ASTRO: NGC 4108 A triple galaxy group

NGC 4108 is a triple galaxy system in Draco about 120 million
light-years distant. It actually is a group of 4 galaxies, one is not
an NGC galaxy so doesn't carry the NGC 4108 catalog entry. There's a
faint indication the NGC 4108 triplet have interacted in the past. It
was NGC 4108B that attracted my interest to the group. It appears to be
a face on spiral, classed SAB(s)d pec?, that has a disrupted arm
structure and a dust lane right across its core. That makes it look
like two half spirals that are merging. Even the core is quite blue
indicating star formation has been recent and plentiful in recent times.
The CGCG says of it: "Blue post-eruptive disrupted spiral with compact
knots and bars."

NGC 4108 lies below it and shows distorted arms apparently pulled toward
NGC 4108B. Also a note at NED says "NGC 4108 and NGC 4108B appear
joined by an H I bridge [Fig. 13(c)]; however, as the size of the bridge
is only on the order of a beam width, most of it could be due to beam
smearing." It is classed as (R')SAc.

NGC 4108A lies west of the other two. It is classed as SBbc:. The arm
structure seems rather weak and certainly not symmetrical. It is
apparently more disturbed when seen at radio frequencies. A note at NED
says: "NGC 4108A has a highly warped H I disk [Fig. 13(d)], with the
major axes of the outer parts of the H I disk being nisaligned (sic) by
~45^deg^ with respect to the optical major axis. The velocity field is
peculiar in that at the southern tip the axis of rotation curves in the
opposite direction one would expect from the warp in the H I disk."

The fourth member of the group, UGCA 272 is listed as E0/S0. It appears
rather featureless and nearly white in color but does have an active
core since it is listed as having a narrow line active galactic nucleus
(NLAGN). Something has stirred up its core to high activity that is
mostly hidden from our direct view.

The image contains quite a few quasars and quasar candidates (UvES), 11
of them. Most only have a photographically determined redshift (noted
by a "p" after the distance) which isn't as accurate as a spectroscopic
redshift. You'll see "pred" after the distance to one galaxy. That is
a predicted redshift whatever that means.

NED shows three galaxy clusters in the image. One that is barely
visible a bit northwest of NGC 4108A. More obvious is the pair to the
west of NGC 4108. Though I'm not sure it if it is one cluster with two
designations or two separate ones at virtually the same distance. There
are two bright, large galaxies though only the southern one is listed as
being a Bright Cluster Galaxy even though both are listed at the same
coordinates as the cluster they anchor. In any case there are quite a
few galaxies at their distance (about 1.5 billion light-years) not only
around the two big galaxies but across the image but for the lower left
corner region. No size was given for either cluster, only a count of 14
and 13 members.

As usual for this year clouds and haze really did a number on the depth
of this image. It is a good 1.5 magnitudes short of my normal limit.
It didn't help that I forgot to turn on temperature compensation and a
warm front went through as the image was being taken. Even focusing
every filter change wasn't enough to keep up with the rising temperature
which kept defocusing the image, especially at the corners. Corners
suffer most when temperature rises, core looses if it falls and isn't
compensated for. Between the two issues this one needs revisiting.
Also, one of the two red frames is very weak. While I'm listing it as
using 2 red frames the result is really very close to only one being used.

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

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

Great image Rick.
I just "upgraded" the status of this group in my observing list, so far it
had the lowest priority.
NGC 4108B is interesting indeed, it could be called the "heart galaxy",
complementing the "heart nebula".

Stefan

"Rick Johnson" schrieb im Newsbeitrag
.com...

NGC 4108 is a triple galaxy system in Draco about 120 million
light-years distant. It actually is a group of 4 galaxies, one is not
an NGC galaxy so doesn't carry the NGC 4108 catalog entry. There's a
faint indication the NGC 4108 triplet have interacted in the past. It
was NGC 4108B that attracted my interest to the group. It appears to be
a face on spiral, classed SAB(s)d pec?, that has a disrupted arm
structure and a dust lane right across its core. That makes it look
like two half spirals that are merging. Even the core is quite blue
indicating star formation has been recent and plentiful in recent times.
The CGCG says of it: "Blue post-eruptive disrupted spiral with compact
knots and bars."

NGC 4108 lies below it and shows distorted arms apparently pulled toward
NGC 4108B. Also a note at NED says "NGC 4108 and NGC 4108B appear
joined by an H I bridge [Fig. 13(c)]; however, as the size of the bridge
is only on the order of a beam width, most of it could be due to beam
smearing." It is classed as (R')SAc.

NGC 4108A lies west of the other two. It is classed as SBbc:. The arm
structure seems rather weak and certainly not symmetrical. It is
apparently more disturbed when seen at radio frequencies. A note at NED
says: "NGC 4108A has a highly warped H I disk [Fig. 13(d)], with the
major axes of the outer parts of the H I disk being nisaligned (sic) by
~45^deg^ with respect to the optical major axis. The velocity field is
peculiar in that at the southern tip the axis of rotation curves in the
opposite direction one would expect from the warp in the H I disk."

The fourth member of the group, UGCA 272 is listed as E0/S0. It appears
rather featureless and nearly white in color but does have an active
core since it is listed as having a narrow line active galactic nucleus
(NLAGN). Something has stirred up its core to high activity that is
mostly hidden from our direct view.

