ARP010

Arp 10 is in Arp's category Spiral galaxies: Split arm. It is located in Cetus about 400 million light years distant. While it appears to have a companion just to the north that galaxy, 2MASX J02182874+0540079, is over 700 million light years further away (1.15 billion total). But it apparently does have a companion. To me, it looks like a star, even on the SDSS image. It is the starlike object right beside the core to the southwest (lower right). It is identified in NED as ARP 010:[BMV2007] Companion with a redshift that puts it about 420 million light-years away. Arp's comment, "Nucleus off center in ring." I can't say I see the "split arm" that caused Arp to put it in that category. Is it the ring that is more a slight oval coil that doesn't quite overlap? Is it the faint arms at the southeast that seem to go in opposite directions? Or is it something else? Arp doesn't explain.

While NED lists the starlike object near the core of Arp 10 as a companion it gives it the classification of Sab? How you get that out of a starlike object is beyond me. NED classes Arp 10 itself as only S?. Looks like a barred spiral with a ring to me. To add to the confusion one paper wonders if the brightest blob in the very blue arc in the northwest part of the galaxy is the core of a second galaxy. In other words, this object is still very much a mystery with all sorts of contrary information that has me going in circles. While not all the papers agree, to me this looks at least like a near head-on collision of two galaxies. If that starlike object is the core of the "bullet" galaxy it apparently lost most of its stars in the process and is now just a core. This could explain the apparent clockwise and counterclockwise shape of the faint arms on the southeast side of the galaxy's disk. Being so face on it may be difficult to tell if the stars really are orbiting in opposite direction. I found nothing indicating any measurements have been done. I'd expect radio telescopes to be best for this chore. One note at NED has this to say about this system:

"Faint "ripples" are seen at very faint levels around the galaxy. These ripples complicate the simple interpretation of Arp 10 as a collisional ring. Recent H I observations by Charmandaris & Appleton(1996) show that the bright inner ring is surrounded by an H I disk which extends beyond the faint "ripples." Although not as simple as ring galaxies like VII Zw 466, Charmandaris and Appleton suggest that the process that formed the rings and shells involved a central collision between a gas-poor early type galaxy and a large-type H I rich disk."

The full article is available for those with good hip waders at
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1997AJ....113..201A&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf

The field's data has not yet been entered into NED's database even though the field has been imaged by the SDSS. So there's little information on the rest of the field. In fact, I've already covered all objects with a known redshift in NED's database. Normally I'd not prepare an annotated image for such a weak field but there's an asteroid that was caught right as it went from normal to retrograde motion. It appears as a faint star with no trail visible as it moved only a bit over one arc second during the exposure. It is 2004 FD41 at magnitude 20.6. So it won't be obvious without it being pointed out. The other asteroid (8604) Vanier is very easy to spot at magnitude 16.8 to the right of Arp 10. It is so bright it even shows in the color filtered images making a short blue-green and red trail before the white trail from the luminosity image. It is moving in normal eastward motion rather than retrograde as most asteroids I pick up earlier in the evening do.

Without any distance indicators, I've marked all galaxies with their catalog entry instead. There are so few cataloged I'm listing every one known to NED along with the red shift distances to the three main ones. There is one galaxy cluster in the image. A line goes to the approximate center identified in NED. No size or galaxy count is given, nor distance of course. I do see lots of faint fuzzies in the area but nothing out of the ordinary except for a small concentration to the NW of that position containing very faint small fuzzies. Enlarge the image for a better view.

While the Hubble Space Telescope imaged quite a few galaxy collisions this wasn't one of them.

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp10.jpeg

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

Related Designations for ARP010

ARP011

Arp 11 falls under Arp's category: Spiral Galaxies: Split Arm. It is located in eastern Pisces not far from M74. It and the galaxy to its northeast (upper left) have a redshift that puts them a half billion light-years away. Arp 11 is cataloged as UGC 00717, an SBb spiral. Its companion to the northeast that it is likely interacting with is UGC 00719 also classed as SBb though not as distorted. Arp makes the comment about UGC 00717; "Outer arms do not start at termination of bar." I guess that depends on how you define the arms. To me, they do come from the bar, make a 180-degree arc coming close to the end of the opposite bar then being flung off wildly at a different angle. The same could be said for its companion UGC 00719.

