Arp 321 AKA Hickson 40

Arp 321, Hickson 40, is a tight group of 5 galaxies, 3 of which are
certainly interacting. Most catalogs list them as a through e but can't
agree as to which is which. I'm following Hickson's lettering in my
annotated image since it fits a NED note that is interesting. Part of
it is reproduced below.

"All galaxies in the group, except galaxy e, are radio sources (Menon &
Hickson 1985). The most relevant structure of the group is the triplet
formed by galaxy b with the two spirals c and e. These last galaxies
provide further examples of disk "eroded" by interaction with a close
companion. In particular the southern spiral arm of galaxy e forms a
characteristic stream of matter toward the two companions, indicating
that the triplet is indeed a physical association. This fact is also
confirmed by the presence in galaxy b of a small nuclear jet pointing
towards galaxy c (UMT) and by the unusual behavior of profiles of both
galaxies. Actually, the luminosity, ellipticity, and position angle
profiles of galaxy b suggest its classification as a disky elliptical or
S0 galaxy. On the contrary, its a_4_ profile shows a strong boxiness
also noted by Rubin et al. (1991). This could suggest that the close
interaction may change the shape of the galaxy more rapidly than its
radial light distribution and, in this framework, galaxy b of this group
could represent an intermediate stage of a merging process.

"The most luminous member of the group (galaxy a) is another example of
dubious classification between S0 and disky elliptical. In fact, even if
the luminosity profile is well represented by the r^1/4^ law, the
geometrical profiles (especially the ellipticity profile) are typical of
an SO galaxy seen at an intermediate inclination angle. Also in the
field of this group some small diffuse objects are visible, mostly
around the galaxy a."

The galaxies are located in Pisces near the Circlet and is a bit over
300 million light-years distant. Actually there's a 6th member of the
group LEDA 082490. It shows the same red shift distance and does seem
to have a bit of distortion at its ansae so may have had a run in with
the others sometime in the past.

Arp classed this one under his rather redundant class Group character:
Groups of galaxies. His comment: "Sharp absorption lane in connection to
S galaxy."

They are classed at NED as:
a) E1
b) SA(r)0 pec
c) SB(rs)b pec
d) SB(s)0/a pec
e) SAB(s)a pec
LEDA 082490 S(0)


This field is not covered by the Sloan survey so most of the galaxies in
the image have no red shift data and most are anonymous.

Arp's image:
http://nedwww.ipac.caltech.edu/level...ig_arp321.jpeg

I've included an annotated 2x enlargement of the group to show a-e and
LEDA 082490.

14" LX200R @ f/10, L=4x10' 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".

another cool image of "dancing with the galaxies" instead of dancing with
the stars!

nice one Rick!


"Rick Johnson" wrote in message
. com...
Arp 321, Hickson 40, is a tight group of 5 galaxies, 3 of which are
certainly interacting. Most catalogs list them as a through e but can't
agree as to which is which. I'm following Hickson's lettering in my
annotated image since it fits a NED note that is interesting. Part of
it is reproduced below.

"All galaxies in the group, except galaxy e, are radio sources (Menon &
Hickson 1985). The most relevant structure of the group is the triplet
formed by galaxy b with the two spirals c and e. These last galaxies
provide further examples of disk "eroded" by interaction with a close
companion. In particular the southern spiral arm of galaxy e forms a
characteristic stream of matter toward the two companions, indicating
that the triplet is indeed a physical association. This fact is also
confirmed by the presence in galaxy b of a small nuclear jet pointing
towards galaxy c (UMT) and by the unusual behavior of profiles of both
galaxies. Actually, the luminosity, ellipticity, and position angle
profiles of galaxy b suggest its classification as a disky elliptical or
S0 galaxy. On the contrary, its a_4_ profile shows a strong boxiness
also noted by Rubin et al. (1991). This could suggest that the close
interaction may change the shape of the galaxy more rapidly than its
radial light distribution and, in this framework, galaxy b of this group
could represent an intermediate stage of a merging process.

"The most luminous member of the group (galaxy a) is another example of
dubious classification between S0 and disky elliptical. In fact, even if
the luminosity profile is well represented by the r^1/4^ law, the
geometrical profiles (especially the ellipticity profile) are typical of
an SO galaxy seen at an intermediate inclination angle. Also in the
field of this group some small diffuse objects are visible, mostly
around the galaxy a."

