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ASTRO: M32 et al (Arp 168)



 
 
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  #1  
Old February 28th 10, 11:27 PM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
external usenet poster
 
Posts: 3,085
Default ASTRO: M32 et al (Arp 168)

M32 is Number 168 in Arp's peculiar galaxy atlas. That puts it in his
Galaxies (not classifiable as S or E): Diffuse counter-tails. How many
times have you seen this companion to M31 yet not seen the counter-tail.
Yeah, me neither. Arp's comment to this one: "Faint diffuse plume
curved away from M31's disk." Odd Arp would consider it neither
Elliptical or Spiral. Every source I checked classed it as a compact
elliptical galaxy, most saying cE2. The "c" for compact. Most sources
say much of its outer halo has been striped away by the tidal forces of
M32 yet the counter tail remains, albeit very faintly. If you blow up
the image some of the stars of M32 are resolved around the left and
bottom edges. At least I think they are members of M32 rather than M31.
Blue M31 stars are seen along the right and top edges of M32 however.

To try and find this nearly invisible plume I exposed for several hours
but skies were awful. Only 4 frames had decent seeing and half way
usable transparency. I didn't realize this at the time as I looked only
at the first and last of the series and they looked good. But CCDSoft's
auto histogram stretch can hide a lot. I didn't realize the first frame
had 8 times the light throughput as the last. I ended up using only 4
of the series as that gave the best image. Including more just made the
plume even harder to see. Note this was taken the day before my high
resolution C179 image and seeing was very good. Good enough to have
binned 1x1 but I wanted the added speed of the 2x2 binning. That was a
good choice as only 40 minutes of 1x1 binned data wouldn't have been as
good due to added read noise. The color data was useless due to clouds
so used the same low resolution data I used for the previous C179 shot.
It wasn't as bad of a match for this image so worked somewhat better.

In the raw data M32 goes to the far lower left corner of the image.
When stretched to bring this out the plume vanished into the background
of M31. Probably why few are aware of its existence. Since this outer
part of M31 is very blue but the plume from M31 rather red I dimmed down
the blue parts of M31 in this area letting the redder features remain.
This makes the plume visible though I'm not sure it is curving like Arp
says. I don't see the curve on his image either.

Some of the same features on my close-up of M32 that I ran earlier are
seen in this lower resolution image. Many other features beyond the
edges of that image are seen as well so I've prepared an annotated image
showing these as well. A few on the edges are shown on both but most
Objects already shown on my "Where in the Universe" image of C179's
annotated image are not included for the most part. Also see that for
details on the labeling scheme used.

G117 is a bit of a puzzle. It is on both Chart 5 and 6 of the atlas but
the lines connect to different star like objects! NED shows the lower
and brighter one to be a globular so that is the one I chose to use.
NED refers to it as SKHV 117. I put a ? by the other object as it has
the PSF of an extended object, rather than a star. Just that it isn't
in NED and only "half in" the Hodge atlas.

The image is full of open clusters. I've only identified a few of them.
In one place I just put OC and ran lines to three in the area. Many
fuzzy patches were not in the Hodge atlas nor NED. I gave up trying to
track them down. I could spend months on this image alone. Just not
worth it.

What I noticed most was the color of the globulars. Many appeared
identical to orange stars but for their PSF not being starlike. Seems
most globulars I image in our galaxy seem to have a slightly blue over
all color thanks to the highly luminously blue straglers. Are M31
globulars lacking in such stars, are we seeing them through lots of
reddening dust? In any case the tendency of neutral to orange color
seems surprising to me.

There are many differences between NED and the Hodge atlas. For
instance the cluster C205 in the upper right corner is at the location
of a very blue starlike object. NED shows no cluster at that point but
does show the round emission object just below and left of it as a
cluster. This whole region seems to be rather poorly mapped to RA/DEC
coordinates. It made it impossible to really pin down which of the many
HII regions in this area are which on my image. While NED says the
position error is 5" on both axes I was finding nothing within that
range. Even when I put those coordinates into the DSS it came up with
nothing in that range either but maybe 10" away their was something that
might be the object but go 10" another direction and there was another
possible object. Move a couple minutes from the area and everything was
fine again, I was agreeing within a tenth of a second of arc, not tens
of seconds as I and the DSS were in this area. The round bubble below
the bright star Hodge sees as a cluster is likely one of the Wolf Rayet
bubbles listed by NED in the area. I just can't tell which one. In NED
its position is nearly that of a cluster with the WR bubbles further
away. I've given up, just enjoy the region. Blow up the image 2x for a
better view.

To take out the bad taste left by the above fiasco scan down about half
way to the bottom and you'll find a small round red blob. That is
listed by NED (coordinates match!) as a Super Nova Remnant they call MLA
0266. Looks like it would be grand as seen from a few thousand light
years rather that a few million.

Arp's image, apparently with the Schmidt camera not 200" (at least his
resolution is well below mine) and rotated so east is up rather than
north is at:
http://nedwww.ipac.caltech.edu/level...ig_arp168.jpeg

14" LX200R @ f/10, L=4x10', RGB=4x10'x3 (same as used for C179 image),
STL-11000XM, Paramount ME
--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".

