ARP144

This is a redo of this pair of Arp galaxies in western Cetus about 2 degrees northeast of Arp 50. At -13 degrees declination I rarely get very good seeing for this pair. Seeing was poor in my 2008 attempt and fair for this one. Seeing it is better and my research was rather weak last time I'm redoing it. I must have entered something wrong as the galaxies aren't centered.

Arp 51 is the small spiral to the lower right of the odd pair of galaxies, Arp 144. Like Arp 50 it is in Arp's category for spirals with high surface brightness galaxies on an arm. The spiral is an IR galaxy in the 2MASS catalog also known as PGC 475 and MCG -02-01-024. Some catalogs incorrectly call it NGC 7828 which is part of Arp 144. NED has no distance data on it. The companion is ChaBG 069 (Chavira blue galaxies catalog) which NED shows as both a galaxy and as part of a galaxy. So which is it? A knot in an arm or a separate galaxy? Notes at NED on both the spiral and the object refer to it as simply an "object". Like for Arp 50, it is near a pulled out arm which is suggestive but certainly not conclusive. To me, it appears to be a background galaxy unrelated to the spiral. This is just the way it looks to me, of course. What do you see? Arp made no comment on this one.

Arp 144 is in Arp's category for material emanating from elliptical or elliptical-like galaxies. I can't understand what he means by this. Obviously, this is two interacting galaxies one an elliptical-like and one a mess. Arp 144 is about 250 million light-years distant. It is composed of at least two galaxies, NGC 7828 and NGC 7829. The latter is the elliptical-like galaxy as it is classed as S0 pec. NGC 7828 is incorrectly shown as Arp 50 in The Sky's database, maybe this accounts for my pointing error. It is classed as Im pec. So does Arp see NGC 7828 "emanating" from NGC 7829? or is it just the halo of stars around NGC 7829's core that is "emanating"? The Kanipe-Webb book is silent on this which isn't surprising. Arp left no comment to guide us either. Adding to the confusion one note says: "The spiral or a pair of galaxies are perturbed by a compact elliptical galaxy." So this source says NGC 7828 may be two galaxies. I find no other mention of this but it seems possible to me. Both galaxies were discovered by Francis Leavenworth in 1886.

Now, what about the very blue star-like object in NGC 7828? Is it a foreground star or is it a very blue knot of stars in the galaxy? The object is listed as a star in the Hubble Guide Star Catalog but the cores of NGC 7828 and 7829 are also listed as stars in the catalog. So this doesn't help any. NED doesn't show anything at this position so is of no help. The PSF in my image is galaxy like rather than a star so I will say it is part of the galaxy.

Adding to the confusion I found this: "According to a note in the IC II, NGC 7829 is a star [13 mag]." Visually 7829 does appear rather starlike and this note dates back to visual descriptions so isn't surprising.

Arp's images of these two are taken from the same 30 minute exposure on 103a-D film under seeing 3 (1" to 1.5") conditions. Much better than I had though some of the star knots in NGC 7829 seen in his image are barely visible in mine with 2.5" to 3" seeing. Good for so low in the sky.

Yes, I know it looks a bit like the Star Trek Enterprise is shooting a massive photon torpedo out its backside. A bit late as much of the starboard side of the saucer section seems to be missing.

The field is well outside the Sloan survey but a few galaxies in the image have distance data so I did prepare an annotated image for those few entries.

The entry for 6dF J0006212-131716 is labeled a galaxy but considering it is star-like and listed with a redshift of z=2.878448 which puts it over 11 billion light-years out I have to think it is really a quasar. 6dF stands for the 6 degree Field Survey. Another odd catalog is the LSCB which is the Low Central Surface Brightness catalog. LEDA = Lyon Extragalactic DAtabase for numbers above 73197. Numbers lower than this are just duplicates of the PGC catalog.

