ASTRO: NGC 3997 et al and there's a lot of them

NGC 3997 is a galaxy that's part of a large group that goes by many
names. The NGC Project uses the name NGC 4007 Group which has its own
baggage I'll get to later. The group is located in Leo just over the
border with Coma Berenices and lies some 220 million light-years away.

NGC 3997 is a rather confusing galaxy. It's structure is very
disjointed with plumes everywhere. One arm appears could be considered
a separate galaxy if the rest of NGC 3997 is masked out. The annotated
image hints at the confusion. The main core is listed as NGC 3997 but
only .24 arc seconds away is NGC 3997 NED01. Since it is only a quarter
of a pixel away I didn't note it. Nor could I see anything on the Sloan
image. Yet NGC 3997 is listed at magnitude 14.02 and 1.7 by 0.6 minutes
while NED 01 is 1.63 by 1.23 minutes at magnitude 15 and listed as I
pec. To me this fits the area better than does the description of NGC
3997.

North of the core is a second somewhat blue object. It's not in NED but
the small area between the it and the core is listed as SDSS
J115748.21+251618.1 a separate galaxy. It is listed as star-like 0.08"
and magnitude 18.5 yet nothing like that is seen on the Sloan image that
I could see. The size is much too small for any feature on the Sloan
image in fact.

If that wasn't confusing enough between the odd arm that could be taken
for an edge on disk galaxy and the core is where NED puts NGC 3997
NED02. I see nothing at that position yet NED sees a galaxy measuring
1.97 by 0.67 minutes. Just the size of that odd feature that could be
taken for an edge on galaxy. Just the position is wrong. Then I
noticed NED gives the error circle as 5". That is sufficient to just
include it. The annotated image points to the center of the error
circle but I do think they mean that object that appears to be an edge
on galaxy. No redshift is given however. It is classed as simply pec
for peculiar. NGC 3997 itself is listed as SBb pec. Also at about its
position, well 9" away, is 2MASXI J1157489+251615, an IR galaxy. It is
listed as .9 by .4 minutes and magnitude 18.1. The position is closer
to the apparent edge on galaxy (arm) than the core but not exactly. Yet
it shows only a 0.5" error circle, the minimum NED normally uses. I
didn't put it on the annotated image as things were getting a bit
crowded. Go up two pixels from the end of the NED02 line and left 2
pixels for its position. The 2MASS catalog calls it a low surface
brightness galaxy. Another piece that looks like it could be a separate
galaxy is the blue object under the core. NED shows nothing at or
around its position but for the objects already mentioned. After this
my head was spinning and I didn't dig deeper. I probably should have.
In any case NGC 3997 looks to me to be the result of a likely merger
with a another galaxy or a merger in progress with all its disjointed
arms and plumes.

Now for some of the other NGC galaxies in the field. At least they
aren't all confusing but there are issues with some of them as well. So
hang on for a sometimes bumpy ride.

NGC 3987 is a classic edge on spiral classed as Sb by all at magnitude
13.9. But note the bright, star-like object in the dust lane right of
its core. This is LEDA 4547376. But suddenly this nice simple picture
gets bumpy because NED says this star-like object is really 1.44 by 0.32
minutes in size at magnitude 16. I can't see this in the Sloan image
however. I just see a small round object.

NGC 3989 is a small spiral classed as S?, Sbc and Sb depending on the
source. It is magnitude 15.6

NGC 3993 is another edge on spiral classed as Sb or S.. depending on the
source. It shines at magnitude 14.2

NGC 3999 is an SO galaxy of magnitude 15.7. No redshift is provided.
This one has some interesting information at the NGC Project about its
identity. "This entry is one of several galaxies discovered at Birr
Castle in the N4005 cluster. According to the 25 April 1878 discovery
note, the position with respect to the mag 8 star (SAO 82077) is 277" in
PA 201.3? (SSW). At this exact offset is a faint galaxy, CGCG 127-117,
at 11 57 56.5 +25 04 05 (2000) and CGCG identifies this galaxy as N3999.
The RNGC position (and identification?) is clearly in error being 0.4
tmin of RA too far E and 4' N. The 1975 coordinates should read 11 56.7
+25 13. Listed in RNGC Corrections #3. This galaxy is not in MCG or
RC3 and was not found by Bigourdan. - by Steve Gottlieb"

NGC 4000 is an, Sc, S? or Sbc depending on the source, galaxy seen
pretty much edge on. It is magnitude 15.5

NGC 4005/NGC 4007 is one of those NGC galaxies with multiple numbers.
It is classed as S?, Sb and S.. and shines at magnitude 13.9. As to the
two numbers the NGC Project has this to say. "N4007 was discovered by
WH (III 325) but was reduced incorrectly and the North Polar Distance in
GC and NGC is two degrees too far south (the offset is 45' south of 4
Comae). This error was caught and corrected by Dreyer in Scientific
Papers of William Herschel. Struve and Rosse (object Alpha on the
sketch of the cluster) later rediscovered it, so it received the second
NGC number N4005, this time at the correct place.

