PDA

View Full Version : Object of the Week, July 27th, 2014 - A galaxy chain near Vega



RolandosCY
July 28th, 2014, 08:12 AM
Object of the Week, July 27, 2014: A galaxy chain near Vega

Object data:
UGC 11341: RA 18h 42’ 51” Dec +40 22 00
NGC 6695: RA 18h 42’ 43” Dec +39 32 51
NGC 6686: RA 18h 40’ 07” Dec +40 08 17
NGC 6685: RA 18h 39’ 59” Dec +39 58 55
IC4772: RA 18h 39’ 56” Dec +40 01 34
NGC 6675: RA 18h 37’ 26” Dec +40 03 30
NGC 6663: RA 18h 33’ 34” Dec +40 02 57
IC 1289: RA 18h 30’ 02” Dec +39 57 52
NGC 6646: RA 18h 29’ 39” Dec +39 51 54
IC 1288: RA 18h 29’ 23” Dec +39 42 48


The tiny constellation of Lyra is well known for its superb planetary nebula, M57, and of course for its bright lucida, zero - magnitude Vega. Rarely would anybody associate Lyra with interesting galaxies. Yet, today’s object of the week is a fine chain of ten galaxies all located within a 2-degrees semicircle north of Vega! I first “discovered” this chain two years ago, while exploring this area after observing NGC 6745, http://www.deepskyforum.com/showthread.php?180-Object-of-the-Week-July-29-2012-NGC-6745-Bird-s-Head-Galaxy.

This galaxy chain has both bright and (mostly) faint members. The main challenge is to ferret these galaxies out of the myriad stars surrounding them, this being a rather star-rich area of the sky. You will need good star-hopping skills to jump from one galaxy to the other, and the fact that most galaxies are not plotted in many atlases adds to the challenge. A combination of custom-made Megastar charts and DSS images made it possible to navigate though the many faint stars. I have provided a chart here, but you will need to make close up charts.

1299

Our starting point is the Double-double, Epsilon Lyrae, a fine sight on its own. 20 arc minutes to the west of Epsilon lies tiny UGC 11341. Through my 18” at 275X it appeared as a small, faint spindle of light about 1’ long. It has a listed photographic magnitude of 15.4, and it should appear a bit brighter visually. Moving Epsilon out of the field certainly helps in finding this little guy.

About 40 arc-minutes due north of UGC11341 we can detect NGC6695. This 13th magnitude galaxy appeared as a N-S oriented faint oval with a subtle central brightening, with a rather low surface brightness. At a recent star-party I was able to detect (albeit with difficulty) NGC6695 with an 11” SCT, so this galaxy is definitely within the reach of medium-sized scopes.

1300

Forty-five arc-minutes to the SW of NGC6695 is the first of two galaxy triplets that we can find in this chain. Although NGC 6685 is listed as the brightest of the trio, I found NGC 6686 more distinct and more readily visible in my 18”. At high powers 6686 appears round with a distinct core and a faint halo. NGC 6685 appears smaller, but the lack of halo made it less apparent to me. The trio is rounded up with faint IC 4172, appearing as a barely detectable tiny puff of light between the two NGC galaxies. Both NGC galaxies were visible with an 11”SCT as averted vision objects.

1301

Half a degree due west from the 6685 trio lies NGC 6675, the brightest and most distinct of the chain’s galaxies. At magnitude 12.4, this galaxy is within reach (under good skies) of smaller instruments. In my 18” at medium and high powers it appears as a roundish patch slightly more than one arc-minute across, with a distinct core. Through an 11-inch SCT under very dark skies it appeared as a small faint circular glow, ever so slightly brighter in the middle. To my surprise, NGC 6675 was readily visible in my 6” achro from my SQM21 skies as an extremely faint tiny round patch that grew slightly with averted vision. I believe that under very dark and steady skies it should be detectable even with the popular 4-inch refractors.

1302

The next move to NGC 6663, 45 arc-minutes due west of NGC 6675 is the longest astro-hop. A triangle made of 7-10th magnitude stars just to the west helps to pinpoint the galaxy. NGC 6663 through my 18” at 294X appears as a very faint and diffuse oval oriented E-W, a bit less than one arc-minute across. Although the listed magnitude is around 13, it visually appears harder than the numbers indicate. I was unable to detect it in an 11”SCT under SQM 21.4 skies, so NGC 6663 is reserved for rather large scopes.

