I have no idea what the minimum aperture might be to see them. Just another 14 arcminutes east of IC 2608 is NGC 3413 (mag 12.7 B), and heading NE from this guy are NGC 3424 (mag 13.1 B) and then NGC 3430 (mag 12.2 B), the distance from one end of this triplet to the other being just about 14 acrminutes. These (3) NGC's are framed very nicely in the same field of view, and 2 bright stars, HD 94086 and HD 94178 complete the visual package. I didn't make any notes regarding any details in these (3) NGC galaxies, I was simply star-drunk by the incredibly rewarding view. Take a look...

http://www.greggsastronomy.com/IMAGES/ngc3395_LRGB.jpg

As always, give it a go and let us know!

Nice choice Paul! I observed Arp 270 on February 21 from SQM 21.7 skies with my 20" telescope:

NGC 3395: Seen as a beautiful S-shaped galaxy. The south-western side is big and split in two. Connected to NGC 3396.
NGC 3396: Seen as an elongated fuzz.

I didn't record more details and I didn't look for any of the other galaxies. So I'll need to revisit this area.


Clear skies,

Wouter

Paul this is one of my favorite Arps. They look like two cats eyes staring at you in the dark in my telescope. (Good Pic)

This is a terrific pair of interacting galaxies Paul, good choice! Here's an observation with my 28 inch from a few years ago:

"This is a beautiful sight - two galaxies dancing as they begin to entwine. I've enjoyed the view at every power from 105x to 408x and each has its charms, but 408x shows the most detail. Wonderful! 21.27SQM."

Attachment 1581 Attachment 1582

I'd like another view under skies in the next couple of months, not only to look more closely but to also check out all the nearby galaxies.

I have to second what Jimi says. In my observing notes for this object in both the 48" and my 25", twice I described this object as cat eyes looking back at me.

Great OOTW!

Great post, Paul. Here are my notes from five years ago, with a 4" f/5.5 Televue:

Non-400 NGC 3430 (I.118), 3424 (II.494), and 3413 (II.493, chart 22d) are a beautiful string. 3413 difficult in comparison and 3424 bright. 3430 strongly elongated.
Herschel 400 NGC 3395 and 3396. It can be seen that -6 is more elongated and thin, and -5 is bright and thick.

Nice object Paul.

The Arp pair belongs to the few object of William Parsons (Lord Rosse) list of spiral galaxies. In other words - NGC 3395 was one of the first galaxies with a visual recorded spiral structure.

Mitchel sketched the object 1855 with the Leviathan (72" reflector)
Attachment 1583

I tried all Rosse spirals with my former 14.5" telescope to comprehend what Parsons and his assistants saw. Also NGC 3395 which shows the brighter arm at the SW.
14.5", 283x, Seeing II, NELM 6m0+
Attachment 1584

N 3395/96, VV 246, Arp 270. I caught this very illusive faint interacting pair last night in my 10" Dob and sketched them. At 111x from my Bortle 3 site they showed as two very faint somewhat elongated knots. Both looked about equally faint, 3396 seemed more elongated than 3395 and both seemed to point at right angles to each other. I'll have to check them in my 12.5'' Dob next time.
Added treat was also viewing the close pair, N 3430 and n 3424 just south of 3395/96.

Phil