I labeled some of the brighter or more interesting looking galaxies. Only three besides Arp 144 have redshift data and one of those is mentioned above. Most are from an automatic plate measurement survey so has little information other than magnitude.

Arp's image of Arp 51:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp51.jpeg

Arp's image of Arp 144
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp144.jpeg

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

Related Designations for ARP144

ARP145

Arp 145 falls into the Arp category material emanating from elliptical or elliptical-like galaxies. In this case what is going on is more obvious. This is a case of a direct hit by an elliptical galaxy (lower left) on a near face on spiral galaxy (upper right). It punched a hole in the spiral right near the core which probably is the reddish blob at the 5:30 position using the hole as the center of the "clock". The two galaxies carry the same designation UGC 1840. The one with the hole is classed as Im pec Ring B. The other has the designation of S0 pec Ring A They are located at about 240-250 million light-years at the east end of Andromeda.

There has been no useful survey I could find of this region. Only a very few galaxies in the field have been cataloged, none with redshift data. Most aren't cataloged at all, including the interesting elongated one above and a tad left of the pair. Only those picked up on the 2MASS infrared survey are cataloged and that one apparently doesn't emit enough 2 micron light to make the catalog. This likely means it is rather dust free or composed mostly of newer stars. But has little to no current star formation.

Arp's photo of these two is at:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp145.jpeg

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

Related Designations for ARP145

ARP146

Astro image tip. Avoid objects in the geostationary satellite belt! No one told me this so I had a night of better than average seeing so decided to try for Arp 146 which is too far south for me to image on an average night being about 6.5 degrees south and of small angular size. That put it at the northern edge of the geostationary satellite belt as seen from my latitude. Such communications satellites aren't really stationary in the sky. They make a small, about 1 degree high figure 8 pattern around their geostationary assigned position. From my location, Arp 146 is right at the northern edge of that pattern. So I ended up imaging lots of communications satellites, one obviously long dead. I removed them from the color frames as well as all but one luminosity frame. One frame only had 3 and I decided to leave them in to give a flavor of what I had to deal with. There were 29 satellite trails in total with 5 in one blue frame. Notice the angled trails. They are decommissioned geostationary satellites. When they are about to run out of station-keeping fuel -- the orbit is unstable and the figure 8 pattern grows with time so fuel is needed to keep the bird within its prescribed spot so fixed dishes still see it -- it is moved several hundred miles higher to get it out of the way. The last of the fuel is used for this. With time the orbit is altered by the nonround earth and pull of the moon and sun until it is somewhat inclined to the equator. That is why I can tell it is a deactivated satellite. Also one is using spin stabilization. That's no longer used as far as I can determine. This causes it to blink as its reflectivity changes with its spin. It doesn't move across the entire image as I terminated the exposure before it had moved all the way across the image. You will see places where the trails fade. This is due to small clouds passing by. They didn't totally block the light but did dim it some for a few seconds. The entire image was dimmed but that isn't seen except by moving objects.

Notice the bright trail just below Arp 146. It is an active geostationary satellite though its trail wavers like the satellite are drunk. The others do as well. This is due to our atmosphere. This is the seeing I am constantly complaining about. It rapidly moves the star around in the sky. It does the same for satellite trails. This one had just the right exposure to show this motion very clearly. The worse the seeing the more "drunk" the trail. The effect of this is to blur the image and is why major observatories are located on mountain tops where they look through far less air than I have to look through. Also, they pick mountains that have what is called laminar air flow. This is a very smooth flow of air that further reduces seeing problems. No mountains and rarely any laminar air flow at my location so stars are fuzzy. I can't do much about it. The third satellite is also a decommissioned one as told by its angled trail.

Now for Arp 146. It is classed by Arp under "Galaxies (not classifiable as S(pherical) or E(liptical)): With associated rings. There are three in this class. The other two are Arp 147 and 148. 147 was the 10 galaxy Hubble made famous and 148 is Mayall's Object, the bullet through a galaxy that is also a famous Hubble image. Hubble hasn't as yet released a pretty image of this one. Nor could I find a frame of it at the HST Legacy site as of January 2017. So I finally beat Hubble to one.