1303

The Vega galaxy chain concludes with a fine galaxy triplet, 45 arc-minutes west of NGC 6663. A distinct N-S line of 8th to 10th magnitude stars is located halfway across the starhop from NGC 6663 and it helps in pointing the triplet’s location. The brightest of the three galaxies is NGC 6646, a roundish faint patch of light in my 18” at high power, with a distinctly brighter center. NGC 6646, which seems to be harder than the listed 12.6 magnitude would suggest, was visible with direct vision in an 11” SCT at high power, and was detected – albeit only with averted vision and then barely – in my 6” achro. Eight arc-minutes northeast of 6646 is IC1289, a tiny circular 14th magnitude patch of faint light. About 15 arcminutes south of NGC 6646 the tiny spindle of IC 1288 may be seen. At magnitude 14, it has a higher surface brightness than IC 1289 and it was readily detected with the 18” at high power, within a trapezium of faint stars. IC 1289 is almost as easy to see as NGC 6646, and was detectable with direct vision in an 11” SCT under dark skies.

1304

So, during the next time you are out, under dark and transparent summer skies, turn your scope to Vega, and
"GIVE IT A GO AND LET US KNOW"
GOOD LUCK AND GREAT VIEWING!

Steve Gottlieb
July 29th, 2014, 03:40 PM
Excellent choice of little-known targets, Rolandos. It's a fun project to ferret out these galaxies within the rich star fields near Vega.

NGC 6695 is a nice barred-spiral. Here's a large scope observation I made three years back --

48" (10/24/11): this excellent two-armed barred spiral appeared fairly bright, moderately large with a slightly curving "bar" that is elongated 2:1 SSW-NNE, ~0.6'x0.3'. Contains a slightly brighter, elongated core. An arm emerges from the NNE end of the bar and curves clockwise, bending NW towards a mag 15.5 star and fading out just before intersecting the star. The second arm is attached at the SSW end extends south, though dims out rapidly before reaching a mag 16 star off the south end. Overall, the galaxy has an elongated "S" appearance.

RolandosCY
July 30th, 2014, 08:42 AM
Excellent choice of little-known targets, Rolandos. It's a fun project to ferret out these galaxies within the rich star fields near Vega.

NGC 6695 is a nice barred-spiral. Here's a large scope observation I made three years back --

48" (10/24/11): this excellent two-armed barred spiral appeared fairly bright, moderately large with a slightly curving "bar" that is elongated 2:1 SSW-NNE, ~0.6'x0.3'. Contains a slightly brighter, elongated core. An arm emerges from the NNE end of the bar and curves clockwise, bending NW towards a mag 15.5 star and fading out just before intersecting the star. The second arm is attached at the SSW end extends south, though dims out rapidly before reaching a mag 16 star off the south end. Overall, the galaxy has an elongated "S" appearance.

Hi Steve! Actually NGC6695 was a "last minute" addition to the list of these galaxies as I had not noticed it until my re-observation of the chain on Jyly 19th! I plan to try to observe it again on August 2nd, as I will not be able to set up my 18" until then. I wish I could see spiral structure with my 18" but I think that's way beyond its capabilities... The DSS photo definitely agrees with your description.

1305

Have you observed any of the other galaxies, either with the 48" or one of your scopes?

Steve Gottlieb
July 30th, 2014, 09:03 PM
I have observations of all the NGC and IC galaxies on Adventures in Deep Space (http://www.astronomy-mall.com/Adventures.In.Deep.Space/steve.ngc.htm) as well the NGC/IC Project (http://www.ngcicproject.org/), under the "Team Members Databases", but some go back nearly 30 years so it's time to revisit this group!

As far as galaxies near Vega, here are four more within 30'-40' that I observed a couple of years back with my 24-inch at 325x.


UGC 11278 = CGCG 201-011 = PGC 62043
18 33 43.7 +38 37 05
V = 14.0; Size 1.0'x0.4'; Surf Br = 12.9; PA = 57d
24": fairly faint to faint, very small, slightly elongated, 18" diameter. Initially, I only noticed a fairly high surface brightness "knot", which is the core, but with averted vision very faint extensions were occasionally seen SW-NE. Located in a rich Cygnus star field near Vega with UGC 11281 4.3' ESE.


UGC 11281 = MCG +06-41-004 = CGCG 201-012 = PGC 62056
18 34 04.8 +38 35 54
V = 14.0; Size 1.5'x0.4'; Surf Br = 13.2; PA = 6d
24": at 325x appeared faint, very elongated 3:1 N-S, 0.7'x0.2', contains a very small bright core ~12" diameter with much fainter extensions. Located in a rich star field 35' SW of Vega with three stars on the south side (two superimposed). The faintest is a mag 15.5 star 25" S of the core, near the tip of the southern extension. UGC 11278 lies 4.3' WNW.


PGC 2127422 = 2MASX J18342727+3827067
18 34 27.4 +38 27 07
B = 15.5; Size 0.5'x0.4'; PA = 46d
24": faint, small, round, 15" diameter. Weak, broad concentration to center. Located 3.7' ENE of mag 7.5 HD 171619 and 10' SSE of UGC 11281.