There are quite a few other galaxies in the immediate area. Only one, MCG +02-04-004 to the southeast of Arp 11 and closer to it than UGC 00719, has a redshift given. It apparently is not part of the group as it appears to be nearly 800 million light years distant, 60% further than the other two. The galaxy just below UGC 00719 is 2MASX J01092954+1421169.

Further out there are galaxies with known redshifts. There is a distant 21st magnitude galaxy best seen in the enlarged cropped image that is 4.2 billion light years distant. It is southwest of Arp 11 and identified in the annotated image which gives the distances to galaxies with a known redshift based on 5 year WMAP data at NED. In the annotated image G preceding the distance is for galaxy while GC is for galaxy cluster and Q for quasar. The label is immediately right of the object. When not possible or identification could be confusing a line is drawn to the object.

I found three quasars in this image. But one is closer than some galaxies in the image and has a physical size indicating I'm seeing the galaxy itself, not just the quasar. Its FWHM is a good two seconds larger than that of the stars on either side of it. A quasar should be a point source. The other two fit the classic quasar. The classic blue color is obvious as well. Both are near the western (right) edge, one at the top the other near the bottom.

The annotated image shows that while Arp 11 and its companion are at about a half million light years they are surrounded by a group of galaxies with a distance of 780 million light years. This is the galaxy cluster SDSS-C4 2083 which NED lists as having 28 members. It is anchored by the large elliptical galaxy 2MASX J01092719+1415359 which is only one second of arc from the center of the cluster. So I've combined it with the cluster center in the annotated image even though its redshift puts it 20 million light years more distant than the cluster itself. This is well within expected variations in a galaxy cluster of this size. This happens twice in this field. Over near the eastern edge is the cluster SDSS-C4 2087 listed at 769 million light years that shares the same position (within one second of arc or one pixel) with the galaxy SDSS J011021.37+141642.2 listed at 713 million light years. This is an even larger discrepancy. No galaxy count is listed for this cluster. It seems to me this is just an extension of the first cluster.

To the right of Arp 11 is another odd galaxy. It appears to be much further away if size is any indication. It is 4.3 minutes nearly due west of Arp 11 and seems to have a tail on its east end that curves northward. With no distance data, I have no idea what it interacted with to create its odd tail. Seems worthy of including in Arp's catalog if he had noticed it but it's outside his image's field.

There are 3 asteroids in the image. The big and bright one is 13th magnitude Alemannia to the lower left of Arp 11. The other two are to the upper right near the top of the image. At magnitude 19.6 (230452) 2002 RF17 may be a bit hard to find. It is labeled in the annotated image. Immediately above it is the very oddly designated (42379) 2013 P-L. It is magnitude 18.2 so easy to spot. It has a designation that was new to me. When not named the designation is normally the year of discovery followed by a letter that denotes when in that year it was found. A means the first half of January, B the second half etc. I is not used. The second letter denotes when in the half month it was found. First found in January of this year would be 2010 AA, Second AB, again I is skipped. Once 25 are found then a number is used so after AZ comes AA1, AB1, AC1... through to AZ1 then AA2, AB2 etc. Hence the designation of asteroid 42379 made no sense to me. It was found in 1960 not 3 years in the future. If that was a name then that would be fine but the minor planet center doesn't show it as being named. It does show it used to be known as 1986 QH. But then the designation changed to 1999 RU119 before it became 2013 P-L. I had to find out more about the 1960 discovery to solve this one. Turns out there was a 1960 survey to find asteroids known as the Palomar-Leiden survey. This one was the 2013th found in that survey. It was then found to be the same as the other two asteroids and the survey designation replaced both with the orbit better defined by the later observations. One mystery solved. Old hat to asteroid hunters but new to me. There are three other survey's used to designate asteroids, the First, Second and Third Trojan Surveys T-1, T-2 and T-3. I've not run across any from those surveys as yet.

