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ASTRO: NGC 4522 A galaxy that is literally being blown away



 
 
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Old November 5th 13, 09:04 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Default ASTRO: NGC 4522 A galaxy that is literally being blown away

NGC 4522 is a near edge on spiral in the Virgo Cluster. It resides in
the constellation of Virgo as well (not all the cluster does) and is
thought to be about 60 million light-years distant. Though its redshift
would put it about twice that distance. This difference indicates it is
really moving rapidly through the Virgo Cluster. So fast that its dust
and gas is being stripped from it. Some of this is visible in my image.
Note the upper right side of the galaxy appears missing. IR images
show it is there but hidden by dust and gas being blown up and to the
right. Some faint star clouds are visible rising above the disk area
that are made up of new stars formed in this dust as it is compressed by
the ram pressure of its high speed run through the cluster's
intergalactic medium. You can read all about it and see the HST image
of the galaxy at: http://www.spacetelescope.org/images/heic0911b/ .

What they don't mention is that it appears to have a double core. Even
the HST image which resolves its stars shows an apparent double core. I
suppose that could be due to dust obscuring the central part of the core
giving the illusion it is double. There certainly is a lot of gas and
dust in that area. I found nothing on this however.

NED classifies the galaxy as SB(s)cd: sp HII. The NGC Project says
simply, Sc. In any case it is a quite interesting galaxy. Including
the full extent of the faint stars off each end of the galaxy it is some
81,000 light-years in diameter. Using the portion that shows in the
JPEG image it is about 62,000 light-years in diameter assuming the 60
million light-year distance.

It has several companions in my image, IC 3715 an irregular dwarf to its
east and UGCA 284 to the west, an elliptical galaxy. Then there's VCC
1496 a Dwarf E5 galaxy of low surface brightness to the southwest and
VCC 1579 a bright S0 galaxy in the lower left corner. Several others
are just outside my field.

There's a very tight pair of red galaxies to the upper right of NGC
4522; [WLH2009] 0550. It has two cores apparently in the same galactic
halo. One has a redshift that puts it 1.37 billion light-years distant
while the other as a "predicted" distance of also 1.37 billion
light-years. This would seem to indicate these are two interacting
galaxies or they are far enough apart they aren't interacting but are
just along the same sight line giving that illusion. I see no tidal
plumes to indicate interaction.

Well to the west of NGC 4522 and a bit south is the galaxy SDSS
J123253.04+090703.0. It has a bright, near starlike core with two faint
extensions on either side that are somewhat warped and get fatter as
their distance from the core increases. Are the tidal plumes? I could
find virtually nothing on this galaxy unfortunately, not even a redshift.

Below NGC 4522 and a bit west is a rather nice galaxy cluster made up of
both blue and gold members. I found it in two catalogs, one listing 19
members and an estimated distance of 3.43 billion light-years (NSCS
J123335+090311) and another listing 15 members and a photographic
redshift putting it 2.87 billion light-years away (WHL
J123334.9+090304). Which is the more accurate I don't know. Though
I've found the WHL entries usually more reliable.

Then there's a galaxy group (GG) of 4 or 6 galaxies to the southeast of
NGC 4522. 5 members have a redshift measurement of which three say 1.18
billion light-years, another 1.16 billion light-years and oddly the one
marked as the Bright Cluster Galaxy at 1.56 billion light-years. Though
its distance was a guess based on the Friend of a Friend method. I
don't pretend to understand this concept which is quite confusing to me
considering its distance estimate is very different from the others,
including another FoF estimate. I've drawn a line to where the galaxy
group I've listed puts its center though that position is +/- 15 seconds
of arc. Oddly its distance is greater than 4 of the members with an
estimate though well below that of the BCG.

It appears to me that there are more faint fuzzy galaxies in the image
than there are field stars from our galaxy. Though seeing wasn't all
that great so that might fuzz some of the stars into galaxy like fuzz balls.

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

Rick
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