ARP318

Arp 318 is a group of 4 galaxies also known as Hickson 16. It is in the constellation of Cetus and is about 160 million light years distant. Hickson 16 consists of 4 galaxies but Arp 318 may consist of 5. Depends on your source. Arp's image only includes 4 of the 5. The 5th is too far for the 200" to image it with the others. With other large objects, Arp went with the 48" Schmidt photo, however. Since he didn't here I'll assume 4 is correct but the 5th is in my image so won't escape my covering it.

The 4 galaxies, right to left are, NGC 833 (HCG16B), NGC 835 (HCG16A), NGC 838 (HCG16C) and NGC 839 (HCG16D). Hickson lettered them brightest to dimmest. NGC 833 is classed as (R')Sa:pec;Sy2 LINER so has an active nucleus likely caused by its interaction with NGC 835. NGC 835 shows tidal plumes from the interaction. It is classed SAB(r)ab: pec LINER with some sources saying it too is a Seyfert 2 galaxy. Its ring like arm and overall shape is somewhat akin to some galaxies thought to have taken a direct center hit by another galaxy. Usually, the ring is further out and more complete. Something has sure clobbered it, Maybe NGC 833.

NGC 838 is also disturbed showing some rather strong dust features. It is classed as SA(rs)0^0 pec: Sbrst. Its classification as a starburst galaxy indicates it too has been altered by an encounter. I'm leaning toward it being the bullet that hit NGC 835 if indeed it was hit by one. With those huge dark dust clouds, it could be in starburst mode for some time. The final galaxy of the four, NGC 839 is classed as Spec sp; LINER Sy2. It too has an active nucleus. It appears to have a bright ring structure as well with a very dark cloud. It's not as red as those in NGC 838 probably indicating less UV light from young stars is hitting it. The UV light causes dust to give off a reddish light called Extended Red Emission. The lack of UV hitting it likely is due to it not being a starburst galaxy and thus not having sufficient supermassive stars to give off the unneeded light. Or the cloud is located such that it is blocked from such light. It's hard to tell. In any case, it, like the other 3, has obviously had a close encounter of the galactic kind. All four were discovered by William Herschel on November 28, 1785. None are in either H400 observing program.

The 5th galaxy is in the lower left corner of my image. It is NGC 848 and has a redshift putting it at 171 million light years, about the same as the other 4 so it is most certainly part of the group. It carries the uncertain classification of (R')SB(s)ab pec? Sbrst. Note the large plumes, especially to the north. So it has also been rather strongly jostled about by one or more of the other 4 galaxies but seems to be making a run for it rather than take further beatings. (I'm typing this with the help of a 12-year-old granddaughter, the anthropomorphic slant is hers though she doesn't know the meaning of the word.) This galaxy was discovered by Ormond Stone In December 1885. While I've seen it included as part of HCG 16 it is too far away to meet Hickson's compact group definition. Its inclusion is an error.

Arp's comment about this 4 galaxy entry is: "Faint, diffuse streamers, peculiar galaxies.

I've included an annotated image showing distances in billions of light years to those objects that NED has redshift data for. G is for galaxy and Q for quasar. QC means quasar candidate and P after the distance means it was determined photographically. This is done by noting the point at which the redshifted UV light suddenly drops off. Theory says this happens at a particular frequency for a resting source. By how far this point is shifted toward the red its redshift and thus distance can be estimated. Of course, if something unforeseen alters the UV spectrum this could be in error though it is usually considered a valid indicator of distance and is how most of Hubble's deep field images are evaluated for their galactic distances. The label is immediately right of the object when possible. When that would cover up something the label is moved to a clear space and a line is drawn to the object.

Usually, distant galaxies are quite reddened but this image has a surprising number of galaxies over a billion light years distant that are still blue to white in color.

This image doesn't go nearly as deep as normal as two subframes were lost to clouds and I didn't realize it at the time. This data loss makes going deep too noisy due to under sampling of the photons I was collecting.

