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Re: [APML] OT: Abell 2151
Hi Tony,
This image is really amazing. The first thing caught my eyes indeed
is not the jet nor the arcs, but the very faint dots in your image.
Right below the arcs and jet, close the the edge of the image, I see
an over-density of faint dots. They may be part of a galaxy cluster
at a higher redshift. Indeed, it was these faint dots >10 years ago
leading to the Hubble Deep Field. Astronomers saw them in first
generation deep CCD images and realized that there may be much much
more distant galaxies than we thought in the 80s.
My research is on high-redshift galaxies (those faint dots) using
large telescopes. I saw many of them on our images. But this is my
first time seeing them on an image taken by amateur. (Well, should
I call you an amateur?) Your image certainly closes the gap between
research and amateur astronomers.
Now, on the "jet". It's not a lensed galaxy, for sure. But I would
call it a "jet-like" structure, rather than a jet. A physical jet,
like the one from M87, is collimated high-speed mass flow. To call
it a jet, we need to measure its speed. It doesn't seem too well
collimated, either. One thing that may support a jet is its radio
brightness. Jets from giant galaxies are usually very bright in
radio, like the M87 jet. In a radio image of IC 1182, I do see some
radio emission corresponding to the jet-like structure. On the other
hand, a twisted galaxy could be also bright in radio. So, we still
don't have a definite evidence for a jet. A best way to answer this
is spectroscopy, to see if the sepctrum of the "jet" looks like a
normal galaxy or like the M87 jet.
On the arcs, they are better candidates for lensed background galaxies.
They really looks like lensed arcs in many other clusters. However,
they look like tidal features, too. Look at these two images:
http://zebu.uoregon.edu/~js/lectures/cannibalism/cannibalism_5.html
http://www.pha.jhu.edu/~ericpeng/bluearc/
The second one is the famous NGC 5128. (N5128 has giant radio jets
but not optical jets.) These shells or arcs are not uncommon for
elliptical galaxies. They came from some galaxy-galaxy interaction
long time ago. If IC 1182 is undergoing some interaction with
the "jet-like" galaxy, it will be not surprising at all to see bright
shells and arcs around it. The best way to see if they are lensed
arcs is, again, spectroscopy. The spectra will tell us if the arcs
are some background objects at higher redshifts, or actually part of
IC 1182. A color image will also help. If they are part of IC 1182,
they should have colors similar to IC 1182.
Some astronomers should work on answering these questions. Your image
is an excellent example showing how an "amateur" iamge can challenge
research astronomers. (I am still wondering if I should call it
amateur.)
Cheers,
Wei-Hao
______________________________________________________________________
Wei-Hao Wang :)
Institute for Astronomy at University of Hawaii
Address: Phone: 808-956-9867
2680 Woodlawn Drive Personal Website:
Honolulu, HI 96822 http://www.ifa.hawaii.edu/~wang
______________________________________________________________________
On Sat, 12 Jun 2004, Tony Hallas wrote:
> Hi Wei-Hao,
>
> Holy Cow ... that's more work than making this image !!! : - )
>
> Take a look at the newer version and you can clearly see that it is a
> jet ... but what's really fascinating are the "arcs" going towards the
> bottom right of the image and the appearence that part of the galaxy where
> they came from is "missing" some galaxy ... that's pretty wild. This detail
> is very, very, very faint ... only a long CCD image under dark skies will
> bring it up... and even then, it's just above the noise threshold.
>
> Tony
>
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