ARP271

ARP 271, in Virgo, is a rather classic Arp pair, much photographed compared to most Arp galaxies. Thus my desire for a better night than I had. It is two spiral galaxies, NGC 5426 (bottom) and NGC 5427 that are just now starting to interact as they orbit by each other, apparently for the first time. Some distortion can be seen in each galaxy. The arms of NGC 5426 seem to be reaching out to connect with NGC 5427. It, in turn, has some tidal effects showing. But we are seeing them in 2D rather than 3D which makes determining the real relationship between these in space difficult to determine. For some insight as to what is happening here, I will refer you to the article and great image taken by the Gemini South telescope with nearly 6 times the resolution I can achieve here. I wish now I'd have taken some H alpha data with this as both galaxies are rich in HII regions as shown by the Gemini South image. http://www.gemini.edu/twinspiral The pair was discovered by William Herschel on March 5, 1785. NGC 5426 made the Herschel II 400 observing program. My notes from that failed to arrive when we moved to Minnesota so I can't give them.

Arp classed the pair under "Group character: connected arms". His comment reads: "Arm's linked. Note bifurcation in arm of N spiral." NGC 5426 is classed by NED as SAc pec. while NGC 5427 is classed as SAc pec. Sy2. The latter meaning it is a Seyfert 2 galaxy with an active nucleus. I find no consensus on their distance. Redshift puts them a bit over 130 million light-years away but various papers I've seen put them closer, more like 90 to 110 million light-years. The ability of Gemini south to resolve so many HII regions would argue for these somewhat closer distances.

While there are a lot of faint fuzzies in the image, most are cataloged under the LCRS catalog, that stands for Las Campanas Redshift Survey. Oddly, the nice big bright entries have no redshift value in NED. For instance, the large orange elliptical NW of Arp 271 is very obvious. It is cataloged as LCRS B140024.4-054536 without a redshift. Most that do carry a redshift are the tiny yellowish orange galaxies. Those fall into two camps, those near Arp 271 are about 1.1 billion light-years distant and those in the SW corner belong to a different group being 1.7 billion light-years distant. But the larger, likely closer galaxies have no redshift data that I could find.

In my north up image the lower galaxy seems to my brain to be nearly face on but in the Gemini image, it appears quite tilted. So I rotated my image for east up and suddenly it looked very 3D and tilted. I've attached the cropped rotated version, see link for full north up version. Is it just me or does it seem to appear to change orientation for you as well?

Arp's image of the pair with the 200" Palomar scope is at:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp271.jpeg

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

Related Designations for ARP271

ARP272

Arp 272 is a trio of galaxies in the Hercules cluster. Arp put it in his category for group character, connected arms. The disks of all three do overlap as seen from earth. Whether they really overlap is questionable. It could be just an alignment due to our viewpoint. Their redshifts are rather different which would argue this is just an illusion though the lower two both have plumes that are likely due to interaction. So they may be related but just passing by each other at rather high speed. The interaction, if any could be happening as we look or happened some time ago with them lining up from our viewpoint. It is hard to tell.

The eastern galaxy is NGC 6050 classified by NED as SB(rs)cd, the western is IC 1179 classified by NED as SB0^0^. They are about a half billion light-years distant. NED doesn't consider IC 1179 part of Arp 272 yet most sources consider it one of the two or three galaxies that make up Arp 272. Again Arp's catalog (1966ApJS___14____1A.pdf) lists Arp 272 as NGC 6054 which can't be correct. In any case, the southern pair was discovered twice by Lewis Swift. Once on June 27, 1886 becoming NGC 6050 and again on June 3, 1888 becoming IC 1179. It is likely he saw these as one galaxy as even in larger scopes than his they can't be seen as two objects. The eastern galaxy seems to only carry the NGC 6050 name at NED but most consider it also as IC 1179. It is classified as SA(s)c.

This brings us to the northern object, UGC 10186. Some sources consider it a piece of the pair that has broken off. I have trouble with that and see it as yet another galaxy. If so this may be a triple system. NED considers it part of Arp 272 and calls it a double system which I find rather confusing as it ignores IC 1179. Seligman however considers IC 1179 the same as NGC 6050. He says the two are PGC 57053 and PGC 57058 right to left. Anyone confused?

