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ASTRO: NGC 4754 and 4762

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Old May 17th 12, 06:22 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Default ASTRO: NGC 4754 and 4762

NGC 4762 and NGC 4754 are said to be a pair of non interacting galaxies.
NGC 4762 is a rather odd galaxy seen exactly edge on. A bright star
like core is seen with a very narrow disk oddly missing any hint of a
dust lane. This leads to it being classed as SB0? by the NGC project
and SB(r)0^0^ at NED. The disk ends with a huge warped plume off each
end. The south end curves sharply to the west but a faint plume
continues southwest and another to the southeast. Off the northeast end
of the upper plume a narrow faint plume continues to the northeast. To
have these various plumes it must have interacted with some other galaxy
in the last billion years or so. Redshift puts its distance at about 60
million light-years. Unfortunately the error bar is rather large at
this range. Tully fisher measurements show 55 million light-years while
an analysis of its globular cluster's brightness put it at 78 million
light-years. Pick one!

The companion is NGC 4754 which is also unusual as the outer oval is
oriented about 45 degrees counter clockwise from the inner oval and bar.
Again, this would seem to require an interaction with another galaxy.
NED classes it as SB(r)0-: and the NGC project says simply SB0. Its
redshift puts it at 77 million light-years which would support the non
interacting status if a true distance indicator. Analysis of its
globulars using a somewhat different process than that used for NGC 4762
puts it at 46 million-light years, Tully-Fisher measurements average 55
million light-years while an analysis of its surface brightness function
puts it at 53 million light-years. Yet another globular cluster
measurement using the same method as for NGC 4762 puts it at 60 million
light-years. Averaging these gives 55 million light-years. Again a
case of pick one.

Still these measurements for each galaxy do overlap suggesting they may
be really at about the same distance. Maybe they aren't non-interacting
after all. There aren't any obvious candidates that I could find to
cause the distortions both of these galaxies exhibit. So while not
interacting today they may have a few hundred million years ago. I
found nothing suggesting this however.

There are two asteroids in the image. The obvious one is (7027)
Toshihanda at magnitude 17.4. The naming citation reads: "Toshihiro
Handa (b. 1959) is a research associate at the Institute of Astronomy,
University of Tokyo. He works in the area of radio astronomy, studying
interstellar matter in our Galaxy and nearby galaxies. He is also
active in public outreach in astronomy and astrophysics."

The other is very hard to see. It is (157814) 1995 WU28 at magnitude
19.1. Its trail runs in front of NGC 4762 which pretty well drowns it
out. See the annotated image for finding it. I took the L images on
either side of the meridian with color frames in-between the first
luminance series were taken mostly to the east side of the meridian
while the last three were taken when it was on the west side.

Not much exciting in the annotated image except for the galaxy group
SDSSCGB 02665 on the east edge of the image. It is said to consist of 4
members at 1.6 billion light years. Two appear quite bright. I see
several other faint one in the immediate area bringing the count to 6 or
so rather than 4. Of the two bright galaxies the upper one lies within
a second of arc of the position given for the group. No redshift is
given for the galaxy itself though it may look like it in the annotated
image. That line however is pointing to the group's position. The
southern bright galaxy does have redshift data and is identified.
Several quasars lie just outside the boundaries of the image frame.
Oddly redshift data is limited to the eastern side of this image.

There are two blue smudge galaxies in the image without any redshift
distance. They could be members of the same group as the two major
galaxies. I've identified them in the annotated image. [SDV2005] 226
is listed as a dwarf elliptical while VCC 2093 is listed as a dwarf E3

14" LX200R @ f/10, L=7x10' RGB=2x10'x3, STL-11000XM, Paramount ME

Prefix is correct. Domain is arvig dot net

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