ASTRO: NGC 4496 An interesting pair

Before reading the below look at the image full image -- not the
annotated one. Are the two galaxies interacting? Are they at the same
distance or is one in front of the other? If the latter which is in
front? OK now read on and see if you are correct.

NGC 4496 is a pair of non interacting galaxies in Virgo. Though some
older papers say they are interacting redshift argues strongly against
it. By redshift NGC 4496A (the northern and larger one) is about 95
million light-years away while NGC 4496B is 220 million light-years
distant, over twice as far. Oddly it appears that NGC 4496B is in front
of its larger "companion" but apparently we are seeing it through the
stars of the larger galaxy. To add to the confusion there are two blue
objects in NGC 4496A that show a redshift the same as NGC 4496B and are
also listed as galaxies. Though they look more like star clusters in
NGC 4496A the data says otherwise. I've marked them with G? in the
annotated image. More confusing is that these objects don't appear
reddened though NGC 4496 appears it could be reddened. I have no idea
if the blue blob just south of NGC 4496B is a member of 4496B or A. If
B it too should be somewhat reddened but isn't.

There's one more monkey wrench in this. All non redshift determinations
of the distance to NGC 4496A put it much closer. They average about 51
million light-years distant. If they are more correct it is a member of
the Virgo Cluster though most papers go with the redshift and say it is
not a member of the galaxy cluster.

One paper that considered them interacting calls VCC 1364 and possibly
VCC 1359 debris from the interaction rather than separate galaxies. NED
has no redshift for either but I included them in the annotated image.
I vote against interaction and that these two are separate low surface
brightness galaxies.

NED classes 4496A as SB(rs)m and 4496B as IB(s)m:. The NGC project only
lists 4496A and says it is SBc. A confusing difference of opinion it
would seem.

Were your right? Arp has long maintained cosmological redshift isn't
necessarily a good distance indicator and high redshift objects, such as
quasars can be far closer than redshift indicates. So far he has little
proof on his side. While not involving quasar redshifts this pair
certainly would be of interest to him I'd think. Odd he didn't put it
on his list.

Besides the normal compliment of galaxies, quasars, quasar candidates
(UvES) and a galaxy cluster there are 5 asteroids in the image. One
very bright and the others faint. All left unusually short trails as
they are slowing down preparing for resumption of prograde motion.

Also there's an interesting discussion at the NGC Project over the
identity of this galaxy. Seems Herschel was rather quick in his entries
for it and for another NGC 4505. They conclude they are one and the
same galaxy even though Herschel described 4496 as being a resolvable
cluster! Also the RC3 say VCC 1364 is NGC 4496 though I doubt it could
have been seen in Herschel's day. Another paper on this problem but not
bringing NGC 4505 in the discussion can be found at:
http://link.springer.com/article/10....627084?LI=true

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

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

Between the time I typed this a few days ago and the time I posted it I
see the site for the link at the bottom of the page is now "New and
Improved". The "improvement" being the paper is now firmly locked
behind a pay wall! It's not worth the high price and barely worth free
that it was a few days ago. I should have rechecked the link before
sending it.
Rick

On 3/4/2013 1:51 AM, Rick Johnson wrote:
Before reading the below look at the image full image -- not the
annotated one. Are the two galaxies interacting? Are they at the same
distance or is one in front of the other? If the latter which is in
front? OK now read on and see if you are correct.

NGC 4496 is a pair of non interacting galaxies in Virgo. Though some
older papers say they are interacting redshift argues strongly against
it. By redshift NGC 4496A (the northern and larger one) is about 95
million light-years away while NGC 4496B is 220 million light-years
distant, over twice as far. Oddly it appears that NGC 4496B is in front
of its larger "companion" but apparently we are seeing it through the
stars of the larger galaxy. To add to the confusion there are two blue
objects in NGC 4496A that show a redshift the same as NGC 4496B and are
also listed as galaxies. Though they look more like star clusters in
NGC 4496A the data says otherwise. I've marked them with G? in the
annotated image. More confusing is that these objects don't appear
reddened though NGC 4496 appears it could be reddened. I have no idea
if the blue blob just south of NGC 4496B is a member of 4496B or A. If
B it too should be somewhat reddened but isn't.

There's one more monkey wrench in this. All non redshift determinations
of the distance to NGC 4496A put it much closer. They average about 51
million light-years distant. If they are more correct it is a member of
the Virgo Cluster though most papers go with the redshift and say it is
not a member of the galaxy cluster.

