Object of the Week March 31, 2013 - M87 and the DRAGN within

M87 - Galaxy

Virgo

12 30 49.7
12 23 24

Mag: 8.3

M87? Really? Yes really!

This weeks OOTW isn’t just about M87 itself. It is about a little known group of objects that M87 represents. Deep within M87 lays an object that is still quite mysterious to astronomers. A true monster if you will.

M87 harbors a DRAGN or a Double Radio Source Associated with a Galactic Nucleus. Much is still being learned about DRAGNs such as what exactly constitutes one, how many are there and how they are formed. There does seem to be a few criteria that are required for a DRAGN to be recognized, such as:

• DRAGNs are exclusively associated with elliptical galaxies.
• Most are associated with extremely large black holes some of which are on the order of millions of solar masses.
• DRAGNs will always have 2 opposing lobes as well as 2 opposing jets. The lobes will contain no more than "2 hotspots" (see image below)

Interestingly these jets, such as those in the quasar 3c405 (Cygnus A), are believed to be traveling at large percentages the speed of light! One more tidbit, DRAGNs can vary in size from the smallest being approximately 30 light years across to the largest being true behemoths at over 6 million lys across, vastly larger than its host galaxy!

Unfortunately, the lobes and jets that comprise a DRAGN are typically invisible to us visual observers. After all, they are radio sources and lie deep withing giant ellipticals. But I bring to you this list more for the mental gymnastics that is associated with such an exotic object. As you observe the DRAGN catalog, know that you’re looking at objects that are true monsters! The radio images here are breathtaking, especially the stacked images that have both radio and optical imagery superimposed on each other. They give a good representation of just how large these objects are relative to their host galaxy!

The list of known DRAGNs contain 85 different objects, 55 of which are dimmer than 16^th magnitude. Save those for the most ideal of conditions! ;) 15 objects on the list are in the 13 – 16^th magnitude range and the remaining 15 objects are brighter than 13^th mag. Of this last group, several are well known. M84, NGC 383, NGC 1275 and NGC 6166 are all DRAGNs. But the title for “Most Famous DRAGN” has to be given to M87.

M87 is a type E+0-1 pec galaxy in Virgo. The jet of M87, which has been a deep sky challenge for as long as I can remember and is practically on every challenge list you receive at spring starparties, is typically reserved for the best of conditions. Little did I know the night I first observed the jet that it was only one half of a DRAGN. And if the jet wasn’t enough to challenge your skills and equipment, M87 holds even more challenges. UGC 7652, a 16.4 mag glow and 16.0^th magnitude MAC 1230+1221 both of which are background galaxies seen through the halo of M87. (UGC7652 lies in between M87 and the MAC) Which have you seen? Here’s a tip to remember, don’t make the mistake I did the first time thinking the UGC is the jet. It’s not!

The list of DRAGNs and their host galaxies will make a good novelty challenge for any observer. Some are relatively bright at 9^th mag. Others will be impossible at 20+! But for the ones we can see, it is just really incredible to know that something truly unique is going on in the cores of these galaxies.

So download the list here and add them to your list of targets. Some objects will be old friends and others may be new.

Attachment 543
(HST jet image)
Attachment 544

Attachment 545
Typical DRAGN


And as always:

“Give it a go and let us know!
Good luck and great viewing!”

Thanks Dragan for the DRAGN :)

Interesting physics behind these jets. Seems like a nice observing program for giant telescopes or radio amateurs.

My experience with the jet and the galaxies around M87 are:
16" - despite several tries a could only see the jet one time under nearly perfect conditions, the jet itself was no thin elongated detail but more like a knot out of the core of M87; both galaxies could be hold with averted vision
27" - both galaxies were easy to detect; under good seeing the jet could be seen as a small elongated low contrast detail, not difficult, but not elongated and thin than expected; with very good seeing the jet show more contrast against the halo and becomes longer and thinner, in good moments I could detect stellar peaks within the jet

27", 586x, NELM 7m+, Seeing II
Attachment 547

Dragan,

very good object. That's about as close as one get's to observing a black hole. Do you know whether the counterjet had been imaged in visible wavelengths?

I have tried to observe the jet several times, but most times not successful. It probably depends mostly on the seeing. Two observations were successful. These are the notes during the first successful one (with 22"):

Increasing the power to 400x, the jet was relatively easy to discern as a short and thin appendix to the core of the galaxy. The length was only 20", in agreement with the literature. During a prior observation of Saturn at the same power, I had tried to memorize this dimension in order to get an estimate of what to expect. As to be expected, structures within the jet were not visible with my Dob. Using the small background galaxies (the small PGC galaxies, not the much brighter and larger NGC galaxies!), I could further verify the correct orientation of the observed structure. These faint galaxies can be helpful under less than optimal conditions and borderline observations.

You are right, you have to be aware about the apparent size of the jet structure, othwerwise the two non-NGC galaxies may be mistaken for the jet.

I will share with the forum a strange and puzzling observation that I have noted about the jet in M87.

When I have guest over at my observatory I ask them what they would like to see in my 48" reflector. most people ask to see the famous jet in M87 if it is up. About four years ago I noted something unusual about the jet. What I was seeing was very strange to me. What I was seeing was on some nights of excellent seeing and transparency the jet was hard to see and on other nights with bad seeing and transparency the jet was really easy to see. This was really confusing to me and made no sense at all. I decided that I would start a log and keep notes on the jet over a long period. The next two years I looked at M87 and the jet ever night that I observed if it was up. I quit taking notes after two years and I confirmed that what I had noted was true that on some night of bad conditions the jet was easy to see and on some nights of good to excellent conditions that it was barely there. I have shared my observations with several professorial astronomers and they have no clue as to why I am seeing this variability visually in the jet.

