ASTRO: Arp 54

Arp 54 is a pair of galaxies, in Cetus 570 million light-years distant.
Arp put in his category for spirals with small, high surface
brightness, companions. The main galaxy is MCG-01-07-007 at magnitude
17.1 while the companion is 17.8 magnitude PGC 009107. To me PGC 009107
is larger compared to the main galaxy than many that Arp put into his
category for those with large companions. So is this really the galaxy
he meant? It isn't on the arm but well away from it. There is a
condensation on the end of the long arm that sort of points to PGC
009107. Is this the companion Arp meant? It better fits the
description. But Arp apparently does mean PGC 009107 as the "small"
companion as his note reads: "Arm toward companion split, contains
nodule." NED classes it as SBc with HII emissions. Some call the pair
an M51 type system due to the somewhat straightened arm leading toward
the companion.

While it is likely that PGC 009107 is a true companion I found no
distance estimates to further prove the relationship.

NED is adding data from the VLT Very Deep Survey. This field is
covered. The result is far more objects in my field being identified
than normal. I can't begin to label all the galaxies with their
distances that are in this image. That would label many hundreds of
objects making the annotated image illegible. I did pick those brighter
than 21nd magnitude in red light within 5 minutes of Arp 54. The number
would triple if I went to 22nd magnitude so I had to stop there. Beyond
5 minutes I only picked up ones that caught my eye. Wading through the
many thousand entries for this field was more than I felt like
attempting. Even with automation I'd be weeks moving labels so as not
to cover up other objects. For the beginners out there the VLT stands
for Very Large Telescope which is located on Cerro Paranal, Chile at an
elevation of 2635 meters (8645 feet). It should be VLTI as it is an
array of 4 8.2 meter telescopes plus four movable 1.8 meter telescopes
which can be combined to make very high resolution interferometric
images, far higher than Hubble can achieve. With it's 8.2 meter mirrors
it gathers over 10 times the light than the 2.5 meter mirror of the
Sloan Survey telescope (but with a much narrower field of view). This
allows it to pick up far more galaxies in a field it covers than the
Sloan Survey does. Too many in my case.

I have some qualms about this survey. Most of the galaxies are starlike
in appearance. Even the "close" ones appear to be stars rather than
galaxies. It doesn't help that during the L exposures a set screw that
has been giving me fits again came loose allowing the left side of the
image to defocus. Still I can't tell even the 16th magnitude galaxies
seen only in this survey from stars. Are they really galaxies? The
redshifts are photographically determined, not spectroscopically. This
can be rather accurate for distant galaxies but I've not seen it applied
to relatively nearby objects before. Galaxies that do show their true
nature are all from the usual catalogs, some are also from this survey
as well. But many faint fuzzies were not picked up by this survey which
bothers me. There were far too many to note but I did put questionmarks
by a few of them. Others that are quite obvious but without redshift
data were left blank. These were from plate surveys or the 2MASS IR
survey but not picked up by this new survey. So why did this deep
survey miss these obvious galaxies yet pick up so many starlike objects?
I just don't know.

I picked up two asteroids, one is known and one is not. Being the image
was taken 13 months ago as I type this there's no way to follow up on
it. By coincidence its trail ends at one of the faint fuzzies no
survey, even the very deep one, picked up so earned a question mark.

Arp's image
http://ned.ipac.caltech.edu/level5/A...big_arp54.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".