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Arp 215 -- A major merger without SEC approval



 
 
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Old October 28th 09, 09:03 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Default Arp 215 -- A major merger without SEC approval

Arp 215, NGC 2782, is thought to be the result of two galaxies that have
almost merged. The core is still elongated and appears double at some
wavelengths. The debris of the merger hasn't yet merged with the
resulting galaxy but likely will. It is classed as SAB(rs)a and is a
starburst galaxy. Some consider it a Seyfert 1 galaxy. Others say this
is an illusion due to the massive star formation going on in its merging
nuclei. The galaxy is about 125 million light-years distant and is found
in southwest Lynx, north of 38 Lynx.

It is peculiar enough to make Arp's catalog under his class: Galaxies
(not classifiable as E or S); adjacent loops. Not having today's
multiple wavelength data he didn't likely didn't know it was a merger
situation. He just knew there were no galaxies in the area that could
have interacted with it so it's distortion was without an obvious
explanation.

While the edge on spiral (SBb) to the southeast, UGC 4872, may seem to
be involved it is three times as far away at 380 million light-years.

As there's quite a bit of information on the background galaxies thanks
to the SDSS, I've made an annotated version showing the distance in
billions of light-years to the more distant galaxies and quasars. Note
the one west of Arp 215 at 3.9 billion light-years is the upper object.
There's a star about 3" south. The galaxy is at magnitude 21.0 in
visual (SDSS G filter) light. Limiting magnitude on the posted image is
about 22.5. It goes a bit below 23 on the Lum FITS. The image is not
as deep as I'd have liked. Transparency wasn't very good these nights
though seeing was fairly good.

Sometimes the SDSS data base in NED mystifies me. Below and a bit right
of Arp 215 are two galaxies, one at 1.3 and the other 1.9 billion
light-years. The galaxy in the middle isn't in the database. But if
you look closely just to the left of it near its northern end is a very
dim star, below 22nd magnitude. The SDSS puts at the location of the
galaxy, noting it is a star and lists its magnitude as 20.4 which is way
too bright for the star but dimmer than the anonymous galaxy. It is
noted with a question mark in the annotated image. I included it to
point out the more distant objects in the image.

There's one quasar identified in the image as well. Most of the
galaxies with red shift data are between 1.2 and 1.4 billion light-years.

SDSS image:
http://astronomerica.awardspace.com/SDSS-18/NGC2782.php

There are a few HST frames in the archive but they need so much work to
salvage and don't appear to add much to this discussion I didn't try to
salvage them.

Arp's image is one of his best. Core does appear possibly double rather
than just a short bar.
http://nedwww.ipac.caltech.edu/level...ig_arp215.jpeg

14" LX200R @ f/10, L-4x10' RGB=2x10'x3, STL-11000XM, Paramount ME

Rick
--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".

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