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...
... 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.
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...
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...
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