Arp's image is at:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp11.jpeg

14" LX200R @ f/10, L=4x10' RG=1x20'x3 B=2x10'x3, STL-11000XM, Paramount ME
Blue was intended to be one 20 minute exposure but I didn't get that part of the script file fully edited it appears.

Related Designations for ARP011

ARP012

Arp 12, NGC 2608 is a "grand design" barred spiral about 110 million light-years away. The bar is short running nearly east to west so at first glance it may appear to have a bar. It is classed by Arp under "Spiral galaxies: Split arm". In this case, the arm on the western side splits into three parts while the arm on the east (left) side is normal. I took and am displaying the image at 0.5" per pixel rather than my normal 1" per pixel. Seeing wasn't really up to it however so I likely would have had better results using my normal 1" pixel. Only thing is, looking at Arp's image it appears seeing on Mt. Palomar was even worse than mine. Must go with imaging this galaxy. It was so poor in fact that he couldn't tell if the second object in the galaxy was a second core (due to a merger) or a star. His comment was; "Nucleus may be double or superposed star." Even with my seeing it is obviously a blue star. Though being able to image using color filters makes the task of separating star from galaxy core much easier. In fact, there's no sign of any merger or disturbing galaxy. So why the one arm is split like it is, remains a mystery. You can see there is an outer halo of the galaxy though such halos are rather common with most spiral galaxies if you expose long enough. Still, it is unusually bright and may have been due to the same cause as the split arm, whatever that was. Several other papers refer to "2 stars superimposed on the bar". I only see the blue star and the nucleus though in my processing the core does look much like as star. Are these the two stars these papers refer to? If so the blue star isn't on the bar but I don't see any hint of other stars but these two.

The galaxy was discovered by William Herschel on March 12, 1785. It is neither of the two Herschel 400 Observing program. NED classifies it as SB(s)b:, the NGC Project says SBb/SBc and Seligman says SB(s)b. They all pretty much agree for once. I measure it at a bit over 60,000 light-years in size.

There's not much else going on in this image. The only other galaxy of note is to the northeast (upper left). It is trying to hide behind a field star (one in our galaxy). It is ASK 281454.0 shining at a rather bright magnitude 18.6. What's surprising is its redshift distance. That is 2.2 billion light years. It must be a spectacular sight to those no farther from it than we are from Arp 12.

Arp's image: http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp12.jpeg

14" LX200R @ f/10, L=8x10'x1, RGB=2x10'x2, STL-11000XM, Paramount ME

Related Designations for ARP012

ARP015

Arp 15 (NGC 7393) is classed as an SB(rs)C pec spiral galaxy. Pec means peculiar in that it certainly isn't a normal galaxy. It also has a ring structure. In this case, the ring is broken and partly made of enormous blue star clusters. Arp classified it under the heading of "spiral galaxies with detached segments". This appears to apply to the star clusters in the broken ring. Obviously, this galaxy has interacted with another but where is it? Possibly it is due to something it ate leaving only it's distorted shape behind. I found little in the literature about this one. It is about 156 million light-years away based on redshift data.

