ASTRO: NGC 3675

NGC 3675 is a beautiful but rarely imaged flocculent galaxy in Ursa
Major. By redshift it is about 46 million light-years distant. Other
measurements, mostly Tully-Fisher, range from 41 to 65 million
light-years. The one claimed to be most accurate in a 2009 paper says
54 million light-years. I found little agreement beyond this. It is
classed as SA(s)b;HII LINER. I'm a bit puzzled over the HII as the only
note at NED mentioning HII said the regions were less than 2" across and
indicated they considered them a minor feature. It is tilted rather
strongly toward an edge on view. This means we see the dust lanes on
the near side much better than those of the far side. In fact the
galaxy has a large halo that further hides the far side from view. I've
applied considerable processing to this region to bring out detail
usually hidden by the halo in the few images of this galaxy I found on
the net. Even the Sloan Survey image has difficulty with detail of the
far side. The core seems to have no real bulge. It even appears
recessed as if the flocculent arms and dust lanes extend further above
and below the disk's plane than does the core. This is likely an
illusion due to my processing to bring out spiral structure right to the
very center; but one I can't seem to shake.

My reason for imaging it is the odd outer dust lane on the east side as
well as the extensive outer faint regions. Are they plumes? Most
images fail to show the outer regions with many stopping at the dust
band not even realizing it is a band rather than the edge of the galaxy
yet it is bright enough to show color rather well.

There's a really strange galaxy above NGC 3675. It is SDSS
J112622.06+434124.4. It has one arm on the east side mostly detached
from the core. There's nothing on it in the literature. I'd love to
see what Hubble's view of it would be. There are several galaxy
clusters in the image. The one due east of NGC 3675 is WHL
J112649.0+433441. The BCG is listed at 4.05 billion light-years but the
cluster with the same location has a photographically determined
redshift of 4.25 billion light-years. I consider the former more likely
the more reasonable estimate. To the west and a bit north is the 22
member group WHL J112459.4+433810. Right near the northwest end of NGC
3675 is the small 7 member group WHL J112557.7+433919. Virtually my
entire field is covered by ZwCl 1122.8+4351. It is listed as being 19
minutes across and containing 99 members. It's morphology is listed as
open which means it lacks any pronounced concentration of galaxies. Yet
another cluster is centered just off the east edge of my image. Several
of its members are in the frame so I drew a line to indicate where the
center is just a few pixels beyond the edge of the image. The cluster
is GMBCG J171.91396+43.71478. The BCG is listed at 2.5 billion
light-years with the cluster's photographic distance at 2.6. Again, the
photographic determination is usually less accurate so I went with the
2.5 figure in the image.

The vast majority of galaxies in the field had no redshift values at
NED. All that did are listed in the annotated image.

I see by the current Astronomy Magazine the term "flocculent galaxy" was
coined by Debra Meloy Elmegreen the current president of the American
Astronomical Society. I didn't realize it was such a new term.

I've also included the Sloan Survey image of this galaxy. It was the
only image I found on the net that indicated there was more to the
galaxy than all the other images I found were showing.

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

Rick
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