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NGC 3628 and Quasars., 



NGC 3628 and Quasars.


Imaging Telescopes Or Lenses
Orion Optics UK DX 250
Imaging Cameras
Starlight Xpress H9C
Vixen GPDX w/ SS2K
PHD · Astroart 3 · NEAT · PixInsight
Guiding Cameras
KWIQ Guider

Acquisition details

Feb. 20, 2010
50×120(1h 40′)
1h 40′
Avg. Moon age:
5.87 days
Avg. Moon phase:

Resolution: 516x412

File size: 46.8 KB

Locations: Home, Weymouth, Dorset, UK, United Kingdom

Data source: Backyard


I recently remarked to a friend that amateurs may be able to image the quasar excess around NGC 3628. We had a good night on Friday and I thought I'd have a go at imaging some of these faint quasars. Most quasars are around mag 19 or less so I was not too hopeful.

I set up my equipment and made doubly sure that the camera was in best focus and that it was dead square to the drawtube. I located NGC 3628 and got PHD up and running, re-centrering the galaxy after calibration. NGC 3628 was reasonably high in the SE and would be rising a little higher, the sky was quite dark and I set up Astroart to acquire 50 x 2minute exposures. Guiding looked good, the images looked sharp and the background was dropping.

Of course it was never going to stay that perfect and the session was disturbed by patchy high level cloud. I lost about 5 of my exposures but still got around 90 minutes of good exposures.

Next day I processed up the exposures and was pleasantly surprised to find that I had captured some of the faint quasars that Halton Arp considers to have been ejected from the centre of NGC 3628. NGC 3628 (z=0.0028) is a nearby, edge-on Sbc peculiar galaxy which is undergoing major internal dynamic activity that is, however, shrouded from our view by a prominent dust lane.

A prominent feature of NGC 3628 is the long HI plumes being outgassed from the galaxy in two directions. The major plume to the ENE is a long, straight optical jet not visible in my image, it is probably just off the left of the image. The weaker X-ray plume runs towards the south along the minor axis of the galaxy, which is weakly seen in my image. The usual explanation for the plume morphology is that it is due to a tidal encounter between NGC 3628 and the nearby similar-sized spiral NGC 3627. The object in the weaker plume nearest the main galaxy is nebulous, shaped like a comet with a blue condensation (F1) at its head. Next along the filament to the SW are stellar-like objects, one quite red and one quite blue. The blue one (F2) is a z=0.995 X-ray quasar. Further along is a small, double, irregular galaxy or knot (F3) and then a larger, elongated and curved galaxy shape (F4). It has a narrow emission line spectrum of redshift z=0.153. Finally we encounter the z=2.15 quasar (F5) which is at the end of the X-ray filament.

Arp considers the fact that these optical objects, including 2 quasars of very different z, lie along the plane of the X-ray filament to be suggestive that the quasars have been ejected from the centre of ngc 3628. He suggests that z relates partly to the age of the quasar and partly to cosmological distance.

As an aside it is interesting to consider that a redshift of z = 2.15 corresponds to seeing the object the way it was 10.6 billion years ago. At these huge distance, a light-travel time of 10.6 billion years doesn't imply a distance of 10.6 billion light-years, because the Universe has expanded significantly since the light left the quasar. In fact this light-travel time corresponds to a distance of 18.1 billion light-years. What this implies about the size of the universe I'm afraid I've no idea!

Both quasars F2 and F5 are aroud magnitude 19.5. In fact you need a bit of imagination to see them in my images but you can definitely see that there is a chain of objects extending away from ngc 3628 along the plume. The point is, are the quasars connected to NGC 3628, or is this just a chace alignment?

Well, that's it. I may go back and get more data but probably not this year.

Most of the technical information is from : ... 1..833AFUL



  • Final
    NGC 3628 and Quasars., 


  • NGC 3628 and Quasars., 


  • NGC 3628 and Quasars., 


  • NGC 3628 and Quasars., 




NGC 3628 and Quasars.,