You can see a shot of it by Arp with the 200" Palomar telescope at http://ned.ipac.caltech.edu/level5/Arp/Figures/arp15.gif A bigger version that shows no more detail is at
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp15.jpeg. Notice either shows more detail than in my shot. This is because seeing at Palomar was better than at my location -- not necessarily because their scope cost millions of dollars more than mine. Seeing refers to how steady the atmosphere is both in the short term and long term. Long term meaning a second or so while short term meaning a few thousands of a second. The first moves the image around on the camera's sensor while the latter blurs it by forming many sharp images of the object all on top of one another each with a different center point. In any case, if you look up at the sky and see the stars twinkling seeing (slow type) is bad. If it isn't twinkling but a scope still can't form an image that's clear then fast seeing is bad. In most cases, you get both at once. Observatories are located in areas of what is called "laminar air flow". Often this is a mountaintop but doesn't have to be. Irregularities in the air cause bad seeing and laminar air flow evens these out (so does smog!) greatly improving seeing. Such air flow is not seen at my location, however. In any case, both types of seeing were very bad when this image was taken so the stars look fuzzy and detail in the galaxy is lost. Reproduced at 0.75" per pixel rather than my normal 1" per pixel (it was taken at 0.5" per pixel), it still looks very out of focus. Thanks to the atmosphere that night it is. It was discovered by William Herschel on October 5, 1785 but isn't in either Herschel 400 observing program.

14" LX200R @ f/10, L=4x10'x1 RGB=2x10'x2, STL=11000XM, Paramount ME

Related Designations for ARP015

ARP016

Arp 16 is better known as M66. It made his atlas under the heading of spiral galaxies with detached segments. It also is part of Arp Arp 317. Making it the only galaxy to have two entries in Arp's atlas. The image seen here was taken back in 2009 under rather poor conditions. The image with Arp 317 was taken under better conditions and processed with more modern tools than I had in 2009. Arp 16 is a rather active galaxy due to interaction with the other members of its group (again see Arp 317). It is this interaction that likely accounts for Arp's "detached segments" seen in this galaxy. To me, they are just clouds of new, blue stars created by interaction with its neighbors.

NED classifies it as SAB(s)b;LINER Sy2, The NGC Project simplifies this to Sb while Seligman says SAB(s)b?. The galaxy's discovery is credited to Charles Messier on March 1, 1780. While some sources credit its discovery to Pierre Méchain who did discover many objects in Messier's catalog that is unlikely in the case of M66. Messier was careful to note those found by Méchain but made no such note for this entry.

See my Arp 317 entry for a better image of this galaxy.

Arp's image: http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp16.jpeg

14" LX200R @ f/10, L=6x5' RGB=1x10', STL-11000XM, Paramount ME

Related Designations for ARP016

ARP017

Arp 17/UGC 03972/VV 349 is located in Camelopardalis about 230 million light-years away by redshift. I found no other distance estimates. Arp included it in his section for spiral galaxies with detached segments. I assume he is referring to the bright arm pointing nearly straight north. Arp left no comment on this one so I have no idea what he thought about this one.

Two notes at NED read: "The northern, smaller component has a higher UV-excess than the other." and "Late barred spiral with companion superimposed at 0.30, 356 from center, 0.3 x 0.12, interaction, the companion is MCG 12-8-8b." Translating, the second comment it is saying: "The companion is 0.3 minutes from the core at position angle 356 degrees (measured through east (left in my image with north up) which measures 0.3 degrees by 0.12 degrees." That's about right for the larger detached section as Arp calls it though there seems to be a smaller one to its lower left.

As noted in the second comment, the MCG catalog considers this two interacting galaxies. Not to be outdone the VV catalog considers it as three! Note the core has a dark line dividing it into east and west parts. Besides the "detached segment (VV 349c) the west core is VV 349a and the eastern is VV 349b. NED labels all three as "Parts of Galaxies". NED classes it as SB?. Saying it is a barred spiral but we have no comment on the arm structure. It didn't get a peculiar designation, however. The UGC says only SB. It resides as a pretty lonely galaxy with nothing much in the area. Certainly, nothing that NED has much information on so I didn't prepare an annotated image with anything but Arp 17 having useful data.

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp17.jpeg

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

Related Designations for ARP017

ARP018

Arp 18/NGC 4088 is in Arp's category for detached segments. I take it to be the piece on the northeastern end. It has a redshift that's 595 km/s while the galaxy has a redshift of 757 km/s So could it be an entirely separate galaxy? Or is the difference due to that part of the galaxy rotating toward us? NED considers it part of the galaxy. A southwestern clump has a similar difference but is receding. For this reason, I am going with NED that it is a part of the galaxy. Since NGC 4088 doesn't appear to be interacting with NGC 4085 at the bottom of my image the question remains as to what caused this odd detached piece?

