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ASTRO: NGC 3953 and others



 
 
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  #1  
Old April 6th 12, 07:08 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Posts: 3,085
Default ASTRO: NGC 3953 and others

NGC 3953 is a rather classic looking barred spiral in Ursa Major one and
a third degrees south of Phecda (Phad and other spellings), the
southeastern star in the bowl of the Big Dipper (Gamma Ursa Major). It
is thought to be about 60 million light-years away. Redshift data puts
it at 57 million light-years so the various methods of measuring its
distance tend to agree. It is classed as a SBb spiral by the NGC
project and SB(r)bc by NED. It is a LINER galaxy with HII emission
though I didn't bring out any in my LRGB image. Probably too small as
the largest regions are said to be about 3" in size. I should think
about adding some HII data to these. The galaxy is about 114,000,000
light-years across, making it about the size of our galaxy. Except for
the many arm segments it may be rather similar to our own galaxy in many
respects.

A note at NED reads: "NGC 3953 ... is notable for its extended, diffuse,
polarized radio emission from the outer disc. No significant radio
emission from the bar and the nucleus has been detected. Significant
Faraday rotation between {lambda}22 cm and 6 cm occurs in the southern
part of the galaxy (RM ~ +15 rad m^-2^)." Another note says: "The
central region of NGC 3953 is more of an oval than a bar." While the
core looks round from our perspective seen from "above" it would likely
look oval. Still I see a rather well defined though short bar at either
side.

A bit below and left of center is the very low surface brightness dwarf
galaxy MCG +09-20-023. Unfortunately no distance data is available at
NED for it. It sure is a ghost of a galaxy. Wish I knew more.

UGC 6840/PGC 37164 is another low surface brightness galaxy, a spiral
this time. I needed much more time than the hour I gave it to bring out
its arms as they are so faint. Only the bar is easily seen. It has
virtually the same redshift as NGC 3953 so to is about 55 to 60 million
light years distant. It is classed as SB(rs)m. The m indicating it is
similar to our large Magellanic Cloud though larger. If the distance is
right it is about 31,500 light years across.

North of UGC 6840 is the quasar SDSS J115205.96+521114.2. Unusual for
being only 3.3 billion light-years distant and for showing hints of the
galaxy it is in. Two ansae are seen indicating it may be a disk galaxy.
NED also classes it as a Bright Line AGN galaxy. It is also cataloged
as an X-ray source (many AGN and quasars are). At magnitude 18.9 it
isn't very bright for a quasar as I've imaged many at three times this
distance that appeared even brighter than magnitude 18.9.

North west of the quasar is a galaxy cluster. NED shows the Bright
Cluster Galaxy anchoring the cluster to be a faint galaxy hiding in the
glare of a much brighter one. It then uses the bright one as the
position of the cluster. The distance to the cluster is based on a less
accurate photographic method rather than actual spectral data so the two
distances don't quite match. The cluster is listed with no size
containing 13 galaxies. The bright galaxy, SDSS J115150.66+521250.1, is
not listed by NED as being a BCG galaxy nor is a red shift value listed.
While the much fainter one, MaxBCG J177.96111+52.21393 BCG, is. The
cluster is MaxBCG J177.96111+52.21393, matching the fainter BCG. So
does this mean the brighter galaxy just happens to be exactly at the
same coordinates as the cluster?

14" LX200R @ f/10, L=6x10' RGB=2x10'x3, STL-11000XM, Paramount ME

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

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  #2  
Old April 23rd 12, 09:39 PM posted to alt.binaries.pictures.astro
Stefan Lilge
external usenet poster
 
Posts: 2,269
Default ASTRO: NGC 3953 and others

Great image Rick.
I have a b/w version of NGC 3953 that I consider to be one of my best images
so far, but no decent colour.
I made two attempts to get colour data, but in both cases the raw images
looked so poor that I did not process them.
Maybe I should combine both sets and see what I can get from all the data
combined...

Stefan

"Rick Johnson" schrieb im Newsbeitrag
. com...
NGC 3953 is a rather classic looking barred spiral in Ursa Major one and
a third degrees south of Phecda (Phad and other spellings), the
southeastern star in the bowl of the Big Dipper (Gamma Ursa Major). It
is thought to be about 60 million light-years away. Redshift data puts
it at 57 million light-years so the various methods of measuring its
distance tend to agree. It is classed as a SBb spiral by the NGC
project and SB(r)bc by NED. It is a LINER galaxy with HII emission
though I didn't bring out any in my LRGB image. Probably too small as
the largest regions are said to be about 3" in size. I should think
about adding some HII data to these. The galaxy is about 114,000,000
light-years across, making it about the size of our galaxy. Except for
the many arm segments it may be rather similar to our own galaxy in many
respects.

A note at NED reads: "NGC 3953 ... is notable for its extended, diffuse,
polarized radio emission from the outer disc. No significant radio
emission from the bar and the nucleus has been detected. Significant
Faraday rotation between {lambda}22 cm and 6 cm occurs in the southern
part of the galaxy (RM ~ +15 rad m^-2^)." Another note says: "The
central region of NGC 3953 is more of an oval than a bar." While the
core looks round from our perspective seen from "above" it would likely
look oval. Still I see a rather well defined though short bar at either
side.

A bit below and left of center is the very low surface brightness dwarf
galaxy MCG +09-20-023. Unfortunately no distance data is available at
NED for it. It sure is a ghost of a galaxy. Wish I knew more.

UGC 6840/PGC 37164 is another low surface brightness galaxy, a spiral
this time. I needed much more time than the hour I gave it to bring out
its arms as they are so faint. Only the bar is easily seen. It has
virtually the same redshift as NGC 3953 so to is about 55 to 60 million
light years distant. It is classed as SB(rs)m. The m indicating it is
similar to our large Magellanic Cloud though larger. If the distance is
right it is about 31,500 light years across.

North of UGC 6840 is the quasar SDSS J115205.96+521114.2. Unusual for
being only 3.3 billion light-years distant and for showing hints of the
galaxy it is in. Two ansae are seen indicating it may be a disk galaxy.
NED also classes it as a Bright Line AGN galaxy. It is also cataloged
as an X-ray source (many AGN and quasars are). At magnitude 18.9 it
isn't very bright for a quasar as I've imaged many at three times this
distance that appeared even brighter than magnitude 18.9.

North west of the quasar is a galaxy cluster. NED shows the Bright
Cluster Galaxy anchoring the cluster to be a faint galaxy hiding in the
glare of a much brighter one. It then uses the bright one as the
position of the cluster. The distance to the cluster is based on a less
accurate photographic method rather than actual spectral data so the two
distances don't quite match. The cluster is listed with no size
containing 13 galaxies. The bright galaxy, SDSS J115150.66+521250.1, is
not listed by NED as being a BCG galaxy nor is a red shift value listed.
While the much fainter one, MaxBCG J177.96111+52.21393 BCG, is. The
cluster is MaxBCG J177.96111+52.21393, matching the fainter BCG. So
does this mean the brighter galaxy just happens to be exactly at the
same coordinates as the cluster?

14" LX200R @ f/10, L=6x10' RGB=2x10'x3, STL-11000XM, Paramount ME

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



 




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