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Old December 18th 10, 10:40 PM posted to
Stefan Lilge
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Posts: 2,269
Default Astro: Arp 7 another less than spectacular galaxy


this looks quite unusual with the (foreground?) star in it. Even though you
didn't get the same detail as on higher objects it is still well resolved.


"Rick Johnson" schrieb im Newsbeitrag
Arp 7, MCG -03-23-009, falls under Arp's category: Spiral Galaxy: Split
arm. It is classed at NED as SB(rs)bc: and has a red shift distance of
265 million light-years. A Tully-Fisher measurement says 19 million
light-years. Now that's a discrepancy! One of these must have been
made by that famous Chinese astronomer Sum Ting Wong. The red shift
measurement seems far more reasonable to me. It is in both the 2MASX
and IRAS catalogs of IR sources so is a strong IR emitting galaxy.

There's a small distorted galaxy just 1.3 minutes south and a bit east
of it. There is no distance measurements of it. It is in the 2MASX
catalog so is a IR strong galaxy. It's also NPM1G -16.0258. 5 minutes
north west is the spiral 2MASX J08500148-1632260, yet another IR rich
galaxy. It has virtually the same red shift as Arp 7. It is likely in
the same group with Arp 7. The similar red shift would support the
redshift distance as being reasonable compared to the Tully-Fisher
determined distance.

Most consider the blue object on the end of one arm a companion galaxy
and call it an M51 type pair. If so NED doesn't list the blue object.
It appears starlike in my fuzzy image. Arp's image does show it
slightly out of round compared to similar brightness stars so this could
be the case.

There's little information on the rest of the field. Only 8 other
galaxies in the field are listed in NED, none with magnitude or distance
data. All members of the 2MASX catalog.

This Arp is below my -15 degree south limit. I tried anyway. The
result is the L images are severely distorted by atmospheric refraction
which, like a prism spread the colors along a line. While I could sort
of compensate when stacking the color data it didn't help the resolution
of the image or the star shapes. I tried some motion blur tools but in
my hands they just made things worse. Some nights I can get away with
going this low, not this night. The diffraction spread pretty well
wiped out the fine detail needed to see the split arm Arp refers to. It
is easily seen in his image however. Arp had no comment on this object.

This was my last January image. Now moving to February objects.
Unfortunately it is another small hard to image galaxy. I have some
spectacular ones coming however. Not before some less than spectacular
ones. At least they are ones you likely have never seen before.

Arp's image:

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

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