NED classifies NGC 4088 as SAB(rs)bc HII, the NGC Project agrees as does Seligman. A very rare agreement for all three! The galaxy was discovered by William Herschel on March 9, 1788. NGC 4085 is classified by NED as SAB(s)c:? HII as does the NGC Project. Seligman is silent as to its classification. NGC 4085 was also discovered by William Herschel but on April 12, 1789, over a year later. Both are in the original Herschel 400 list. My comments about Arp 18 (I didn't know it was an Arp galaxy at the time) from May 4, 1984 on an excellent night with my 10" f/5 at powers up to 150x reads: "Bright easy oval, somewhat brighter to the northeast (detached segment?) Nucleus ill-defined." My entry for NGC 4085 the same night with the same scope reads "Small faint oval with bright center. Fits in the same 150x field with NGC 4088. Nice pair." The last two words were penciled in at a later date and are not part of the computer file, only the printout. It was discovered by William Herschel on March 9, 1788 and is in the original Herschel 400 program. My notes from May 4, 1984 using a 12.5" f/6 scope at up to 150x on an excellent night reads "bright, easy oval, some brighter to the NE. Nucleus ill-defined."

Arp's image: http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp18.jpeg

14" LX200R @ f/10, L=6x10'x2 RGB=2x10'x3, STL-11000XM, Paramount ME

Related Designations for ARP018

ARP019

Arp 19/NGC 145 falls under Arp's category of 3 armed spiral galaxies. It is about 175 million light-years away in the constellation of Cetus. NED classes it SB(s)dm. I'm not so sure I agree with the 3 arm bit. Two are obvious with the third looking like it is detached from the bar the other two come from. In fact, there seems to be a fourth shorter "arm" as well starting from a very bright knot to the west of the third "arm". Both have a faint curving outer arc. What caused this is the mystery to me. Checking literature turned up no real mention of a third or fourth arm. Most references read something like this one: "Small, bright bar with no definite nucleus. 2 strong knotty arms with some branching, one stronger and longer, forming an incomplete loop." I don't quite agree with the "no definite nucleus" part. Looks to me to be one. It's quite a bit more orange than any other part of the bar and seems the rotation point of the galaxy as well. Maybe they didn't have the benefit of a color image. It was discovered by John Herschel on October 9, 1828.

While there are a ton of other galaxies in the image, including what appears to be a galaxy cluster just to the east of Arp 19 I found little on them and no hint of a mention of a galaxy cluster. This field is out of the SDSS area. Many of the galaxies are in the British anonymous catalog but with little useful information. In fact, only two other galaxies have redshift data available. The odd apparently double cored galaxy to the northeast of Arp 19 is LCSB S0087P (LCSB=Low Central Surface Brightness) at 336 million light years. Apparently, that dim line through the core is why it is in the catalog. Otherwise, its core sure doesn't appear to be of low brightness to me. I don't find anything on it or what is behind its odd appearance. There's another galaxy with a possible double core about the same distance from Arp 19 but to the southeast. It is 2MASX J00315490-0510555. I have no distance data on it. It probably is two unrelated galaxies, one a small elliptical, that are along the same line of sight.

The only other galaxy with redshift data I could find is the large bright, very orange, elliptical galaxy PGC 001962 at magnitude 15. Its redshift indicates a distance of about 334 million light-years. Essentially the same as LCSB S0087P. They are likely related. The very blue galaxy northwest of it is 2MASX J00321025-0505417. Just to the right of it is a very blue nearly round galaxy APMUKS(BJ) B002936.06-052218.5. Yeah, one of the many anonymous ones in the image. The galaxy speared by the satellite trail southeast of Arp 19 is 2MASX J00320683-0513177. The trail has a gap in it due to it being on two frames. The gap is the time it took to download one frame and start the next.