Arp 146 is composed of two galaxies PGC 509 S pec (Ring B) and PGC 510 S0 pec (Ring A). PGC 509 is the ring while 510 the bullet that made the ring. Why the bullet is usually referred to as Ring A I've not figured out. It is rarely a ring though this one seems to have just one arm that looks much like a ring. The galaxies are just under a billion light years away thus rather small in angular size. While 510 is classed as S0 it does seem to have a single spiral arm. S0 galaxies aren't supposed to have defined arms but be just a spindle of stars. That isn't the case here.

I could find no redshift data for any other galaxy in the image. Not even a MASX IR galaxy is in the image. Only those whose positions were automatically measured by APMUKS. It gathers little data other than position and crude photometric data. So this is a part of the sky not well studied.

The asteroid to the lower right of Arp 146 is (38878) 2000 SL121 at magnitude 17.8

Arp 146 is located in Cetus the whale right up against the border with Pisces and Aquarius. Right in the geostationary belt for my latitude. Grrr.

Arp's photo of this is at:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp146.jpeg

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

Related Designations for ARP146

ARP147

Seems the same time Hubble was taking this object, Arp 147, a pair of ring galaxies, so was I. The pair is also known as IC 298 so even the IC catalog has this as one object. It was discovered by Stephane Javelle on December 29, 1893.

With no backlog to process and no wood to cut -- we pulled down yet another "widow maker" from our vast mess created from this summer's tornado which missed us "by that much", and cut it up into fireplace lengths -- Hubble was able to process their version and rush it to the news media. So while imaging another Arp galaxy I did a quick process of my version of the same object. Though in my case it is more "a perfect .10" Obviously theirs is better but the real reason for downgrading mine by a factor of 100 is that the star beside the two galaxies is far more prominent in my image than theirs and is in the right spot for a decimal point. Also, I'd like to point out my telescope cost several billion dollars less than theirs and needs no shuttle to service it. So there!

The Hubble version, in case you have been down a rabbit hole, is at:
http://hubblesite.org/newscenter/archive/releases/2008/37/
Note that their image is not really true color as it used blue for the blue channel, white light for the green channel and infrared for the red channel. This makes for stronger reds and blues than if seen by the human eye. I used true color filters so this should be pretty much the correct colors if your eye could see color in such a faint object. Note that getting closer doesn't help. It just gets bigger at the same rate we see more total light. Spreading that extra light over the extra area just makes it the same brightness. So no matter how close you get to it the human eye wouldn't see color, it would always be too faint. Surprising but true. So I guess it really doesn't matter how the colors are mapped. Black and white is the only "true color" for this object and most others I feature.

It appears the galaxy on the left has passed right through the one on the right. That is, the one passed through the other turning it into a zero. In the process, the one was distorted so as to have two rings rather than spiral arms that it likely had before so it too is considered a ring galaxy. In my shot, it too looks a bit like the "Saturn Galaxy" in a recent update. The reddish part of the ring toward the bottom left was likely the core of the now zero galaxy prior to the collision. Its strong blue color is due to rapid star formation triggered by the collision. It looks like the "one" galaxy was stripped of its dust and gas by the collision so has no raw materials for star formation. Considering its slightly overall red color it likely had used up most of its dust and gas long ago and hasn't had much active star formation for a billion years or so. The pair is thought to be about 400 million light-years from us. The small blue galaxy down and left of my "perfect .10" is UGCA 057. I can find nothing on it, however.

About that big galaxy in the upper right corner... Unfortunately, it is one of those with no info available other than its catalog name of APMUKS(BJ) B030818.97+011155.2. You'd think more would be known about such a big guy but apparently not.

