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ASTRO: UGC 4261 Merging Galaxies



 
 
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Old August 5th 14, 02:40 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Default ASTRO: UGC 4261 Merging Galaxies

Sloan gives it two designations SDSS J081056.60+364942.6 and SDSS
J081056.19+364941.3 besides one matching the position of UGC 4261 in the
UGC catalog, SDSS J081056.11+364945.4. Oddly NED doesn't consider any
as "Part of Galaxy" which I find odd. It is obviously two interacting
galaxies.

UGC 4261 is a mess in southern Lynx about 300 million light-years away.
It consists of three rather bright blobs with plumes and loops
indicating this is a merger in progress. One paper from 1994
http://adsabs.harvard.edu/cgi-bin/bi...6A...291...57R says
it is likely forming a ring galaxy through a merger. I'd put it on the
to-do list for a couple hundred million years from now but I doubt that
would be productive.

The Sloan survey gives it three different positions. One is for the
center of the blob, a bit east of the three bright parts. The another
is the lower of the three bright parts while the NED position for UGC
4261 is the middle blob of the three. Only the center blob has a
spectral redshift measurement that I find. (Since I wrote this a Friend
of a Friend redshift for the lower blue blob has been added to NED
giving it an insignificantly less redshift.) The third Sloan position
is the upper bright blob. The Sloan image shows the middle blob much
redder than the blue upper and lower blobs. My color data without IR
and UV that Sloan includes mapped to visual colors shows the middle one
slightly red with the other two slightly blue but the difference is
small. I barely see it with my old eyes. With three blobs could it be
three merging galaxies? I've not seen that suggested. If you look at
the high resolution Sloan image the lower blob is made up of several
smaller, overlapping blobs. Unfortunately, this one isn't in the Hubble
Legacy Archive. I'd love to see what the HST shows for this one! I've
included the Sloan image at 0.198" per pixel which shows the main
eastern loop and the western "jet" to be made up of individual star
clouds or star clusters. I think it likely that the western "jet" is
really a loop like the eastern one just seen edge on. Purely my
speculation of course. Note there is a faint fuzzy round plume at the
end of this southwestern "jet". I needed more time to bring it out than
the skies allowed. Though I hadn't realized it was there or would have
tried harder to find more time.

There are no other galaxies in the image at 300 million light-years
which would make even a two galaxy merger seem unlikely in such an
uncrowded part of the sky. There are four galaxies with a redshift
putting them about 415 million light-years away. Due to rounding they
are listed at 0.41 and 0.42 billion light-years though they are in
closer agreement than that indicates. There are many galaxies without
redshift data in the image. Two appear to be an interacting pair in the
southwestern corner of the image and are labeled but show "na" for a
redshift look back time as that wasn't available. Another is seen
through the edge on disk of a galaxy with redshift data. I doubt they
are related but annotated the little guy anyway.

Above UGC 4261, half way to the top of the frame is an area that appears
to be a scattered galaxy cluster. NED lists these points as galaxies
but without redshift data but for one a bit off the eastern (left) end
which has a look back time of 4.93 billion years. Is this a cluster and
is this galaxy a member? NED shows now cluster in the area but for one
I have marked well to the east with 9 members, 4 of which are in a tight
triangle shaped area with a photographically determined look back time
of 4.31 billion years.

Two rather bright asteroids appear in the image as well. Since the
color data was taken a different night the color trails they'd normally
leave at this brightness aren't seen. Details are on the annotated image.

When I went to make the annotated image I found something I've never
seen at NED. Several dozen stars with redshifts that of a quasar.
Obviously that can't be. NED lists them two different ways. Some as
just stars as I mention which they go on to show as either Candidate
QSOs or Rejected Candidate QSOs. If rejected there's a problem with the
redshift. In ALL cases the redshift was photographically determined.
This is usually reliable but if something between us and the star is
absorbing certain frequencies it could mislead this type of
determination. Is that happening here? I find nothing on it. The
others are listed both as stars and as UvS for Ultraviolet Source as
found by the Galex satellite. All of these are shown also as Candidate
QSOs much as UvES objects I've annotated before though those were listed
first as UvES then as stars while these are stars first. I suppose this
means NED is a bit doubtful about them being QSOs. Again I find nothing
to support my guess. In any case none of the UvS objects were "Rejected
Candidate QSOs". I listed some of the non UvS candidates before running
into the first of several rejected ones. There were so many and I was
getting a bit leery of them being real QSOs that I stopped annotating
them. I did annotate all UvS Candidate QSOs however listing them simply
as UvS as the full designation would have made the annotation messier.
The "p" after the look back time indicates it and the following z value
were photographically determined. I only listed one rejected QSO
candidate, the first I found. It is hiding right by a field star that
is apparently brighter making it had to see so I drew a line to it.

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Rick
--
Prefix is correct. Domain is arvig dot net

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