Observing the Shakhbazian Compact Groups of Galaxies

Shkh 1 - Shkh 26


Shakhbazian 1 (Shkh 1, SHK 1)

10h 52m 15s; +40° 43' 31" - mag 17

DSS 10' × 10'

The leader of the Shakhbazian catalogue is by no means a leading object for visual observing. Alike numerous other SCGG this faint cluster - which consists of about 20 completely stellar galaxies - is situated in Ursa Maior. Many extragalactic objects can be found in this area - including a good number of Shakhbazian groups. With an apparent diameter of ca. 1 arcminute and a visual magnitude of the brightest member of > 17 mag this object should be pretty hard to resolve even in large telescopes. On the DSS image Shkh 1 appears as a Y-shaped "star" cluster. Actually the well-known deep sky observer Tom Clark spotted Shkh 1 with a 36-inch Dobsonian. He described the visual impression of Shkh 1 as an "ill-defined glow".

Personally I was unable to detect Shkh1 in the 18-inch neither under good sky conditions (fst mag 6.5) nor under excellent alpine skies (fst mag 7.0).


Shakhbazian 3 (Shkh 3, SHK 3, MCG+9-19-19A, VV 153)

11h 15m 52s; +53° 45' 14" - mag 15.5 - 16 

DSS 5' × 5'

Looking at the DSS image, Shakhbazian 3 in Ursa Maior appears more inconspicuous than its predecessor. Nevertheless this group should have a slightly higher surface brightness due to a minor angular diameter (ca. 0.5 arcminutes). The additional designation VV 153 indicates that Shkh 3 was recognized as a peculiar system of galaxies and recorded in the Atlas and Catalogue of Interacting Galaxies by Vorontsov-Velyaminov (1959). Although clearly resolvable on the POSS/DSS, Shkh 3 is again indicated by the same author as a single object (MCG+9-19-19A) in the Morphological Catalogue of Galaxies (1962). 

Shkh 3 is composed of 6 stellar galaxies. Unfortunately no magnitude information about individual members could be found. The total visual magnitude of the unresolved group should be about 16. Shkh 3 was a surprise to me -  particularly after having experienced Shakhbazian 1 as impossible to see in the 18-inch telescope. Under excellent sky conditions (fst mag 7.2) high magnification (> 300 ×) seemed to reveal Shkh 3 as an exceedingly dim spot of light at the absolute limit of detection. It appeared to melt into a faint star halo close at north and it was visible with averted vision and only about 25 percent of the time. Well, it is questionable if other observers would call that a proof observation...


Shakhbazian 5 (Shkh 5, SHK 5, HCG 50)

1.  PGC 34447 -  11h 17m 06s; +54° 55' 01" - mag 18.4 (b)
2.  PGC 34444 -  11h 17m 04s; +54° 55' 15" - mag 19.3 (b)
3.  PGC 34448 -  11h 17m 06s; +54° 55' 25" - mag 19.2 (b)
4.  PGC 34453 -  11h 17m 09s; +54° 55' 14" - ?
5.  PGC 34452 -  11h 17m 08s; +54° 55' 03" - mag 18.5 (b)

DSS 5' ×x 5'

Shkh 5 is also recorded as Hickson 50 and obviously the most unusual and challenging member of the 100 galaxy groups for both visual and CCD observers. With less than 1 arcminute of diameter it is the most inconspicuous Hickson group as well. Usually the total magnitudes of individual Hickson member galaxies range between 14 and 16. The weak magnitudes listed above - adopted from the original Hickson catalogue - are blue (b) magnitudes. The visual appearance is nearly two magnitudes brighter. In the present case the brightest of five almost stellar galaxies PGC 34447 (HCG 50A) is about 16 mag visually. It became evident in the 18-inch at high power under exceptionally dark alpine sky (fst mag 7.2)! Howewer, visibility of other companion galaxies dropped off rapidly to zero.

Nevertheless this exceptional group of galaxies is still interesting because of its vicinity to the planetary nebula Messier 97 (Owl Nebula), a famous deep sky showpiece in the "big dipper" area. The angular separation between Shkh 5 and M 97 is about 20 arcminutes. Another interesting galaxy (PGC 34279; mag 16) is situated close to the southeast of the planetary nebula, but not member of Shkh5/HCG 50.


Shakhbazian 14 (Shkh 14, SHK 14)

14h 25m 21s; +47° 14' 45" - mag > 16 

DSS 5' × 5'

This galaxy group in Boötes is very similar to Shkh 5, showing half a dozen of faint stellar galaxies in a mere 1 arcminute diameter on the POSS print. Visually it is an irregular and diffuse patch with no sign of individual galaxies. The cluster is also at the very limit of visibility in the 18-inch.