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp318.jpeg

14" LX200R @ f/10, L=3x10' RGB=2x10'x3, STL-11000XM, Paramount ME

Related Designations for ARP318

ARP319

Arp 319 is better known as Stephan's Quintet. It is really a group of 4 galaxies with a 5th galaxy in the foreground though there is a true fifth member Arp didn't include it. The interloper galaxy is NGC 7320. It is apparently the largest of the group and the bluest. It is really a member of the so-called "Deer Lick" group located less than a degree away. It is located only some 40 million light-years away while the other 4 are about 270 million light-years from us. At one time this group was put forth by some to disprove redshift as a distance measure to the universe. Since NGC 7320 is close it has a small redshift while the other 4 have a large redshift. But if all were at the same distance then redshift was called into question. It took Hubble to answer this for sure. It could resolve stars in NGC 7320 but only massive star clusters in the others. This was consistent with the redshift distances and it is now accepted that 7320 is a Deer Lick member seen in front of the far more distant group. Actually, we do have 5 members of this distant group. To the left, a bit is a barred spiral whose arms make a nice ring, NGC 7320C. It is now known to be a member of the group and may be responsible for some of the tidal plumes. So there really are 5 galaxies in Stephan's quintet, just that one isn't the one we thought was a member for many years.

For a shot taken with a far larger telescope on Kitt Peak than mine see: http://www.noao.edu/image_gallery/html/im0414.html

Actually, there are several more members of the group. Just that like 7320 is well away from its group these other members aren't as close by. One is LEDA 141041 even further east than the first 5. Then there's the very awkwardly named [WYV2002] 6 in the upper left corner of the image. Just out of the image due east of the cluster is NGC 7320B yet another member of the group. These are the only ones I found with redshift values to show they are very likely group members. In the lower part of the image is NGC 7320A which looks almost a twin of NGC 7320B I missed catching. Both these last two are members of the 2MASS flat galaxy catalog. On the west side of the image is the S0 looking galaxy PGC 69218. It too has no redshift data but could possibly be a member of the group.

I find it interesting that while NGC 7320 is now known not to be a member NGC 7320B and NGC 7320C are members (as may be 7320A). The annotated image identifies the galaxies that have redshifts and those two without redshift data that might be members of the group as well as the interloper, NGC 7320 itself. There's one quasar in the image hard to pick out from NGC 7319 appearing more like a bright spot in the galaxy. Also, a star forming knot in the tidal plume coming from NGC 7319 is listed in NED as a separate galaxy though I think it is just a star cloud in the plume, one of several in that plume.

So how did this group come to be so tidally damaged? There are many theories. A note at NED summarizes them this way: "To explain the peculiar morphology of Stephan's Quintet, a number of different interaction scenarios have been suggested. Some of these scenarios involve ram pressure stripping during a head-on collision between two galaxies. For example, Peterson & Shostak (1980) suggest that a head-on collision between NGC 7318B and NGC 7319 removed the gas and caused the radio continuum ridge between them. A different scenario was suggested by Shostak et al. (1984): a prograde tidal encounter of NGC 7320C and NGC 7319 occurred, pulling gas out of these galaxies, creating the long tail south of NGC 7319. This was followed by a high-speed collision between NGC 7318A and NGC 7318B. Other scenarios involve a collision between an "intruder galaxy" (usually NGC 7318B) and intragalactic gas that had previously been tidally stripped or ram pressure-stripped in an earlier encounter between two different galaxies in the group (van der Hulst & Rots 1981; Moles et al. 1997). Moles et al. (1997) suggest that a direct collision between the outlying galaxy NGC 7320C and NGC 7319 occurred in the recent past (10^8^ yr ago), removing a large quantity of gas from these galaxies. After this event, NGC 7318B entered the group at high velocity, colliding with this stripped gas and triggering star formation." Pick one of your choosing or come up with another. Seems to be still open for more ideas. Look up Arp 7319 at NED and read the notes for even more suggestions from users of the radio part of the spectrum.

What I never saw mentioned is that NGC 7320 seems to have its own plume extending to the southeast (left and some down). Is it from NGC 7320 or is it really from NGC 7318B but mostly hidden by NGC 7320 until it finally appears after passing behind it? I found nothing on this feature.

Arp's image: http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp319.jpeg

14" LX200R @ f/10, L=6x10' RGB=2x10'x3, STL-11000XM, Paramount ME

Related Designations for ARP319

ARP320

Arp 320/Copeland's Septet is a group of 7 galaxies though you'll see 9 main galaxies in the center of the field. A finder chart of the 7 that are members of the "official" septet http://www.ngcicproject.org/dss/n/3/n3753.jpg
Note the blob above the label for NGC 3754 is a plate defect so you won't see it in my image. It is also known as Hickson 57. The main galaxy in the group is NGC 3753 also known as ARP 320. The reason for so many names is just that each astronomer has some reason to study it and puts it in their catalog. Before long there are a ton of catalog entries for the same thing. Besides NGC 3753 is also known as: UGC 06602, VV282a, KUG1135+222, CGCG127-012S, CGCG1135.4+2216, MCG+04-28-010, PGC03616, UZC J113753.8+215852 and [BDG09] J113753.9+215853 to name a few. The group is also known as Copeland's septet, HCG 057, WBL 343-005, USGC U404 and UZC-CG 142, RSCG 43 and others. Confused yet?