The nice thing about this is that Hubble didn't image these guys, only Arp 147 so maybe I scooped Hubble after all.

My shot was taken at 0.5" per pixel rather than my normal 1" per pixel as this is one small object. Seeing that night wasn't all that good but better than I normally get so doubt I'll go back and try again. Besides, Hubble has me beat on this one anyway. Can't fight its multi-billion dollar bankroll!

I cropped the image to show just the center one-quarter of the total image area as there wasn't much of interest in the rest of the image. Also, this crop makes it the same physical size as my 1" per pixel images. Thus keeping bandwidth for emails at a manageable level.

Arp's version is at:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp147.jpeg

14" LX200R @ f/10, L=6x20'x1 RGB=3x10'x2, STL-11000XM, Paramount ME

Related Designations for ARP147

ARP148

Arp 148 is more commonly known as Mayall's Object. It is a pair of colliding galaxies about a half billion light-years away. One galaxy has "just" pierced the heart of another and is bursting out the other side. This is best seen in the rather famous Hubble image of this pair.
http://imgsrc.hubblesite.org/hu/db/images/hs-2008-16-aa-large_web.jpg

The Hubble site covers this guy very nicely. Here is what it has to say about this object.
"Arp 148 is the staggering aftermath of an encounter between two galaxies, resulting in a ring-shaped galaxy and a long-tailed companion. The collision between the two parent galaxies produced a shockwave effect that first drew matter into the center and then caused it to propagate outwards in a ring. The elongated companion perpendicular to the ring suggests that Arp 148 is a unique snapshot of an ongoing collision. Infrared observations reveal a strong obscuration region that appears as a dark dust lane across the nucleus in optical light. Arp 148 is nicknamed Mayall's object and is located in the constellation of Ursa Major, the Great Bear, approximately 500 million light-years away. This interacting pair of galaxies is included in Arp's catalog of peculiar galaxies as number 148."

Arp's photo of it with the 200" Palomar scope shows no more than mine, maybe less. At least this time seeing was just barely good enough for me to use 0.5" per pixel when taking my image.
http://ned.ipac.caltech.edu/level5/Arp/Figures/arp148.gif

If you look closely you'll find a great many of the faint "stars" in my image are really distant anonymous galaxies.

14" LX 200R @ f/10, L=9x10'x1 RGB=3x10x2, STL-11000XM, Paramount ME

Related Designations for ARP148

ARP149

Arp 149, IC 803, is a pair of interacting galaxies in Coma Berenices about 370 million light-years away. Arp put it in his category: Galaxies with Jets. He made no comment on this one. I'm not sure what he is seeing as the jet. Is it the very faint plume to the northwest coming from the eastern (left) galaxy or is it the much brighter plume from the western one to the southwest? I have no idea. The galaxy on the right is PGC 215304 and the one to the left is PGC 42367. The pair was discovered by Stephane Javelle on April 25, 1892.

This was taken a night of very good seeing that didn't last. I need at least 100 minutes of L data (160 or more would be better) when imaging at 0.5" per pixel. But seeing went south and I was able to use only 80 minutes of data and preserve the resolution I was getting. In fact, the image is slightly undersampled on the 7 usable frames I obtained! That only happened once before. Galaxies down to 23rd magnitude are seen on the processed image. Not bad for such noisy data.

There are a ton of great galaxies in this image, in fact, the vast majority of the "stars" in this image (except the blue ones) are actually galaxies. If it isn't perfectly round or quite bright then it's likely a galaxy. I could identify nearly 1000 on this 0.0516 square degree field. Unfortunately, this is another field that NED has entered SDSS data for but that data seems to contain no redshift data. So, again, I didn't bother an annotated image as all it would contain is the coordinates of the galaxy which is how Sloan images are cataloged.

Not only didn't Arp have any comment on this pair, I found virtually nothing on it.