This data was taken September 13, 2007. I didn't have the tools to do it justice back then. I need to reshoot this one. It also contains ARP 71, Arp 122 and Arp 172. Details are in the annotated image. The annotated image shows details on many other galaxies in the cluster and beyond it.

Arp's image: http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp272.jpeg

14" LX200R @ f/10, L=6x10' RGB=3x10', STL-11000XM, Paramount ME

Related Designations for ARP272

ARP273

Arp 273 is a near collision in progress. The large galaxy is UGC 1810, the other spiral, UGC 1813. They are located about 330 million light-years away at the southeast corner of Andromeda. It's obvious that UGC 1810 is highly distorted. One arm looks more like Saturn's F ring than a spiral arm and seems to make a complete ring about the galaxy. It's hard to tell if NGC 1813 is distorted. It looks greatly distorted to me as the arms are almost straight but that is seen in other barred spirals. But it has faint a faint arm that curls back and runs along the arm while the ends of the bar, if it is a bar, seem to end differently. The left one ends in a faint blob while the right one seems to curve back from the arm of UGC 1810 as if repelled by it. Obviously, it isn't but sure gives that appearance. In any case, they curve very differently, likely due to the near collision. To appear so large at such a great distance these have to be two very large spiral galaxies. Indeed they are. I measure UGC 1810 as being 210,000 light-years in diameter. It is probably larger unless seen exactly face on. I measure NGC 1813 at 160,000 light-years including the long eastern plume.

When galaxies pass by like this they trigger massive star formation. We see it in the arms of the bigger galaxy UGC 1810, this is common, but it is confined to the very core of UGC 1813. This is not unusual. Also, UGC 1810 is a LINER galaxy. It doesn't seem to have an active core, so we know the near miss hasn't yet caused a feast for the black hole by sending matter its way. Yet UGC 1813 seems to have a heck of a lot of disturbance at its core to trigger so much star formation. This all goes to show it is very hard to predict just what will happen in a near miss like these two have encountered. Nor do we know what long-term changes it will trigger. I can't even find if the two are gravitationally bound. If so they will merge in the future.

This is one of the rare images I can display at my full resolution of 0.5" per pixel. Something my seeing rarely allows, unfortunately.

Arp's image: http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp273.jpeg

14" LX200R @ f/10, L=6x10'x1 RGB=2x10'X2, STL-11000XM, Paramount ME

Related Designations for ARP273

ARP274

Arp 274/NGC 5679 consists of three galaxies in the constellation of Virgo. Arp put them in his category of "double galaxies with connected arms." His note reads: "Perturbation of arm by small galaxy to east." He is drawing several conclusions here that may not be correct. The first is the connected arms classification. NED has this to say about the two main spirals: "Delta V > 1000 km/sec; probably an optical pair." That is they consider the two galaxies redshifts to be too different for them to be anything more than an optical pair. I'm not sure that alone is sufficient but I also see no evidence of interaction between these two. Putting the two together I have to agree they are most likely an optical pair. Note too, in the annotated image there are several galaxies with redshifts that match the center galaxy and several that match the western member. It appears we really do have two different galaxy families in the image, the largest of each family nearly along the same line of sight as seen from earth.

That brings up Arp's note. It is true the eastern end of the middle galaxy's eastward arm has a sudden kink. This apparently was sufficient for Arp's conclusion that this is due to perturbation by the small galaxy off the arm. But this is the only evidence for this conclusion. In all other M51 type interactions in his Atlas, the entire arm is distorted not just the end. It's hard to explain just a sudden change like this as caused by an outside gravitational field. The effect should gradually begin. Maybe as seen in the third dimension it does. But how you tell this from a 2D image I don't know without further redshift data on that arm. The other problem is that there is no distance determination available for the small third galaxy. It too could be unrelated. It may be related, but, to me, it is far from being a solid conclusion. The odd fringes of stars off the small one may help this argument some. However, I'd expect them to show some orientation toward the main galaxy rather than at right angles if this were the case. Again, a 3D view might show this is the case. I need far more evidence before accepting this, however. NGC 5679 was discovered by William Herschel on February 12, 1793, but isn't in either of the Herschel 400 observing programs.

The low surface brightness galaxy to the southeast of Arp 274 is UGC 09385. The UGC catalog lists it as a dwarf galaxy! It certainly has a low number of stars but with a diameter of about 50 million light-years, it is not very dwarf-like in size.

