ASTRO: Arp 42

Arp 42/NGC 5829 and IC 4526 falls under Arp's category of spiral
galaxies with a low surface brightness companion on an arm. Though in
this case I can't see that the companion is on a spiral arm nor that it
is of low surface brightness. It seems rather bright in my image. The
wrap around arm is very faint however. The pair are located in
constellation of Bootes about... Houston we've had a problem. Seems the
red shift distance to NGC 5829, the nice spiral is 265 million
light-years but the "companion" has a red shift distance of 620 million
light-years according to NED. If correct, it isn't a companion at all
but a distant background galaxy. Adding to the confusion is that both
are members of the Hickson 73 galaxy group. This is described in a note
at NED as: "Hickson 73 - Group is actually formed by a bright low
redshift galaxy - detected also at radio wavelengths - plus an accordant
triplet at much higher redshift. Galaxy e is a background object."
These 5 galaxies are noted on the annotated image with the prefix 73 and
the Hickson letter followed by its red shift distance. Why the 6th blue
galaxy at the distance as NGC 5829 isn't included in the group I don't
know. It would seem worthy of inclusion.

Arp's comment on this one indicates he likely didn't realize they
weren't related when he commented: "Faint bifurcated arm to companion,
one faint arm on companion coiled in same direction as parent."

The close spiral is classed at NED as SA(s)c with HII emission. The
"companion" is classed as Im.

Note the two very blue spots in the bifurcated arm. The lower one is
bigger than the upper. At NED it is shown as a HII region in the VV
catalog and a galaxy in the Sloan survey. NED however has an essential
note saying it is most likely an HII region in the arm. The upper one
only has a Sloan entry and also as a galaxy. NED has no essential note.
Still I think it likely is another HII region in the galaxy.

Near the northeastern member of the Hickson group is the center of a
small galaxy cluster, MaxBCG J225.70820+23.36644 at 2.3 billion
light-years. Its center is marked by a bright galaxy at the same
distance. The cluster is listed as having 14 members with no diameter
given. South of Arp 42 is another galaxy cluster marked by a bright
galaxy. The cluster is [EAD2007] 349 with 28 members but no diameter.
It's about 2.3 billion light-years distant estimated with the core
galaxy at 2.2 billion light-years. At the very bottom of my image near
the center is the center of Abell 2017 with a diameter of 24 minutes, a
richness class of 1 (which someone else with need to interpret) and a
distance of 1.5 billion light-years. Seems we have a lot of likely
overlapping galaxy clusters here. At least 6 more are within a few
minutes beyond the north and south edges of my image. But the one
apparently obvious cluster I see about 2 minutes northeast of the galaxy
at 1.6 billion light-years that is northeast of Arp 42 isn't listed at
NED. There's a dozen or more in a 1 minute radius, none of which have a
red shift distance though they are listed at NED, usually with a Sloan
position.

To the upper right of Arp 42 is one Arp missed. Two very distant
galaxies merge into one in my image except their different color gives
them away. One is blue with a tail going down, the other rather red
with a tail going to the right. Only the blue one has a red shift which
puts it at 1.4 billion light-years. They look like two merging
tadpoles. The blue galaxy is SDSS J150202.65+232518.8, the red one
2MASX J15020259+2325187. Now to convince Hubble to take a look, though
it hasn't even looked at Arp 42 as yet.

I did it again. In the upper left corner is an asteroid trail.
Unfortunately, it is another unknown at the Minor Planet Center. It was
taken April 9, 2010 so too late to follow up on it virtually a year
later. It will be unknown a while longer it appears.

Speaking of a year later. I'm about to be lapped and fall more than a
year behind. The calendar will beat me unfortunately. I see I have 16
more to process by the 21st of April, nearly one a day not to fall
behind. No way I'll make that. At least last night's snow is melting
so I won't have to work on it. Back to processing.

Arp's image
http://nedwww.ipac.caltech.edu/level...big_arp42.jpeg

14" LX200R @ f/10, L=4x10' RGB=2x10x3, 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".

