Astro: Fireworks in February, Arp 29

Arp 29 is far better known as NGC 6946, the Fireworks Galaxy. This is
because it is undergoing massive star formation and close enough that we
can easily resolve many of the HII regions as well as a massive star
cluster. The cluster is well resolved in the upper left corner of the
Gemini North image. http://antwrp.gsfc.nasa.gov/apod/ap050125.html My
image scale and seeing weren't sufficent to fully resolve it so only a
few of the stars show with the rest forming what appears to be a blue
reflection nebula. Note the Gemini image has south up while mine is
north up. Another reason for its common name is all the super nova that
have been seen blowing in it. The last was in 2008. NED list 9 known
super nova in this galaxy; SN 1917A, N 1939C, SN 1948B, SN 1968D, SN
1969P, SN 1980K, SN 2002hh, SN 2004et and SN 2008S. 27 supernova
remnants are also known in this galaxy according to NED.

But none of this is the reason it is in Arp's catalog. He included it
under Spiral galaxies with one heavy arm. Most in this category have a
rather obvious heavy arm. I'm not even sure which arm he is speaking of.
Maybe its the one to the northeast (upper left) of the core in my
image. Though his comment addressed the supernovas saying "Supernova
once observed in tip of thick arm." This may refer to the 1948
supernova though it was well back of what I'd call the "tip" of the
eastern arm. Though closer to the end than those appearing in other
arms.

Every paper I found shows a different distance to this obviously nearby
galaxy. In fact two different papers analyzed the 1980 super nova and
came up with wildly different distance estimates! One decided it was
18.5 million light-years away, the other over 41 million light-years.
One is obviously wrong very wrong. The APOD link above says 10 million
light-years, closer than any paper I found. So I'll give the wide range
of about 10 to 20 million light-years as its distance. This galaxy is
in the Milky Way and thus heavily obscured. This likely complicates
distance estimates. It certainly is close enough for Cephid variables
to be seen but unless the dust between us and the galaxy is accurately
known the distance becomes uncertain.

I should have taken far more data on this one. I see a hint of a long
blue arm going north. The field is full of clouds. Some so close to
the galaxy I can't tell if they are pieces of the galaxy or pieces of
junk in our galaxy. Most likely in ours. Note the area just along the
western edge of Arp 29 that has no stars, just a faint fuzz patch. A
brighter but smaller one below it doesn't seem to obscure stars. I see
no reason to question my flats so suspect these clouds are real. But
they are right at the noise level. Something a lot more time would
certainly help decide.

I had a gaggle of satellites go through the images. I tried to clone
them out -- with only 4 images any noise rejection I tried also added
noise -- and hope I didn't add any artifacts doing so. I'm sure a few
stars in our galaxy got erased however. But there are so many in this
field we can spare a few. So many they really blew up the JPEG size of
this image.

Arp's image with the 200" is at:
http://nedwww.ipac.caltech.edu/level...big_arp29.jpeg
He was pushing the field corrector to its limits with the wide field
needed to cover this one. Note the distorted stars at the corners.

14" LX200R @ f/10, L=4x10' RGB=2x10'x3, 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".

Rats, I found a new way to screw up. I've posted an early version of an
image rather than the final one. This time I posted an early draft of
the text. Here's the correct one (spelling errors fixed and additional
text).

Arp 29 is far better known as NGC 6946, the Fireworks Galaxy. This is
because it is undergoing massive star formation and close enough that we
can easily resolve many of the HII regions as well as a massive star
cluster. The cluster is well resolved in the upper left corner of the
Gemini North image. http://antwrp.gsfc.nasa.gov/apod/ap050125.html My
image scale and seeing weren't sufficient to fully resolve it so only a
few of the stars show with the rest forming what appears to be a blue
reflection nebula. Note the Gemini image has south up while mine is
north up. Another reason for its common name is all the super nova that
have been seen blowing in it. The last was in 2008. NED list 9 known
super nova in this galaxy; SN 1917A, N 1939C, SN 1948B, SN 1968D, SN
1969P, SN 1980K, SN 2002hh, SN 2004et and SN 2008S. 27 supernova
remnants are also known in this galaxy according to NED.

But none of this is the reason it is in Arp's catalog. He included it
under Spiral galaxies with one heavy arm. Most in this category have a
rather obvious heavy arm. I'm not even sure which arm he is speaking of.
Maybe its the one to the northeast (upper left) of the core in my
image. Though his comment addressed the supernovas saying "Supernova
once observed in tip of thick arm." This may refer to the 1948
supernova though it was well back of what I'd call the "tip" of the
eastern arm. Though closer to the end than those appearing in other
arms.

Every paper I found shows a different distance to this obviously nearby
galaxy. In fact two different papers analyzed the 1980 super nova and
came up with wildly different distance estimates! One decided it was
18.5 million light-years away, the other over 41 million light-years.
One is obviously wrong very wrong. The APOD link above says 10 million
light-years, closer than any paper I found. So I'll give the wide range
of about 10 to 20 million light-years as its distance. This galaxy is
in the Milky Way and thus heavily obscured. This likely complicates
distance estimates. It certainly is close enough for Cepheid variables
to be seen but unless the dust between us and the galaxy is accurately
known the distance becomes uncertain. I suspect it is differences in
dust estimates that account for much of the uncertainty of the distance
to this galaxy.

I should have taken far more data on this one. I see a hint of a long
blue arm going north. The field is full of clouds. Some so close to
the galaxy I can't tell if they are pieces of the galaxy or pieces of
junk in our galaxy. Most likely in ours. Note the area just along the
western edge of Arp 29 that has no stars, just a faint fuzz patch. A
brighter but smaller one below it doesn't seem to obscure stars. I see
no reason to question my flats so suspect these clouds are real. But
they are right at the noise level. Something a lot more time would
certainly help decide.