Of the galaxies to the southeast of Arp 274 at 330 million light years, the eastern one seems to have a comet sticking out of its southern end. NED lists it as a separate galaxy, SDSS J143557.41+051822.4. No redshift is given. Maybe it has a second arm hidden behind the foreground galaxy giving this illusion.

There are several galaxies at 800 million light-years scattered across the image indicating yet another family. This field also contains more quasars than average. One, in the lower right corner, is listed both as a galaxy and quasar at 1.9 billion light-years. Its spiral arms are clearly visible in my image. I'd think a quasar would be so bright as to drown out the galaxy at my resolution. It must be a very weak quasar.

Along the top of the image toward the left is the asteroid (237813) 2002 CP84 at an estimated magnitude of 18.4. That appears reasonable in this case.

Arp's image
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp274.jpeg

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

Related Designations for ARP274

ARP275

Arp 275/NGC 2881 is a pair of colliding galaxies in Hydra nearly a quarter billion light-years from earth. Arp had no category for colliding galaxies. Though he did have one for interacting galaxies. Many dozen of his galaxies were interacting but only 6 made this category, This was the first of the 6. Unlike most entries, he had no comment for this entry.

The two galaxies making up Arp 275 are also known as VV 293a and VV 293b with VV 293a being the one on the left (east). It is the only one of the pair to have redshift measurements. It isn't classified at NED other than mention it has HII regions. VV 293b to the west is classified at NED as Sbc? pec. A note at NED from the MCG catalog says; "Bright, interacting. Two galaxies Fd in close contact with very large deformations." A note with the VV catalog says; "On the (red) POSS print the two major bodies are not in contact against the background of a homogeneous disk." I can't tell from any image if they are in contact. To me, it appears that the eastern galaxy may be slightly in front of the western one. Since I can't really tell where one galaxy ends and the next begins I measure the long axis of the projected pair at about 74,000 light-years. So these aren't very big galaxies, even including the plumes created by their interaction. The pair was discovered by Lewis Swift on February 9, 1886 using a 16" refractor.

The only other galaxy in the image with any information is IC 2482 in the southeast corner of my image. It is listed as an E+ at NED and much closer than Arp 275 at about 175 million light-years. A note at NED says of it; "The gradient of brightness in halo is smaller than in a normal E." Oddly it is quite a bit brighter and larger in angular size than Arp 275 yet wasn't discovered until March 14, 1899 by Herbert Alonzo Howe using a 20" f/15 Alvan Clark-George Saegmuller refractor at Chamberlin Observatory in Denver. How Swift missed it I don't know. While it is partly off my frame I measured its the length of the side fully on the frame and doubled that to get a size of 156,000 light-years. Twice the size of Arp 275. My sister-in-law lives in a southern suburb of Denver and every time I've been there the seeing has been awful. Seems like a poor place for an observatory from my limited sample. The observatory is right in Denver only about 3 blocks east of the University of Denver campus of which it is a part, right beside tennis courts and ball diamond (both unlit last I knew). Conditions must have been much better in 1899! It still is open two nights a week to show the public the moon and planets, about all you can see from that location today. Howe managed to find 60 IC objects from there. Not much light pollution in his day.

Nothing else in the frame has any distance information useful for an annotated image so I didn't prepare one.

Arp's image: http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp275.jpeg

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

Related Designations for ARP275

ARP276

Sometimes an image turns out very differently than you expect. This certainly is one of those. I never suspected the galaxy was buried in galactic cirrus. I saw a hint of it in the raw files as they came in. Only the brightest part showed however and looked like a reflection. So when I stacked and calibrated the images it came as a shock to find the field full of the Integrated Flux Nebula.

Arp 276 consists of two galaxies which are barely showing signs of interaction. Since we can't see them in 3D its possible one is well in front of the other such that gravitational interaction is minimal. Some distortion of the southern galaxy's NE end is evident but that's about it. Radio data shows these to be rather normal galaxies giving little hint of a collision in progress from what I found. Arp notes; "Both intersecting edges seem dimmed." Hard to say if that's due to anything more than one obscuring the other. I'd like to see spectral data for the overlap region.