The group is about 410 to 440 million light years distant and somewhat red. I suspect this is due to lots of dust between us and the group though one galaxy does show some blue color. But two of the redder galaxies have "retired" nuclei. This means star formation has virtually ceased though some emission lines of LINER galaxies are still seen. This usually is interpreted to mean they are about to become red and dead galaxies. Several papers mention this color problem but none I saw gives an answer or even a guess as to why the group but for NGC 3754 is so red. Some of it was discovered by Ralph Copeland on February 9, 1874 (NGC 3746, 3750 and 3753) and the rest on April 5, 1874 (NGC 3745, 3748, 3751 and 3754). He got their position rather wrong by about 1.5 minutes of Right Ascension and about 15 arcmin of NPD. Enough that my field would have missed it using Copeland's position. But since no other group is in the area and its description fits his identification is certain. As to why 4 were found in April and 3 in February, I couldn't discover.

Just under NGC 3748 is PGC 36010 an S0/a galaxy that some consider part of Arp 320 but Copeland didn't see so it is not Copland's Octet. It is part of HCG 57 however. Look around the annotated image and you will see quite a few other galaxies, mostly dwarfs compared to the seven in the septet, also at the 410 to 440 million light-year distance indicating this is quite a large group.

It is quite obvious NGC 3753 is interacting with NGC 3750 by the huge plumes it has. I suppose the vertical one off the west end may be coming from NGC 3750. NGC 3753's southeastern plume almost looks like it is sticking its tongue out. Its dust lane is quite disturbed. Often a sign it ate something recently. While SLOAN shows a point source object just northwest of its upper end it doesn't show any entry for the plume. I thought it might be some low surface brightness dwarf that just happened to line up with NGC 3753 but apparently, it is just a plume. Assuming it is a plume and including the northwestern plume, I measure the full size at 300,000 light-years. Measuring just the bright disk I get 110,000 light-years.

NGC 3748 shows plumes as well indicating it did interact with one of the galaxies in the group but which one? Including plumes, it is 162,000 light-years across. The disk is much smaller at 55,000 light-years. NGC 3746 I measure at 135,000 light-years in size. I measure NGC 3750 at 140,000 light-years, NGC 3751 at 145,000 light-years and NGC 3745 at 90,000 light-years including the faint plume, mainly to the east. Omitting the plume I get 40,000 light-years making it the smallest of the 7.

The asteroid to the lower left (southeast) is (30376) 2000 JE65 at magnitude 17.7.

Arp's image: http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp320.jpeg

14" LX200R @ f/10, L=4x10' RGB=2x10'x3, STL-11000XM, Paramount ME

Related Designations for ARP320

ARP321

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 are a bit over 300 million light-years distant. Actually, there's a 6th member of the group LEDA 082490. It shows the same redshift 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 redshift data and most are anonymous.

Arp's image:
http://nedwww.ipac.caltech.edu/level5/Arp/Figures/big_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

Related Designations for ARP321

ARP322

There are two Arp systems in this image, Arp 214 and Arp 322. They are unrelated. Arp 214 is also NGC 3718. It was discovered by William Herschel on April 12, 1789 though not in either of the Herschel 400 programs which I find rather strange. Arp put it in his category for galaxies with irregularities, absorption and resolution. I don't know what he means by resolution but it certainly is irregular and has a strange absorption dust lane. These features are caused by its long-ago interaction with NGC 3729 to the east. Arp's comment on it reads: "Barred spiral, sharp nucleus, narrow absorption lanes through center." He never mentions the huge plumes drawn out by its interaction with NGC 3729 which itself is rather disturbed but didn't make Arp's atlas. It was also discovered by William Herschel on April 12, 1789 but did make the original Herschel 400 observing program. My comment on it from April 16, 1985 on a fair but humid night with my 10" f/5 at 50x reads "Small galaxy, gradually brighter toward center though no defined nucleus was seen. Smaller and fainter than NGC 3718 in the same field which is easier and more interesting."