The asteroid above the bright star near the top of the image right of center is (32122) 2000 LD10 at magnitude 19.2. About 3 minutes further west and a tad south is the much shorter and fainter trail of 2010 EW38 at magnitude 20.1.

Arp's image
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp149.jpeg

14" LX200R @ f/10, L=8x10'x1 RGB=2x10x2', STL-11000XM, Paramount ME

Related Designations for ARP149

ARP150

Arp 150 is part of the 4 galaxy group known as Hickson Compact Group 95 and is located about 500 million light-years away. Unfortunately, I was hit by clouds and only got one third the data I had wanted. I planned on getting the rest but forgot to put it on my list. I didn't realize I'd not gotten the data until too late. It didn't help that I had imaged the first night at 0.5" per pixel and never had a night after that, that was up to the needed seeing quality until I forgot about it. So the image below is very thin and noisy. Color data was very poor. It will have to do for now. I found this text comment about the group but the image it refers to was missing. I believe a is the top galaxy, c the middle one with b the lower left and d lower right. The suspected elliptical is very orange in color in my lousy color data as a distant elliptical "should" be. I could find nothing on it, however, not even a catalog name. While the curving arc is easily seen in my image I didn't get enough data to show the jet very well. It is the linear feature coming out of the "middle" spiral to a point just right of the core of the top elliptical. It shows better in Arp's photo.
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp150.jpeg

In comparing the two I'm mystified by a faded object in my image. His photo shows a star-like object in the arc right above (in Arp's image -- left in mine) the big elliptical galaxy. While it appears to be bright enough to see clearly in my image it only shows very faintly. I don't know why. It also is seen well in the POSS II red and blue images. Apparently, I was hit by clouds even harder than I thought. Someday I'll redo this one.

The other two galaxies in the group are MCG +01-59-046 Sc spiral (right) and MCG +01-59-048 Scd spiral (left). Both are at about the same half billion light years as Arp 150.

Other galaxies in the image are anonymous as far as I can determine.

My thin data image is displayed at 0.5" per pixel rather than my normal 1".

14" LX200R @ f/10, L=4x10x1 RGB=2x10x3, STL-11000XM, Paramount ME

Related Designations for ARP150

ARP151

Arp 151 is a rather odd object. It appears to be a compact galaxy with a long jet (40") that has a bright knot in the middle of it. Or maybe it is a chain of three galaxies as the Vorontso-Velyaminov Interacting Galaxy Catalog indicates saying it is VV144a, b, and c. But http://i273.photobucket.com/albums/jj229/Astronomerica/SDSS-48/NGC5820-SDSS.jpg gives the exact same coordinates for each entry! All point to the lower compact object. Arp put it in his class Galaxies (not classifiable as E or S): with jets. He said nothing about it, however. It appears in many catalogs as many different types of objects. NED says it is a Seyfert 1 galaxy. It's in the 2MASS survey as an infrared object. The Markarian catalog lists it as an ultraviolet excess galaxy. It is in the Second Byurakan Survey of Emission Line Objects as an emission line source. The SDSS lists it as a quasar. That one surprised me greatly. The Luyten Blue Star Catalogue lists it as a blue star! It is in several X-ray catalogs as an X-ray source and some catalogs actually consider it a galaxy. Talk about an identity crisis! A note at NED says this galaxy was the first Luyten blue "star" recognized to be a galaxy. I assume this refers to the blue knot in its center. NED gives its length as 29.4" while I measure it at 53", nearly twice as long. Why such a large difference?

Its redshift distance is about 300 million light-years. NED classes it as an S0 peculiar Seyfert 1 galaxy. If it is a quasar it must be the closest one as I can't recall any less than a billion light-years away, maybe nearly 2 billion. It is located in Ursa Major, about a quarter of the way from M97 to M109.