The northern galaxy is NGC 0935 classed as Scd. The southern is IC 1801, an SBb galaxy. Redshift shows it slightly in front of NGC 0935 but this is not a reliable indicator. The pair is about 175-180 million light-years away by redshift data. Each galaxy has hosted a supernova. SN 2006F was seen in NGC 0935 and SN 1976 was seen 30 years earlier in IC 1801. NGC 935 was discovered by Lewis Swift on September 18, 1885 but he apparently didn't see IC 1801. That had to wait 12 years until found by Stephane Javelle on December 27, 1897.

This region hasn't been surveyed by the SDSS. The group is in central Aries. I need to redo it with a lot more exposure time to pick up the integrated flux a lot better than I did with my normal rather limited exposure time. NED shows only a dozen other galaxies in my image, none of which has any redshift data.

The Integrated Flux Nebula or Galactic Cirrus as it is also called is fine dust above and below the plane of our galaxy that is lit by the combined light of the stars in our galaxy's spiral arms. Some of it is reflection nebula, this part is white to blue-white in color. Some though are made up of particles that glow a red color in the ultraviolet light of our galaxy's most massive stars. This is called Extended Red Emission or ERE and accounts for the reddish areas of the nebula. Normally we think of reflection nebula being lit by the light of one or a few super bright stars that are nearby. But this nebula is lit by the combined light all the stars in our galaxy though mostly this is from the supermassive stars that define the spiral arms as they account for most of the light emitted by the disk of our galaxy. While brighter pieces of it were cataloged in the LBN catalog in the 60's based on the Palomar Sky Survey plates it wasn't until 1975 that some idea of its real extent was realized by Alan Sandage who used the 48" Schmidt to image it in a 4 hour exposure. Even then it was rather dim as film just didn't have the sensitivity to see this faint nebula, even in such a large scope. Today's electronic detectors, akin to those in digital cameras but designed for long exposure work and used at rather low temperatures (I usually run at -35C) to reduce noise by a factor of 1000 or more replaced film. The first map of it was made by the IRAS satellite as much of the ERE emission was in its infrared passbands. It was its images that gave it the "Galactic Cirrus" name as it looks much the same as earthly cirrus clouds. Since then more extensive maps have been made by Earth-based astronomers in near infrared as well as visible light wavelengths. See http://www.galaxyimages.com/UNP1.html for one such effort. Still, I'd not seen anything indicating it was "big and bright" in this part of Aries though I'd seen some fainter portions in the vicinity of M15.

Some with a wider field and faster telescopes than mine might want to take some really deep images of this area and find the extent of this portion of the IFN. My system is too narrow field for such a task.

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp276.jpeg

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

Related Designations for ARP276

ARP277

Arp 277 is in Arp's category for interacting galaxies. While there are many dozen interacting galaxies in his catalog he has only 6 entries for this category, all NGC galaxies. This pair is NGC 4809 (top) and NGC 4810 (bottom). Both are classed as Im pec and are found in Virgo. Neither shows any organized structure that I can see. Redshift indicates a distance of a bit under 60 light-years while Tully and Tully-Fisher measurements put them a bit over 70 million light-years distant. The redshift distance would make them likely members of the famous Virgo galaxy cluster. The pair was discovered by R. J. Mitchel on April 18, 1855.

At the top of the image is NGC 4799. I moved Arp 277 low and right to get it into the image. It too shows hints of distortion. There seems a hint of a tail going due west from the galaxy. My exposure is too short to show it as more than a hint. The SDSS image seems to show it as well but there's a problem. The galaxy is on two different SDSS images processed slightly differently. The result is the southern frame seems to show the plume while it is not very distinct in the upper frame. So is it just noise or real? I'd hoped this would have been enough exposure to answer this but it wasn't. Still, I think there's some reality to it. I'll need to try again. NGC 7499 has a redshift distance of about 140 million light-years and is classed simply as S or S? and is listed as a Seyfert galaxy. If the redshift is correct it is apparently well beyond the Virgo cluster. Seyfert status gives some validity to it having had an interaction and thus makes the faint hint of a plume possible. It was discovered by William Herschel on April 30, 1786. It isn't in either Herschel 400 observing program.