Attached Thumbnails
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Name:	ARP168M32L4X10RGB4X10X3.jpg
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Size:	525.2 KB
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Name:	ARP168M32L4X10RGB4X10X3ID.jpg
Views:	298
Size:	352.2 KB
ID:	2834  
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  #2  
Old March 3rd 10, 08:49 PM posted to alt.binaries.pictures.astro
Stefan Lilge
external usenet poster
 
Posts: 2,269
Default ASTRO: M32 et al (Arp 168)

Rick,

very good highres picture. Colours detail is also very good.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
. com...
M32 is Number 168 in Arp's peculiar galaxy atlas. That puts it in his
Galaxies (not classifiable as S or E): Diffuse counter-tails. How many
times have you seen this companion to M31 yet not seen the counter-tail.
Yeah, me neither. Arp's comment to this one: "Faint diffuse plume
curved away from M31's disk." Odd Arp would consider it neither
Elliptical or Spiral. Every source I checked classed it as a compact
elliptical galaxy, most saying cE2. The "c" for compact. Most sources
say much of its outer halo has been striped away by the tidal forces of
M32 yet the counter tail remains, albeit very faintly. If you blow up
the image some of the stars of M32 are resolved around the left and
bottom edges. At least I think they are members of M32 rather than M31.
Blue M31 stars are seen along the right and top edges of M32 however.

To try and find this nearly invisible plume I exposed for several hours
but skies were awful. Only 4 frames had decent seeing and half way
usable transparency. I didn't realize this at the time as I looked only
at the first and last of the series and they looked good. But CCDSoft's
auto histogram stretch can hide a lot. I didn't realize the first frame
had 8 times the light throughput as the last. I ended up using only 4
of the series as that gave the best image. Including more just made the
plume even harder to see. Note this was taken the day before my high
resolution C179 image and seeing was very good. Good enough to have
binned 1x1 but I wanted the added speed of the 2x2 binning. That was a
good choice as only 40 minutes of 1x1 binned data wouldn't have been as
good due to added read noise. The color data was useless due to clouds
so used the same low resolution data I used for the previous C179 shot.
It wasn't as bad of a match for this image so worked somewhat better.

In the raw data M32 goes to the far lower left corner of the image.
When stretched to bring this out the plume vanished into the background
of M31. Probably why few are aware of its existence. Since this outer
part of M31 is very blue but the plume from M31 rather red I dimmed down
the blue parts of M31 in this area letting the redder features remain.
This makes the plume visible though I'm not sure it is curving like Arp
says. I don't see the curve on his image either.

Some of the same features on my close-up of M32 that I ran earlier are
seen in this lower resolution image. Many other features beyond the
edges of that image are seen as well so I've prepared an annotated image
showing these as well. A few on the edges are shown on both but most
Objects already shown on my "Where in the Universe" image of C179's
annotated image are not included for the most part. Also see that for
details on the labeling scheme used.

G117 is a bit of a puzzle. It is on both Chart 5 and 6 of the atlas but
the lines connect to different star like objects! NED shows the lower
and brighter one to be a globular so that is the one I chose to use.
NED refers to it as SKHV 117. I put a ? by the other object as it has
the PSF of an extended object, rather than a star. Just that it isn't
in NED and only "half in" the Hodge atlas.

The image is full of open clusters. I've only identified a few of them.
In one place I just put OC and ran lines to three in the area. Many
fuzzy patches were not in the Hodge atlas nor NED. I gave up trying to
track them down. I could spend months on this image alone. Just not
worth it.

What I noticed most was the color of the globulars. Many appeared
identical to orange stars but for their PSF not being starlike. Seems
most globulars I image in our galaxy seem to have a slightly blue over
all color thanks to the highly luminously blue straglers. Are M31
globulars lacking in such stars, are we seeing them through lots of
reddening dust? In any case the tendency of neutral to orange color
seems surprising to me.

There are many differences between NED and the Hodge atlas. For
instance the cluster C205 in the upper right corner is at the location
of a very blue starlike object. NED shows no cluster at that point but
does show the round emission object just below and left of it as a
cluster. This whole region seems to be rather poorly mapped to RA/DEC
coordinates. It made it impossible to really pin down which of the many
HII regions in this area are which on my image. While NED says the
position error is 5" on both axes I was finding nothing within that
range. Even when I put those coordinates into the DSS it came up with
nothing in that range either but maybe 10" away their was something that
might be the object but go 10" another direction and there was another
possible object. Move a couple minutes from the area and everything was
fine again, I was agreeing within a tenth of a second of arc, not tens
of seconds as I and the DSS were in this area. The round bubble below
the bright star Hodge sees as a cluster is likely one of the Wolf Rayet
bubbles listed by NED in the area. I just can't tell which one. In NED
its position is nearly that of a cluster with the WR bubbles further
away. I've given up, just enjoy the region. Blow up the image 2x for a
better view.

To take out the bad taste left by the above fiasco scan down about half
way to the bottom and you'll find a small round red blob. That is
listed by NED (coordinates match!) as a Super Nova Remnant they call MLA
0266. Looks like it would be grand as seen from a few thousand light
years rather that a few million.

Arp's image, apparently with the Schmidt camera not 200" (at least his
resolution is well below mine) and rotated so east is up rather than
north is at:
http://nedwww.ipac.caltech.edu/level...ig_arp168.jpeg

14" LX200R @ f/10, L=4x10', RGB=4x10'x3 (same as used for C179 image),
STL-11000XM, Paramount ME
--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".



 




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