ASTRO: UGC 11007 and a few friends

UGC 11007 is a mostly one armed spiral in Draco. It's distance is
unknown. While it shares the field with two NGC galaxies they appear
far closer leaving the mystery of UGC 11007's odd shape unanswered. It
is classed as simply as SB, no peculiar designation.

The two NGC galaxies are also interesting. NGC 6491 is classed Sab.
NED has two redshift measurements for it. The main one they prefer says
it is about 240 million light-years distant while the other says 280
million light-years. As such measurements go this isn't a major
difference at all. It is a very red spiral. I'd have suspected a bar
with the elongated core and red color (red spirals tend to be barred).
It has a blue plume of recent star formation that really stands out
against the rather bland galaxy. Was that triggered by NGC 6493?

NED has only one redshift for NGC 6493 that puts it at about 268 million
light-years, between the two for NGC 6491 but closer to the less
accepted value. Again these differences could reflect random motion
differences. It is classed SAB(r)cd. While blue it isn't as blue as
many of its type. It's arm structure is rather non symmetric. This
could be natural or possibly indicate interaction with some other galaxy
in the past. Flip a coin. In any case this is an interesting group.

There's redshift data for only one other galaxy in the field. Draw a
line from NGC 6493 through UGC 11007 and continue on a bit less than
twice that distance and go up slightly. You come to VII Zw 747
described as a "blue large knotty disc compact". It is listed at about
525 million light-years distant so definitely unrelated to the NGC galaxies.

Another galaxy caught my eye. It is nearly directly above NGC 6491, two
thirds of the way to the top of my image. It looks like a comet with a
short curving dust tail going up and to the right. In the end of the
"dust tail" is a very faint galaxy (7 o'clock from a orange star). That
faint, star-like galaxy is SDSS J175000.63+614047.9 at magnitude 21.6.
I mention it only because the far brighter and larger comet-like galaxy
isn't listed at NED at all! Yes it is a galaxy as I found it on the
POSS plates. These interesting but uncatalogued galaxies drive my brain
nuts. Why are the far fainter one listed but these odd ones are
sometimes missing? There's another comet like galaxy in the image.
This one is above and a bit left of UGC 11007 in the cropped and
enlarged image. It too isn't in NED. They don't seem to like
comet-like galaxies it would appear. Again some far fainter ones are
listed.

Arp was fond of saying that all galaxies are peculiar if you look close
enough. This field would seem to support that idea.

14" LX200R @ f/10, L=4x10' R=3x10'x3 GB=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".

Neat group Rick. A pity that they are so faint.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
.com...
UGC 11007 is a mostly one armed spiral in Draco. It's distance is
unknown. While it shares the field with two NGC galaxies they appear
far closer leaving the mystery of UGC 11007's odd shape unanswered. It
is classed as simply as SB, no peculiar designation.

The two NGC galaxies are also interesting. NGC 6491 is classed Sab.
NED has two redshift measurements for it. The main one they prefer says
it is about 240 million light-years distant while the other says 280
million light-years. As such measurements go this isn't a major
difference at all. It is a very red spiral. I'd have suspected a bar
with the elongated core and red color (red spirals tend to be barred).
It has a blue plume of recent star formation that really stands out
against the rather bland galaxy. Was that triggered by NGC 6493?

NED has only one redshift for NGC 6493 that puts it at about 268 million
light-years, between the two for NGC 6491 but closer to the less
accepted value. Again these differences could reflect random motion
differences. It is classed SAB(r)cd. While blue it isn't as blue as
many of its type. It's arm structure is rather non symmetric. This
could be natural or possibly indicate interaction with some other galaxy
in the past. Flip a coin. In any case this is an interesting group.

There's redshift data for only one other galaxy in the field. Draw a
line from NGC 6493 through UGC 11007 and continue on a bit less than
twice that distance and go up slightly. You come to VII Zw 747
described as a "blue large knotty disc compact". It is listed at about
525 million light-years distant so definitely unrelated to the NGC
galaxies.

Another galaxy caught my eye. It is nearly directly above NGC 6491, two
thirds of the way to the top of my image. It looks like a comet with a
short curving dust tail going up and to the right. In the end of the
"dust tail" is a very faint galaxy (7 o'clock from a orange star). That
faint, star-like galaxy is SDSS J175000.63+614047.9 at magnitude 21.6.
I mention it only because the far brighter and larger comet-like galaxy
isn't listed at NED at all! Yes it is a galaxy as I found it on the
POSS plates. These interesting but uncatalogued galaxies drive my brain
nuts. Why are the far fainter one listed but these odd ones are
sometimes missing? There's another comet like galaxy in the image.
This one is above and a bit left of UGC 11007 in the cropped and
enlarged image. It too isn't in NED. They don't seem to like
comet-like galaxies it would appear. Again some far fainter ones are
listed.

Arp was fond of saying that all galaxies are peculiar if you look close
enough. This field would seem to support that idea.

14" LX200R @ f/10, L=4x10' R=3x10'x3 GB=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".