ARP022

Arp 22/NGC 4027 is located in Corvus at a distance of 60 to 93 million light-years. It seems every place I look I get a different distance. Back to that in a bit. Arp put it in his category for one-armed spiral galaxies. One of his smallest categories with only 3 entries. His 3 armed spiral category also has 3 entries.

Actually, it has a second arm. It's short but there. So what caused the huge difference? Most now think it is the result of a merger. I found some papers saying there were some oddities in its rotational velocities though they didn't link this to a merger, just described the oddity. While possible I'm not convinced. It is part of a very famous group. The NGC 4038 group. NGC 4038-9 is better known as Arp 244 -- the Antennae Galaxies. These are in the process of merging and only about 40 minutes of arc away. Has this influenced the merger concept here?

Arp 22 actually consists of two galaxies NGC 4027 and the triangular blue dwarf NGC 4027A about 4 minutes to the south. I did find papers showing that these two are interacting. NGC 4027 has drawn a lot of HI from the dwarf into a ring about itself that is severely warped. This likely indicates the two were much closer in the past and NGC 4027 could have cannibalized more than HI stealing much of the star mass of NGC 4027A. To me, the interaction is more likely the cause of the huge arm as well as rotation issues. For more on this interaction see:
http://adsabs.harvard.edu/full/1992ApJ...400..516P

It was discovered by William Herschel on February 7, 1785 and is in the original Herschel 400 observing program. My notes from April 16, 1985 on a humid night with fair transparency using my 10" f/5 at 50x reads: "Large, irregularly lit but mostly very faint galaxy. Large size makes viewing especially difficult. 31 crater in the field doesn't help any!" I don't quite understand my "large size" description.

Unfortunately, at -19 degrees this one is well down below where I can normally image. This night was no exception. In order to get the best seeing, I have to image near the meridian when the object is highest in my skies. That puts it in my Meridian tree which blocks about 90 minutes of sky mostly to the west of the Meridian. When I realized seeing might support imaging it, seeing had been lousy but suddenly improved, I swung down to get it. I got one frame before it went into the tree. I took a second as the tree didn't seem to bother much but I was wrong about that. Now I had to wait 80 minutes for it to exit the tree. After 70 it seemed clear so took another frame. Wrong, the tree was still creating a diffraction mess with its pine needles (It's a red pine). The fourth image was clear of the tree. But now the wall of the observatory was becoming a problem and I had to stop. I took the color data the following night when seeing was poor but it was out of the meridian tree and on the east side where the wall wasn't an issue but it ran into the Meridian tree ruining one green frame so this is why only 1 rather than two were used. I saw this coming so put green last since it is of least importance with most galaxy color shots. Still, all this, especially the tube currents from rapidly falling temperatures, left me with odd diffraction spikes and flat-bottomed stars. Working this low is rare so never had a chance to retake it on a better night. All this mainly hurt bright stars not the galaxy though seeing this low is always lousy so detail is sorely lacking. I had to give it a try. Several more Arp Atlas galaxies are this low that I've never been able to image but will try if I ever get a night that allows it. One is three degrees lower so will be really difficult but if I live long enough I might get it.

Now to the distance issue. NED puts its redshift distance at 93 million light-years but gives a Tully-Fisher measurement at 83 million light-years. For 4027A it gives a red-shift distance of 97 million light-years. Since it is still feeding HI to its big brother we know they have to be very close to the same distance so can ignore this latter figure. Checking the redshift of the Antennae NED shows 92 million light-years for the redshift distance. Good agreement. It shows no other measurements for NGC 4038. ESO has taken a very good image of NGC 4027: http://www.eso.org/public/images/potw1030a/ There they put it at 75 million light-years. Checking on other sources for the nearby Antennae Galaxies I found several at APOD. Most had no mention of distance but one did: http://apod.nasa.gov/apod/ap100507.html and put it at 60 million light-years. Since Hubble has imaged the Antennae what do they say? One place they say 62 million light-years another 60 million light-years and these two refer to the SAME image. Another image by the HST says 63 million light-years. Since Arp 22 is part of this group it's distance should be about the same. So is it in the 60, 70, 80 or 90 million light-year range? I looked at dates but there's no help there. It is more the source rather than the date that rules. You'd think with something this familiar there'd at least be some agreement between sources. Apparently not.

