Realm of the galaxies: central part of the Coma Cluster

[Martin Meredith]

I wasn't meaning to look at this yesterday evening but scanning the charts in the middle of a session the density of galaxies was too much to avoid having another look at Abell 1656, better known as the Coma Cluster. This is only the central part, with the two main supermassive ellipticals NGC 4884 (left) and NGC 4874 (right). Most of the objects on view here are galaxies! The cluster is part of the Coma-Virgo supercluster and is near the North galactic pole, so little own-galaxy dust to dim things in the intervening 320 million light years or so..

COM4937.pdf

This screenshot of the relevant chart gives an idea of galaxy positions and orientations. I haven't checked thoroughly for faint galaxies in my image but I think there may be mag 20 and fainter lurking in there.

 

 

However, to see the details it is better to look at the pdf (which is part of the Pretty Deep Maps set that can be downloaded from the link in my sig): 

COM4937.pdf

NGC 4921 and 4911 look to be very photogenic galaxies just off to one edge that I hope to look at tonight.

cheers

Martin

 

[Mike JW]

Hi Martin

Abell Clusters - now that is another fascinating tour. I once started a tour with the 20" and decided I really needed a 24"!!!!!!!. Wonderful time visually trying to tease out the galaxies using AV and then confirming against a chart. Really needed to be somewhere at altitude and 100 clear nights a year. I wonder what I could achieve with my 7" scope with its wider fov - not enough time to pursue all this fun and interest. Mike

[Paul73]

Wow! That is a really impressive number of galaxies.

Thanks for posting.

Paul

[Martin Meredith]

Thanks Mike and Paul. I was in that region again last night taking a look around the other parts of the cluster and will post some images in this thread over the coming days. 

This is the south east part (on the sky -- I prefer to think of it as SW on the chart). The wiggly line of galaxies a the top correspond to those on the left in the main image above. Again, lots of galaxies here, but I particularly wanted to look at the two face-on spirals. The one at the left edge is NGC 4921 which is type Sab (moderately loose-armed spiral). While listed at magnitude 13.5, it has quite low surface brightness at 23.7. It took me a long time to see any decent structure in the arms. Long exposure photos show a lot more going on that I have been able to capture. 

 

Just S of this galaxy and at around 2 o'clock with respect to the elliptical NGC 4923 which is on the edge of the shot is a bright (magnitude 17.9) quasar (redshift 0.24).

The other galaxy to highlight is the face-on spiral at the base of the image. This is NGC 4911, magnitude 13.7 and with a higher surface brightness of 22.3. This is of type SABb which I believe corresponds to a loose spiral with a hint of a bar -- something I'm sure many of could do with right now  -- but I need to revisit the galaxy classification system to be sure about that! I see a kind of 'poppy' petal structure here with the bright central nucleus and offset disks in the negative close up below.

There are plenty of other interesting galaxies in the field, mainly ellipticals and S0 type galaxies (the type at the juncture of Hubble's tuning fork where ellipticals blend with spirals). The shot contains 6 NGCs and 3 ICs. One day I will count how many NGCs/ICs there are in the entire Coma Cluster but it must run into several dozens.

Further out still to the SE is NGC 4926 and 4926A but I didn't stray out there on this occasion.

Martin

[Mike JW]

Hi Martin - are you hooked on this cluster?  It happened to me visually. So much of interest. I dare not go there. I have just found a wide fov shot I did of the area with 5" Apo at f3.5 but it is not worth posting. It picked up numerous members of the cluster.

Galaxy Classification I find difficult to remember and even harder when it comes to assigning a galaxy a designation.

My understanding is: SO = a lenticular galaxy (as you say at the juncture of the tuning fork diagram). However SO according to the H. de V. diagram can mean 'impossible to tell if it has a bar'

SABb is from Hubble De Vaucouleurs Diagram. SAB = an intermediate spiral with a hint of a bar (I assume this means not clearly defined) the b means it has slightly looser arms than "a". 

I often try to take a guess at the designation of a galaxy as it appears on screen - most the time I am way off, even with the charts beside me.

Enjoyed the post.

Mike

[RobertI]

Astounding. Galaxies abound like water fleas in a pond. When I have some time I'd like to compare the map to the image in more detail.