ASTRO: M101 satellite dwarf galaxy NGC 5585

NGC 5585 is one of four dwarf satellite galaxies of M101. Therefore it
is about the same distance as M101 which is usually state to be 25 to 27
million light-years away though the redshift for NGC 5585 is about 18
million light-years. NGC 5585 is the largest of the 4 by quite a
margin. Also it is the furthest from M101 at 3.33 degrees. At 25
million light-years it would be 36 thousand light-years across which is
about the same size as the large Magellanic cloud. One note, from 1985.
at NED says: "Knotty HII regions are distributed over the disk where the
arm structure is not clear." Yet another older reference, 1964, says:
"Bright middle. No definite nucleus. Weak irregular arms well resolved
up to the central region. Low surface brightness." Could these very
different descriptions be due to the difference between film and early
CCD imaging? NGC 5585 is classed by NED as SAB(s)d with HII. The
regions are said to be 2" in size or smaller. That is below my
resolution this night. This would be interesting to revisit with a H
alpha filter to bring out these many regions.

Many of the background galaxies in this image are about 1.4 to 1.6
billion light-years away. While scattered across the image I found
three different galaxy clusters all in the same part of the image that
are 1.5 billion light-years away. None of the three had a diameter
listed. Do they overlap? What about those at that distance on the
other side of the image? I searched a 1 degree radius but found no one
cluster to explain this wide group at about the same distance.

As is often the case I did find an obvious galaxy not listed in NED. It
is Northwest of NGC 5585 and is marked by a question mark. The vast
majority of galaxies in the image have no redshift listed at NED so
aren't labeled.

14" LX200R @ f/20, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Rick
--
Prefix is correct. Domain is arvig dot net

Make that f/10 rather than f/20.

Rick

On 6/25/2012 2:38 AM, Rick Johnson wrote:
NGC 5585 is one of four dwarf satellite galaxies of M101. Therefore it
is about the same distance as M101 which is usually state to be 25 to 27
million light-years away though the redshift for NGC 5585 is about 18
million light-years. NGC 5585 is the largest of the 4 by quite a margin.
Also it is the furthest from M101 at 3.33 degrees. At 25 million
light-years it would be 36 thousand light-years across which is about
the same size as the large Magellanic cloud. One note, from 1985. at NED
says: "Knotty HII regions are distributed over the disk where the arm
structure is not clear." Yet another older reference, 1964, says:
"Bright middle. No definite nucleus. Weak irregular arms well resolved
up to the central region. Low surface brightness." Could these very
different descriptions be due to the difference between film and early
CCD imaging? NGC 5585 is classed by NED as SAB(s)d with HII. The regions
are said to be 2" in size or smaller. That is below my resolution this
night. This would be interesting to revisit with a H alpha filter to
bring out these many regions.

Many of the background galaxies in this image are about 1.4 to 1.6
billion light-years away. While scattered across the image I found three
different galaxy clusters all in the same part of the image that are 1.5
billion light-years away. None of the three had a diameter listed. Do
they overlap? What about those at that distance on the other side of the
image? I searched a 1 degree radius but found no one cluster to explain
this wide group at about the same distance.

As is often the case I did find an obvious galaxy not listed in NED. It
is Northwest of NGC 5585 and is marked by a question mark. The vast
majority of galaxies in the image have no redshift listed at NED so
aren't labeled.

14" LX200R @ f/20, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Rick


--
Prefix is correct. Domain is arvig dot net

Great image Rick.
I have imaged this galaxy but only in b/w (and it probably will stay that
way as it is too faint for colour for me), so no Halpha knots for me...

Stefan

"Rick Johnson" schrieb im Newsbeitrag
.com...
NGC 5585 is one of four dwarf satellite galaxies of M101. Therefore it
is about the same distance as M101 which is usually state to be 25 to 27
million light-years away though the redshift for NGC 5585 is about 18
million light-years. NGC 5585 is the largest of the 4 by quite a
margin. Also it is the furthest from M101 at 3.33 degrees. At 25
million light-years it would be 36 thousand light-years across which is
about the same size as the large Magellanic cloud. One note, from 1985.
at NED says: "Knotty HII regions are distributed over the disk where the
arm structure is not clear." Yet another older reference, 1964, says:
"Bright middle. No definite nucleus. Weak irregular arms well resolved
up to the central region. Low surface brightness." Could these very
different descriptions be due to the difference between film and early
CCD imaging? NGC 5585 is classed by NED as SAB(s)d with HII. The
regions are said to be 2" in size or smaller. That is below my
resolution this night. This would be interesting to revisit with a H
alpha filter to bring out these many regions.

Many of the background galaxies in this image are about 1.4 to 1.6
billion light-years away. While scattered across the image I found
three different galaxy clusters all in the same part of the image that
are 1.5 billion light-years away. None of the three had a diameter
listed. Do they overlap? What about those at that distance on the
other side of the image? I searched a 1 degree radius but found no one
cluster to explain this wide group at about the same distance.

As is often the case I did find an obvious galaxy not listed in NED. It
is Northwest of NGC 5585 and is marked by a question mark. The vast
majority of galaxies in the image have no redshift listed at NED so
aren't labeled.

14" LX200R @ f/20, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Rick
--
Prefix is correct. Domain is arvig dot net