Normally I prepare an annotated image but there's so little on this field I'll give it a pass. Only two other galaxies have any redshift data and after the fiasco of finding a reliable distance for Arp 22 is it even worth it? Still here goes. The blue galaxy immediately east (left) of the dwarf NGC 4027A is I SZ 108A. You have to go into some rare catalogs with this field! It stands for the First Southern Zwicky list in case you were wondering. It does have a redshift which puts it at 300 million light-years distant, 3 to 5 times further that Arp 22. South of Arp 22 and very slightly west (right) is a rather orange galaxy. This is 6dF J1159269-192436 (6 degree Field Survey) with a redshift distance of 774 million light-years. And that's it. So what about the small blue galaxy above I SZ 108A? Wish I knew. NED doesn't seem to know it exists. Since there's a I SZ 108A where is I SZ 108? NED again is ignorant on the subject. Maybe it doesn't exist. If you get the feeling I went to all this work to image this guy and then find mostly ignorance when I try to look up the field, you'd be right.

The asteroid down toward the lower right that angles upward at a rather steep angle is (111121) 2001 VV8.

Arp's image
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp22.jpeg

14" LX200R @ f/10, L=4x10' RB=2x10'x3 G=1x10'x3, STL-11000XM, Paramount ME

Related Designations for ARP022

ARP023

Arp 23 is a one-armed spiral galaxy in Canes Venatici. It is also known as NGC 4618. Oddly there are two one-armed spirals in the image but only the larger made it into Arp's atlas. The smaller is NGC 4625. Redshift puts Arp 23 at 36 million light-years distant while two Tully-Fisher measurements at NED say 25 million light-years. NED classifies it as SB(rs)m HII while the NGC Project says simply SBm and Seligman agrees with NED. The galaxy was discovered by William Herschel on April 9, 1787. It made the original Herschel 400 list. My notes from April 28, 1984 with my 10" f/5 at up to 150 power on an excellent night read: "Bright with little detail seen, Didn't note the ringtail even though a great night. Other galaxies in the field may have distracted me, especially the one to the north (NGC 4625 I now know) which seemed bright enough to be plotted on the Tiron Atlas but was not."

NGC 4625 was discovered by William Herschel on April 9, 1787, the same night as NGC 4625 but is in neither of the Herschel 400 observing programs. It is classified as SAB(rs)m pec by NED and Seligman and SBm/P by The NGC Project. It too appears to be a one-armed spiral but didn't make Arp's list like NGC 4618 did. The two are considered an interacting pair so at about the same distance. Very long exposures in UV light show that the stars of Arp 20 extend to and wrap around NGC 4625 proving they are an interacting pair. Is this interaction the cause of both having only one main arm? See http://cseligman.com/text/atlas/ngc46.htm#4625 for more on this interaction and deep images of the pair.

Arp's image: http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp23.jpeg

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

Related Designations for ARP023

ARP024

Arp 24/NGC 3445 is a galaxy Arp put in his one arm spiral category. It also would have fit in his spirals with large, high surface brightness companions. It is located in Ursa Major about 100 million light-years from us. NED classifies it as SAB(s)m, The NGC Project says Sc while Seligman says SBm?. It was discovered by William Herschel on April 8, 1793. Though isn't in either Herschel 400 observing programs. Its companion on the end of its lone arm is PGC 32784 at about the same distance by redshift. It seems connected to Arp 24 by a tidal plume coming from the single arm of Arp 24. Both NED and Seligman classify it as Sm. Seligman give its size as 9,000 light-years making it a dwarf galaxy. Seligman gives the size of Arp 24 as 35,000 light-years.

One of the other NGC galaxies in the image is NGC 3440. It is also about 100,000 light-years distant so part of the same group as NGC 3445 and NGC 3458 discussed below. NGC 3440 appears distorted with its core region off center. NED classifies it as SBb?. The NGC Project agrees but leaves off the question mark. Seligman doesn't attempt to classify it. The galaxy has two blue blobs in the extended northeastern part of the galaxy. The brighter one is listed by NED as a separate galaxy at the same distance while the other is shown as an ultraviolet object with no distance data. If one or both of these are due to something it is digesting that could explain its off-center core. The galaxy was discovered by William Herschel on the same night he found what was to become Arp 24.