Rick, that's a beautiful spiral, really nice.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
ter.com...
Arp 42/NGC 5829 and IC 4526 falls under Arp's category of spiral
galaxies with a low surface brightness companion on an arm. Though in
this case I can't see that the companion is on a spiral arm nor that it
is of low surface brightness. It seems rather bright in my image. The
wrap around arm is very faint however. The pair are located in
constellation of Bootes about... Houston we've had a problem. Seems the
red shift distance to NGC 5829, the nice spiral is 265 million
light-years but the "companion" has a red shift distance of 620 million
light-years according to NED. If correct, it isn't a companion at all
but a distant background galaxy. Adding to the confusion is that both
are members of the Hickson 73 galaxy group. This is described in a note
at NED as: "Hickson 73 - Group is actually formed by a bright low
redshift galaxy - detected also at radio wavelengths - plus an accordant
triplet at much higher redshift. Galaxy e is a background object."
These 5 galaxies are noted on the annotated image with the prefix 73 and
the Hickson letter followed by its red shift distance. Why the 6th blue
galaxy at the distance as NGC 5829 isn't included in the group I don't
know. It would seem worthy of inclusion.

Arp's comment on this one indicates he likely didn't realize they
weren't related when he commented: "Faint bifurcated arm to companion,
one faint arm on companion coiled in same direction as parent."

The close spiral is classed at NED as SA(s)c with HII emission. The
"companion" is classed as Im.

Note the two very blue spots in the bifurcated arm. The lower one is
bigger than the upper. At NED it is shown as a HII region in the VV
catalog and a galaxy in the Sloan survey. NED however has an essential
note saying it is most likely an HII region in the arm. The upper one
only has a Sloan entry and also as a galaxy. NED has no essential note.
Still I think it likely is another HII region in the galaxy.

Near the northeastern member of the Hickson group is the center of a
small galaxy cluster, MaxBCG J225.70820+23.36644 at 2.3 billion
light-years. Its center is marked by a bright galaxy at the same
distance. The cluster is listed as having 14 members with no diameter
given. South of Arp 42 is another galaxy cluster marked by a bright
galaxy. The cluster is [EAD2007] 349 with 28 members but no diameter.
It's about 2.3 billion light-years distant estimated with the core
galaxy at 2.2 billion light-years. At the very bottom of my image near
the center is the center of Abell 2017 with a diameter of 24 minutes, a
richness class of 1 (which someone else with need to interpret) and a
distance of 1.5 billion light-years. Seems we have a lot of likely
overlapping galaxy clusters here. At least 6 more are within a few
minutes beyond the north and south edges of my image. But the one
apparently obvious cluster I see about 2 minutes northeast of the galaxy
at 1.6 billion light-years that is northeast of Arp 42 isn't listed at
NED. There's a dozen or more in a 1 minute radius, none of which have a
red shift distance though they are listed at NED, usually with a Sloan
position.

To the upper right of Arp 42 is one Arp missed. Two very distant
galaxies merge into one in my image except their different color gives
them away. One is blue with a tail going down, the other rather red
with a tail going to the right. Only the blue one has a red shift which
puts it at 1.4 billion light-years. They look like two merging
tadpoles. The blue galaxy is SDSS J150202.65+232518.8, the red one
2MASX J15020259+2325187. Now to convince Hubble to take a look, though
it hasn't even looked at Arp 42 as yet.

I did it again. In the upper left corner is an asteroid trail.
Unfortunately, it is another unknown at the Minor Planet Center. It was
taken April 9, 2010 so too late to follow up on it virtually a year
later. It will be unknown a while longer it appears.

Speaking of a year later. I'm about to be lapped and fall more than a
year behind. The calendar will beat me unfortunately. I see I have 16
more to process by the 21st of April, nearly one a day not to fall
behind. No way I'll make that. At least last night's snow is melting
so I won't have to work on it. Back to processing.

Arp's image
http://nedwww.ipac.caltech.edu/level...big_arp42.jpeg

14" LX200R @ f/10, L=4x10' RGB=2x10x3, 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".