The galaxies are a bit over 50 million light-years distant and found in Ursa Major. Both galaxies are experiencing strong star formation as a result of their interaction.

Arp 322 is the other entry to Arp's Atlas in this image. It is 4 of the 5 galaxies seen below Arp 214. It is much more distant at a bit less than 400 million light-years. The 5 galaxies constitute the Hickson Compact Group #56. The eastern member is not considered part of Arp 322. Arp put it in his section for galaxy chains. Other than mentioning that the chain is near Arp 214 he made no other comment on this entry. Did he leave out the eastern galaxy because its halo didn't overlap any other or because it didn't fit his idea of a "chain"? Without any comment on this, your guess is as good as mine.

Arp's image of #214:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp214.jpeg

Arp's image of #322:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp322.jpeg

14" LX200R @ f/10, L=4x12' RGB=4x10', STL-11000XM, Paramount ME

Related Designations for ARP322

ARP323

Arp 323 is part of Hickson 98 or maybe the entire group, sources vary. In any case, it is a galaxy group in western Pisces about 345 million light years. The bright pair is NGC 7783. Some catalogs show them as 7783 and 7783A while others say 7783A and 7783B or like NED NGC 7783 NED 01 and NGC 7783 NED 02. All left to right. In the MCG catalog, they are MCG +0-60-58 and MCG +0-60-59. Though the Kanipe-Webb book shows the western one as 7783 and the eastern as MCG +0-69-59. All very confusing. In the Hickson catalog, they are 98A and 98B respectively. The galaxy to the north is MCG +0-60-60 or Hickson 98D with the southern one below a field star being NGC 7783C or Hickson 98C. I'll use Hickson letters as they are something most agree on.

Hickson 98A is listed by NED as being SB0. 98B is S0 with 98C being just E and 98D as Sc or S0^+?. This latter galaxy isn't a true member of the group it seems as its redshift puts it at nearly twice the distance of A and B at 650 million light years. C's redshift shows 354 million light years which is close enough to be a true member of the group. There's a 5th galaxy in Arp's image, just southwest of C. It is SDSS J235412.56+002113.3 with no redshift or classification data given. Is it a member of the group? Maybe, as a similar galaxy that apparently is a member is seen to the upper right of the bright star above Arp 323. It is SDSS J235402.45+002723.7 at 360 million light years. See the annotated image for it and other objects in the field, especially asteroids. Galaxies are noted by G and their distance in billions of light years, quasars by Q followed by their distance also in billions of light years. The label is just to the right of the object unless I had to move it because of problems. In that case, I have drawn a line to the object. Two lines denoting the faint asteroid's start and stop points. All were moving east to west, left to right.

Note the long tidal tail descending to the southeast of Hickson 98B. It isn't mentioned by Arp nor did I see it on any image of this group I saw on the net. I've not done an exhaustive search but so far I find no mention of this "spike" anyplace I've looked. It barely shows in the POSS 2 plates if you enhance the heck out of the FITS version. It shows better on the Sloan image. After despiking Arp 192 have I now spiked Arp 323? It came as a complete surprise to me when I was processing the image. I came close to processing it out as a ghost image of some sort but it is real. My attempts to bring it out likely have it more sharply defined than it really is. Yet another to be retaken with far more imaging time in a few months.

The reddish oblong blur coming up from the bottom left of center is due to a 5th magnitude M5 star a bit out of the field of view. Enhancing the tidal plume also enhanced it quite a bit. I've toned it down considerably but couldn't eliminate it totally.

This image sets my personal record (Edit: since broken) for the number of asteroids seen in one image. I found 12 known ones down to magnitude 20.3. You'll need a monitor that can see deep into the black to find them all. In order of brightness they are:

Number Designation Magnitude
(47428) 1999 XK172 16.3
(105177) 2000 OA27 17.4
(58662) 1997 XJ2 17.6
2009 QR51 19.2
(60164) 1999 UF28 19.5
(125650) 2001 XV68 19.5
(182255) 2001 FM108 19.5
2005 SL88 19.5
2009 QJ58 19.8
2007 DE113 20.0
2006 UR118 20.2
2005 UK299 20.3

There appears to be the 13th asteroid, it is unknown to the Minor Planet Center. Unfortunately, this was taken in September 2009 and I only found it when I first looked at the luminance data in May 2010. So it was impossible to follow up on it. It is number 7 that I've found too late for follow-up. I had to go back and count them as I had been just guessing before. I've marked it with a question mark on the annotated image.