The third NGC galaxy in the image is NGC 3458. NED classifies it as SAB: I do see a very short bar in an otherwise mostly featureless blob of a galaxy. The NGC Project, however, says it is S0 and Seligman doesn't try to classify it. It too was discovered by William Herschel the night he found the other two in this field. It isn't in either of the Herschel 400 programs.

For details about the other galaxies in the image see the annotated version. RQQ stands for Radio Quiet Quasar while CQ means Candidate Quasar.

Arp's image: http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp24.jpeg

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

Related Designations for ARP024

ARP025

Arp 25/NGC 2276 is an interesting, many armed face on spiral. Arp put it in his category for spiral galaxies with one heavy arm. The most famous member of this category is M101. The galaxy is located in Cepheus. The distance is a bit vague. Redshift puts it at 110 million light-years. A single Tully Fisher measurement at NED says 120 million light years and a post at the HST website says 150 million light-years. Quite a difference. Arp's comment on this one under Arp 25's entry reads: "See also 114. Tubular arm, straight at first, then bent. Secondary arm from straight portion." Obviously, this refers to the southern arm that is somewhat separated from the rest of the galaxy and points in the general direction of NGC 2300. It's hard to write about Arp 25 without including nearby NGC 2300. So hard in fact that Arp made a second entry for NGC 2276 to include NGC 2300. Arp 25 was discovered by August Winnecke on June 26, 1876. Hubble image of part of NGC 2276 including the arm is at http://upload.wikimedia.org/wikipedia/commons/2/25/NGC_2276_Hubble_WikiSky.jpg

Arp 114 consists of NGC 2276 (Arp 25) and NGC 2300 and is in his category for elliptical and elliptical-like galaxies close to and perturbing spirals. Here Arp's comment concerns only NGC 2276 and ignores NGC 2300! It reads: "Spiral somewhat pec., may be perturbed. See No 25." While it is in a category assuming it is perturbed the comment says only it may be perturbed. For once I agree, it may be but that isn't all that certain. I see arguments either way. The big one that they aren't related is their redshift. By that measurement, NGC 2300 is some 24 million light-years closer than NGC 2276. But there are many non-redshift measurements of its distance that range from 101 to 134 million light-years and average out to about 115 million light-years. Then there's the above-mentioned 150 million light-year distance at the HST website. These would make them more likely to be true companions. But look at the redshift distances on the annotated image. They seem to fall into two groups. One that fits NGC 2276 at about 110 million light years and one that matches NGC 2300 much closer distance. But with a sample size of 2 and 3, this is far from deciding the issue!

The HST site argues strongly for interaction with this post: http://www.spacetelescope.org/images/opo9305a/ This shows a huge enveloping cloud of hot gas seen in in X-rays around NGC 2300. It extends to NGC 2276. One possible explanation is an interaction between the two. But it certainly isn't required for this to occur.

NED classes NGC 2276 as SAB(rs)c, the NGC Project says simply Sc I. NED says of NGC 2300 it is SA0^0^ while the NGC Project says simply that it is an elliptical. Few sources I found agree with the elliptical classification. Most consider it a S0 type galaxy as NED suggests. This because some structure is seen in the outer halo of the galaxy. I am puzzled by the strong red color I got. While I found few color images of NGC 2300 on the net, the few I did find have it as nearly white. It was discovered by Alphonse Borrelly in 1871. I can't pin down the exact date.

Arp's image of Arp 25:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp25.jpeg

Arp's image of Arp 114 (including Arp 25)
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp114.jpeg

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

Related Designations for ARP025

ARP026

Arp 26, more famously known as M101 made Arp's atlas under the category of spiral galaxies with one heavy arm. Located in Ursa Major its distance is rather uncertain. An average of many comes to about 20 million light-years. Arp's comment on this entry reads "Note straight arm, bright knot on east appears almost stellar." I took this image while supernova SN 2011fe was near maximum brightness. It is marked at the bottom of my image between tick marks. M101 is classified as SAB(rs)cd HII by NED, SBc by the NGC Project and SAB(rs)cd? by Seligman. While recorded in Messier's list it was actually discovered by his close friend Pierre Méchain on March 27, 1781.