The galaxies are located in Pisces near the Circlet and is a bit over
300 million light-years distant. Actually there's a 6th member of the
group LEDA 082490. It shows the same red shift distance and does seem
to have a bit of distortion at its ansae so may have had a run in with
the others sometime in the past.

Arp classed this one under his rather redundant class Group character:
Groups of galaxies. His comment: "Sharp absorption lane in connection to
S galaxy."

They are classed at NED as:
a) E1
b) SA(r)0 pec
c) SB(rs)b pec
d) SB(s)0/a pec
e) SAB(s)a pec
LEDA 082490 S(0)


This field is not covered by the Sloan survey so most of the galaxies in
the image have no red shift data and most are anonymous.

Arp's image:
http://nedwww.ipac.caltech.edu/level...ig_arp321.jpeg

I've included an annotated 2x enlargement of the group to show a-e and
LEDA 082490.

14" LX200R @ f/10, L=4x10' 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".

"Rick Johnson" wrote in message
. com...
Arp 321, Hickson 40, is a tight group of 5 galaxies, 3 of which are
certainly interacting. Most catalogs list them as a through e but can't
agree as to which is which. I'm following Hickson's lettering in my
annotated image since it fits a NED note that is interesting. Part of
it is reproduced below.

snip

Very nice. I've always liked your gal;axy images.

George

Rick,

I'd wish I had such interesting objects as in this image to process, but I
have been testing my new reducer for the Skywatcher ED80, which made me
image standard stuff recently....

Stefan

"Rick Johnson" schrieb im Newsbeitrag
. com...
Arp 321, Hickson 40, is a tight group of 5 galaxies, 3 of which are
certainly interacting. Most catalogs list them as a through e but can't
agree as to which is which. I'm following Hickson's lettering in my
annotated image since it fits a NED note that is interesting. Part of
it is reproduced below.

"All galaxies in the group, except galaxy e, are radio sources (Menon &
Hickson 1985). The most relevant structure of the group is the triplet
formed by galaxy b with the two spirals c and e. These last galaxies
provide further examples of disk "eroded" by interaction with a close
companion. In particular the southern spiral arm of galaxy e forms a
characteristic stream of matter toward the two companions, indicating
that the triplet is indeed a physical association. This fact is also
confirmed by the presence in galaxy b of a small nuclear jet pointing
towards galaxy c (UMT) and by the unusual behavior of profiles of both
galaxies. Actually, the luminosity, ellipticity, and position angle
profiles of galaxy b suggest its classification as a disky elliptical or
S0 galaxy. On the contrary, its a_4_ profile shows a strong boxiness
also noted by Rubin et al. (1991). This could suggest that the close
interaction may change the shape of the galaxy more rapidly than its
radial light distribution and, in this framework, galaxy b of this group
could represent an intermediate stage of a merging process.

"The most luminous member of the group (galaxy a) is another example of
dubious classification between S0 and disky elliptical. In fact, even if
the luminosity profile is well represented by the r^1/4^ law, the
geometrical profiles (especially the ellipticity profile) are typical of
an SO galaxy seen at an intermediate inclination angle. Also in the
field of this group some small diffuse objects are visible, mostly
around the galaxy a."

The galaxies are located in Pisces near the Circlet and is a bit over
300 million light-years distant. Actually there's a 6th member of the
group LEDA 082490. It shows the same red shift distance and does seem
to have a bit of distortion at its ansae so may have had a run in with
the others sometime in the past.

Arp classed this one under his rather redundant class Group character:
Groups of galaxies. His comment: "Sharp absorption lane in connection to
S galaxy."

They are classed at NED as:
a) E1
b) SA(r)0 pec
c) SB(rs)b pec
d) SB(s)0/a pec
e) SAB(s)a pec
LEDA 082490 S(0)


This field is not covered by the Sloan survey so most of the galaxies in
the image have no red shift data and most are anonymous.

Arp's image:
http://nedwww.ipac.caltech.edu/level...ig_arp321.jpeg

I've included an annotated 2x enlargement of the group to show a-e and
LEDA 082490.

14" LX200R @ f/10, L=4x10' 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".