The SDSS lists the knot a bit less than halfway along the "jet" as a separate galaxy SDSS J112535.23+542314.3/ASK 236801.0 and not part of a galaxy. They show a redshift distance only 4 million light-years closer than Arp 151. So is it a knot or a separate galaxy? Is Arp 151 eating it for lunch and the "jet" a resulting tidal plume of stars possibly drawn away from the galaxy with only the core remaining to appear like a knot that by coincidence of perspective seems to lie on the "jet"? Looking closely there appears to be another knot at the northwestern end of the Jet. It is far fainter than the one near the middle. It carries the designation 2MFGC 08934 and is an IR source as 2MASX J11253416+5423312. What exactly constitutes the flat galaxy in the image I don't know. Lack of redshift data means it could be a background object. Or is it a three galaxy chain as some papers indicate? Also, I seem to see a faint hint of a "jet" or plume going to the southeast of the main condensation as well.

The obvious round "bubble" centered on a point halfway between the blue knot and the northwest end of the "jet" caught me by surprise. I only see hints of it in Arp's image. Slightly stronger hints are seen in the POSS 2 plates. I was about ready to put down to some sort of reflection from the star to the north when I saw it clearly in the SDSS image. It is real but not mentioned in the few papers I looked at on this galaxy. Is it part of the galaxy, an unknown planetary nebula seen in front of the galaxy or something else? I find nothing on it. The color is wrong for a planetary so I'll go with part of the galaxy for now.

This has to be one complex object that is not getting much study. Is there a fourth galaxy involved here? Just to the west of the northern end of Arp 151, and well shown in Arp's image is a small, 20th magnitude, galaxy, SDSS J112531.90+542321.8. With no redshift data, its distance is unknown.

My processing of this one was severely hurt by the halos from the 8th magnitude F0 star just to the north. This was the image that finally got me to start saving for new filters that didn't have this halo problem as the Astrodon Generation 1 filters that came with the camera (used) when I bought it over 5 years ago do. I didn't get them until months later, unfortunately. Anyway, that star cast a lot of noise about this area creating a processing nightmare. The galaxy to the west, ASK 236801.0 appears to have some tidal plumes about it. But those may be noise from the glare of the star as it has a redshift distance of nearly 1 billion light-years and thus not involved with Arp 151 in any way. Though the SDSS image does seem to show some fuzz to the eastern side of it. They too were bothered by halos from the star, just not as severe as mine.

There appear to be two galaxy groups in the image, one with a distance of a bit over 900 million light-years is centered near the left edge of the image. Its coordinates match that of a galaxy. I've marked them at ASK 237033.0 indicating the distance to the galaxy and cluster respectively. The galaxy is also in the 2MASX catalog as a microwave source. The cluster is SDSS-C4-DR3 3275. NED lists it as having 12 members but gives no size. I see 13 in my image alone at about this distance. With the center of the cluster near the left edge, I'd expect a lot more east of my image. There are three more galaxies in the image at 640 million light-years, also along the left edge. They must be in some group as well. Again I didn't go searching farther east than my image to try and find it.

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp151.jpeg

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

Related Designations for ARP151

ARP152

Arp 152 is one of the most famous Arp galaxies and often in the news. Here's a link to such a current news item. http://www.universetoday.com/2009/07/02/messier-87-shows-off-for-hundreds-of-earth-bound-astronomers/ It has one of the universe's largest fireworks going off in its core, powered by a giant black hole. This creates a jet. It is the jet that put it in Arp's catalog of course. While we only think of M87 when galactic jets are mentioned Arp has 4 of them in his catalog. Two were well placed this spring and I hoped to image them along with M87 but thanks to the perpetual clouds this didn't happen. I've attached 2 different processing version of this one image; one processed normally except the core has been reduced to show the jet, the other a closeup 2x enlargement of the core and jet region processed just for the jet.
I've also included an annotated image.

