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ASTRO: Arp 302 Another at 0.5" per pixel



 
 
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  #1  
Old January 2nd 11, 07:18 PM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Posts: 3,085
Default ASTRO: Arp 302 Another at 0.5" per pixel

Arp 302 is a pair of interacting galaxies known as UGC9618 located 460
million light-years away in the constellation of Bootes. Arp put it in
his class: Group Character: Double Galaxies. Apparently he missed the
tidal star clouds around especially the northern member.

The southern galaxy is a Sc blue spiral. It shows some rather strong
HII emission but isn't considered a starburst galaxy as it lacks the
needed IR light. The northern member however is quite different. It is
a red spiral classed at NED as Sb and is a LINER galaxy indicating its
core is very active. It is classed as a starburst galaxy and does have
strong IR emission showing active star formation. This is odd.
Normally red spirals are considered dead spirals. Ones in which star
formation has ceased so they are dying as all the new blue stars are
long burned out leaving only yellow and red stars giving it a reddish
hue. But here we have massive stars being formed though this is hidden
to us by warm dust we see as IR light. I do note the very ends of its
arms are blue. Usually in a starburst galaxy the majority of the star
formation is in the core. These spirals are often barred spirals but
this apparently isn't one of them.

While this field is covered by the Sloan survey NED shows no distances
for any galaxies in the field besides the two making up Arp 302. Below
Arp 302 is a tight trio of galaxies almost in a line. The two on the
left look like one on the POSS plates but are separated by a narrow dark
band in my image as well as the Sloan image. The right object is much
bluer than the left but far smaller in angular size. Looks like a piece
broken off the left piece but the color difference makes it obvious they
are separate objects. I have no distance data so can't tell if they are
really close together or not but at least NED does list them. The third
member of the group just to their right isn't listed at NED but the
faint 23rd magnitude galaxy beside it at the one o'clock position is.
There are many interesting galaxies but about all I have on them is a
magnitude estimate and their coordinates. Thus I didn't bother to
prepare an annotated version.

I'd like to know more about the edge on spiral near the right edge of
the image at the same level as Arp 302. It too is a red spiral and
seems to have blue stars at the very ends of its arms. Coincidence? Or
it it related to Arp 302 and had a run in with it in the distant past
causing these blue ends? Wish I knew. There's just nothing much on
these galaxies unfortunately Even Arp made no comment about them.

Normally I image at 1" per pixel binning the image 2x2. But this night
seeing was far better than normal so I went to 0.5" per pixel by not
binning. To keep the image size within reason for the internet I only
downloaded the center one quarter of the image by area. When seeing
permits I often enlarge the image to 0.67" per pixel. No need here as
it already is at 0.5" per pixel. Still the stars are very tight. Many
only 1.2" to 1.4" FWHM. This is likely my highest resolution Arp image
to date, slightly better than Arp 149 taken the previous night. But
like the previous night the good seeing didn't last. I'd hoped to take
12 L images but after only 7 seeing went very bad. So bad in fact I had
to shut down. Color data was taken binned 2x2 the following night. I'd
hoped I'd be able to get more L data that night but seeing was 2.5"
(about normal) and far from what I needed to go to the 0.5" pixel. I
never did get more Luminance data. So the image is noisier than I'd
like but the detail makes it worth it.

Arp's image
http://nedwww.ipac.caltech.edu/level...ig_arp302.jpeg

Besides my image I've attached the Sloan image of this area.

14" LX200R @ f/10, L=7x10'x1, RGB=2x10, 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".

Attached Thumbnails
Click image for larger version

Name:	ARP302L7X10X1RGB2X10.jpg
Views:	326
Size:	242.0 KB
ID:	3285  Click image for larger version

Name:	UGC9618-SDSS.jpg
Views:	173
Size:	50.6 KB
ID:	3286  
  #2  
Old January 16th 11, 09:53 PM posted to alt.binaries.pictures.astro
Stefan Lilge
external usenet poster
 
Posts: 2,269
Default ASTRO: Arp 302 Another at 0.5" per pixel

Mighty image Rick. A blue face on and a yellow edge on make a nice pair.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
ster.com...
Arp 302 is a pair of interacting galaxies known as UGC9618 located 460
million light-years away in the constellation of Bootes. Arp put it in
his class: Group Character: Double Galaxies. Apparently he missed the
tidal star clouds around especially the northern member.

The southern galaxy is a Sc blue spiral. It shows some rather strong
HII emission but isn't considered a starburst galaxy as it lacks the
needed IR light. The northern member however is quite different. It is
a red spiral classed at NED as Sb and is a LINER galaxy indicating its
core is very active. It is classed as a starburst galaxy and does have
strong IR emission showing active star formation. This is odd.
Normally red spirals are considered dead spirals. Ones in which star
formation has ceased so they are dying as all the new blue stars are
long burned out leaving only yellow and red stars giving it a reddish
hue. But here we have massive stars being formed though this is hidden
to us by warm dust we see as IR light. I do note the very ends of its
arms are blue. Usually in a starburst galaxy the majority of the star
formation is in the core. These spirals are often barred spirals but
this apparently isn't one of them.

While this field is covered by the Sloan survey NED shows no distances
for any galaxies in the field besides the two making up Arp 302. Below
Arp 302 is a tight trio of galaxies almost in a line. The two on the
left look like one on the POSS plates but are separated by a narrow dark
band in my image as well as the Sloan image. The right object is much
bluer than the left but far smaller in angular size. Looks like a piece
broken off the left piece but the color difference makes it obvious they
are separate objects. I have no distance data so can't tell if they are
really close together or not but at least NED does list them. The third
member of the group just to their right isn't listed at NED but the
faint 23rd magnitude galaxy beside it at the one o'clock position is.
There are many interesting galaxies but about all I have on them is a
magnitude estimate and their coordinates. Thus I didn't bother to
prepare an annotated version.

I'd like to know more about the edge on spiral near the right edge of
the image at the same level as Arp 302. It too is a red spiral and
seems to have blue stars at the very ends of its arms. Coincidence? Or
it it related to Arp 302 and had a run in with it in the distant past
causing these blue ends? Wish I knew. There's just nothing much on
these galaxies unfortunately Even Arp made no comment about them.

Normally I image at 1" per pixel binning the image 2x2. But this night
seeing was far better than normal so I went to 0.5" per pixel by not
binning. To keep the image size within reason for the internet I only
downloaded the center one quarter of the image by area. When seeing
permits I often enlarge the image to 0.67" per pixel. No need here as
it already is at 0.5" per pixel. Still the stars are very tight. Many
only 1.2" to 1.4" FWHM. This is likely my highest resolution Arp image
to date, slightly better than Arp 149 taken the previous night. But
like the previous night the good seeing didn't last. I'd hoped to take
12 L images but after only 7 seeing went very bad. So bad in fact I had
to shut down. Color data was taken binned 2x2 the following night. I'd
hoped I'd be able to get more L data that night but seeing was 2.5"
(about normal) and far from what I needed to go to the 0.5" pixel. I
never did get more Luminance data. So the image is noisier than I'd
like but the detail makes it worth it.

Arp's image
http://nedwww.ipac.caltech.edu/level...ig_arp302.jpeg

Besides my image I've attached the Sloan image of this area.

14" LX200R @ f/10, L=7x10'x1, RGB=2x10, 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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