ASTRO: Arp 120 The Eyes have it

Arp 120 is better known as The Eyes or NGC 4438 with NGC 4435. They are
part of the Virgo Galaxy Cluster located some 60 million light years
away. Arp's classification of this one is under Elliptical and
elliptical like galaxies: Close to and perturbing spirals. Only problem
is NGC 4435 may not be perturbing NGC 4438. It does have a large halo
about it, the full extent not seen in my shot bit it is very symmetrical
and shows no hint of distortion. They have two very different red shift
values. So different that if they did interact it was over almost
before it started. Raising the question of how one galaxy could so
perturb another in such a short time. NGC 4435 (undistorted) has a red
shift typical of the distance to the cluster, 801 km/s but that of NGC
4468 is only 71 km/s. So it is moving toward us relative to the
companion at 730 km/s or 1.6 million miles per hour. This gives only
about 20 million years for them to really react to each other. Most
collisions take billions of years, not millions. So if NGC 4435 isn't
the culprit who is? One answer is that NGC 4438 could be the result of
a merger that's already happened and the debris hasn't as yet returned
to the galaxy. The multiple planes of dust lanes near the core would
argue for this, the fact only one core can be seen would argue against
it. So this one is still has a lot more questions than answers from
what I find in the literature.

The tidal cloud about NGC 4438 must be very thin however and contain
little dust. Notice the reddish object in the darker triangular area
north of the bright part of the galaxy. This is not a foreground star
but the distant galaxy SDSS J122746.38+130229.4 which is about 1.6
billion light years distant. To be seen through the tidal plume at that
great distance the plume must be very sparse and consist mostly of
widely spaced stars with little dust and gas. Another galaxy is seen in
the galaxy but may be in front of NGC 4438. It is the obvious
elliptical just below the brightest part of the galaxy at the edge of
the main halo an east of the tidal plume. It is VCC 1040 and has a blue
shift so is moving toward us. It is classed as a dwarf elliptical and
thus too small to be involved but does show the wide variation of red
shift to be found in this galaxy cluster.

Most class NGC 4435 as SB0 and NGC 4438 a mess. No two seem to agree.
The NGC Project just says S... while NED says SA(s)0/a pec. NED says
both are LINER galaxies. Interaction is one thing that can create an
AGN (Active Galactic Nucleus) but certainly not the only thing so this
doesn't help too much to answer the interaction question.

Then there's the rather peculiar galaxy to the northwest of Arp 120, the
very blue IC 3355. SDSS gives it three separate numbers. A note at NED
says;"Faint not disrupted progenitor. In its tail 3 diffuse companions
in a blue haze." I can't find the third one however. IC catalog
considers it just one irregular Magellanic galaxy. It has a red shift
similar to that of NGC 4435.

The large glow at the lower right is the outskirts of M86 most of which
is well off frame.

In the annotated image galaxies that are members of the cluster are
identified by name but no distance is given as they are all about 60
billion light-years give or take 10 million or so. Exact distances are
hard to determine since the velocities of member galaxies can vary
greatly making red shift a poor distance indicator. Those with red
shifts that put them far beyond the cluster are noted by their distance
in billions of light-years. Several quasars out to past 11 billion
light-years are noted. Some galaxies I can't determine any distance for
but may or may not be cluster members are identified by name with a "?"
to indicate this uncertainty. In all cases no red shift data was
available. You will note that sometimes a cluster galaxy is right
beside a distant galaxy but telling which is which without the labels
could be difficult.

I took this data several years ago. Due to clouds this spring I never
did redo it as intended. Seeing was very poor and I was using a focuser
that wasn't up to the job. The result is limiting magnitude is about
21.2 instead of my normal 22.5 and detail is a bit lacking due to 4"
seeing. Maybe this spring I can redo it with a lot more data to get far
more of the halos around both galaxies. Also I pushed the color more
than normal to bring out the subtle color differences in the plume.
This cause IC 3355 to turn super blue. Indicating it has really massive
star formation going on and may be more interesting than Arp 120.

SDSS
http://astronomerica.awardspace.com/...-4435-SDSS.jpg

Arp's image:
http://nedwww.ipac.caltech.edu/level...ig_arp120.jpeg

14" LX200R @ f/10, L=8x10' RGB=2x10', 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".

wrote:
Rick -


NGC 4438 is severely warped by a close encounter with giant elliptical
M 86 of the Virgo group. NOAO recently released a study of this
encounter noting "A deep new image of the Virgo cluster has revealed
monumental tendrils of ionized hydrogen gas 400,000 light-years long
connecting the elliptical galaxy M86 and the disturbed spiral galaxy
NGC 4438."
See http://www.noao.edu/outreach/press/pr08/pr0807.html


Thanks, I somehow missed that!