Magnitudes are estimates by the Minor Planet Center and may vary slightly from what they appear to be in my image. Color may be involved as my chip is blue sensitive so those that are red will appear dimmer than they really are in the luminosity image.

The SDSS image is attached with the tail showing faintly after I enhanced the image more than they did. I can't imagine this is a reflection of some sort. Though their image has its share of nasty reflections! For both of us to have the same reflection is too much to swallow. I've attached the SDSS image as well as mine and the annotated image.

Arp's image:
http://nedwww.ipac.caltech.edu/level5/Arp/Figures/big_arp323.jpeg

14" LX200R @ f/10, L=4x10' RGB=2x10'x3, STL-11000XM, Paramount ME

Related Designations for ARP323

ARP324

Arp 324 is a chain of galaxies in a western corner of Hercules right on the border with Serpens Caput. It is located in the corner I call the realm of Abell galaxy clusters. As there's a line of 3 them with Abell 2147 at the south end. 2152 and 2151 are the other two, 2151 is the famous Hercules Galaxy Cluster. In fact, Arp 324 is almost at the center of 2147 cluster which is about 475 million light years distant. Arp put Arp 324 in his Group character: Chain of galaxies category. How many he saw in the chain I don't know. Some sources say 6 some 9. Arp's comment on the group: "Diffuse elongation of E's along line joining them." I think he is referring to the two main ellipticals which seem to exist in one diffuse, very elongated halo. Whether this is real or a line of sight illusion I don't know. I found nothing on this question. In any case, such elongated halos are a pretty good sign that these halos are tidal in nature. Not easy to pull stars from such massive elliptical galaxies so I assume it was these two interacting that caused these tidal features. The northern galaxy is classed as cD:E+ which is a rare type of extremely large elliptical galaxy usually found to be anchoring a galaxy cluster, which is exactly what it is doing. It is known as UGC 10143. The smaller southern one is PGC 056770 or MCG +03-41-051 and is classed simply as an E3 galaxy.

I really doubt this is a true galaxy chain but more a line of sight apparent chain of random galaxies in the cluster. Some of which, like the two big ellipticals and III Zw 075 below are interacting pairs.

Between the two main elliptical galaxies is a "cute" ring spiral galaxy with two fine arms coming off the ring. It is UGC 10143 NOTES01 or PGC 056777. It is a puzzle to me. Everyone considers it part of the chain. Here's a typical comment on it: "Compact red object with a faint envelope. This is a component of a chain (connected by a luminous band) of which the compact galaxy III Zw 075 is also a member." By red they mean infrared which I don't pick up. So it is more blue-white in my image. The problem is its redshift is considerably greater than that of the others putting it about 600 million light-years from us, 125 million further than the Abell Cluster that contains Arp 324. Sometimes a galaxy can pick up high speed due to the gravitational interaction with its cluster neighbors. That may explain it or it may not be a member of the group. I'm leaning toward the latter. It is quite obviously classed as SAB(r)ab.

III Zw 075 is the pair of elliptical galaxies below the ring spiral that are only 6" apart. Each has a slightly different redshift. I don't know why the note above implied it was a single galaxy. They appear to be a pair of interacting compact dwarf spherical galaxies in the Abell cluster. They seem to exist in a common envelope of stars though this may be an illusion.

At the bottom of the "chain" is a flat edge on spiral. It is UGC 10143 NOTES03 or KUG 1559+160. It is nearly impossible to find a catalog that includes all of these. Several include most, however. Like the ring spiral, its redshift is a bit out of line with the Abell cluster. In this case, it is about 75 million light-years closer by its redshift than Abell 2147. Since most cluster galaxies are elliptical I'm leaning toward this one not being a member as well.

Another spiral like galaxy "in the chain" is 2MASX J16021582+1557252. It is between the upper large elliptical and the ring spiral. Its northern arm seems far bigger and brighter than the southern. It might be two superimposed galaxies though NED and SDSS only list the one at in this immediate area. It, like the other spirals, has a redshift that doesn't fit the two main ellipticals for Abell 2147. It is about 100 million miles beyond them based on its redshift.