"All major catalogs identify this galaxy as N4005 although you could
argue that by prior discovery, III 325 = N4007 should take historical
precedence. In any case, it is clear that N4005 = N4007.
Unfortunately, because of the two degree error the NGC position falls
close to N4003. So, Reinmuth (Die Herschel-Nebel), Carlson's NGC/IC
Correction list, CGCG, UGC, MCG all equate N4007 with N4003 ignoring
Dreyer's correction. See Catalogue Corrections, Malcolm Thomson and
NGCBUGS. - by Steve Gottlieb"

NGC 4015 is a double galaxy. NED01 is a nice elliptical (rare in this
group) of magnitude 13.8 while its companion with nearly the same
redshift is a near edge on classed S? and shines at magnitude 12.81.
There is a dark dust cloud seen over the elliptical. Since dust is
exceedingly rare in such galaxies could it come from the edge on
companion? Or is the alignment with that galaxy just a coincidence?

NGC 4018 is another near edge on galaxy. They seem unusually common in
this group! It is listed as being Sab by all sources I checked and is
magnitude 14.7. We end the NGC list with one everyone agrees about.
Sure wish that was the rule rather than the exception with this bunch!

I've indicated other members of the group by name in the annotated
image. If I thought their angular size indicated they were a member but
no redshift data was available to confirm this I listed the name
followed by a question mark.

While many galaxy clusters were listed for the field only two could be
marked with an obvious core galaxy. One is southeast of the center of
my image. It is MaxBCG J179.54663+25.05842. It's core galaxy is very
obvious with some detail in my image. It's distance is only 1.8 billion
light-years and contains 15 members in an unspecified radius. The BCG
is also listed in the 2MASS catalog of IR sources so may still be
feeding. At least it is full of dust being heated by unseen newly
minted stars. The other cluster is on the far western edge of my image.
It is GMBCG J179.11209+25.16277. It is listed as having 11 members.
It BCG also is in the 2Mass catalog as an IR source. In the case of the
first cluster there was no redshift value for the BCG. For this cluster
there is but it differs from that of the cluster itself. The cluster is
listed at 3.4 billion light-years and the galaxy at 3.2 billion
light-years. The galaxy's redshift is by spectroscopic measurement
while the cluster is photographic. So I expect the 3.2 billion
light-year figure is the one to use here.

The NGC 4005/7 group extends well beyond my field of view. Those with
wider fields will pick up far more than I have so this is a good group
target for small systems. I'd like to see what you get. Under dark
skies it should be quite spectacular.

14" LX200R @ f/10, L=8x10' RGB=2x10'x3, STL-11000XM, Paramount ME

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

Rick,

that's a quite amazing field you have imaged here. Lots of detailed
galaxies.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
.com...
NGC 3997 is a galaxy that's part of a large group that goes by many
names. The NGC Project uses the name NGC 4007 Group which has its own
baggage I'll get to later. The group is located in Leo just over the
border with Coma Berenices and lies some 220 million light-years away.

NGC 3997 is a rather confusing galaxy. It's structure is very
disjointed with plumes everywhere. One arm appears could be considered
a separate galaxy if the rest of NGC 3997 is masked out. The annotated
image hints at the confusion. The main core is listed as NGC 3997 but
only .24 arc seconds away is NGC 3997 NED01. Since it is only a quarter
of a pixel away I didn't note it. Nor could I see anything on the Sloan
image. Yet NGC 3997 is listed at magnitude 14.02 and 1.7 by 0.6 minutes
while NED 01 is 1.63 by 1.23 minutes at magnitude 15 and listed as I
pec. To me this fits the area better than does the description of NGC
3997.

North of the core is a second somewhat blue object. It's not in NED but
the small area between the it and the core is listed as SDSS
J115748.21+251618.1 a separate galaxy. It is listed as star-like 0.08"
and magnitude 18.5 yet nothing like that is seen on the Sloan image that
I could see. The size is much too small for any feature on the Sloan
image in fact.

If that wasn't confusing enough between the odd arm that could be taken
for an edge on disk galaxy and the core is where NED puts NGC 3997
NED02. I see nothing at that position yet NED sees a galaxy measuring
1.97 by 0.67 minutes. Just the size of that odd feature that could be
taken for an edge on galaxy. Just the position is wrong. Then I
noticed NED gives the error circle as 5". That is sufficient to just
include it. The annotated image points to the center of the error
circle but I do think they mean that object that appears to be an edge
on galaxy. No redshift is given however. It is classed as simply pec
for peculiar. NGC 3997 itself is listed as SBb pec. Also at about its
position, well 9" away, is 2MASXI J1157489+251615, an IR galaxy. It is
listed as .9 by .4 minutes and magnitude 18.1. The position is closer
to the apparent edge on galaxy (arm) than the core but not exactly. Yet
it shows only a 0.5" error circle, the minimum NED normally uses. I
didn't put it on the annotated image as things were getting a bit
crowded. Go up two pixels from the end of the NED02 line and left 2
pixels for its position. The 2MASS catalog calls it a low surface
brightness galaxy. Another piece that looks like it could be a separate
galaxy is the blue object under the core. NED shows nothing at or
around its position but for the objects already mentioned. After this
my head was spinning and I didn't dig deeper. I probably should have.
In any case NGC 3997 looks to me to be the result of a likely merger
with a another galaxy or a merger in progress with all its disjointed
arms and plumes.

