Markarian’s chain is a collection of galaxies stretching from the constellation of Virgo to Coma Berenices. Its best-known galaxies lie at a distance of 50 million light years, located in the virgo cluster. Some well known galaxies in the Markarian’s chain are M86, M84, NGC 4438, NGC 4435, NGC 4477, NGC 4473 and NGC 4461. Despite some galaxies being discovered by Charles Messier, and some others by William Herschel, it was ultimately named after Benjamin Markarian, who was the first to note a physical relation in the 60’s. Galaxies in the chain span 50.000 to 130.000 lightyears in diameter, and are of various types, giving it an unique composition and look. 

Apart from hosting a ton of interesting and varying types of galaxies, Markarian’s chain also has less known features to go after - the most common one being the Ha bridge between M86 and NGC 4438 which was first noted in 2008 by KENNEY ET AL.. Apart from this, the faint yet abundant IFN in this region makes for a great challenge and interesting looking wider region… and going to the other extreme, one will find many mesmerising details in the background such as galaxy clusters and many other small galaxies. 

As part of this DSC project, the wider region was photographed, resulting in a big 3°25’ x 1°10’ mosaic composed from 2 panels. This wide field includes galaxies like M90 and M89, both of which show features rarely shown, such as M90’s Ha outflow and M89’s halo, both of which we will have a closer look at, later in this write-up.

This variety of interesting features, all with their own difficulty, made Markarian’s chain the ideal target for the Deep Sky Collective - in order to reveal the outflows in full detail as well as ensure background structures and galaxy details, our goal was primarily set on Ha and Lum data.
With the large FOV group of the DSC we started gathering data in February and imaged for about 5 months, followed by 2 months of pre- and post-processing the data. We had a total of 17 people working on the project - 1 Editor, 1 Stacker , 15 photographers and myself coordinating - in the end we managed to get a total of 461h15m of integration over two panels - the longest ever on this field. Note that 202h40m of that total is Ha and 138h05m is Lum.










Before getting into any details in the picture, I want to thank everybody who contributed to this project. As always, it was a pleasure working together with everybody!


Tim Schaeffer - @Tim Schaeffer
Carl Björk - @Palmito
Steeve Body - https://steevebody.com/

Jasper Capel - @Jasper C
Logan Carpenter - @Logan Carpenter
John Dziuba - @John Dziuba
Antoine and Dalia Grelin - www.galactic-hunter.com
Stephen Guberski - @Stephen Guberski
Akask Jain - @Meeps51
Stephan Hamel - insta: @stephan_astrophotography
Florent Herrbach - @Florent Herrbach
Jason Jacks - @jmdl101
Justin P. - @Justin P
Sophie Paulin - @ Lyaphine
Kevin Trillsam - @Kevin Trillsam
Jens Unger - @Jens Unger
Mikhail Vasilev - @Mikhail Vasilev


Special thanks to: 

• Carl, who, as always, put in a remarkable effort stacking over 4400 files and stitching most of the stacks into the final mosaic.
• Steeve, for another super impressive and well-rounded edit.
• Stephan, who gave us his excellent widefield Bortle 3 data that was used for MSGR

None if this would be possible without them!










–– Interesting features in our image ––



Ha outflow in M86  and M90  

The most eye-catching features in this field are, without a doubt, the Ha regions between M86 and NGC 4438 on the left hand side of the photo as well as the one in M90, found on the right hand side.
As mentioned in the beginning of the text, the Ha emissions, also referred to as “Ha bridge”, between M86 and NGC 4438 were discovered in 2008 by KENNEY ET AL.. What makes this region particularly fascinating is that the Ha emission physically connects the two galaxies, rather than being a mere line-of-sight coincidence from our perspective on Earth. In fact, this connection is a strong indicator of a collision between the two galaxies - in their paper, Kenney et al. hypothesise the possibility that this collision stripped cold gas from NGC 4438 which in turn was ionised/heated by “shocks, ram pressure drag, or thermal conduction, producing most of the Ha filaments.” Moreover, this research sheds light on how gravitational interactions heat the ISM (Interstellar Medium) in elliptical galaxies and how galaxy collisions within clusters lead to their transformation.
Besides this feature between M86 and NGC 4438, which has received a lot of attention in recent years in the amateur community, the DSC’s framing also includes M90, a rather rarely photographed galaxy that has similar looking Ha emissions. One key difference however is that M86’s Ha emissions are a result of  a collision with another galaxy, whereas M90 undergoes so called “Ram Pressure Stripping” - a result of its high-speed movement through the particularly dense and hot ICM in the virgo cluster. This in turn stripes gas from its disk and ionises it in the process, leaving behind the observed tail of Ha. An in-depth description of this phenomenon is given in a paper by A. Boselli et al.. 

A detailed look at both Ha regions in the DSC image is given below. Other, high resolution, professional data can be seen here.


©DSC: Close look at the Ha emission in M86 and M90




M89’s Halo

Another rarely revealed feature in our image is M89’s striking halo. When looking at many images online, only the central, bright part is visible whereas the faint outer halo is not - with our image we’re happy to provide a deep look at this halo and can make out the various layers of the shell as well as the jet that was unfortunately cut off in our framing. 
This halo was discovered by David Malin back in 1979 and was found to lie at a distance of 150,000 ly from the galaxy’s centre and is believed to be a result of gravitational interactions between galaxies in this cluster - an event commonly observed in these environments. Furthermore it should be noted that this Halo also has an X-Ray counterpart, which could be the result of interactions with the intracluster medium (ICM) or galaxy mergers. 


©DSC: Messier 89 and its halo




Background galaxies

As mentioned in the beginning of the text, this region is filled with countless foreground and background galaxies. Having a close look at our image, the immense number of galaxies can be seen, most as just red dots or as part of bigger clusters. Given the depth and wide field captured, zooming in truly is a surreal experience and we invite everyone to go check out the full-resolution version on our website!


©DSC: Close-ups of 2 regions with galaxy clusters




IFN

Finally, there is the awesome layer of IFN all over the field, giving it extra depth and range. Revealing this IFN was quite challenging given that it is super faint in this region - in the end our countless hours from dark sky locations allowed us to pull this dust from the background and complete the full image!


©DSC: Starless LRGB data, emphasising the IFN and some bigger background galaxies








For any further questions about the project, feel free to leave a reach out to us using the contact form or by leaving a comment!

If you want to see our image in greater detail, feel free to go to our gallery, where the image is uploaded in full resolution ( 11200 × 3848px), enabling you to explore the picture by yourself and being able to zoom in on every tiny detail!
Link to our gallery: https://deepskycollective.com/gallery



Integration overview

Here you find a list of integration contribution from all 17 photographers




We hope that you enjoy this image!

Text written by @Tim Schaeffer , organiser and co-ordinator of the project and fact checked & proofread by the DSC team.