I've included an image taken on August 25, 2011 shortly after the discovery of the supernova and well before it reached maximum brightness. A second taken on September 24, 2011 shows it one day after maximum brightness as it was cloudy the night of maximum brightness. I've also included a 3-20-2007 image at a larger image scale but done back when I really didn't know what I was doing. The seeing was better but my processing and imaging techniques were primitive.

Arp's image: http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp26.jpeg

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME both supernova images
14" LX200R @ f/10, L=6x20' RGB=2x10', STL-11000XM, Paramount ME 2007 image

Related Designations for ARP026

ARP027

Arp 27/NGC 3631 is a grand design spiral in Ursa Major. Redshift shows it to be about 62 million light-years distant. A Tully-Fisher measurement says 70 million light-years. Pretty good agreement as these things go. Arp puts this one in his category of spiral galaxies with one heavy arm. NED classes it as SA(s)c. At magnitude 10.6 this is a good one for visual observers. Arp's comment on this one reads: "Note straight arm, absorption tube crossing from inside to outside of south arm." The straight arm he refers to is easy to spot. The absorption tube is likely the dark feature from upper left to lower right crossing the narrow arm. A narrow line of star clusters continues on what would be the upper side if it continued further southwest. 3 clouds might be along the lower side of it.

Often I've mentioned "So many galaxies, too few grad students." Finally, I hit one a student (undergraduate) worked on in 2007. She didn't have time to finish her project as it was a summer stipend only but has a web page up on what she did find. So rather than me rattle on I'll refer you to her web page on it.
http://www.astro.wisc.edu/~crystal/index.html

My annotated image has one galaxy listed as an AGN but Sloan lists it as a quasar. It looks like a galaxy in my image, I see no starlike point that would be expected from a quasar. Still, I've listed it as G/Q.

I found some images of the galaxy at the Hubble Legacy Archive. I made a mono image from the best of them. None are all that good and the wrong bands for good color. At Hubble's limited field and higher resolution, the galaxy looks very normal. Even the "straight arm" looks normal along the part that is within its limited field of view. Due to the high noise level in the image, I'm reproducing it at half scale. This is sufficient to show Hubble can resolve the brightest blue stars in this galaxy. Some of the knots in my image are made up of the light of only two or three of them in some cases. If they were standing alone some would be within my reach.

The Sloan survey shows several "galaxies" within the disk of Arp 27. I didn't include these when I made the annotated image as I felt they were just parts of the galaxy and not really separate galaxies. Some were marked as PoG for this reason but most are shown without that label. Those that are within the Hubble field are seen to be just PoG as I suspected. This pretty well convinces me those outside the field are likely not separate galaxies either.

I found few images of this one taken by amateurs. That surprised me as it is within easy reach of most imagers and is a rather classic galaxy. Just not one you hear of very often.

The image is noisier than I'd like as the night cooled more than I expected. I was imaging at -25C when the temperature suddenly fell to well below that. I was running unregulated for three of the 4 luminance images. The temperature fell about 2C every 10 minutes! I was unable to fully compensate for the dark current because of this. The software records the temperature it was taken at but only at one point in the exposure, the end. This tells the software the wrong temperature and it under compensates for the dark current noise. I had to guess an average temperature to use for each frame and edit the header to that value. I'm sure I didn't always hit it right judging by the resulting noise figure. Still, it will have to do until I can reimage it.

The galaxy was discovered by William Herschel on April 14, 1789 and is in the first Herschel 400 program. My notes from April 16, 1985 with my 10" f/5 with humidity reducing transparency some at up to 150x reads: "Large, nearly face on spiral with a starlike nucleus. Outer halo is quite large and grows even bigger with averted vision."

