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SHAKHABAZIAN COMPACT GALAXY GROUPS


Mike JW
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THIS THREAD IS DEVOTED TO EEVA OBSERVATIONS OF THE SHK COMPACT GALAXY GROUPS - enjoy the journey.

In 1957 Shakhabazian noted on the Palomar Sky Atlas a group of 17 red stellar like objects clustered within 1 arc minute. It was thought they were a cluster of red stars. Later analysis (1972) showed them to be galaxies. This group then became known as Shakhabazian 1 (SHK 1). In 1973 a systematic search of the Palomar Sky Survey plates revealed more groups – compact groups of compact galaxies (CCCG). There are 377 groups. Being compact then their gravitational forces at play within the groups, are heating up interstellar gas, twisting some of the galaxies. There are three broad categories spherical, chains and peripheric (on the edge of the area). There are some which do not fit into these three categories. They are true groups and lie beyond our local super-cluster. Many groups have strong radio sources.

The criteria for the groups are as follows:

  • The groups consist of 5 to 15 members.
  • The apparent magnitude of the individual galaxies is between 14 and 19 mag.
  • The groups are compact, i.e., the distances between galaxies are only 3-5 times the diameters of galaxies.
  • Nearly all member galaxies are extremely red, with at most 1-2 blue galaxies in a group.
  • Members of groups are compact (relatively high surface brightness, borders not diffuse).
  • The groups are isolated.

ShCGs were originally called compact groups of compact galaxies because the images of most of the constituent galaxies in these groups seemed very compact. Later observations of these groups with high angular resolution revealed that member galaxies are mostly of E and S0 types. Also it has now been shown that the group members are not particularly compact so the more recent papers now call them Shakhbazian Compact Galaxy Groups (SCGGs) or SHKs. Red shifts for these groups are slowly being determined – about 70 groups so far.

RESOURCES - a list in excel format.

Shakhbazian Galaxy Groups.xlsx

Mike and Martin

Edited by Mike JW
sorted grammar
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  • 2 weeks later...

SHK 225  in Pegasus. Look carefully and you will this group in the centre. This is a small group with just 8 members.

458598579_SHK22505Nov20_08_42_51.thumb.jpg.587c230800f5a86919e25058b7bf2b52.jpg

Close up - these guys are faint. The fuzz at top right is PGC 1953277 - mag 17.6, (not part of the group). Drop straight down and a touch left, just below the centre is a fuzz with extensions - PGC 1952668, mag 18.6.(number 5 in the SHK group). The remaining 7 members are distributed around the centre of the image (not the bright star).

597715340_SHK22505Nov20_08_42_35.jpg.112b553039e9ded8da1e680ec04490df.jpg

 

SHK 340 - in Pisces. This SHK is slightly unusual because there are two distinct groupings near to each other. The 13 members of the obvious group are to the right of the fov. The obvious fuzz spots are all PGC, mag 17 galaxies (5 in total) with the remaining 7 in the area. I appear to have picked up other fainter galaxies (or very faint stars) as well in this area.

To the left of the fov can be seen a distorted circle of galaxies and a bright-ish star.

1570368401_SHK34005Nov20_08_36_06.jpg.6261adcdce2860bb5c83eb9a0f3f783f.jpg

 

Mike

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SHK 176 in Andromeda. I called this group - 'you must be joking'. Take a look at the full frame shot - I had to triple check that I was in the right area. There are 10 members - oh yeah!. Look to the left of the central bright star - surely not!

1839870519_SHK17608Nov20_13_50_52.thumb.jpg.3ce98973db7e87b407ded6d8eb1d67e3.jpg

Close up - it took me awhile to find the best setting to make them all obvious. Even then the 10th member is only just visible - dead centre - a faint elongated fuzz which NED gives as mag 18.5 and no further info. I really needed to collect some more subs but cloud was approaching.

506674060_SHK17608Nov20_14_16_30.jpg.6b69b8dde773e0dbed82f33a9dbfcd43.jpg

 

Mike

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  • 2 months later...

12/01/21 - I spent much of the session in Triangulum which included these three SHK Groups. Visually they may not be appealing (many do make for some attractive patterns) but the challenge is to locate them and tease them out from the background. Very little data exists for the components.

SHK 178 - in the rush of the session, to maximise the clear window I was certain I had found this tiny group and had them reasonably central. However the following day I realised I was not on target, only to be delighted that I had just got them in the frame. The full frame shot is included to show the difficulty of the challenge. Good luck at spotting them! - and this is with a 15" scope.

