ASTRO: Arp 78 Reprocessed

NGC 40 was my last December 2011 post. I'm ready to move into 2012 and
be in the current year -- not for long obviously.

Arp 78/NGC 772 is a spiral galaxy in Aries about 100 million light-years
away. Arp put it in his category of spirals with small, high surface
brightness companions on their arms. He also has a category for
galaxies with one heavy arm. Since the companion isn't on a spiral arm,
just nearby, I'd have thought the heavy arm category suited it better.
Though the companion may be the cause of the "heavy arm". NED classes
Arp 78 as SA(s)b with HII emission while the NGC project's simpler
classification is simply Sb I. Neither call it peculiar which I find,
well, peculiar. To me it isn't just the long drawn out heavy blue arm
but all the debris scattered about it due to a past interaction that
would earn it such a designation. At a distance of 100 million
light-years the galaxy would be some 234,000 light-years across
including the fainter extensions and plumes to the south east and north
west. Including just the brighter inner region makes it 150,000
light-years across. Anyway you look at it this is a large spiral galaxy.

The companion is NGC 770. It is at the same redshift as Arp 78
indicating they are true companions. All the debris in the area could
indicate it is the interacting galaxy that did the damage though it is
little distorted which bothers me a bit. Not a lot as it is a highly
condensed, high mass galaxy that could withstand such an interaction
with a spiral without a lot of obvious damage. NED classes it as E3:.
The colon indicates some question over this classification. The NGC
project says simply E. Most papers indicate they are likely interacting.

While the Sloan Survey has imaged this field the data hasn't as yet been
picked up by NED leaving me little to go on. NED lists a quasar behind
the galaxy of magnitude 19.63 but gives only a very general position.
Looking at the Sloan image I find a knot in Arp 78 has right at its
southeast end a very strong, very blue, round object of the correct
brightness. Without NED's ultraviolet capability it appears white in my
image. I've noted it but with two ?? as I'm quite unsure of the
identification. It is [HB89] 0156+187 for those wishing to follow up on
this.

To the west of NGC 770 is a galaxy, 2MASX J01590722+1857368, at a
distance of 880 million light-years. NED lists it as a "Poss. dwarf
gal." I find this very odd. For that that distance it would be about
115 thousand light-years across. By that measurement our galaxy is also
a possible dwarf galaxy! They don't show any question about the
accuracy of the redshift measurement. To compound this issue, LEDA
212884 at 860 million light-years would be even larger at 142,000
light-years. It too is listed by NED as a "Poss. dwarf gal." When I
first wrote up Arp 78 NED didn't have any redshift data on these two
galaxies. I mentioned without it there was no way to know if they too
were companions or not. I didn't note if NED had the "Poss. dwarf gal."
note at that time. If so, the note may be a hold over from 2008 when
the redshift data was unavailable. Other than that I know of no way to
explain this situation. Wish I'd kept better notes back then.

To the east of Arp 78 is a small galaxy at 110 million light-years. It's
only identification in NED is [WGB2006] 015624+18430_g. It is likely
part of the same group as Arp 78 and NGC 770. It would be a true dwarf
at about 16,000 light-years in diameter. NED has nothing to indicate
this however nor does it try to classify it. [WGB2006] is the Woods,
Geller, Barton catalog in case you were wondering.

The only other galaxy with redshift data is UGC 1445 at about twice the
distance of Arp 78. NED lists it as an S0 galaxy. In fact it appears
to me to be a rather classic example of this type of galaxy. Bright
core and featureless, rather red disk of old stars indicating star
formation ceased some time ago in the galaxy.

There are 7 asteroids in the image, a couple very faint. When I
originally looked up this data I covered only three of them. Until
recently the Minor Planet Center only allowed you to go back two years
when looking up asteroids. They have greatly improved the speed and
accuracy of their computer system. Now they allow you to go back much
further though not all asteroids will show up this far back in time.
Also some have no magnitude data or it is obviously very wrong. Two it
listed at magnitude 4 and 5! But the positions were very close. In
fact more accurate than the old 2 year system was. Sometimes it only
returned the asteroid number and not the yearly designation. When this
happened by entering that into the ephemeris calculator I was able to
get the full name. So they have a bug or two to work out but I do like
the improved accuracy and ability to go back further in time to when I
wasn't being very good about recording such data.

This, as you might guess from my references to 2008 is a reprocess of an
old image. Color was poor on it and there were other issues. I thought
this version sufficiently improved to rate a repost. The reason the
color was poor was I only captured 1 useable color frame for each color.
Back then I wasn't able to deal with the noise that this created in
the color data when digging deep. I now have the tools to handle this
thus resulting in better color in the faint areas and background.

14" LX200R @ f/10, L=4x10' RGB=1x10', STL-11000XM, Paramount ME

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

Nice detail Rick. I wasn't aware of the plumes to the south of NGC 772.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
. com...