This covers the basic 6 galaxies in the "chain". While other sources list more I'm unable to identify them with any certainty. Some are listed by their MAC entry. The only listing of this catalog I have is accurate only to about 1 minute of arc in Declination and 15" in RA. Another PGC 56783 is non-existent in all of my sources. As best as I can determine at least two of these are referring to the little interacting trio of galaxies above the two major ellipticals and a bit west. From south to north they are SDSS J160214.00+160111.2, SDSS J160213.92+160127.2 and SDSS J160214.72+160127.5. Redshift data shows the first two are members of the Abell 2147 cluster. I have no data on the third member, it appears to be involved with the halo so probably is also a true member of the cluster.

Other nearby likely members of the cluster are SDSS J160211.40+160021.5 down and right of the trio above (the two leftmost galaxies point to it), SDSS J160215.30+160220.1 fainter and above the triplet and beside a dim blue star, SDSS J160217.58+160010.6 a bright elliptical at the top of the halo about the northern main cD elliptical and SDSS J160217.96+160027.9 the faint round galaxy just above the last galaxy. Continuing north along the same line as the last two but further north than the triplet is the rather bright elliptical member of the cluster and maybe Arp's chain, SDSS J160219.55+160209.6. Most of the other ellipticals in the image appear to be members of the cluster as well. Though a few are far beyond the cluster yet are as big and bright as cluster members.

If you've been following my posts I've been noticing the SDSS often missed very blue galaxies. So the extremely blue galaxy west of Arp 324 caught my eye. It seems an exception because it was picked up by the SDSS as SDSS J160154.20+160016.7 and has a redshift that puts it in the Abell cluster. So not all of these super blue galaxies are not picked up.

Down near the bottom left of center is a very weird galaxy with a redshift of 510 million light-years and thus likely a cluster member. It is right beside a rather bright blue star to its east. It is classed as S0 but seems to have a very odd blue ring around it. NED's primary listing for it is GIN 464. Blow up the image to see the ring detail.

Trying to do a typical annotated version of this image is virtually impossible. I'd have labels on top of labels making a mess and taking me far more time than I have available. So I've just pointed out a few objects, not members of Arp 324 or Abell 2147 that caught my eye. Objects like SDSS J160143.48+155706.3, a quasar at 12 billion light years shining at magnitude 21.3. A question mark indicates a galaxy not in NED that I think should be as far dimmer galaxies are included.

For those who have been asking the limiting magnitude of this image isn't as deep as I'd have liked, humidity cut down transparency. It is about magnitude 22 for tiny compact galaxies, 22.3 for stars and about 21.8 for fuzzy galaxies. All these are measured in green light.

Arp's image:
http://nedwww.ipac.caltech.edu/level5/Arp/Figures/big_arp324.jpeg

14" LX200R @ f/10, L=6x10', RGB=2x10'x3, STL-11000XM, Paramount ME

Related Designations for ARP324

ARP325

Arp 325 is a chain of galaxies, one minute of arc long, in very southern Aquarius. There is very little on these. No catalog I could find lists them as separate galaxies. Most just number them 1 through 5, usually north to south rather than in RA order as most other such groups are numbered or lettered. Best I can do is either say they are VV 167 or MCG -04-52-014 and number them NED 01 through 05 top to bottom. I wish I could tell you more about this chain but I can't. I find only one redshift measurement of one of the galaxies in the chain. It is obviously wrong and NED says the same. It shows it coming toward us when it's quite obvious this is a very distant chain and thus would have a high speed away from us not a small one toward us. Neither Hubble nor SLOAN has examined this field. Arp had no comment on this field either. The Rodney Dangerfield of Arp galaxies it would appear.

This is by far the most southerly object I've tried to image. At -21 degrees it is well below my -15 degree cutoff. But the night was super steady giving me a chance. Still, the result is about 4" seeing but compared to the 8" that's normal this low that is darned good. I can't image it at its highest point due to the Meridian Tree which blocks that part of the sky. it was only about 14 to 18 degrees above my horizon when imaged, Some of this time part of the aperture was blocked by the wall of the observatory, blue and green data suffered most from this. If I'd been thinking I'd have taken the Red lowest since that low I lose a lot of blue and some green light but dummy did it backwards. This made color balance very difficult. There was no G2V star in the image (they are rather rare) nor could I use my normal formula for calculating the correction as I didn't know the light lost to the observatory wall. So this is a WAG beyond all reason. Still, it looks OK, just don't go saying these colors are right! I probably should have used this super night to take something high that could have used 0.5 pixels. In fact, that was planned for the next object. But the seeing didn't hold so I blew that one. But did get an Arp I didn't expect to ever image so something came of it at least.