Shakhbazian 16 (Shkh 16, SHK 16, 1Zw 167, Arp 330)

1.  MCG+9-27-94 -  16h 49m 11s; +53° 25' 12" - mag 15.3
2.  MCG+9-27-91 -  16h 49m 08s; +53° 23' 34" - mag 16.0
3.  MCG+9-27-92 -  16h 49m 12s; +53° 24' 18" - mag 16.6
4. MCG+9-27-95 -  16h 49m 15s; +53° 26' 54" - mag 16.2
5. MCG+9-27-96 -  16h 49m 11s; +53° 25' 58" - mag 16.3
6.  anonymous 16h 49m 04s; +53° 23' 27" - mag 16.8
7.  anonymous 16h 49m 17s; +53° 27' 15" - mag 17.0

 

DSS 10' × 5'

N457/1850; 222 ×, fst 6.7

One of the most spectacular galaxy groups is Shkh 16, located in Draco. As can be seen on the above DSS image it is a literally breathtaking chain of seven compact galaxies, almost 5 arcminutes in length. It seems oddly enough that this amazing arrangement of tidally disturbed galaxies - also recorded as Arp 330 in the Atlas of Peculiar Galaxies - has been ignored by Paul Hickson during his search for compact groups on the POSS.

The most conspicuous member MCG+9-27-94 is fairly bright, small and irregularly round in the 18-inch. The other galaxies are quite fainter, but actually all five MCG galaxies in Shkh 16 are reported to be visible in a 14 inch telescope by Ronald C. Stoyan. An anonymous galaxy (6) required larger aperture, turning out to be a considerably faint "star" with no trace of hazy surroundings. Another stellar 17th magnitude galaxy (7) was invisible in the 18-inch because of its vicinity to a 9th magnitude star close northeast of the chain, which light could not be kept out of field at any magnification. In my view Shkh16/Arp 330 is the most beautiful Shakhbazian group by far.


Shakhbazian 19 (Shkh 19, SHK 19, MCG+3-34-39, VV 678)

13h 28m 20s; +15° 50' 20" - mag > 15.5

DSS 3' × 3'

Also recorded as MCG and VV object, horseshoe shaped galaxy group Shkh 19 is very similar to Shkh 3. Honestly, this object should be defined as a "hardcore" deep sky treat. Shkh 19 is one of the most challenging targets in the Shakhbazian list. Being less then 0.5 arcminutes in diameter, it required dark and highly transparent sky (fst mag 7.2), furthermore high power (> 300 ×) and hence very good seeing conditions to be observed in the 18 inch reflector. The group became evident with averted vision as an extremely faint and stellar haze at the limit of visual detection, however, alike Shkh 3 it could not be seen constantly. 


Shakhbazian 21 (Shkh 21, SHK 21)

1.  anonymous  23h 46m 48s; -01° 44' 16" - mag ~14
2.  anonymous  23h 50m 48s; -01° 43' 33" - mag ~15

DSS 5' × 5'

Examining the DSS image it is hard to believe that Shkh 21 consists of more than 120 galaxies. Actually most of these galaxies are as faint as the POSS limiting magnitude, thus being barely visible or completely unconspicuous even on the sky survey print. For visual observation Shkh 21 is everything else than spectacular. Only two galaxies are bright enough to be spotted in larger amateur telescopes. The first one appears clearly visible, almost round and somewhat diffuse. A further non-stellar galaxy lies close to northeast and is slightly fainter. Other galaxies should be invisible in the 18 inch Newtonian unless used under exceptionally dark and transparent skies.


Shakhbazian 26 (Shkh 26, SHK 26, Abell 1143)

1.  MCG+8-20-69A  11h 02m 12s; +50° 20' 58" - mag 13.4
2.  MCG+8-20-67A  11h 01m 49s; +50° 23' 50" - mag 16.0

 

DSS 8' × 10'

N457/1850; 205 ×, fst 6.7

Actually various Shakhbazian groups are closely related to rich galaxy clusters, representing their highly dynamical central regions. Examples for this distinctive subclass of SCGG are Shkh 40 (A 193), Shkh 65 (A 1284), Shkh 166 (A 2247) and Shkh 26 in Ursa Maior, which is identical with Abell 1143 (distance class 5; magnitude of tenth-brightest galaxy: 17.2). Moreover, the galaxy group within the rich cluster is a particular object. It consists of 27 extremely small galaxies in a mere 5 × 5 arcminutes field. However only two galaxies were visible in the 18-inch. Circles mark the locations of both galaxies on the DSS image.

A special feature of Shkh 26 is its first galaxy MCG+8-20-69A (mag 13.4; at left), which is one of the brightest individual galaxies of all Shakhbazian galaxy groups. Examining the DSS image MCG+8-20-69A turns out not to be a single galaxy, but an exceedingly compact chain of 5 - 7 stellar objects in the most varied size and brightness. Visually, this "galaxy" appears in the 18-inch (276 ×) as an irregularly elongated nebula and slightly textured. The second galaxy visible in Shkh 26/A 1143 (MCG+8-27-67A) appears as a double system on the POSS. Through the eyepiece it became evident as a very faint and oval patch.


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