I've made an annotated version of the image. Toward the right side, I've noted the position of a galaxy cluster with 12 members (NSCS J125416+024611). It has about the same position as listed for the galaxy SDSS J125416.01+024600.0 also shown on the image. The cluster likely lies beyond the galaxy. The position for the galaxy doesn't quite match that of a very large, low surface brightness galaxy. But there is no galaxy shown at NED where the galaxy is located. Nor is there any distance listed. So I show 2 question marks for it, one for the location error and another for no distance. (Edit: I've since determined the galaxy is indeed that very dim tiny near starlike object. The large low surface brightness galaxy is SDSS J125415.87+024545.1) It's listed magnitude of 18.9 is fainter than I'd estimate the galaxy but brighter than anything in the area other than the galaxy. There is a tiny galaxy at the exact position shown. It is far fainter than magnitude 18.9 however. This all seems to be an error in the SDSS or in NED's representation of it. My line goes to that faint galaxy. You will likely need to enlarge the image to even see it as it is lost in the eastern edge of the big galaxy. It's likely a member of the galaxy group and thus 2.8 billion light-years distant. That leaves the identity of the large blue galaxy unknown. I'd put its coordinates at J125415.88 +024545.0 (about 3" west and 13 south of NED's position).

This area seems full of confusion. Also in the immediate area is SDSS J125414.47+024616.7. SDSS lists it as a quasar. But it certainly is fuzzy, not starlike, in my image. A check of the SDSS image also shows it as fuzzy though the core is very compact and bright like a star. It's also in the Veron-Cetty+Veron 2006 edition of A Catalogue of Quasars and Active Nuclei as a Seyfert 1 galaxy. Maybe it is both. I've listed it as Q/G. It is rather close for a quasar at only 2.9 billion light-years. It may be a quasar in a galaxy in the galaxy cluster listed at 2.8 billion light-years.

There are two asteroid trails in the image: (65702) 1992 EK4 at an estimated magnitude of 19.0 the upper right and (45722) 2000 GA56 at an estimated magnitude of 18.5 to the upper left. They are noted on the annotated image.

Arp's image
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp277.jpeg

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

Related Designations for ARP277

ARP278

This is Arp 278 or NGC 7253, a pair of interacting galaxies. They are about 200 million light-years from us. NED, my distance source seems to have a problem here. It lists the distance to each individual one as about 191 to 194 million light years. So take your pick. This image was taken at 0.5" per pixel on a good night rather than my usual 1" per pixel my seeing often limits me to. The asteroid leaving a prominent trail is (307771) 2003 WS42 at magnitude 18. Note the dim spot two-thirds of the way along the trail. This is due to clouds which reduced my transparency for about 10 minutes during the 60 minutes that I collected luminosity data. Down in the lower right corner is UGC 11981, a face on spiral galaxy about 278 million light-years from us. This image was cropped somewhat but not so much as to lose the spiral. NED classifies it as SA(s)c. Also, there are a lot of faint fuzzies in the background.

The pair was discovered by Albert Marth on September 9, 1863 and is located in Pegasus. Both galaxies are almost as large as the Milky Way Galaxy we live in so rather large for spiral galaxies. The upper galaxy is classified by Seligman as SABc? while the lower is Sc?.

Arp's image: http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp278.jpeg

14" LX200R @ f/10, L=2x20'x1 RGB=2x10x2, STL-11000XM, Paramount ME

Related Designations for ARP278

ARP279

ARP 279, NGC 1253 and NGC 1253A is a pair of interacting galaxies in Eridanus that are about 70 to 75 million light-years away. Close by compared to most Arp galaxies. Arp put them in his class, Double Galaxies: Interacting. Arp had no comment about these two. The main galaxy is classed as S(B)c by the NGC Project and SAB(rs)cd by NED. The companion is SB(s)m per NED. How you get a barred spiral out of that mess is beyond me. It does have that curving arm-like feature but I'm not sure what it was before the encounter. Comparing my version of this companion to that in Arp's image I'm surprised how bright a couple star clusters are in my image compared to his. This difference holds in the POSS 1 and 2 plates as well. They seem overly bright in my raw FITS files as well so it isn't processing. Maybe instead of knots, they are variable stars in our galaxy caught with both at maximum. Considering I took the data over an eight day period and they show the same in both I find that unlikely. So, for now, its unexplained. My color data for this one is highly suspect. I need to retake the color due to heavy cloud issues. Some of the blue stars are really red I believe. Trying to adjust I just made a mess of the galaxy so left it as is.

For some reason, this pair reminds me of a big fish or maybe sea turtle chasing a small ray that is slashing its tail trying to get away. The big one is leaving a double wake behind it. In any case, these are both distorted in very unusual ways, even for Arp's catalog. NGC 1253 was discovered by William Herschel on September 20, 1784. Like most Arp galaxies he discovered it isn't in either of the Hershel 400 observing programs. I suppose since the Astronomical League also has an Arp program they didn't want many duplications. Only a guess since their various programs do have duplications.

