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ASTRO: Arp 95



 
 
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  #1  
Old May 19th 11, 08:17 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Posts: 3,085
Default ASTRO: Arp 95

Arp 95 is a triple galaxy system located in Bootes about 425 million
light-years from us. Arp put these three under Galaxies with companions
on arms: Elliptical galaxy companions. By this the lower one to the
right isn't included. The lower galaxy is not classed at NED. It
appears to be a Magellanic type dwarf to me. Possibly a spiral or
irregular. Certainly not elliptical as it would need to be to fit the
category. There is no redshift distance for it either so can't say for
certain it is even a member of the group. The elliptical has the same
redshift as the big spiral so certainly is a member of the group. The
only hint of distortion is that there appears to be a weak tidal plume
off the northwestern arm of the spiral, opposite the elliptical. Was it
caused by either of the apparent companions? I found nothing to help
answer this. Arp's comment reads: "Star-like condensation in spiral.
Connection to E galaxy inferred, not seen." The "star-like
condensation" turns out to be just that, a foreground star. At least
the SDSS lists it as a star and it appears to be a star in the Sloan
image. While enlarged by seeing in my image it shows the typical PSF
(point spread function) of a star rather than a star cloud or galaxy so
I agree with the Sloan image.

The spiral is classed at NED as SBb and is listed as a starburst galaxy
indicating a lot of hidden star formation is going on at its core.
While this can be triggered by interaction that's now known to not be
necessary. So was it triggered by interaction with one of the
companions? If so I'd vote, not for the elliptical but for the
distorted Magellanic spiral below it. It, at least, looks messed up
though again that could be misleading.

You'll notice I've avoided putting any identification on the three
galaxies, just using their descriptions. This is because there is some
confusion here. NED claims the little Magellanic galaxy to the south is
IC 4461 and the big spiral is IC 4462 with the elliptical being MGC
+5-34-78. Most other sources say the spiral is IC 4461 and the
elliptical IC 4462 with the Magellanic like galaxy to the south being
MGC +05-34-76. Actually all sources agree to the two MGC identities.
Its the IC ones that they disagree on. SIMBAD is really confusing. If
you go by their data base by entering the name it agrees with most other
sources saying the Elliptical is IC 4462 and spiral IC 4461 but if you
use SIMBAD to provide coordinates for the POSS plates at
http://stdatu.stsci.edu/cgi-bin/dss_form/ then it agrees to NED not its
own database! Confused? NED lists the small southern galaxy as being
only 0.1 magnitudes dimmer than the big spiral. This can't be right.
It goes on to list the elliptical as 0.7 magnitudes fainter than the
spiral. Again, this can't be right. Also the IC catalog is basically a
visual catalog. That is the entries were found initially by visual
observers. Wouldn't it be natural the bigger and brighter ones would be
seen not the biggest and brightest then the smallest and dimmest
omitting the elliptical? Thus I feel NED is the one that is screwed up
here. I can't figure out what is going on with SIMBAD other than a
split personality. Webb and Kanipe identify the galaxies with the
majority, that is the two northern galaxies being the IC entries.
Dennis Webb has told me such mix-ups were common. Determining who was
right was often impossible but trying to be as accurate as possible
delayed the book by a year or more.

There is little on the rest of the field. The galaxy to the left in the
enlarged, cropped image is MAPS-NGP O_326_3139474. This plate
measurement catalog is the only entry in NED for this rather major
galaxy compared to most of the field. NED shows no entry for it in the
SDSS or any other catalog. Though the SDSS does list the star to its
northwest. Having nothing more than what the automated plate
measurement comes up with there is no distance estimate for it or any
other galaxy in the field. This is really a dead zone as far as
information goes.

When taking this, one red frame was lost to clouds so I retook it after
the clouds cleared and the other color frames were shot. Or I tried to.
Somehow I told the software to take a blue frame rather than red and
didn't catch it until now. So this one has one red, two green and 3
blue frames thanks to my error. This did make getting decent red in the
image difficult and likely explains why the elliptical is more white
than yellow orange of a typical elliptical. Though on the SDSS image it
is a much paler color than usual for ellipticals using their 7 color
scheme that includes three near infrared channels that turns most
ellipticals far redder than they really are. So my color may not be as
red deficient as it appears. Another for the retake list however.

There is no annotated image since only the two northern galaxies have
red shift data already mentioned above.

Arp's image is at:
http://ned.ipac.caltech.edu/level5/A...big_arp95.jpeg

14" LX200R @ f/10, L=4x10' (one dimmed by clouds) R=1x10'x3 G=2x10'x3
B=3x10'x3, 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".

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  #2  
Old May 20th 11, 01:33 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
external usenet poster
 
Posts: 3,085
Default ASTRO: Arp 95

Somehow in converting to JPG a funny blue circle appeared that wasn't in
the original TIFF. Also the background color shifted outside the circle
to the red side of what was in the TIFF. Never had PS do that before.
I didn't catch it until looking at the posted images. I resaved and
apparently all is fine now. I don't get it. Here's the images as intended.

Rick

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ID:	3545  
 




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