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".

wrote:
Rick -


NGC 4438 is severely warped by a close encounter with giant elliptical
M 86 of the Virgo group. NOAO recently released a study of this
encounter noting "A deep new image of the Virgo cluster has revealed
monumental tendrils of ionized hydrogen gas 400,000 light-years long
connecting the elliptical galaxy M86 and the disturbed spiral galaxy
NGC 4438."
See http://www.noao.edu/outreach/press/pr08/pr0807.html


Dang, I hit send by accident.

Glen,

Thanks, I somehow missed that.

Unfortunately, it now means I have to reprocess it yet again. Seems I
saw a lot of junk from 4438 to M86 and processed it out thinking it a
gradient. Not sure how well it matches the link info but some pieces
sure seem to fit. Was very noisy due to the 80 minute exposure time.
Will need a lot more in a few months. Still I have to trust my flats
more than I did here.

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".

Great picture Rick. A good picture of this pair is still missing in my
collection.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
om...
Arp 120 is better known as The Eyes or NGC 4438 with NGC 4435. They are
part of the Virgo Galaxy Cluster located some 60 million light years
away. Arp's classification of this one is under Elliptical and
elliptical like galaxies: Close to and perturbing spirals. Only problem
is NGC 4435 may not be perturbing NGC 4438. It does have a large halo
about it, the full extent not seen in my shot bit it is very symmetrical
and shows no hint of distortion. They have two very different red shift
values. So different that if they did interact it was over almost
before it started. Raising the question of how one galaxy could so
perturb another in such a short time. NGC 4435 (undistorted) has a red
shift typical of the distance to the cluster, 801 km/s but that of NGC
4468 is only 71 km/s. So it is moving toward us relative to the
companion at 730 km/s or 1.6 million miles per hour. This gives only
about 20 million years for them to really react to each other. Most
collisions take billions of years, not millions. So if NGC 4435 isn't
the culprit who is? One answer is that NGC 4438 could be the result of
a merger that's already happened and the debris hasn't as yet returned
to the galaxy. The multiple planes of dust lanes near the core would
argue for this, the fact only one core can be seen would argue against
it. So this one is still has a lot more questions than answers from
what I find in the literature.

The tidal cloud about NGC 4438 must be very thin however and contain
little dust. Notice the reddish object in the darker triangular area
north of the bright part of the galaxy. This is not a foreground star
but the distant galaxy SDSS J122746.38+130229.4 which is about 1.6
billion light years distant. To be seen through the tidal plume at that
great distance the plume must be very sparse and consist mostly of
widely spaced stars with little dust and gas. Another galaxy is seen in
the galaxy but may be in front of NGC 4438. It is the obvious
elliptical just below the brightest part of the galaxy at the edge of
the main halo an east of the tidal plume. It is VCC 1040 and has a blue
shift so is moving toward us. It is classed as a dwarf elliptical and
thus too small to be involved but does show the wide variation of red
shift to be found in this galaxy cluster.

Most class NGC 4435 as SB0 and NGC 4438 a mess. No two seem to agree.
The NGC Project just says S... while NED says SA(s)0/a pec. NED says
both are LINER galaxies. Interaction is one thing that can create an
AGN (Active Galactic Nucleus) but certainly not the only thing so this
doesn't help too much to answer the interaction question.

Then there's the rather peculiar galaxy to the northwest of Arp 120, the
very blue IC 3355. SDSS gives it three separate numbers. A note at NED
says;"Faint not disrupted progenitor. In its tail 3 diffuse companions
in a blue haze." I can't find the third one however. IC catalog
considers it just one irregular Magellanic galaxy. It has a red shift
similar to that of NGC 4435.

The large glow at the lower right is the outskirts of M86 most of which
is well off frame.

In the annotated image galaxies that are members of the cluster are
identified by name but no distance is given as they are all about 60
billion light-years give or take 10 million or so. Exact distances are
hard to determine since the velocities of member galaxies can vary
greatly making red shift a poor distance indicator. Those with red
shifts that put them far beyond the cluster are noted by their distance
in billions of light-years. Several quasars out to past 11 billion
light-years are noted. Some galaxies I can't determine any distance for
but may or may not be cluster members are identified by name with a "?"
to indicate this uncertainty. In all cases no red shift data was
available. You will note that sometimes a cluster galaxy is right
beside a distant galaxy but telling which is which without the labels
could be difficult.

I took this data several years ago. Due to clouds this spring I never
did redo it as intended. Seeing was very poor and I was using a focuser
that wasn't up to the job. The result is limiting magnitude is about
21.2 instead of my normal 22.5 and detail is a bit lacking due to 4"
seeing. Maybe this spring I can redo it with a lot more data to get far
more of the halos around both galaxies. Also I pushed the color more
than normal to bring out the subtle color differences in the plume.
This cause IC 3355 to turn super blue. Indicating it has really massive
star formation going on and may be more interesting than Arp 120.

SDSS
http://astronomerica.awardspace.com/...-4435-SDSS.jpg

Arp's image:
http://nedwww.ipac.caltech.edu/level...ig_arp120.jpeg

14" LX200R @ f/10, L=8x10' RGB=2x10', 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".