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp27.jpeg

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

Related Designations for ARP027

ARP028

Arp 28 sits in a rather empty part of the sky. It is in Arp's class: Spiral Galaxies: One heavy arm. In some cases, I've had trouble seeing which arm Arp was talking about but this one is quite obvious for a change. Arp 28 is also known as NGC 7678 and is located near the center of the Great Square of Pegasus. It is classed as SAB(rs)c and is both a Seyfert 2 and starburst galaxy. It appears that heavy arm as a lot to do with the starburst classification. Arp's note: "Note straight heavy arm." The heavy arm is somewhat straight but so are other arm segments of the galaxy. It certainly is a disturbed galaxy. Redshift puts it about 140 million light-years away. A single Sosies measurement shows a slightly closer distance of 115 million light years. I'm not sure such a measurement is all that accurate for a highly disturbed galaxy but then neither is redshift if the galaxy has had a close encounter that has accelerated it. The galaxy was discovered by William Herschel on September 15, 1784 but isn't in either of the Herschel 400 programs.

So has it encountered another galaxy? There's none in my image but that's my error. UGC 12619 is just below the bottom edge of my image. Somehow I didn't see it was there so put Arp 28 in the center of the image rather than a few minutes above center which would have then shown this galaxy. Redshift puts it at about 160 million light years. A bit further than Arp 28. Is it the culprit? It is a dim, low surface brightness galaxy with very disturbed spiral structure. It's classed as SAB(s)dm.

The area of Arp 28 is outside the SDSS search area nor has Hubble imaged it. NED has little detail on any of the other galaxies in the image. You have to look hard to find many. The largest and brightest, a blue galaxy to the northwest of Arp 28 isn't in NED. Only IR galaxies from the 2MASX survey are listed. Those tend to look red though that isn't necessarily the case.

This image appears on page 55 of the November 2017 issue of Sky and Telescope Magazine. It is the first image in an article on square galaxies. It never mentions its Arp number but does mention it as being in his Atlas.

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp28.jpeg

14" LX200R @ f/10, L=4x10 RGB=2x10x3, STL-11000XM, Paramount ME

Related Designations for ARP028

ARP029

Arp 29 is far better known as NGC 6946, the Fireworks Galaxy. This is because it is undergoing massive star formation and close enough that we can easily resolve many of the HII regions as well as a massive star cluster. The cluster is well resolved in the upper left corner of the Gemini North image. http://antwrp.gsfc.nasa.gov/apod/ap050125.html My image scale and seeing weren't sufficient to fully resolve it so only a few of the stars show with the rest forming what appears to be a blue reflection nebula. Note the Gemini image has south up while mine is north up. Another reason for its common name is all the supernova that have been seen blowing in it. The last was in 2008. NED list 9 known supernovae in this galaxy; SN 1917A, N 1939C, SN 1948B, SN 1968D, SN 1969P, SN 1980K, SN 2002hh, SN 2004et and SN 2008S. 27 supernova remnants are also known in this galaxy according to NED.

But none of this is the reason it is in Arp's catalog. He included it under Spiral galaxies with one heavy arm. Some in this category have a rather obvious heavy arm but here I'm not even sure which arm he is speaking of. Maybe it's the one to the northeast (upper left) of the core in my image. Though his comment addressed the supernovas saying "Supernova once observed in tip of thick arm." This may refer to the 1948 supernova though it was well back of what I'd call the "tip" of the eastern arm. Though closer to the end than those appearing in other arms.

Every paper I found shows a different distance to this obviously nearby galaxy. In fact, two different papers analyzed the 1980 supernova and came up with wildly different distance estimates! One decided it was 18.5 million light-years away, the other over 41 million light-years. One or both are very wrong. The APOD link above says 10 million light-years, closer than any paper I found. So I'll give the wide range of about 10 to 20 million light-years as its distance. This galaxy is in the Milky Way and thus heavily obscured. This likely complicates distance estimates. It certainly is close enough for Cepheid variables to be seen but unless the dust between us and the galaxy is accurately known the distance becomes uncertain. I suspect it is differences in dust estimates that account for much of the uncertainty of the distance to this galaxy.

I should have taken far more data on this one. I see a hint of a long blue arm going north. The field is full of clouds. Some so close to the galaxy I can't tell if they are pieces of the galaxy or pieces of junk in our galaxy. Most likely in ours. Note the area just along the western edge of Arp 29 that has no stars, just a faint fuzzy patch. A brighter but smaller one below it doesn't seem to obscure stars. I see no reason to question my flats so suspect these clouds are real. But they are right at the noise level. Something a lot more time would certainly help decide.