So from my experience if you are trying to see the jet in M87 keep at it. For no reason that I have been able to determined that it is much easer to see on some nights than others and the sky conditions have little to do with it. I hope one day to find out why the jet is so variable visually.

Quote:

---

Originally Posted by reiner

Dragan,

very good object. That's about as close as one get's to observing a black hole. Do you know whether the counterjet had been imaged in visible wavelengths?

---

Thanks Reiner!

No, I can't say I've ever heard of the counterjet being observed nor imaged visually. Personally I'd have to think its an impossibility as it would lay, in theory, on the other side of the core.

I did hunt around the internet for a radio image depicting both jets but I did not find one. To be quite honest, some of that radio stuff boggles me and I'm not really all that certain what it is I'm looking at sometimes! :idontknow:

But maybe someone here on DSF with more knowledge than me may know of such an image.

Quote:

---

Originally Posted by Jimi Lowrey

I will share with the forum a strange and puzzling observation that I have noted about the jet in M87.

When I have guest over at my observatory I ask them what they would like to see in my 48" reflector. most people ask to see the famous jet in M87 if it is up. About four years ago I noted something unusual about the jet. What I was seeing was very strange to me. What I was seeing was on some nights of excellent seeing and transparency the jet was hard to see and on other nights with bad seeing and transparency the jet was really easy to see. This was really confusing to me and made no sense at all. I decided that I would start a log and keep notes on the jet over a long period. The next two years I looked at M87 and the jet ever night that I observed if it was up. I quit taking notes after two years and I confirmed that what I had noted was true that on some night of bad conditions the jet was easy to see and on some nights of good to excellent conditions that it was barely there. I have shared my observations with several professorial astronomers and they have no clue as to why I am seeing this variability visually in the jet.

So from my experience if you are trying to see the jet in M87 keep at it. For no reason that I have been able to determined that it is much easer to see on some nights than others and the sky conditions have little to do with it. I hope one day to find out why the jet is so variable visually.

---

Jimi,

I looked through my notes. The night I first observed the M87 jet in Barbarella back in '09 I labelled seeing as 5/10 and transparency as 7/10.

Now here's an interesting note. Last March with Mark and John, we observed the jet again and that night I had both seeing and transparency estimated as 5/10 with seeing varying all night.

The very next object we observed that night was the Catseye, NGC6543 in Draco. My notes are as follows:

Seeing is awful! Green glow with a central star visible. No detail in nebula

Go figure :thinking:

I had a nice view of M87's jet last April from Likely Place California with my 28 inch, which to date is the best view I've had in my own scope. I had my lifetime view several years ago through the Bok 90 inch scope at Kitt Peak which, as you might expect, was tremendously wonderful - the jet was an exceedingly thin spike with several condensations along its length. Through my scope last April the jet was observed in average seeing but otherwise good conditions - transparent, calm, 21.68 SQM skies. I used 695x for the best view and although the jet appeared fairly stubby it was readily visible. My thought at the time was that I was seeing the two brightest condensations in the jet rather than the jet itself but the view was spellbinding even so - any visual manifestation of a super massive black hole is pretty awesome!

Attachment 548

I've failed to see the jet at least a hundred times over the years and I've always thought the reason was poor seeing because, well, the seeing was poor. I did have success once with my old 20 inch under better than normal seeing / darkness / transparency conditions but even so it was a tough observation. I haven't had the pleasure of viewing M87 under steady seeing conditions so I can't add anything to Jimi's dilemma, but that is a head scratcher.

I spent one hour with M87 last night. The conditions were fairly good expect of seeing, SQM 21.6 mag/arcsec and NELM 6.8. I was able to see UGC 7652 and MAC galaxy on the SW side with a 18" dobson. Also several "dots" were inside the M87 halo but the jet was invisible. Seeing wasn't good and M87 core warped to different shapes @ 457x. I have to try again tonight.

Iiro,

Be sure to look right in the core of M87 from my experience showing it to lots of different people some look to far out in the halo of M87 Howard's drawing above is a great and very realistic drawing of the jet as it appears in the eyepiece.

Here was another great night and sky conditions were little bit better than night before. SQM reached 21.70 and NELM 6.9. Now I spent over an hour with M87 and was able to see something in the right place several times. The jet wasn't sharp because of seeing (?) but there was clearly somekind of overhang pointing to NW from the core. It was visible only occasionally. 5 mm Baader Hyperion gave the best views @ 457x. The jet is very close the core like Jimi said above. Two small galaxies on the SW side were much easier than the jet.

Have you noticed somekind of granularity or extremely faint stars inside the halo with bigger telescopes? I seem to see something with averted vision but couldn't be sure.

http://deepsky.arkku.net/Sketches/messier87_jet.gif
Messier 87, 4.4.2013 00:50, 18" newton, 457x, 9', SQM 21.7, NELM 6.9

That's it Iiro! M87 does have lots of lots of globulars and there are also background galaxies in the area so you were probably starting to see them. They're very faint though - in the 18th magnitude range - so they may be out of reach for all but the very largest scopes.

On Monday night I was able to see the jet in my 20" at 427x. I only saw it as two drops in the surface brightness of the surrounding glow of the galaxy itself, one on either side of the jet. I'll try again on a night with better seeing so I can magnify more.

Came across this bit of information on Galaxyzoo. Apparently, the old school thought that DRAGNs are only associated with elliptical galaxies may be wrong. Many spiral galaxy DRAGNs, or SDRAGN's candidates have been discovered and more research is being done. Only time will tell but I found it interesting.

Have a look here https://blog.galaxyzoo.org/2016/12/2...e-be-s-dragns/