CGCG 201-013 = MCG +06-41-005 = PGC 62087
18 35 16.6 +38 27 28
B = 15.2; Size 0.65'x0.4'
24": faint, small, round, 15" diameter, faint stellar nucleus. Picked up while viewing UGC 11278 and 11281 16' and 20' NW. Located 13' E of mag 7.5 HD 171619 and 28' SW of Vega!

RolandosCY
August 1st, 2014, 09:52 PM
Hi Steve, I did check your NGC project notes, they appear to be quite similar to what I did observe. Regarding the four galaxies you mention I will prepare charts for them, but it seems unlikely I will manage to observe them this weekend - they will be high in my priority list though. I hope you and the other guys at Lassen National Park get a chance to (re-) observe the Vega galaxy chain....

RolandosCY
August 3rd, 2014, 02:47 PM
Hi Steve, I did check your NGC project notes, they appear to be quite similar to what I did observe. Regarding the four galaxies you mention I will prepare charts for them, but it seems unlikely I will manage to observe them this weekend - they will be high in my priority list though. I hope you and the other guys at Lassen National Park get a chance to (re-) observe the Vega galaxy chain....
Here are sketches of two of the galaxies that Steve has suggested (UGC 11278 and UGC 11281) as well as UGC 11313 (on the other side of Vega that I "discovered" by preparing charts. All three galaxies, as well as CGCG 201-013 were quite faint in my 18" but all could be held with direct vision at least fdor some of the time.

13141315

Steve Gottlieb
August 3rd, 2014, 04:17 PM
Very nice observations, Rolandos! I've also observed UGC 11313 and found it fairly tough in my 17.5-inch -- even from a good Sierra Nevada site (2200 meters). Vega is not in a location you normally go searching for galaxies, but there are plenty around.


UGC 11313 = MCG +06-41-011 = CGCG 201-024 = PGC 62205
18 39 19.5 +38 56 24
V = 14.4; Size 1.9'x0.4'; Surf Br = 13.9; PA = 23d

17.5" (7/18/01): this fairly small, edge-on galaxy is located 30' NE of Vega! At 220x appears extremely faint, elongated ~3:1 SSW-NNE, 1.0'x0.3'. Required averted vision and concentration to glimpse. Forms a right angle with mag 11.5 and 13 stars 2.2' S and 2.6' E, respectively.

Clear Skies
August 5th, 2014, 12:26 PM
Using a 12" SCT, I can pitch in "only" 7 out of 10. All 179x / 27':

NGC 6695
13 September 2009, SQM 21.17
Very faint, elongated north to south and slightly brighter in the center (this brighter central part is almost round). 1/4 FoV to the north is a slightly elongated, large triangle of mag. 10 stars pointing WSW with the base aligned NNW-SSE.

NGC 6686
5 September 2009, SQM 21.01
Observed simultaneously with the galaxies NGC6685 and IC4772.
A small, faint, round patch, even in brightness, no detail visible, slightly brighter than NGC6685 and IC4772 are but difficult to observe without AV.
1/5 FoV to the WSW is a pale white mag. 7.5 star (SAO47678).

NGC 6685
5 September 2009, SQM 21.01
Barely observable without AV, using AV a faint, round glow, gradually brighter towards the center, no nucleus visible. To the NE are two mag. 14.5 stars aligned SSE to NNE (not a double star in WDS). To the NNW is a mag. 14 star with an extremely faint, small, round patch to its north (half of the distance towards NGC6685): IC4772.

IC4772
5 September 2009, SQM 21.01
Sharing the FoV with the galaxy NGC6685 to the south: An extremely faint, small, round patch, barely observable without AV, even in brightness. PGC2159464 is not visible. To the SSW is a mag. 14 star, 1/4 FoV to the NNW is a pale white mag. 7.5 star (SAO47678), to its WNW is a small, faint, round patch: NGC6686.

NGC 6675
13 September 2009, SQM 21.17
A slightly NE-SW elongated patch, almost round, even in brightness. Directly NNE is a mag. 13 star, slightly farther to the NNW is a mag. 14 star, slightly farther to the WNW is another mag. 13 star.
1/5 FoV to the NW is a yellowish mag. 8 star (component A of the double star Soulie 209).

NGC 6663
5 September 2009, SQM 21.01
Visible only when using AV, an extremely faint glow, little more than a lighter toned background, round and even in brightness. To the SW are two mag. 14 stars aligned NW to SE, twice as far to the NE are a mag. 14 (NW) and a mag. 14.5 (SE) star aligned SE to NW (not a double star in WDS). 1/3 FoV to the NNW is the double star STT356.

NGC 6646
13 September 2009, SQM 21.17
An east to west elongated patch, brighter in the center (elongated in the same direction). Using AV the nucleus is faintly visible. To the north is a mag. 8 star, approximately the same distance to the SE is a mag. 9 star, 1/3 FoV to the SW is a mag. 8 star.

Not observed: UGC 11341, IC 1289 & IC 1288.