One paper that considered them interacting calls VCC 1364 and possibly
VCC 1359 debris from the interaction rather than separate galaxies. NED
has no redshift for either but I included them in the annotated image. I
vote against interaction and that these two are separate low surface
brightness galaxies.

NED classes 4496A as SB(rs)m and 4496B as IB(s)m:. The NGC project only
lists 4496A and says it is SBc. A confusing difference of opinion it
would seem.

Were your right? Arp has long maintained cosmological redshift isn't
necessarily a good distance indicator and high redshift objects, such as
quasars can be far closer than redshift indicates. So far he has little
proof on his side. While not involving quasar redshifts this pair
certainly would be of interest to him I'd think. Odd he didn't put it
on his list.

Besides the normal compliment of galaxies, quasars, quasar candidates
(UvES) and a galaxy cluster there are 5 asteroids in the image. One
very bright and the others faint. All left unusually short trails as
they are slowing down preparing for resumption of prograde motion.

Also there's an interesting discussion at the NGC Project over the
identity of this galaxy. Seems Herschel was rather quick in his entries
for it and for another NGC 4505. They conclude they are one and the
same galaxy even though Herschel described 4496 as being a resolvable
cluster! Also the RC3 say VCC 1364 is NGC 4496 though I doubt it could
have been seen in Herschel's day. Another paper on this problem but not
bringing NGC 4505 in the discussion can be found at:
http://link.springer.com/article/10....627084?LI=true

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

Rick


--
Prefix is correct. Domain is arvig dot net

Rick,

now that's what I call spectacular.
I would have thought that they are interacting.
When reading your interesting text I had the same idea as yourself, that Arp
would/should be interested in this object.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
...

Before reading the below look at the image full image -- not the
annotated one. Are the two galaxies interacting? Are they at the same
distance or is one in front of the other? If the latter which is in
front? OK now read on and see if you are correct.

NGC 4496 is a pair of non interacting galaxies in Virgo. Though some
older papers say they are interacting redshift argues strongly against
it. By redshift NGC 4496A (the northern and larger one) is about 95
million light-years away while NGC 4496B is 220 million light-years
distant, over twice as far. Oddly it appears that NGC 4496B is in front
of its larger "companion" but apparently we are seeing it through the
stars of the larger galaxy. To add to the confusion there are two blue
objects in NGC 4496A that show a redshift the same as NGC 4496B and are
also listed as galaxies. Though they look more like star clusters in
NGC 4496A the data says otherwise. I've marked them with G? in the
annotated image. More confusing is that these objects don't appear
reddened though NGC 4496 appears it could be reddened. I have no idea
if the blue blob just south of NGC 4496B is a member of 4496B or A. If
B it too should be somewhat reddened but isn't.

There's one more monkey wrench in this. All non redshift determinations
of the distance to NGC 4496A put it much closer. They average about 51
million light-years distant. If they are more correct it is a member of
the Virgo Cluster though most papers go with the redshift and say it is
not a member of the galaxy cluster.

One paper that considered them interacting calls VCC 1364 and possibly
VCC 1359 debris from the interaction rather than separate galaxies. NED
has no redshift for either but I included them in the annotated image.
I vote against interaction and that these two are separate low surface
brightness galaxies.

NED classes 4496A as SB(rs)m and 4496B as IB(s)m:. The NGC project only
lists 4496A and says it is SBc. A confusing difference of opinion it
would seem.

Were your right? Arp has long maintained cosmological redshift isn't
necessarily a good distance indicator and high redshift objects, such as
quasars can be far closer than redshift indicates. So far he has little
proof on his side. While not involving quasar redshifts this pair
certainly would be of interest to him I'd think. Odd he didn't put it
on his list.

Besides the normal compliment of galaxies, quasars, quasar candidates
(UvES) and a galaxy cluster there are 5 asteroids in the image. One
very bright and the others faint. All left unusually short trails as
they are slowing down preparing for resumption of prograde motion.

Also there's an interesting discussion at the NGC Project over the
identity of this galaxy. Seems Herschel was rather quick in his entries
for it and for another NGC 4505. They conclude they are one and the
same galaxy even though Herschel described 4496 as being a resolvable
cluster! Also the RC3 say VCC 1364 is NGC 4496 though I doubt it could
have been seen in Herschel's day. Another paper on this problem but not
bringing NGC 4505 in the discussion can be found at:
http://link.springer.com/article/10....627084?LI=true

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

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