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Arp 79 and 117 reprocessed



 
 
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  #1  
Old May 10th 15, 09:14 PM
WA0CKY WA0CKY is offline
Senior Member
 
First recorded activity by SpaceBanter: Feb 2008
Posts: 689
Default Arp 79 and 117 reprocessed

This is a reprocess of an image taken back in 2009. My processing toolkit was limited as was my ability to use what tools I had. So it was time to redo it after I looked at it and got an instant yuck reaction in my stomach. I cheated by starting with a partly processed TIFF luminance image and since the color data looked good but for color balance I used it as I had processed it the first time except to adjust color balance some, mainly to remove air glow that tends to be strong at my latitude. Also I wasn't doing annotated images back then. There was enough else going on I needed to go into that I had skipped in the original post 6 years ago.

This is a two for one Arp image that contains both Arp 79 and Arp 117. Arp 79 is listed by Arp under the category for spiral galaxies with high surface brightness companions. But there's no such companion. Arp's only comment on the object refers to the two star knots in the southern arm saying; "Small separation between two knots in arm." There is an orange field star in the other arm but I don't see how that looks anything like a companion galaxy either. Some have said he is referring to the brightening of the arm where those two star knots are located but since he refers to them and the brightening looks nothing like a companion I can't imagine that was his intent. It does have a strange feature, a straight blue bar of stars that appears separate from the galaxy seen below the two star knots. It's far from being of high surface brightness but could be considered a companion I suppose. I find nothing on it.

The right of two star knots in the arm is SDSS J141007.08+173647.6 which NED does call a galaxy rather than part of a galaxy but I've see many such star knots listed this way so I don't put a lot of credence into that classification. The other star knot isn't listed at NED at all nor is the bar. Seems there's lots of mystery to this one. While it looks like a small spiral it is actually pretty normal sized at 70,000 light-years. It's just its distance that makes it seem small. It is sometimes known as NGC 5490C (NGC 5490 is at the bottom of my image) and is classified as SB(s)bc.

Arp 117 is listed by Arp under his classification for elliptical-like galaxies close to and perturbing spirals. Thus by his classification the small galaxy is perturbing the big one. Arp apparently sees this as a warping of the spiral for which he notes: "Flattening of spiral's nucleus appears to be in a different plane than the arms." I'm not so sure I see what he is talking about. The core is very bright with a short but bright bar. Does he see this as a spiral seen edge on inside a face on set of arms? Other than this I don't see what he is talking about. While both galaxies have the same redshift and thus likely about the same distance from us it also could be their relative motions are actually quite different but their distance difference covers this up. I'd think there'd be distortions in the smaller companion as well as the spiral. I don't see that the companion is anything but very normal looking. It is IC 982, a SA0+ galaxy and the spiral is IC 983 a SB(r)bc galaxy. Note that except for the pseudo ring structure its classification is the same as that of Arp 79 even though they appear very different.

Arp 117 was discovered by Stephane Javelle on May 27, 1891. IC 982 is about 80,000 light-years across while the spiral IC 983 is absolutely huge at over 325,000 light-years dwarfing everything around it.

Note in the annotated image there are many dwarf galaxies with a redshift indicating they are part of the same group. Many having almost exactly the same redshift in fact.

The other major galaxy in the image is NGC 5490 that for some reason I didn't get entirely on the frame. It is listed simply as an Elliptical galaxy and has a very similar redshift to the two Arp systems. Indicating it is likely part of the same group. It was discovered by William Herschel on March 14, 1784. It is in the second Herschel 400 observing program. I can't directly measure its size on my image since it is partly out of the frame. Using NED's diameter it would be about 125,000 light years in size using a distance of 250,000 million light-years determined by mostly type 1A super nova measurements though redshift places it a bit closer and thus smaller. It may be its own group as there are other galaxies around it with redshifts a bit less than that of the two Arp systems.

14" LX200R @ f/10, L=4x10' RGB=2x10' binned 3x3, STL-11000XM, Paramount ME

Rick
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Last edited by WA0CKY : May 10th 15 at 09:19 PM.
  #2  
Old May 23rd 15, 06:37 PM posted to alt.binaries.pictures.astro
Stefan Lilge
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Posts: 2,269
Default Arp 79 and 117 reprocessed

Rick,

amazing how deep you got in such short time.
I imaged IC 983 in March under decent skies (just processed) with a bit
short of four hours total exposure time and IC 983 looks very faint in my
image.
As it is not worth a separate post I'll just attach it to this message:

Taken under decent skies in northern Germany with a 10" Meade ACF at f/8 on
a G11 mount, Trius SX694 camera, 3.8 hours total integration time, all
binned 2x2.

Stefan


"WA0CKY" schrieb im Newsbeitrag ...


This is a reprocess of an image taken back in 2009. My processing
toolkit was limited as was my ability to use what tools I had. So it
was time to redo it after I looked at it and got an instant yuck
reaction in my stomach. I cheated by starting with a partly processed
TIFF luminance image and since the color data looked good but for color
balance I used it as I had processed it the first time except to adjust
color balance some, mainly to remove air glow that tends to be strong at
my latitude. Also I wasn't doing annotated images back then. There was
enough else going on I needed to go into that I had skipped in the
original post 6 years ago.