NGC 40 was my last December 2011 post. I'm ready to move into 2012 and
be in the current year -- not for long obviously.

Arp 78/NGC 772 is a spiral galaxy in Aries about 100 million light-years
away. Arp put it in his category of spirals with small, high surface
brightness companions on their arms. He also has a category for
galaxies with one heavy arm. Since the companion isn't on a spiral arm,
just nearby, I'd have thought the heavy arm category suited it better.
Though the companion may be the cause of the "heavy arm". NED classes
Arp 78 as SA(s)b with HII emission while the NGC project's simpler
classification is simply Sb I. Neither call it peculiar which I find,
well, peculiar. To me it isn't just the long drawn out heavy blue arm
but all the debris scattered about it due to a past interaction that
would earn it such a designation. At a distance of 100 million
light-years the galaxy would be some 234,000 light-years across
including the fainter extensions and plumes to the south east and north
west. Including just the brighter inner region makes it 150,000
light-years across. Anyway you look at it this is a large spiral galaxy.

The companion is NGC 770. It is at the same redshift as Arp 78
indicating they are true companions. All the debris in the area could
indicate it is the interacting galaxy that did the damage though it is
little distorted which bothers me a bit. Not a lot as it is a highly
condensed, high mass galaxy that could withstand such an interaction
with a spiral without a lot of obvious damage. NED classes it as E3:.
The colon indicates some question over this classification. The NGC
project says simply E. Most papers indicate they are likely interacting.

While the Sloan Survey has imaged this field the data hasn't as yet been
picked up by NED leaving me little to go on. NED lists a quasar behind
the galaxy of magnitude 19.63 but gives only a very general position.
Looking at the Sloan image I find a knot in Arp 78 has right at its
southeast end a very strong, very blue, round object of the correct
brightness. Without NED's ultraviolet capability it appears white in my
image. I've noted it but with two ?? as I'm quite unsure of the
identification. It is [HB89] 0156+187 for those wishing to follow up on
this.

To the west of NGC 770 is a galaxy, 2MASX J01590722+1857368, at a
distance of 880 million light-years. NED lists it as a "Poss. dwarf
gal." I find this very odd. For that that distance it would be about
115 thousand light-years across. By that measurement our galaxy is also
a possible dwarf galaxy! They don't show any question about the
accuracy of the redshift measurement. To compound this issue, LEDA
212884 at 860 million light-years would be even larger at 142,000
light-years. It too is listed by NED as a "Poss. dwarf gal." When I
first wrote up Arp 78 NED didn't have any redshift data on these two
galaxies. I mentioned without it there was no way to know if they too
were companions or not. I didn't note if NED had the "Poss. dwarf gal."
note at that time. If so, the note may be a hold over from 2008 when
the redshift data was unavailable. Other than that I know of no way to
explain this situation. Wish I'd kept better notes back then.

To the east of Arp 78 is a small galaxy at 110 million light-years. It's
only identification in NED is [WGB2006] 015624+18430_g. It is likely
part of the same group as Arp 78 and NGC 770. It would be a true dwarf
at about 16,000 light-years in diameter. NED has nothing to indicate
this however nor does it try to classify it. [WGB2006] is the Woods,
Geller, Barton catalog in case you were wondering.

The only other galaxy with redshift data is UGC 1445 at about twice the
distance of Arp 78. NED lists it as an S0 galaxy. In fact it appears
to me to be a rather classic example of this type of galaxy. Bright
core and featureless, rather red disk of old stars indicating star
formation ceased some time ago in the galaxy.

There are 7 asteroids in the image, a couple very faint. When I
originally looked up this data I covered only three of them. Until
recently the Minor Planet Center only allowed you to go back two years
when looking up asteroids. They have greatly improved the speed and
accuracy of their computer system. Now they allow you to go back much
further though not all asteroids will show up this far back in time.
Also some have no magnitude data or it is obviously very wrong. Two it
listed at magnitude 4 and 5! But the positions were very close. In
fact more accurate than the old 2 year system was. Sometimes it only
returned the asteroid number and not the yearly designation. When this
happened by entering that into the ephemeris calculator I was able to
get the full name. So they have a bug or two to work out but I do like
the improved accuracy and ability to go back further in time to when I
wasn't being very good about recording such data.

This, as you might guess from my references to 2008 is a reprocess of an
old image. Color was poor on it and there were other issues. I thought
this version sufficiently improved to rate a repost. The reason the
color was poor was I only captured 1 useable color frame for each color.
Back then I wasn't able to deal with the noise that this created in
the color data when digging deep. I now have the tools to handle this
thus resulting in better color in the faint areas and background.

14" LX200R @ f/10, L=4x10' RGB=1x10', STL-11000XM, Paramount ME

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