ASTRO: FGC 1315 and NGC 3917

FGC 1315/UGC 06802 is a flat galaxy in Ursa Major two degrees below
Phecda, the southwestern star in the bowl of the Big Dipper. While I'm
fascinated by flat galaxies like this one, NGC 3917 is a nice flocculent
spiral, a type with many arm segments rather than the full arms of a
grand design spiral. So this was a double for me. I centered on the
flocculent spiral since it was the more photogenic of the two. By
redshift FGC 1315 is 67 million light-years distant while NGC 3917 is
closer at 53 million light-years. Both are further away by Tully Fisher
measurements, 74 and 57 million light-years respectively. Either way
they are apparently more than 10 million light-years apart so not
related, just in the same line of sight as seen from our galaxy. There
are quite a few galaxies scattered around the field. Assuming their
redshift distance is correct, FGC 1315 has a diameter of about 45,000
light-years while NGC 3917 is much larger at 75,000 light-years. Not
seen edge on so its flatness can't be determined very well, NGC 3917
appears to me to also have a very small central bulge. In fact it did
make the 2 micron flat galaxy catalog as 2MFGC 09297. This catalog has
less strict standards for flatness.

The annotated image gives the details. Only one quasar is in the image.
While a couple of very small galaxies look like short asteroid trails
they are just other, likely very distant, edge on galaxies that might
have made the Flat Galaxy Catalog if closer so their flatness could be
measured. The bulge must be no more than 1/7th the galaxies length to
make the catalog.

Lots of red galaxies can be seen in the lower right corner of my image.
They are likely members of the galaxy Cluster ABELL 1387, whose center
is out of my field of view. It is listed as having 50 to 79 galaxies in
a cluster that is 28 minutes of arc across. That's more than the height
of my image frame. It is class III which means it has no obvious center
with no condensation toward the center. It's distance is listed at
about 1.68 billion light-years which is a good fit for the redshift of
the few galaxies in the corner of my image with redshift data.

LEDA 2399182 is a very blue compact galaxy between NGC 3917 and the
ABELL cluster. Seen on the Sloan Survey image it appears it could be a
double core galaxy. Or possibly two very blue round galaxies seen
nearly atop one another. At a distance of only 67 million light-years
they are very small with the diameter of the object being only about
4,000 light-years. If two each is likely about 3,000 light-years
across. Compact indeed.

This one was taken on about the best night I had last November but winds
were running over 40 mph that night. I can work up to about 30 mph but
at 40 there's some elongation of the stars. Though oddly it isn't even
across the field with sometimes stars right near each other showing
different elongation. I am still scratching my head over how that can
be. When I get high winds seeing is usually poor. Another oddity is
that it was about average this night.

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

Rick
--
Prefix is correct. Domain is arvig dot net

Rick,

amazing how much detail you managed to get in this almost edge on galaxy and
the thin one is a nice add on.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
...

FGC 1315/UGC 06802 is a flat galaxy in Ursa Major two degrees below
Phecda, the southwestern star in the bowl of the Big Dipper. While I'm
fascinated by flat galaxies like this one, NGC 3917 is a nice flocculent
spiral, a type with many arm segments rather than the full arms of a
grand design spiral. So this was a double for me. I centered on the
flocculent spiral since it was the more photogenic of the two. By
redshift FGC 1315 is 67 million light-years distant while NGC 3917 is
closer at 53 million light-years. Both are further away by Tully Fisher
measurements, 74 and 57 million light-years respectively. Either way
they are apparently more than 10 million light-years apart so not
related, just in the same line of sight as seen from our galaxy. There
are quite a few galaxies scattered around the field. Assuming their
redshift distance is correct, FGC 1315 has a diameter of about 45,000
light-years while NGC 3917 is much larger at 75,000 light-years. Not
seen edge on so its flatness can't be determined very well, NGC 3917
appears to me to also have a very small central bulge. In fact it did
make the 2 micron flat galaxy catalog as 2MFGC 09297. This catalog has
less strict standards for flatness.

The annotated image gives the details. Only one quasar is in the image.
While a couple of very small galaxies look like short asteroid trails
they are just other, likely very distant, edge on galaxies that might
have made the Flat Galaxy Catalog if closer so their flatness could be
measured. The bulge must be no more than 1/7th the galaxies length to
make the catalog.

Lots of red galaxies can be seen in the lower right corner of my image.
They are likely members of the galaxy Cluster ABELL 1387, whose center
is out of my field of view. It is listed as having 50 to 79 galaxies in
a cluster that is 28 minutes of arc across. That's more than the height
of my image frame. It is class III which means it has no obvious center
with no condensation toward the center. It's distance is listed at
about 1.68 billion light-years which is a good fit for the redshift of
the few galaxies in the corner of my image with redshift data.

LEDA 2399182 is a very blue compact galaxy between NGC 3917 and the
ABELL cluster. Seen on the Sloan Survey image it appears it could be a
double core galaxy. Or possibly two very blue round galaxies seen
nearly atop one another. At a distance of only 67 million light-years
they are very small with the diameter of the object being only about
4,000 light-years. If two each is likely about 3,000 light-years
across. Compact indeed.

This one was taken on about the best night I had last November but winds
were running over 40 mph that night. I can work up to about 30 mph but
at 40 there's some elongation of the stars. Though oddly it isn't even
across the field with sometimes stars right near each other showing
different elongation. I am still scratching my head over how that can
be. When I get high winds seeing is usually poor. Another oddity is
that it was about average this night.

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

Rick
--
Prefix is correct. Domain is arvig dot net