This is a two for one Arp image that contains both Arp 79 and Arp 117.
Arp 79 is listed by Arp under the category for spiral galaxies with high
surface brightness companions. But there's no such companion. Arp's
only comment on the object refers to the two star knots in the southern
arm saying; "Small separation between two knots in arm." There is an
orange field star in the other arm but I don't see how that looks
anything like a companion galaxy either. Some have said he is referring
to the brightening of the arm where those two star knots are located but
since he refers to them and the brightening looks nothing like a
companion I can't imagine that was his intent. It does have a strange
feature, a straight blue bar of stars that appears separate from the
galaxy seen below the two star knots. It's far from being of high
surface brightness but could be considered a companion I suppose. I
find nothing on it.

The right of two star knots in the arm is SDSS J141007.08+173647.6 which
NED does call a galaxy rather than part of a galaxy but I've see many
such star knots listed this way so I don't put a lot of credence into
that classification. The other star knot isn't listed at NED at all nor
is the bar. Seems there's lots of mystery to this one. While it looks
like a small spiral it is actually pretty normal sized at 70,000
light-years. It's just its distance that makes it seem small. It is
sometimes known as NGC 5490C (NGC 5490 is at the bottom of my image) and
is classified as SB(s)bc.

Arp 117 is listed by Arp under his classification for elliptical-like
galaxies close to and perturbing spirals. Thus by his classification
the small galaxy is perturbing the big one. Arp apparently sees this as
a warping of the spiral for which he notes: "Flattening of spiral's
nucleus appears to be in a different plane than the arms." I'm not so
sure I see what he is talking about. The core is very bright with a
short but bright bar. Does he see this as a spiral seen edge on inside
a face on set of arms? Other than this I don't see what he is talking
about. While both galaxies have the same redshift and thus likely about
the same distance from us it also could be their relative motions are
actually quite different but their distance difference covers this up.
I'd think there'd be distortions in the smaller companion as well as the
spiral. I don't see that the companion is anything but very normal
looking. It is IC 982, a SA0+ galaxy and the spiral is IC 983 a SB(r)bc
galaxy. Note that except for the pseudo ring structure its
classification is the same as that of Arp 79 even though they appear
very different.

Arp 117 was discovered by Stephane Javelle on May 27, 1891. IC 982 is
about 80,000 light-years across while the spiral IC 983 is absolutely
huge at over 325,000 light-years dwarfing everything around it.

Note in the annotated image there are many dwarf galaxies with a
redshift indicating they are part of the same group. Many having almost
exactly the same redshift in fact.

The other major galaxy in the image is NGC 5490 that for some reason I
didn't get entirely on the frame. It is listed simply as an Elliptical
galaxy and has a very similar redshift to the two Arp systems.
Indicating it is likely part of the same group. It was discovered by
William Herschel on March 14, 1784. It is in the second Herschel 400
observing program. I can't directly measure its size on my image since
it is partly out of the frame. Using NED's diameter it would be about
125,000 light years in size using a distance of 250,000 million
light-years determined by mostly type 1A super nova measurements though
redshift places it a bit closer and thus smaller. It may be its own
group as there are other galaxies around it with redshifts a bit less
than that of the two Arp systems.

14" LX200R @ f/10, L=4x10' RGB=2x10' binned 3x3, STL-11000XM, Paramount
ME

Rick


--
WA0CKY

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  #3  
Old May 24th 15, 08:40 PM
WA0CKY WA0CKY is offline
Senior Member
 
First recorded activity by SpaceBanter: Feb 2008
Posts: 689
Default

Considering your camera half again more sensitive then mine it is surprising. I do collect twice the photons which helps. Still most of it likely comes from my skies. I suspect that when I consider my skies poor most would consider them great. What few lights are around me are below the forest canopy so they don't reach the skies. Though I do avoid to the southwest as a town about 27 km (as the photons fly) is super lit. Merchants all complain how hard it is to make a living yet waste a huge amount of electricity lighting the bellies of flying ducks with tons of unshielded street lights ("artistic" bare bulb fixtures). Well those very few that fly at night. As seen in the famous "Earth at Night" image the town is brighter than most with 5 times the population. Still it likely doesn't hurt as much as I think it does. Just the contrast is so great with the rest of my skies so dark. It does make it hard to catch objects in that part of the sky. After a few months of bad weather that's where the objects I missed due to weather now are and their lights block me for doing them well.

Rick

Quote:
Originally Posted by Stefan Lilge View Post
Rick,

amazing how deep you got in such short time.
I imaged IC 983 in March under decent skies (just processed) with a bit
short of four hours total exposure time and IC 983 looks very faint in my
image.
As it is not worth a separate post I'll just attach it to this message:

Taken under decent skies in northern Germany with a 10" Meade ACF at f/8 on
a G11 mount, Trius SX694 camera, 3.8 hours total integration time, all
binned 2x2.

Stefan
 




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