Object of the Week Apr 29, 2012 - NGC 4088 (AKA Arp 18 = VV 357)

NGC 4088

Galaxy in Ursa Major
12 05 34.1 +50 32 23 (J2000)
V = 10.6; Size 5.8'x2.2'; Surf Br = 13.2; PA = 43°
Aliases: Arp 18 = VV 357 = UGC 7081 = MCG +09-20-089 = CGCG 269-033 = PGC 38302

The spring skies has so many yummy treats for galaxy lovers, whether it's structure in bright galaxies, interacting pairs, groups, clusters, exotic types, whatever -- it's hard to pick out a favorite for an OOTW! But NGC 4088 is one tasty item to chew on --

In my 18-inch at 280x, this showpiece appears very bright, large, elongated 5:2 SW-NE, roughly 5'x2', and contains a bright elongated core. The galaxy is very asymmetric, with an unusually mottled or clumpy appearance and an irregular outline. At the NE end, a portion of a spiral arm dangles from the end of the central body and hooks slightly towards a mag 13.5 star located 3.7' NE of center. A corresponding feature on the SW end of the galaxy, bending south, is much more subtle. Just east of the south side of the core the surface brightness drops, either due to a dust lane or a large dust adjacent to the core and then brightens a bit again just following the dust patch.

In Lowrey's 48-inch, the appearance is startling and matches the detail in the DSS image. The galaxy extends 5.5'x2' SW-NE. Near the center is an elongated, extremely bright core. The very bright central portion extends from the core in a roughly 2'x0.5' region towards the SW but is concave a bit, bending slightly towards the south. This feature appears similar to a slightly distorted central bar. Just south of this central bar is a dust lane extending SW to NE that parallels the bar, though it's more contrasty to the NE of the core.

The dust lane separates the bright bar feature from a very long arm that extends the entire length of the galaxy along the south side and vaguely emerges from the southwest end of the bar. This arm is clumpy with a couple of large, bright knots to the south of the core and another prominent knot towards the east end of the galaxy (1.7' NE of the core). Beyond this knot the arm quickly dims, fans out a bit and bends to the north towards a mag 13.5 star.

Emerging from the northeast end of the core is a second prominent arm that immediately doubles back towards the southwest on the north side. This arm nearly parallels the central bar to the north and is separated by a less contrasty darker strip or lane. This clumpy arm contains a fairly prominent knot only 0.6' NW of the core. After this point the arm dims dramatically continuing a bit further southwest. The two main arms, along with the central bar create a squashed irregular "Z" appearance.

Attachment 186


And remember,

GIVE IT A GO AND LET US KNOW!

GOOD LUCK AND GREAT VIEWING!

Very timely as usual Steve. Nice writeup. I went into my tape as I have not written up my report but I was inspired to write this one up since you mention it. Wonderful night at DSR, south of Hollister, CA at 2k feet 4-21-2012 in 21.65 sky with 4-5/5 seeing and 4/5 transparency. This is from my trusty 18" f/3.7 StarMaster with almost the first Lockwood mirror of this type. 7mmNagler/ParaCorr for 278x. I spent a lot of time on this to try to squeeze what I could from it. Love this object with this being my best logged observation to date.

1/3 fov [5.9'] The little 'tic' that comes out of it is at 7:30 in my view and hints at being almost stellar at times. A quite easily noticed dark lane extends along down and to the right of the core and is in the direction of the major axis of the galaxy. Core brightens quite a bit and approaches stellar at a point just west of the center of the main object body. The tic in bottom left in my view is slightly elongated along the major axis but between it's strongest core and the main galaxy there is a weakening in the star glow. The dark relief on the NW side of the core is also along the major axis but is much less obvious where movements assists it averted only detection. Limiting stellar object is a star SE of the core by half the object's length [mag 16.6g 12 05 42 +50 30 42]

From my observing guides, NGC4088 Attachment 188 (which I have yet to observe).

An really spectacular but often overlooked object.

With 16" and 315x I could separate the galaxy into four parts. PGC 38369 could be seen as a faint glow 5' SE.

Attachment 189

Here's a sketch I made with a 10-inch: Attachment 190

Nice to have another 18" observation for comparison, Marko, and two excellent sketches from Uwe and Sue. I missed MCG +09-20-092 = PGC 38369 at roughly V = 15.4 in my 18", but of course logged it easily in Lowrey's scope.

Attachment 212

I first observed 4088 in 2009 when its bright supernova brought it to my attention, and found that the wonderful shape of the galaxy was every bit as wonderful as the supernova. I've been back a few times for a look but never under a true dark sky - maybe next weekend when I go back to Likely RV in northern California.

Here is my observations under NELM 6.5 skies with my 22". Not very detailed.

22" @ 293 and 377x - Detailed bright 2:1 elongated spiral galaxy. Several clumps were detected, most of which could be connected to form an arm. The most prominent clumps are on the east edge of the galaxy. PA = 45º and 4.2’ long.

Attachment 225