1611260730_SHK17813Jan21_12_23_32.png.4d2a75611944883e6dc9e6cd4aa49e4f.png

Here is the zoomed in shot of the group near the top edge of the full frame.

The brightest galaxy is mag 17.1 (at the top), the rest form a circle below it and are mag 18 or fainter!!

1902234004_SHK17813Jan21_12_24_03.png.3eb00f0d6535c01aa566f38c8ff76f23.png

SHK 177 - I did better on this group - right in the centre this time. The brightest is mag 18.2 , there are 10 in the group. However head off down the shot a bit to the right of 6 o clock and there is a suspicious semi circle of stars? (look fuzzy to me - galaxies?)

1253811120_SHK17713Jan21_12_10_44.png.ef02a6c90c514ee0c567e141dc224441.png

Finally SHK 179  - they are in there! - honest! To the right of centre - a circle of 4 + star and then 4 more below it, the brightest is mag 17.9.  Quite right if you do not believe me.

826536923_SHK17913Jan21_12_37_36.png.454e5a276e83ab1dbeffa4ab282d6222.png

Here is the zoomed in shot

1845803437_SHK17913Jan21_12_38_07.png.db5e4ea299b97f6751df21d6862a5cd8.png

 

Three SHKs in the session was a sufficient challenge but rewarding to find them and to ponder what I was viewing.

Mike

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Tracking these things down even with 'artificial aids' is a great part of the challenge. It would be no fun at all with a big sensor 😉 

Its great to see the Shakhbazian thread building up too. I'd like to think we could observe them all between us over the next few years. The minimum declination is quite modest at -15. 

I'd love to get hold of the original 1957 article which I believe has been translated. 

Martin

PS Here's an interesting relatively early article in English: http://articles.adsabs.harvard.edu/pdf/1976sgov.meet..251A

 

Edited by Martin Meredith
re-read the first post which answered the question, doh!
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Minor point, but I noticed when doing a web search there are at least 4 ways to spell the author's surname that appear in the literature (Shakhbazian, Shakbazian, Shahbazian and Shahbazyan), often with two forms appearing on the same web page or article! Judging from the article I cited it seems the preferred one is Shahbazian, which unfortunately doesn't sit easily with the widely-adopted SHK designation...

Martin 

 

 

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Just to add to the opportunities for confusion and missing things I notice that the abbreviation ShCG has  also been used for Shakhbazian compact galaxy group.

for example:

https://iopscience.iop.org/article/10.1086/307726/fulltext/39976.text.html

Alvin Huey's guide to some of these groups is interesting. It may have been mentioned in this thread already. I could not find it so here's the link:

http://faintfuzzies.com/Files/ShkGroups v1.pdf

Bill

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Thanks Bill.

The galaxy groups were first called SCGCGs (Shakbazian Compact Groups of Compact Galaxies), then SCGG (Shakbazian Compact Galaxy Groups) as it was realised that not all the galaxies were compact, then called ShCG (Shakbazian Compact Groups). 

Personally I do not find the Alvin Huey Guide of much use - the star charts (of the various guides) have never really worked for me. Give me RA/DEC co-ordinates and Pretty Deep Maps, combined with a DSO image of the area (I often use SkySafari for that when out observing) and I am a happy chap.

Mike

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I use Simbad a lot, and it can be quite hard sometimes to find the correct catalogue reference (e.g. Abell PNe use A66 <number> or PN A66 <number>)

For the various Shakbazian references, you just need to use ShK <number>

Callum

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Hi Callum - As you say we just need to use ShK and number.  I use https://vizier.u-strasbg.fr/viz-bin/VizieR?-meta.foot&-source=VII/89B as my online source of info, type in the SHK number, then on the next screen, click on the 'FULL' column, then when the next screen comes up click on the CDS portal button and up will come the aladin lite image........ The trouble with this is if I do this when observing it tends to slow down my laptop as I will have camera/jocular/ internet/lists/ST4 also running.  

Mike

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Here's SHK 147 from a couple of nights back. This one looks like either a cross or an arrow, pointing almost due North as it happens (or maybe pointing at the dust shadow on my sensor). The lowest element is clearly stellar. It is hard to find any magnitude or distance estimates. The galaxy at 4 oclock just outside the circle is apparently at 2.5 billion LYs and mag 19.2 and the faintest SHK member galaxy of this 7-strong group is at the head of the arrow, and looks somewhat fainter.

