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ASTRO: Holmberg III



 
 
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  #1  
Old July 20th 14, 07:26 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Posts: 3,085
Default ASTRO: Holmberg III

Erik Holmberg (1908-2000) was a Swedish astronomer who studied galaxies.
In fact he was the driving force behind the UGC galaxy catalog. Oddly
8 of the galaxies in that catalog also are 8 of the 9 galaxies in his
Holmberg catalog of galaxies. Why these 8 and no others I've not
determined. If anyone knows please let me know.

Of the 9, 5 of them are in Ursa Major. Holmberg III is one of the
exceptions though only barely being only a degree north of Ursa Major in
the southeastern corner of Camelopardalis less than a degree west of
Draco. It is UGC 8303 in his more famous catalog. I should note that
while the UGC was all his idea and he verified everything in it, he
allowed it to be published under only the name of his student that did
most of the grunt work. His study of galaxy interactions was done long
before computers yet he discovered some of the major principles of
galaxy interaction and a few that turned out wrong once computers could
crunch the numbers though he acknowledged those areas as weak due to the
lack of being able to crunch enough data. One of his major finds in the
1940's was that most of the tidal distortion happened after closest
approach rather than before. Galaxies could look very normal right up
to and through closest approach only to be badly torn apart after this
time.

But as to why Holmberg III in this image made his list I don't know.
One of his 9, Holmberg II made Arp's atlas of peculiar galaxies. Many
others are irregular dwarf galaxies which too are very peculiar looking
but that's the case with nearly all irregular dwarf galaxies. Then
there's Holmberg III which is a very normal looking spiral that doesn't
seem to fit the other 8 at all other than it is of very low surface
brightness and rather blue. The obvious traits of all 9. But there are
innumerable low surface brightness blue galaxies, many nearby like his 9
that aren't on his list. Of the 9 I can image 8 (VI is too low
declination and not all interesting looking). I only have two left to
go I and VII and one has had data taken, just not processed yet.

Holmberg III is, as mentioned, a slow surface brightness, face on,
spiral galaxy with a surprisingly small core. Red shift puts it some 54
million light-years distant while 2 Tully Fisher measurements come up
with the widely differing values of 65 and 111 million light-years for
an average value of 89 million light-years. Flip your three headed coin
on this one! Assuming the 89 million light-year distance it is a rather
large galaxy at 86,000 light years. It is only 52,000 light years across
if the 54 million light-year distance is used. The larger distance of
111 million light years gives 107,000 light-years making it about the
size of the Milky Way but a far dimmer version.

There's very little information available on the field. Only two other
galaxies in the image have redshift data. That shows the three are not
related to each other in any way. While the center of the poor Abell
762 galaxy cluster is located just below UGC 04883 in the upper left
corner I can't identify any galaxy in the frame that may be part of the
group which has no size data and contains less than 30 members. It's
distance is listed at 1.69 million light-years which doesn't match
anything known in the image. Some rather reddened galaxies are in the
area which might be part of the cluster. I just don't have enough
information to say. CGCG 332-036 below Holmberg III seems to have a
plume to the east where there's a small compact red galaxy. Are the two
interacting? Probably not but no way to know with so little information.

One asteroid, (208879) 2002 TF58 did manage to appear in the image. With
the luminance frames taken at two different times due to clouds in the
middle, right at the meridian unfortunately, its trail appears in two
parts. Color data was taken a different night so there's no color trail
for it as it was well out of frame at the time.

The GALEX (GALaxy Evolution eXplorer) satellite reported several UvES
objects in the image which could be quasars but without redshift data
there's no way to know. I didn't bother to label them as they look
exactly the same as the many blue stars in the image.