The image contains quite a few quasars and quasar candidates (UvES), 11
of them. Most only have a photographically determined redshift (noted
by a "p" after the distance) which isn't as accurate as a spectroscopic
redshift. You'll see "pred" after the distance to one galaxy. That is
a predicted redshift whatever that means.

NED shows three galaxy clusters in the image. One that is barely
visible a bit northwest of NGC 4108A. More obvious is the pair to the
west of NGC 4108. Though I'm not sure it if it is one cluster with two
designations or two separate ones at virtually the same distance. There
are two bright, large galaxies though only the southern one is listed as
being a Bright Cluster Galaxy even though both are listed at the same
coordinates as the cluster they anchor. In any case there are quite a
few galaxies at their distance (about 1.5 billion light-years) not only
around the two big galaxies but across the image but for the lower left
corner region. No size was given for either cluster, only a count of 14
and 13 members.

As usual for this year clouds and haze really did a number on the depth
of this image. It is a good 1.5 magnitudes short of my normal limit.
It didn't help that I forgot to turn on temperature compensation and a
warm front went through as the image was being taken. Even focusing
every filter change wasn't enough to keep up with the rising temperature
which kept defocusing the image, especially at the corners. Corners
suffer most when temperature rises, core looses if it falls and isn't
compensated for. Between the two issues this one needs revisiting.
Also, one of the two red frames is very weak. While I'm listing it as
using 2 red frames the result is really very close to only one being used.

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

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

The dust lane where it doesn't below is strange. Polar dust ring
galaxy? I don't know if that is dust obstructing the view or there are
just no stars there. Either way it is very strange. The arm structure
is chaotic as well. 40 years ago while snorkeling on a coral reef I saw
two narrow armed sea stars battling. The looked something like the
galaxy with their arms all skewed trying to get at each other. They
seemed to want the same scrap of food. It was a slow motion battle and
I didn't have time to stick around to see how it turned out.

Rick

On 10/19/2013 2:21 PM, Stefan Lilge wrote:
Great image Rick.
I just "upgraded" the status of this group in my observing list, so far
it had the lowest priority.
NGC 4108B is interesting indeed, it could be called the "heart galaxy",
complementing the "heart nebula".

Stefan

"Rick Johnson" schrieb im Newsbeitrag
.com...

NGC 4108 is a triple galaxy system in Draco about 120 million
light-years distant. It actually is a group of 4 galaxies, one is not
an NGC galaxy so doesn't carry the NGC 4108 catalog entry. There's a
faint indication the NGC 4108 triplet have interacted in the past. It
was NGC 4108B that attracted my interest to the group. It appears to be
a face on spiral, classed SAB(s)d pec?, that has a disrupted arm
structure and a dust lane right across its core. That makes it look
like two half spirals that are merging. Even the core is quite blue
indicating star formation has been recent and plentiful in recent times.
The CGCG says of it: "Blue post-eruptive disrupted spiral with compact
knots and bars."

NGC 4108 lies below it and shows distorted arms apparently pulled toward
NGC 4108B. Also a note at NED says "NGC 4108 and NGC 4108B appear
joined by an H I bridge [Fig. 13(c)]; however, as the size of the bridge
is only on the order of a beam width, most of it could be due to beam
smearing." It is classed as (R')SAc.

NGC 4108A lies west of the other two. It is classed as SBbc:. The arm
structure seems rather weak and certainly not symmetrical. It is
apparently more disturbed when seen at radio frequencies. A note at NED
says: "NGC 4108A has a highly warped H I disk [Fig. 13(d)], with the
major axes of the outer parts of the H I disk being nisaligned (sic) by
~45^deg^ with respect to the optical major axis. The velocity field is
peculiar in that at the southern tip the axis of rotation curves in the
opposite direction one would expect from the warp in the H I disk."

The fourth member of the group, UGCA 272 is listed as E0/S0. It appears
rather featureless and nearly white in color but does have an active
core since it is listed as having a narrow line active galactic nucleus
(NLAGN). Something has stirred up its core to high activity that is
mostly hidden from our direct view.

The image contains quite a few quasars and quasar candidates (UvES), 11
of them. Most only have a photographically determined redshift (noted
by a "p" after the distance) which isn't as accurate as a spectroscopic
redshift. You'll see "pred" after the distance to one galaxy. That is
a predicted redshift whatever that means.

NED shows three galaxy clusters in the image. One that is barely
visible a bit northwest of NGC 4108A. More obvious is the pair to the
west of NGC 4108. Though I'm not sure it if it is one cluster with two
designations or two separate ones at virtually the same distance. There
are two bright, large galaxies though only the southern one is listed as
being a Bright Cluster Galaxy even though both are listed at the same
coordinates as the cluster they anchor. In any case there are quite a
few galaxies at their distance (about 1.5 billion light-years) not only
around the two big galaxies but across the image but for the lower left
corner region. No size was given for either cluster, only a count of 14
and 13 members.

As usual for this year clouds and haze really did a number on the depth
of this image. It is a good 1.5 magnitudes short of my normal limit.
It didn't help that I forgot to turn on temperature compensation and a
warm front went through as the image was being taken. Even focusing
every filter change wasn't enough to keep up with the rising temperature
which kept defocusing the image, especially at the corners. Corners
suffer most when temperature rises, core looses if it falls and isn't
compensated for. Between the two issues this one needs revisiting.
Also, one of the two red frames is very weak. While I'm listing it as
using 2 red frames the result is really very close to only one being used.

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

Rick


--
Prefix is correct. Domain is arvig dot net