There's little data on the rest of the field. One of the few galaxies with redshift data is west and a bit south of Arp 325. It is near the western (right) edge of the 1.5x cropped image. It is 2MASX J22060492-2106160 or LEDA 832620. NED shows it to be about 780 million light-years distant. There are two other galaxies at this distance in the image and another just off the bottom center of my image. All are similar to the galaxies in Arp 325. Could they all be part of the same group of galaxies? If so that would give a distance estimate for the group. The other chains like this one in Arp's catalog are all made up of similar elliptical galaxies of the same color. Here the northern and southern galaxies seem bluer and much smaller in angular size. I don't know what, if anything, this means.

I've attached a rather sparse annotated image showing them as well as one quasar. The quasar is magnitude 19.0, wavelength unknown, normally that would be quite bright on one of my images. It is rather dim in this one due to atmosphere extinction that low in my skies. I'd have liked to have added exposure time but first, the Meridian Tree objected (it blocks 2 hours around the meridian then the clouds seeing did. Never had a night of sufficient seeing after that to get more data. With so little data on the field, I can't but guess at my limiting magnitude. So I'll guess at about 20, over 2 magnitudes lost over a normal image. I wonder how much more there is in this field I missed.

Arp's image
http://nedwww.ipac.caltech.edu/level5/Arp/Figures/big_arp325.jpeg
Notice how he was able to easily separate the northern galaxy from a star below it. This separation is barely visible in my image due to the seeing so low in the sky.

14" LX200R @ f/10, L=4x10' RGB=2x10'x3, STL-11000XM, Paramount ME

Related Designations for ARP325

ARP326

Another twofer deal on Arp Atlas entries. Most of them are completely unrelated objects that happen to be in the same field. Not this time. Arp 33 is part of Arp 326. Arp 326 is in Arp's category, Galaxy groups, chains of galaxies. The chain is located in Virgo right near the southwestern corner of Bootes. As can be seen in the annotated image this isn't a real chain but consists of galaxies of at least 2 different groups. Since redshift data is available for only 3 of the 7 galaxies Kanipe and Webb consider part of the chain its hard to determine what is really going on here. The chain members, as defined by Kanipe and Webb are (from north to south):

MAPS-NGP O_559_0677185 530 mly
CGCG 045-052, Spiral at 530 mly
SDSS J133727.40+063044.4 Not in Webb/Knipe's list
MAPS-NGP O_559_0677872
UGC 08610, Sa at 530 mly
MAPS-NGP O_559_0792305 520 mly
ARP 33/UGC 08613, SB at 340 mly
LEDA 214126, E? 340 mly

The classification of LEDA 214126 seems way off, Looks pretty much a spiral to me. For this reason, I left the classification off of the annotated image. UGC 08596 at 320 million light-years, classed as simply S and UGC 08623 classed as Sd at 340 million light-years. It is seen edge-on and is extremely flat. So flat it made the Flat Galaxy Catalog. It would appear these two are likely members of the same group as Arp 33/UGC 08613. Why Kanipe and Webb left out SDSS J133727.40+063044.4 I don't know. It is slightly brighter than MAPS-NGP O_559_0677872 just below it. While I identified MAPS-NGP O_559_0682366 NED had little on it. Just seemed big and bright enough to deserve mention. It looks like a nice face on spiral but NED omits a classification for it.

This brings us to Arp 33. While a member of the Arp 326 "chain" it made the Atlas under the Integral Sign category. It is a bit better integral sign than most of the others in that category, some of which require a lot of imagination to see as that math symbol. NED considers Arp 33 to also include LEDA 214126 which is also part of the Arp 326 group. Arp did include it in his image of Arp 33. The VV catalog considers UGC 08613 to be 4 galaxies; VV 6a through VV 6d. NED, however, says these are just parts of the galaxy. Something likely drew Arp 33 out into the integral shape. VV 6c and d seems a possibility. UGC 08596 shows a rather distorted arm on its east side and is also a possible cause of Arp 33's distorted shape.

NED and the Sloan survey identify a lot of other objects around Arp 33 that are similar to the VV objects. None of them are listed as being part of the galaxy, however. I've identified a few of them. It would get too crowded to identify them all. How some are part of the galaxy and the rest not I haven't figured out.