The galaxy was discovered by William Herschel on September 9, 1798 and is in the original Herschel 400 program. My notes from May 21, 1985 on a very good night with my 10" f/5 at up to 180x reads "Large, obviously face on spiral. Structure in arms very easy to see tonight. In fact, it is a rival to M-51 for ease in seeing the spiral structure. It nearly fills the field at 120x and is a fantastic sight tonight."

I had a gaggle of satellites go through the images. I tried to clone them out -- with only 4 images any noise rejection I tried also added noise -- and hope I didn't add any artifacts doing so. I'm sure a few stars in our galaxy got erased, however. But there are so many in this field we can spare a few. So many they really blew up the JPEG size of this image.

There are a few other galaxies in the image and one missing one. NED lists a 15.6 magnitude galaxy, [OBC97] N05-1 at the top of my image that should be easily visible but there's nothing there. Those easiest to find are all south-west of Arp 29. The one hiding behind a star is 2MASX J20332396+6005088. Below and east (left) of it is the slightly bigger and brighter 2MASX J20333573+6002118. Neither have any other data, unfortunately. The same lack applies to 2MASX J20324060+6000181 in the very southwest corner of my image. I didn't quite catch all of it. You'd think one this big and bright would at least have a magnitude estimate but nothing. Guess the 2MASS survey didn't want to detract from the fireworks of Arp 29.

Arp's image with the 200" is at:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp29.jpeg
He was pushing the field corrector to its limits with the wide field needed to cover this one. Note the distorted stars at the corners.

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

Related Designations for ARP029

ARP029SN

Arp 29 is far better known as NGC 6946, the Fireworks Galaxy. This is because it is undergoing massive star formation and close enough that we can easily resolve many of the HII regions as well as a massive star cluster. The cluster is well resolved in the upper left corner of the Gemini North image. http://antwrp.gsfc.nasa.gov/apod/ap050125.html My image scale and seeing weren't sufficient to fully resolve it so only a few of the stars show with the rest forming what appears to be a blue reflection nebula. Note the Gemini image has south up while mine is north up. Another reason for its common name is all the supernova that have been seen blowing in it. The last was in 2017. NED list 10 known supernovae in this galaxy; SN 1917A, N 1939C, SN 1948B, SN 1968D, SN 1969P, SN 1980K, SN 2002hh, SN 2004et and SN 2008S, and 2017eaw. 27 supernova remnants are also known in this galaxy according to NED. This image features the 2017 supernova. The text below is taken from my earlier image of the galaxy before the supernova was seen.

But none of this is the reason it is in Arp's catalog. He included it under Spiral galaxies with one heavy arm. Some in this category have a rather obvious heavy arm but here I'm not even sure which arm he is speaking of. Maybe it's the one to the northeast (upper left) of the core in my image. Though his comment addressed the supernovas saying "Supernova once observed in tip of thick arm." This may refer to the 1948 supernova though it was well back of what I'd call the "tip" of the eastern arm. Though closer to the end than those appearing in other arms.

Every paper I found shows a different distance to this obviously nearby galaxy. In fact, two different papers analyzed the 1980 supernova and came up with wildly different distance estimates! One decided it was 18.5 million light-years away, the other over 41 million light-years. One or both are very wrong. The APOD link above says 10 million light-years, closer than any paper I found. So I'll give the wide range of about 10 to 20 million light-years as its distance. This galaxy is in the Milky Way and thus heavily obscured. This likely complicates distance estimates. It certainly is close enough for Cepheid variables to be seen but unless the dust between us and the galaxy is accurately known the distance becomes uncertain. I suspect it is differences in dust estimates that account for much of the uncertainty of the distance to this galaxy.

I should have taken far more data on this one. I see a hint of a long blue arm going north. The field is full of clouds. Some so close to the galaxy I can't tell if they are pieces of the galaxy or pieces of junk in our galaxy. Most likely in ours. Note the area just along the western edge of Arp 29 that has no stars, just a faint fuzzy patch. A brighter but smaller one below it doesn't seem to obscure stars. I see no reason to question my flats so suspect these clouds are real. But they are right at the noise level. Something a lot more time would certainly help decide.