 1193964982_SHK14720Jan21_20_37_21.png.5839d1ccb75c3926d3b1bfdc7942f8d3.png

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SHK 359 - Bootes,

A delightful circular group of  seven galaxies - the obvious ones in the circle. They all have PGC designation and range from mag 17 to 19. The brightest galaxy - bottom galaxy of the pair on the right is about 450 million lyrs away whereas data for some of the others suggests they are a mere 1.35 billion lyrs away (or there a bouts).

The yellow line points to a quasar, mag 19.6 and a distance of 4.3 billion (light travel time) and because the universe is expanding it is now 5.1 billion lyrs away. 

There are as usual various other galaxy fuzz spots in the shot. Some of them have a very similar redshift value to the SHK members so could be members of the group?

Mike

1452359085_SHK35922Jan21_18_43_33.png.087f04a0641dbad39af2b95fee0bbac9.png

 

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  • 4 weeks later...

19/2/21 - SHK 244 in Cvn. This is a group of  10 galaxies, 9 in a circle and the tenth just off to one side. They were easy to spot on the first sub. My attention was immediately caught by the obvious large member. The close up shows it is in fact two galaxies and judging by the spread of the grey fuzz, I wonder if they are interacting. Redshift puts them at about 1.2 billion lyrs away. Aladin (Simbad, NED data) suggest this a compact galaxy group - so maybe more than two galaxies. The grey fuzz that extends up from the left coincides with a galaxy designation. The fuzz extension going up from the right side also coincides with another galaxy designation. In the close up view I have reduced the noise to minimum so the grey fuzz bits that are left are likely to be real objects. They do seem do coincide with the Aladin view of the area which labels plenty of GinCl (galaxy in cluster) - galaxies in the region of mag 19/20.

 

582412728_SHK24420Feb21_09_46_32.png.f71018d3ddf72d272555119937387189.png1052245737_SHK24420Feb21_09_46_53.png.63a9d24c52c883d854c7ff5095628b08.png

Edited by Mike JW
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That's a really great 'hexagon' SHK group. You don't often see much galactic detail in these groups (at least I don't) but here several of the members show some structure. It definitely looks like you've caught a mag 20.0 galaxy at about 1 oclock and a 19.4 quasar too (looking quite bright). The 15" seems to be performing really well. Envy...

Martin

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Hi Martin,

Here is SHK 244 - with the the Jocular circles - (for those folk reading this who are not familiar with Jocular, the grey circles are Quasars, the red circles are galaxies, the blue circles are SHK 244 members). It looks like I picked up the three quasars top right but nothing in the bottom grey circle. I have reduced the noise right down and grey fuzz spots (galaxies? - they seem to coincide with NED data etc - not all of them checked) abound.

Mike

 

365847946_SHK24421Feb21_07_32_43.png.5ecafd853b56f2a3383423d95fe168af.png

Edited by Mike JW
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  • 2 weeks later...

I came across this delightful little arc of galaxies which make up 4 members of SHK 346 in Hydra. The chain itself is less than one arcminute in length.

These are not particularly faint. I only have data for the uppermost and lowermost members of the chain. The uppermost is mag 13.0 -- but in the K band! The lower one is mag 17.9 in the B band. The fainter of the pair above the chain is 18.9 in B and listed at 2.1 billion light years distance.

There are 8 members listed though as is often the case there are more than 8 galaxy candidates in the vicinity.

346116993_SHK34604Mar21_22_10_09.jpg.56ab9ab8f52eced9d836096123118218.jpg

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  • 2 months later...
Posted (edited)

Serpens has just one SHK - number 360 and what a gem it is, well worth a visit. The scope was not tracking very well but Jocular managed to stack the subs well enough to get this view. As with most of the SHKs it is easy to pass them by. Many of the fuzz spots in the wider fov shot are mag 19 galaxies.

1731572799_SHK36001Jun21_11_46_30.thumb.png.ca8c26dc0fbe81059b1f99f2def07789.png

14 members make up SHK 360 with the brightest central galaxy coming in at mag 16.9 and down to mag 21 (rather pleased to pick this up). The complete group is not likely to be a true group as distance ranges from 1.378Gly to 1.440Gly. Using the NED data the reality is there are two (or more?) galaxy groups that we see in line of sight.

1286268341_SHK36001Jun21_11_47_33.png.95ff003a185afb5fccea16a3a665b9ba.png

Mike

Edited by Mike JW
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