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ASTRO: NGC 1174 Are reports of its death premature?



 
 
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  #1  
Old May 22nd 14, 07:47 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Posts: 3,085
Default ASTRO: NGC 1174 Are reports of its death premature?

NGC 1174 made my to-do list for being a good example of the newly
discovered class of galaxies called Red Spiral Galaxies. Also it has
some very interesting structure. Located in western Perseus about 4.25
degrees east of M34. It is thought to be about 120 million light-years
away. NED classes it as SB(r)bc: while the NGC Project closely agrees
saying SBb-c. The only other galaxy in the image with redshift data is
NPM1G +42.0108 at twice the distance, 245 million light-years. It is
the elliptical like galaxy due east (left) of NGC 1174 not far from the
left edge of the image. Only a very few other galaxies are even listed
in NED, none with classification, distance or magnitude. All are from
the 2MASS survey. Therefore I didn't bother to make an annotated image.

Red spirals are somewhat of a puzzle in that they shouldn't exist by
some theories of spiral galaxy formation. The arms are thought to be
created by density waves powered by the light pressure of massive stars
and the shockwave from the super novas they create when they die. Thus
they are a self perpetuating feature. But they need a supply of new
stars to keep them going. New star formation creates a lot of super hot
blue stars needed to power the density waves. Thus spiral arms are blue
with their light dominated by these super stars. If star formation
ceases super hot stars die and with it, the theory goes, so does the
spiral structure. Yet these red spirals too weak in such stars to have
the spiral structure seen. Something else is going on or these stars
are not seen.

Most red spirals are seen in galaxy clusters and there is a theory for
them saying that as they get drawn in to the center region of the
cluster from the outskirts where most blue spirals live that this
somehow slowly strangles star formation but does so gently enough the
spiral structure remains for at least a short period. You can read more
about that at:
http://www.universetoday.com/21457/u...ies-strangled/
our you can read the gory details (hip waders may be useful) at:
http://arxiv.org/abs/0910.4113 .

The theory says this happens mostly to larger spiral galaxies. Well NGC
1174 is a large galaxy. I get a size of just about 100,000 light-years
and as spirals go that is big. But it isn't in a galaxy cluster. It is
considered part of a very sparse and widely separated group known as the
NGC 1186 group. It is so spread out no other member is in my image.
Certainly not anything like what the theory of strangled spirals
requires. Nor is this a case of the galaxy being reddened by dust in
our galaxy as even more distant galaxies right near it are quite blue.
Unless the dust is only directly in line with NGC 1174 and is a small
cloud would that happen. Spectroscopic data would prove the issue one
way or the other but that's not available. I'll just say I can't buy
all the coincidences needed for this to be dust reddening either in our
galaxy or because NGC 1174 is in a dusty cocoon.

One answer may be that these galaxies do have current star formation
going on but had so much formation in the past that the red stars from
that era are still around in vast numbers thus skewing the color to red
even though there are a normal number of stars being formed in a spiral
galaxy. Studies of some of these with IR and UV light seems to support
this. For this you need a galaxy with 10 billion times the mass of the
sun. Is NGC 1174 that big? I don't know. It certainly appears to have
the dust and gas needed for sustained star formation. In any case again
this study was done using cluster galaxies from the same Galaxy Zoo
articles referred to in the above links. You can read about this idea at:
http://astrobites.org/2012/06/06/red...-are-not-dead/ The URL
pretty much tells the story.

The field contains weak IFN which is strongest to the lower left. I see
hints of it in the POSS plates so am quite confident it is real. This
might be a good field for those that spend many hours on a target would
find interestingly dusty. I don't begin to have the needed time into my
image to bring it out.

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

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

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  #2  
Old June 19th 14, 10:10 PM posted to alt.binaries.pictures.astro
Stefan Lilge
external usenet poster
 
Posts: 2,269
Default ASTRO: NGC 1174 Are reports of its death premature?

Rick,

interesting object and interesting read.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
...

NGC 1174 made my to-do list for being a good example of the newly
discovered class of galaxies called Red Spiral Galaxies. Also it has
some very interesting structure. Located in western Perseus about 4.25
degrees east of M34. It is thought to be about 120 million light-years
away. NED classes it as SB(r)bc: while the NGC Project closely agrees
saying SBb-c. The only other galaxy in the image with redshift data is
NPM1G +42.0108 at twice the distance, 245 million light-years. It is
the elliptical like galaxy due east (left) of NGC 1174 not far from the
left edge of the image. Only a very few other galaxies are even listed
in NED, none with classification, distance or magnitude. All are from
the 2MASS survey. Therefore I didn't bother to make an annotated image.

Red spirals are somewhat of a puzzle in that they shouldn't exist by
some theories of spiral galaxy formation. The arms are thought to be
created by density waves powered by the light pressure of massive stars
and the shockwave from the super novas they create when they die. Thus
they are a self perpetuating feature. But they need a supply of new
stars to keep them going. New star formation creates a lot of super hot
blue stars needed to power the density waves. Thus spiral arms are blue
with their light dominated by these super stars. If star formation
ceases super hot stars die and with it, the theory goes, so does the
spiral structure. Yet these red spirals too weak in such stars to have
the spiral structure seen. Something else is going on or these stars
are not seen.

Most red spirals are seen in galaxy clusters and there is a theory for
them saying that as they get drawn in to the center region of the
cluster from the outskirts where most blue spirals live that this
somehow slowly strangles star formation but does so gently enough the
spiral structure remains for at least a short period. You can read more
about that at:
http://www.universetoday.com/21457/u...ies-strangled/
our you can read the gory details (hip waders may be useful) at:
http://arxiv.org/abs/0910.4113 .

The theory says this happens mostly to larger spiral galaxies. Well NGC
1174 is a large galaxy. I get a size of just about 100,000 light-years
and as spirals go that is big. But it isn't in a galaxy cluster. It is
considered part of a very sparse and widely separated group known as the
NGC 1186 group. It is so spread out no other member is in my image.
Certainly not anything like what the theory of strangled spirals
requires. Nor is this a case of the galaxy being reddened by dust in
our galaxy as even more distant galaxies right near it are quite blue.
Unless the dust is only directly in line with NGC 1174 and is a small
cloud would that happen. Spectroscopic data would prove the issue one
way or the other but that's not available. I'll just say I can't buy
all the coincidences needed for this to be dust reddening either in our
galaxy or because NGC 1174 is in a dusty cocoon.

One answer may be that these galaxies do have current star formation
going on but had so much formation in the past that the red stars from
that era are still around in vast numbers thus skewing the color to red
even though there are a normal number of stars being formed in a spiral
galaxy. Studies of some of these with IR and UV light seems to support
this. For this you need a galaxy with 10 billion times the mass of the
sun. Is NGC 1174 that big? I don't know. It certainly appears to have
the dust and gas needed for sustained star formation. In any case again
this study was done using cluster galaxies from the same Galaxy Zoo
articles referred to in the above links. You can read about this idea at:
http://astrobites.org/2012/06/06/red...-are-not-dead/ The URL
pretty much tells the story.

The field contains weak IFN which is strongest to the lower left. I see
hints of it in the POSS plates so am quite confident it is real. This
might be a good field for those that spend many hours on a target would
find interestingly dusty. I don't begin to have the needed time into my
image to bring it out.

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

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

 




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