The galaxy was discovered by William Herschel on September 9, 1798 and is in the original Herschel 400 program. My notes from May 21, 1985 on a very good night with my 10" f/5 at up to 180x reads "Large, obviously face on spiral. Structure in arms very easy to see tonight. In fact, it is a rival to M-51 for ease in seeing the spiral structure. It nearly fills the field at 120x and is a fantastic sight tonight."

There are a few other galaxies in the image and one missing one. NED lists a 15.6 magnitude galaxy, [OBC97] N05-1 at the top of my image that should be easily visible but there's nothing there. Those easiest to find are all southwest of Arp 29. The one hiding behind a star is 2MASX J20332396+6005088. Below and east (left) of it is the slightly bigger and brighter 2MASX J20333573+6002118. Neither have any other data, unfortunately. The same lack applies to 2MASX J20324060+6000181 in the very southwest corner of my image. I didn't quite catch all of it. You'd think one this big and bright would at least have a magnitude estimate but nothing. Guess the 2MASS survey didn't want to detract from the fireworks of Arp 29.

Arp's image with the 200" is at:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp29.jpeg
He was pushing the field corrector to its limits with the wide field needed to cover this one. Note the distorted stars at the corners.

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

Related Designations for ARP029SN

ARP030

Arp 30 seems to be a pair of galaxies but that is not the case. The southern galaxy alone is the reason it made his catalog under his category: Spiral galaxies: One heavy arm. I'd expect the heavy arm to be obvious but in this case, it doesn't seem all that obvious to me. I think it is the southern arm, likely due to the piece that appears almost broken off though that's more a contrast feature of my processing than a real feature. There is also a faint arm on the west side that extends out from the main galaxy and it appears a piece of arm is sticking out from behind the east side of the northern, foreground, galaxy. The latter appears to be an extension of the arm I first mentioned going south as the likely heavy arm. It seems to have brightened again when behind the companion. Arp's image appears to show a bright arm arc above the galaxy's core. It shows strong on his image, weakly on mine and not at all in the SDSS image. It appears to be very color dependent. So where is the "heavy arm"? I just don't know. Arp gave no clue that I've found. It isn't the edge on galaxy that is trying to fake a heavy arm. Arp knew it to be a separate galaxy.

Both galaxies carry the NGC 6365 designation with the northern one being NGC 6365B (PGC 60171) and the southern NGC 6365A NED classes them as Sdm? and SBcd? with the later noted as a Seyfert 1 galaxy. This Seyfert classification could be due to interaction with its partner feeding its black hole. I don't have enough information to say for sure. There is even some debate which galaxy is in front of which. While there is an absorption line along the the southern galaxy's edge where it meets the northern one which could be caused by dust in the northern one and the apparent arm that comes out from behind the northern one, one paper cites an absorption feature in the northern galaxy that could be caused by a arm of the southern. I don't buy that however. The other features seem to strong to ignore. Red shift data puts them at 363 and 368 million light-years north to south. Another indication the northern is in front though their relative motions could easily differ enough to negate this. Likely they are really closer together than this would indicate as well. Still they can't be really close as neither appears distorted to any obvious degree. The only oddity is the heavy arm.

The NGC project catalogs the northern galaxy as NGC 6365 with the southern listed as UGC 10832. (Most other sources say it is both.) The northern one is UGC 10833 as that catalog lists the two separately. The NGC project classifies the northern galaxy the same as NED but leaves off the question mark. A note there indicates visually in a 17.5" scope the southern member is extremely faint. This brightness difference seen visually may account for the project not considering the NGC number as covering both.

I found no papers indicating these two could be a connected system, nor do I see any tidal features that could be due to them even being all that close but Arp's comment on the pair is; "Companion appears physically connected to flat-on spiral system." By saying "appears" he isn't saying it really is nor does he say the appearance isn't correct. He just leaves it as undecided. I'll say I see no evidence or even hint of any that they really are connected. The pair was discovered by Lewis Swift on August 15, 1884. I found no indication he realized it was two objects.

Not a lot going on in this image but I've done an annotated version showing the quasars and distances to other galaxies in the image that I found data on. NGC 6365 was discovered by Lewis Swift on August 15, 1884.

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp30.jpeg

14" LX200R @ f/10, L=4x10 RGB=2x10x3, STL-11000XM, Paramount ME

Related Designations for ARP030