14" LX200R @ f/10, L=8x10, RGB=2x10' (wanted more but clouds didn't
cooperate), STL-11000XM, Paramount ME

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

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  #2  
Old July 22nd 14, 03:39 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
external usenet poster
 
Posts: 3,085
Default ASTRO: Holmberg III

I got my eyes crossed UGC 8308 is Holmberg VIII not Holmberg III.
Holmberg III is UGC 4841. Sorry for the mistake. I was off only by a "V"

Rick

On 7/20/2014 1:26 AM, Rick Johnson wrote:
Erik Holmberg (1908-2000) was a Swedish astronomer who studied galaxies.
In fact he was the driving force behind the UGC galaxy catalog. Oddly
8 of the galaxies in that catalog also are 8 of the 9 galaxies in his
Holmberg catalog of galaxies. Why these 8 and no others I've not
determined. If anyone knows please let me know.

Of the 9, 5 of them are in Ursa Major. Holmberg III is one of the
exceptions though only barely being only a degree north of Ursa Major in
the southeastern corner of Camelopardalis less than a degree west of
Draco. It is UGC 8303 in his more famous catalog. I should note that
while the UGC was all his idea and he verified everything in it, he
allowed it to be published under only the name of his student that did
most of the grunt work. His study of galaxy interactions was done long
before computers yet he discovered some of the major principles of
galaxy interaction and a few that turned out wrong once computers could
crunch the numbers though he acknowledged those areas as weak due to the
lack of being able to crunch enough data. One of his major finds in the
1940's was that most of the tidal distortion happened after closest
approach rather than before. Galaxies could look very normal right up
to and through closest approach only to be badly torn apart after this
time.

But as to why Holmberg III in this image made his list I don't know. One
of his 9, Holmberg II made Arp's atlas of peculiar galaxies. Many
others are irregular dwarf galaxies which too are very peculiar looking
but that's the case with nearly all irregular dwarf galaxies. Then
there's Holmberg III which is a very normal looking spiral that doesn't
seem to fit the other 8 at all other than it is of very low surface
brightness and rather blue. The obvious traits of all 9. But there are
innumerable low surface brightness blue galaxies, many nearby like his 9
that aren't on his list. Of the 9 I can image 8 (VI is too low
declination and not all interesting looking). I only have two left to
go I and VII and one has had data taken, just not processed yet.

Holmberg III is, as mentioned, a slow surface brightness, face on,
spiral galaxy with a surprisingly small core. Red shift puts it some 54
million light-years distant while 2 Tully Fisher measurements come up
with the widely differing values of 65 and 111 million light-years for
an average value of 89 million light-years. Flip your three headed coin
on this one! Assuming the 89 million light-year distance it is a rather
large galaxy at 86,000 light years. It is only 52,000 light years across
if the 54 million light-year distance is used. The larger distance of
111 million light years gives 107,000 light-years making it about the
size of the Milky Way but a far dimmer version.

There's very little information available on the field. Only two other
galaxies in the image have redshift data. That shows the three are not
related to each other in any way. While the center of the poor Abell
762 galaxy cluster is located just below UGC 04883 in the upper left
corner I can't identify any galaxy in the frame that may be part of the
group which has no size data and contains less than 30 members. It's
distance is listed at 1.69 million light-years which doesn't match
anything known in the image. Some rather reddened galaxies are in the
area which might be part of the cluster. I just don't have enough
information to say. CGCG 332-036 below Holmberg III seems to have a
plume to the east where there's a small compact red galaxy. Are the two
interacting? Probably not but no way to know with so little information.

One asteroid, (208879) 2002 TF58 did manage to appear in the image. With
the luminance frames taken at two different times due to clouds in the
middle, right at the meridian unfortunately, its trail appears in two
parts. Color data was taken a different night so there's no color trail
for it as it was well out of frame at the time.

The GALEX (GALaxy Evolution eXplorer) satellite reported several UvES
objects in the image which could be quasars but without redshift data
there's no way to know. I didn't bother to label them as they look
exactly the same as the many blue stars in the image.

14" LX200R @ f/10, L=8x10, RGB=2x10' (wanted more but clouds didn't
cooperate), STL-11000XM, Paramount ME

Rick



--
Prefix is correct. Domain is arvig dot net
 




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