There happened to be 4 asteroid trails in the image. Three are easy to find in a triangle to the west of Arp 19. The one to the northwest near the only bright star in the area (northeast a bit from the star) is (95329) 2002 CQ11 with an estimated magnitude of 19.2. Below that bright star almost due east of Arp 19 is a very dim and small orange galaxy. Just west of it is (109137) 2001 QO54 at magnitude 19.6. Continuing due west to a larger brighter but still faint smudge of a blue galaxy bring you to (112051) 2002 JL9 just below the galaxy. It is the brightest in the image at magnitude 18.7 The 4th, also moving in the same downward angle with a similar length trail is the faintest and hardest to find. Go back to the previous asteroid by the faint star and go just below the asteroid trail to an orange star. Down and right of it is a rather white star. Go down from that star and very slightly right, Near the bottom of the image is the faint trail of 2005 WC36 at magnitude 20.0.

Arp's image
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp19.jpeg

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

Related Designations for ARP019

ARP020

Arp 20/UGC 3014 is a triple-armed (by Arp's classification) spiral located about 190 million light-years from us in Taurus. NED classifies it as SB? while Seligman says SABb? I measure its size at 52,000 light-years though Seligman says 60,000 light-years. I can't stretch it that far. The third arm seems to come from the core rather than the ends of the bar. How it remains stable is a mystery to me. I'd think it rapidly destroyed by tidal forces. Apparently not. The other arms seem distorted. Yet there's nothing around that appears to have interacted with it. Maybe all this is due to some galaxy it is currently digesting. That could explain the third arm and distortion of the other two.

Arp's image: http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp20.jpeg

14" LX200R @ f/10, L=4x10'x2 RGB=2x10'x3, STL-11000XM, Paramount ME

Related Designations for ARP020

ARP021

Arp 21 is located in eastern Leo Minor a bit over 400 million light-years distant. It falls into Arp's class: Spiral Galaxies; 3 armed. That much seems fairly certain. Things get rather fuzzy beyond this. For instance, where's the third arm? I really don't see a definite third arm in his image, my image or the Sloan image. Is it the fuzzy detached spur running parallel to the arm wrapping around the bottom of the core ending to the north by a round object? Or is the odd looping feature east of the south going arm that is strangely drawn-out ending in a sudden backward "j" shape? Arp made no comment on this one. NED does say it is a three-armed spiral. It just classes it as a spiral, however.

Now about that "round object" northeast of the core. The SDSS has two entries for it. One calls it a star while the other says it is a galaxy with a redshift also about 400 million light-years distant. Arp 21 is in the Vorontsov-Velyaminov Interacting Galaxies catalog as VV552b. That would indicate they too considered that object a galaxy. Now about that "b"; where's VV552a you ask? Nearly 4 hours west and 17 degrees north! Confusing isn't it? VV552? It apparently doesn't exist. The catalog has no separate entry for the round object. I used the galaxy designation and distance in my annotated image.

Arp 21 was picked up by IRAS so is a strong IR emitting galaxy indicating a lot of star formation is going on hidden behind dust warmed by the stars it hides. This makes it likely the galaxy did encounter another in the recent past. It might be the round object or one of the other galaxies in the area.

Looking around the area, even in the limited field of the cropped, enlarged image, there's a lot of distorted galaxies. Near the right edge of the cropped image is a red spiral that has a faint plume going north. In the lower left corner is a ring galaxy much like M94 with its very faint outer ring. Both would seem to be due to long ago encounters. There's an obvious pair of red elliptical interacting galaxies northeast of Arp 21. At the top are two, very blue, interacting galaxies. They have one entry in a rather obscure catalog, MAPS-NGP O_318_0293285. That stands for Minnesota Automated Plate Scanner - North Galactic Pole. Minnesota and North Pole describe my winter perfectly. Looking around the full image will turn up others. This is a very interesting field. Unfortunately, I found virtually no papers on any of the objects, including Arp 21. Seems oddly ignored in the literature.

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp21.jpeg

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

Related Designations for ARP021