I had a gaggle of satellites go through the images. I tried to clone
them out -- with only 4 images any noise rejection I tried also added
noise -- and hope I didn't add any artifacts doing so. I'm sure a few
stars in our galaxy got erased however. But there are so many in this
field we can spare a few. So many they really blew up the JPEG size of
this image.

There are a few other galaxies in the image and one missing one. NED
lists a 15.6 magnitude galaxy, [OBC97] N05-1 at the top of my image that
should be easily visible but there's nothing there. Those easiest to
find are all south west of Arp 29. The one hiding behind a star is
2MASX J20332396+6005088. Below and east (left) of it is the slightly
bigger and brighter 2MASX J20333573+6002118. Neither have any other
data unfortunately. The same lack applies to 2MASX J20324060+6000181 in
the very southwest corner of my image. I didn't quite catch all of it.
You'd think one this big and bright would at least have a magnitude
estimate but nothing. Guess the 2MAS survey didn't want to detract from
the fireworks of Arp 29.

Arp's image with the 200" is at:
http://nedwww.ipac.caltech.edu/level...big_arp29.jpeg
He was pushing the field corrector to its limits with the wide field
needed to cover this one. Note the distorted stars at the corners.

14" LX200R @ f/10, L=4x10' RGB=2x10'x3, 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".

Nice shot Rick. Arp didn't seem to be too choosy if he counted this one as
being "peculiar".

Stefan

"Rick Johnson" schrieb im Newsbeitrag
om...
Rats, I found a new way to screw up. I've posted an early version of an
image rather than the final one. This time I posted an early draft of the
text. Here's the correct one (spelling errors fixed and additional text).

Arp 29 is far better known as NGC 6946, the Fireworks Galaxy. This is
because it is undergoing massive star formation and close enough that we
can easily resolve many of the HII regions as well as a massive star
cluster. The cluster is well resolved in the upper left corner of the
Gemini North image. http://antwrp.gsfc.nasa.gov/apod/ap050125.html My
image scale and seeing weren't sufficient to fully resolve it so only a
few of the stars show with the rest forming what appears to be a blue
reflection nebula. Note the Gemini image has south up while mine is north
up. Another reason for its common name is all the super nova that have
been seen blowing in it. The last was in 2008. NED list 9 known super
nova in this galaxy; SN 1917A, N 1939C, SN 1948B, SN 1968D, SN 1969P, SN
1980K, SN 2002hh, SN 2004et and SN 2008S. 27 supernova remnants are also
known in this galaxy according to NED.

But none of this is the reason it is in Arp's catalog. He included it
under Spiral galaxies with one heavy arm. Most in this category have a
rather obvious heavy arm. I'm not even sure which arm he is speaking of.
Maybe its the one to the northeast (upper left) of the core in my image.
Though his comment addressed the supernovas saying "Supernova once
observed in tip of thick arm." This may refer to the 1948 supernova
though it was well back of what I'd call the "tip" of the eastern arm.
Though closer to the end than those appearing in other arms.

Every paper I found shows a different distance to this obviously nearby
galaxy. In fact two different papers analyzed the 1980 super nova and
came up with wildly different distance estimates! One decided it was 18.5
million light-years away, the other over 41 million light-years. One is
obviously wrong very wrong. The APOD link above says 10 million
light-years, closer than any paper I found. So I'll give the wide range
of about 10 to 20 million light-years as its distance. This galaxy is in
the Milky Way and thus heavily obscured. This likely complicates distance
estimates. It certainly is close enough for Cepheid variables to be seen
but unless the dust between us and the galaxy is accurately known the
distance becomes uncertain. I suspect it is differences in dust estimates
that account for much of the uncertainty of the distance to this galaxy.

I should have taken far more data on this one. I see a hint of a long
blue arm going north. The field is full of clouds. Some so close to the
galaxy I can't tell if they are pieces of the galaxy or pieces of junk in
our galaxy. Most likely in ours. Note the area just along the western
edge of Arp 29 that has no stars, just a faint fuzz patch. A brighter but
smaller one below it doesn't seem to obscure stars. I see no reason to
question my flats so suspect these clouds are real. But they are right at
the noise level. Something a lot more time would certainly help decide.

I had a gaggle of satellites go through the images. I tried to clone them
out -- with only 4 images any noise rejection I tried also added noise --
and hope I didn't add any artifacts doing so. I'm sure a few stars in our
galaxy got erased however. But there are so many in this field we can
spare a few. So many they really blew up the JPEG size of this image.

There are a few other galaxies in the image and one missing one. NED
lists a 15.6 magnitude galaxy, [OBC97] N05-1 at the top of my image that
should be easily visible but there's nothing there. Those easiest to find
are all south west of Arp 29. The one hiding behind a star is 2MASX
J20332396+6005088. Below and east (left) of it is the slightly bigger and
brighter 2MASX J20333573+6002118. Neither have any other data
unfortunately. The same lack applies to 2MASX J20324060+6000181 in the
very southwest corner of my image. I didn't quite catch all of it. You'd
think one this big and bright would at least have a magnitude estimate but
nothing. Guess the 2MAS survey didn't want to detract from the fireworks
of Arp 29.

Arp's image with the 200" is at:
http://nedwww.ipac.caltech.edu/level...big_arp29.jpeg
He was pushing the field corrector to its limits with the wide field
needed to cover this one. Note the distorted stars at the corners.

14" LX200R @ f/10, L=4x10' RGB=2x10'x3, 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".