The image contains three asteroids. West to east (right to left), they are (102745) 1999 VZ111 at magnitude 18.2, 2006 ST289 at a very optimistic estimated magnitude of 19.8 and one not yet known to the Minor Planet Center. I did it yet again. Imaged an asteroid but discovered it a year too late to do anything about it so it is still undiscovered. It was taken April 7, 2010 and not processed until now. I do have to clean up this backlog somehow.

The 200" had sufficient field of view to do the entire group with its corrector lens in place. These online images are not made from the original plates but from first generation prints, Arp processed to bring out the detail he was interested in.

Arp's image of Arp 33
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp33.jpeg

Arp's image of the group Arp 326
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp326.jpeg

14" LX200R @ f/10, L=8x10' RGB=2x10'x3, STL-11000XM, Paramount ME

Related Designations for ARP326

ARP327

ARP 327, also known as Hickson 34, is a small group of 4 galaxies headed by NGC 1875, a very large E2 galaxy with a possible AGN (Active Galactic Nuclei). Its redshift puts it at about 410 million light years. The other members have slightly different redshift distances but this is likely due to interaction among themselves. Since NGC 1875 is the big gorilla of the group I'll assume it is little bothered by the companions and thus its redshift is the best indicator of the group's distance.

The other galaxies in the group, north to south carry the same designation in most catalogs, just that they are numbered or lettered west to east which also happens to be north to south. The PGC catalog does list them separately so that's what I'll use for the other three. North to south, they are PGC 17173 an 18th magnitude S0 galaxy, PGC 17175 a 17th magnitude SBd galaxy and PGC 17176 a 17th SA0 galaxy. It is PGC 17176 that seems most torn up by the gravity of the system.

A note at NED says this about the system:
The four galaxies of the group form a characteristic chain. This kind of configuration is frequently found in compact galaxies groups and is easily explained by the N-bodies simulations of clustering (White et al. 1987) which often produce filamentary structures.

Arp did classify this group under his classification "Group Character: Chains of galaxies. This was long before the paper explaining them.

There appears to be a possible 5th member of the chain, much fainter and not nearly as red. It is HCG 034:[RHF91] 02 per NED. Since HCG is their notation for Hickson Compact Groups they must consider it part of Hickson 34. Though there's no redshift data to determine if it is really a member or just a line of sight interloper. Its different color bothers me. Arp apparently didn't include it in Arp 327. In fact, he didn't include NGC 1875 in his group! His description is; "Three distorted galaxies in general line toward east." Thus he is leaving NGC 1875 out of the chain for some reason. Probably because it isn't distorted though I don't see much if any distortion in PGC 17173 either.

Unfortunately, the night was poor when I took this with my seeing a bit worse than 3". I needed a much better night to get much detail. I'll have to try again next winter.

The red galaxy NE of Arp 327 with its core offset to the right side is 2MASX J05215739+0643182 which appears to have a redshift distance of just under 400 million light years. So it could be related to the galaxies in Arp 327.

The largest galaxy SW of Arp 327 2/3rds of the way to the lower right corner is CGCG 421-036. It is a bit over 400 million light-years away so again, likely a member of the same group. Even closer to the corner not far from CGCG 421-036 is 2MASX J05205314+0633047. It is at the same redshift distance as CGCG 421-036. Continuing due west almost to the edge you come to another galaxy at this distance, 2MASX J05203488+0633083. Continuing west and north a bit is a galaxy mostly off the image but its eastern edge is seen just poking into the image above a pair of equally bright stars. This is UGC 03291 also at the same distance. So it appears the group that Arp 327 is part of is quite large and extends off my image to the west. Something I suspected so put it a bit east of center but not as far east as I should have.

Since the SDSS hasn't surveyed this area yet, there isn't much information on the few other galaxies in the image. Many are apparently anonymous.

Arp's image of the chain, including the two galaxies he excluded, is at:
http://nedwww.ipac.caltech.edu/level5/Arp/Figures/big_arp327.jpeg
He had much better seeing than I did. I believe this image was taken with a somewhat blue sensitive emulsion, likely 103a-D coupled with a yellow filter. A combination he seemed to like I've recently learned. Why I don't quite understand. My guess would be, of the choices available to him, it best matched a visual representation. It would tend to even out the red of population 2 stars and the blue of population 2 stars giving a more even response across the spectrum. That's my guess, I've seen nothing on it.

14" LX200R @ F/10, L=4X10' RGB=2X10'X3, STL-11000XM, Paramount ME

Related Designations for ARP327