This field is little studied so not much information on the other galaxies in the image. Only the three biggest galaxies besides the Arp 279 pair have any redshift data. They are KUG 0311-031 near the bottom edge a bit west of Arp 279. It is in both the ultraviolet galaxy catalog (KUG) and the IR catalog (2MASX J03134761-0256056) so is both a strong UV and IR emitting galaxy. One NED note says it is "leaf shaped". I don't see that in my image. NED shows a redshift that puts it about 273 million light-years away.

The other two galaxies are along the western edge. The lower is 2MASX J03131021-0254121 at 274 million light years, thus a neighbor of KUG 0311-031. Well, above it is 2MASX J03130881-024319 an S0 galaxy about 375 million light years distant. The brighter background galaxies are mostly listed only in the APMUKS catalog which is just an automated plate survey of objects in the UK Schmidt telescope in Australia. A few are from the 2MASS survey of IR galaxies. Most are not in any catalog I could find.

Three satellites/space debris cross the image. Two are sun glints with faint trails and angle down and to the right. The brighter one goes nearly horizontally across the upper part of the image. I didn't remove them for some reason.

Arp's image
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp279.jpeg

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

Related Designations for ARP279

ARP280

Arp 280/NGC 3769 is a pair of probably interacting galaxies in Ursa Major at a distance of 50 million light-years most say. Redshift puts it a bit closer at 44. It is a member of the Ursa Major Cloud of galaxies which are thought to range about 50 to 55 million light-years distant and includes M108 and M109 as its most famous members. Arp put it in his class of interacting double galaxies. It was discovered by William Herschel on February 5, 1788. It isn't in either Herschel 400 program though is within easy reach of an 8" telescope from dark skies at a visual magnitude of 11.7.

Note the knot in the western end of the major member. Everything I saw on this pair refers to it as a knot, including the Kanipe-Webb book on the Arp Atlas. But in my color image, it came out with an orange core and blue outer parts as if it were a separate galaxy. Knots are almost always blue. If red then its H alpha red due to large clouds of ionized hydrogen in them. This got me searching further. I found a Hubble image (attached) that shows it clearly is a separate barred spiral galaxy. NED doesn't include it either as part of a galaxy or as a separate galaxy. Is it a distant galaxy or a dwarf spiral being digested by Arp 280? Its arms are distorted but I still think it more likely a background galaxy. It wouldn't take much to change my mind, however.

The western member is by far the larger and is classed as SB(r)b:. The NGC project has it as Sb. Considering it appears to have an obvious bar I am a bit puzzled by the NGC project's classification. The eastern member is classed SBm Pec by NED. Looks more like a blob with a few knots to me. The eastern blue blob (a pair actually) carries its own designation PGC036008 Its redshift puts it at 44 million light-years. The same as NGC 3769. So they are a true pair.

In the southwest corner of the image is the galaxy cluster MaxBCG J174.22470+47.81605 at 3.1 billion light-years with 32 members. The diameter isn't listed, however. Is the red galaxy at 3.1 billion Light-years that is well east (left) of Arp 280 a member? If so it is pretty large.

The large galaxy west of this cluster at a distance of about 470 million light-years is UGC 06576, an SB0 galaxy with a very large faint outer disk. It appears to have a small companion to its southwest at about the same distance.

A couple very blue quasars are in the image. In processing it I couldn't help but notice a super blue starlike object east of Arp 280. I was sure it would be a quasar when I went to look it up but nope. It is listed as a white dwarf and X-ray source in the ROSAT catalog All-Sky Survey Bright Source Catalog of X-ray sources, 1RXS J113836.9+475459. That's one hot white dwarf. So where is its planetary nebula? Has it already dissipated? It is labeled as WD/X in the annotated image.

After writing this I found limited data on the western part of this galaxy pair at the Hubble Legacy site. I did a quick enhancement of the mono data there. It supports the idea the blob at the north end of NGC 3769 is indeed a separate galaxy.

Arp's image
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp280.jpeg

14" LX200R @ f/10, L=4x10' RGB=2X10'X3, STL-11000XM, Paramount ME

Related Designations for ARP280