Now for some of the other NGC galaxies in the field. At least they
aren't all confusing but there are issues with some of them as well. So
hang on for a sometimes bumpy ride.

NGC 3987 is a classic edge on spiral classed as Sb by all at magnitude
13.9. But note the bright, star-like object in the dust lane right of
its core. This is LEDA 4547376. But suddenly this nice simple picture
gets bumpy because NED says this star-like object is really 1.44 by 0.32
minutes in size at magnitude 16. I can't see this in the Sloan image
however. I just see a small round object.

NGC 3989 is a small spiral classed as S?, Sbc and Sb depending on the
source. It is magnitude 15.6

NGC 3993 is another edge on spiral classed as Sb or S.. depending on the
source. It shines at magnitude 14.2

NGC 3999 is an SO galaxy of magnitude 15.7. No redshift is provided.
This one has some interesting information at the NGC Project about its
identity. "This entry is one of several galaxies discovered at Birr
Castle in the N4005 cluster. According to the 25 April 1878 discovery
note, the position with respect to the mag 8 star (SAO 82077) is 277" in
PA 201.3? (SSW). At this exact offset is a faint galaxy, CGCG 127-117,
at 11 57 56.5 +25 04 05 (2000) and CGCG identifies this galaxy as N3999.
The RNGC position (and identification?) is clearly in error being 0.4
tmin of RA too far E and 4' N. The 1975 coordinates should read 11 56.7
+25 13. Listed in RNGC Corrections #3. This galaxy is not in MCG or
RC3 and was not found by Bigourdan. - by Steve Gottlieb"

NGC 4000 is an, Sc, S? or Sbc depending on the source, galaxy seen
pretty much edge on. It is magnitude 15.5

NGC 4005/NGC 4007 is one of those NGC galaxies with multiple numbers.
It is classed as S?, Sb and S.. and shines at magnitude 13.9. As to the
two numbers the NGC Project has this to say. "N4007 was discovered by
WH (III 325) but was reduced incorrectly and the North Polar Distance in
GC and NGC is two degrees too far south (the offset is 45' south of 4
Comae). This error was caught and corrected by Dreyer in Scientific
Papers of William Herschel. Struve and Rosse (object Alpha on the
sketch of the cluster) later rediscovered it, so it received the second
NGC number N4005, this time at the correct place.

"All major catalogs identify this galaxy as N4005 although you could
argue that by prior discovery, III 325 = N4007 should take historical
precedence. In any case, it is clear that N4005 = N4007.
Unfortunately, because of the two degree error the NGC position falls
close to N4003. So, Reinmuth (Die Herschel-Nebel), Carlson's NGC/IC
Correction list, CGCG, UGC, MCG all equate N4007 with N4003 ignoring
Dreyer's correction. See Catalogue Corrections, Malcolm Thomson and
NGCBUGS. - by Steve Gottlieb"

NGC 4015 is a double galaxy. NED01 is a nice elliptical (rare in this
group) of magnitude 13.8 while its companion with nearly the same
redshift is a near edge on classed S? and shines at magnitude 12.81.
There is a dark dust cloud seen over the elliptical. Since dust is
exceedingly rare in such galaxies could it come from the edge on
companion? Or is the alignment with that galaxy just a coincidence?

NGC 4018 is another near edge on galaxy. They seem unusually common in
this group! It is listed as being Sab by all sources I checked and is
magnitude 14.7. We end the NGC list with one everyone agrees about.
Sure wish that was the rule rather than the exception with this bunch!

I've indicated other members of the group by name in the annotated
image. If I thought their angular size indicated they were a member but
no redshift data was available to confirm this I listed the name
followed by a question mark.

While many galaxy clusters were listed for the field only two could be
marked with an obvious core galaxy. One is southeast of the center of
my image. It is MaxBCG J179.54663+25.05842. It's core galaxy is very
obvious with some detail in my image. It's distance is only 1.8 billion
light-years and contains 15 members in an unspecified radius. The BCG
is also listed in the 2MASS catalog of IR sources so may still be
feeding. At least it is full of dust being heated by unseen newly
minted stars. The other cluster is on the far western edge of my image.
It is GMBCG J179.11209+25.16277. It is listed as having 11 members.
It BCG also is in the 2Mass catalog as an IR source. In the case of the
first cluster there was no redshift value for the BCG. For this cluster
there is but it differs from that of the cluster itself. The cluster is
listed at 3.4 billion light-years and the galaxy at 3.2 billion
light-years. The galaxy's redshift is by spectroscopic measurement
while the cluster is photographic. So I expect the 3.2 billion
light-year figure is the one to use here.

The NGC 4005/7 group extends well beyond my field of view. Those with
wider fields will pick up far more than I have so this is a good group
target for small systems. I'd like to see what you get. Under dark
skies it should be quite spectacular.

14" LX200R @ f/10, L=8x10' RGB=2x10'x3, STL-11000XM, Paramount ME

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