Object of the Week March 2, 2014 – NGC3509 (Arp 335)

[Dragan]

NGC 3509
Arp 335
UGC 6134
PGC 33446

Leo

RA 11 04 23.6
DEC 04 49 43

Type: Galaxy
Class: SA(s)bc pec

Size: 2.3' x 1.1'

Magnitude: 13.0

Discovered by Herschel in 1786 and later cataloged by Dr. Halton Arp as Arp 335 in his Peculiar Catalog, NGC 3509 is quite a galaxy. On the surface, images of NGC3509 give it an obvious tadpole appearance of which you could conclude that you're looking at one galaxy. But the interesting fact is that its actually two. Astronomers using the HST released a paper (http://adsabs.harvard.edu/abs/2003AJ....126.2717L) in 2003 stating that NGC 3509 is an elliptical experiencing a slow on-going interaction with a smaller galaxy. Best I could determine is that if you were to look at the inner edge of the main part of the galaxy, the blueish knot is actually the core of the interacting partner. Having observed this object quite a few times over the years. I always just assumed that it was just one galaxy.

As I did research for this weeks OOTW, I noticed in Dr. Arps book that two knots apparent in NGC3509 are labeled as KPG265a and KPG265b. (The knot I mention above is KPG265a)These designations are from the Karachentsev Isolated Pairs of Galaxies Catalog created in 1972 by Russian astronomer I.D. Karachentsev. So did astronomers know for certain that NGC3509 was a multiple system back in 1972? I guess they must have, correct?

Visually NGC3509 is moderately large but dim. Though I have found just a couple observing reports online with scopes in the 15-16" range, having a rather large surface area makes its listed magnitude of 13 quite deceiving. This OOTW can definitely be tough to eek out detail. In my 25" from my western Illinois skies, I tend to make out an uneven oval shaped glow. Below are a couple of my notes

March 2012 - 25" f/5
"sort of faint elongated glow. single arm visible with averted. At 350x and 393x I can see the arm easier and it extending back and towards the core. The core is non stellar with a knot near the edge"

I did manage to observe this galaxy once with the 48" in which the tadpole shape was quite obvious as was the knot mentioned above:
February 2009 488x
"wow does this look like a tadpole! The single arm is apparent and wraps beautifully back towards the galaxy's core. The core appears stellar and bright with a small bright know right at the inside edge"

Its funny how I looked at this knot thinking it was most likely a star forming region of 3509. Little did I know that years later I would find out that it was in fact the core of another galaxy! NGC3509 is well placed this time of year in Leo. Next time you're out, check and see just how much detail you can get out of this galactic collision!

And remember,

"Give it a go and let us know!
Good luck and great viewing!"


1102 1101

[Bill Weir]

If my sky hadn't gone to milk on Friday night I would have made my way into Leo where I have a few Herschels left to tidy up and this is one of them. Spent a bit too much time (successfully) working on VV790b and Howell-Crisp 1 under the nights my less than ideal conditions. It's the problem of living on an island. You can't always drive past the bad.

Thanks for the tip. Now I know to look for a little more.

Bill

[Steve Gottlieb]

Great object, Dragan. Here are my notes from a couple of years back through Jimi's scope --

NGC 3509 = Arp 335 displayed a fascinating amount of structure at 375x, though conditions were subpar in terms of transparency and seeing. The appearance is very asymmetric with the brighter "central" portion elongated SW-NE and containing a very small, round, bright core. A small knot is just 15" S of the core. Attached on the NE side of the central body is a well defined, easily visible tidal arm that gracefully sweeps to the NE and then hooks sharply counterclockwise towards the south. The total length of the arm is perhaps 1.5', though it ends about 45" E of the core. The SW side of the galaxy has no corresponding arm, but is slightly brighter along the south edge. A mag 16.5-17 star is 30" SW of the core on the west edge. PGC 93108 lies 3.0' NW. The PGC galaxy is listed as C2 (collider) in the 2009 Atlas and Catalog of Collisional Ring Galaxies (Madore et al) and the knot close south of the core is listed as C1.

[Uwe Glahn]

Thanks for the reminder Dragan...what an object!

I was out a night later I read your OOTW and revisit it with the 27". The night was one of the best which our observing place can show, faintest star around 7mag, fog in the valleys and dry air above.

With my old 16" NGC 3509 was always a disappointment, because I could only pick up a large but faint 1:2 elongated glow. No signs of the arms. The situation changed with three times more reflecting area. Within seconds of direct vision the two main arms were visible. The brighter NE arm were a little bit longer with a wider hook. Within the hook I could pick up a small spot. From the hook back SW the arm gets much fainter. I could only detect the arm as a thin streak with averted vision. The shorter SW starts with the brighter KPG 265A region. It looks like a double core. I could not resolve the fainter KPG 265B. The faint star SW of the core could be detected steadily with averted vision.

27", 419x, fst 7m0+, Seeing III
http://www.deepsky-visuell.de/Zeichnungen/NGC3509.jpg

[FaintFuzzies]

Great object Dragan!

Here is my observation (copied from my now temporarily out of print book)
22" f/4.1 reflector @ 305, 377, 458 and 575x NELM=6.8, S: 7/10 and T: 8/10 - so that was a pretty good night.

NGC 3509 shows a nice graceful single spiral arm leaving the core on the NE edge arcing to the east and back to the SW and fading very slowly then abruptly due east of the core. Stellar nucleus and a very faint small knot due south. PA = 45º and about 1.5’ long. An extremely faint star is just off the SW edge.


So I did see KPG 265a, but not B.

PS: I am inconsistent in posting here or anywhere. In fact, I haven't posted on CN since July! Astronomy is slowly taking a back burner for a while, a bit longer than I'd like, but other elements are taking my time.

[Ivan Maly]

It was first cataloged as an interacting system VV 75, which is now considered (in NED) to be a single galaxy. Further, although KPG 265 is listed there as a "galaxy pair", KPG 265A is considered synonymous with NGC 3509 NED01, a "part of galaxy". I have noticed on other occasions that KPG seemed to inherit cases of complex but singular galactic morphology from the early VV. Arp simply called it "miscellaneous - large luminous system". It looks like a reasonably symmetric spiral to me (in photos), except that one arm is longer. The two compact knots are symmetrical with respect to the core, as such features commonly are in a spiral system. Good to know that, as Steve mentions, the explanation of the peculiar elements of its morphology can now be found in the interaction with the photographically far separated PGC edge-on to the NW.