M87 is one of the anchor galaxies of the Virgo cluster. Its mass along with that of a couple other supermassive elliptical galaxies seem to define the center of this cluster. One of these M49 is involved with Arp 134. I've reduced the brightness of M87 considerably to allow the jet to be seen. Many of the star-like points around and within the galaxy that make it appear to be in a faint star cluster are really some of its many globular star clusters. There were just too many to try and include them in the annotated image. But virtually all fuzzy stars around and in it are listed at NED as star clusters. Unfortunately, they list both open and globular clusters the same. I think it safe to assume these are all globular clusters.

M 87 was discovered by Johann Koehler on May 5, 1779. Messier didn't hear of the discovery and found it himself on March 18, 1781.

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp152.jpeg

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

Related Designations for ARP152

ARP155

I started a run on ARP 155, also known as NGC 3656 and went to bed. When I got up I found the temperature had dropped nearly 20C during the exposure. This was a major test of my temperature compensating focuser which constantly readjusts the focus based on the temperature every few minutes. I figured thermal lag in the scope would have it ahead of the curve but it was right on. The only problem is my image scale changes and the final image was a good 40 pixels bigger than when it started. So simply stacking them didn't work. I had to resize every frame to compensate. What a pain. There is software to do this but it is expensive (I since got it anyway). A bit more than I wanted to spend at the time this was taken. Also as the image size changes so does the vignetting meaning the flats for the start were right but those for the end didn't begin to compensate for the vignetting correctly. I had to use pseudo flats to compensate. That meant I couldn't dig down into the noise level like I would have liked. But it is my first image under perfectly clear skies in 7 months so I can't complain too much.

In any case, the image did turn out quite well after all day of trying to compensate for the temperature problems. Still since seeing wasn't very good I should retake this one but in over 8 years that hasn't happened.

This galaxy is about 135-140 million light-years away based on the redshift data I found. I located three papers I could read online without paying for them and all three came to very different conclusions about this galaxy. One said it was just an irregular galaxy. That is hard to swallow. Another said it was the product of a near collision of two galaxies but didn't specify what types. They seemed to indicate the result was an elliptical irregular galaxy. The third said it was the collision of two disk galaxies (spirals). To me, it appears like a spiral and an elliptical collided. Though that blue ring that lines up with the dust lane is hard to explain by any standard theory. So is a dust lane that looks like two dark wedges. While it may appear the part of the ring to the left is closest to us and the part to the right then goes behind the core of the galaxy I think the opposite is true. That would make the dark lane actually dust in that ring while the left part clear of the core would be the part farthest from us. Very unsymmetrical either way but the first makes more sense to me. Also possible is that the ring is entirely in front of the other galaxy. Figure it all out and your Ph.D. is waiting. Arp put it in his class for galaxies (not classifiable as S or E) that are disturbed with interior absorption.

Adding to the interest are the reddish star-like objects around it. Those are not stars but dwarf galaxies orbiting it. Farther out are three spiral galaxies that are quite red. This is odd. Spiral galaxies like they are should be reddish in the core but then blue in the arms unless star formation has ceased some time ago. This is seen in the spiral galaxies toward the edge of the frame. Makes me wonder if the red color of the dwarfs and these three spirals isn't due to dust thrown out of the colliding galaxies into deep space around them. Not having access to spectral data on these galaxies I can't tell but it seems possible. Oops. Since this was written distance data on some of these became available and is shown on my annotated image. These aren't dwarf around Arp 155 as papers I saw indicated but distant galaxies reddened by their several billion light-years distance.

Note the spiral at the bottom below NGC 3656. That's PGC 34975. It has one arm severely tidally disrupted and pulled out from it by some distant collision. The arm wraps faintly around the western side of the galaxy then back north of the galaxy ending northeast of the galaxy. The area between it and the rest of the disk is faintly visible as well. Its redshift shows a distance of 370 million light years so it isn't related to NGC 3656 in any way. Just a coincidence that adds interest to the image.

ASK 236497.0 to the lower right is listed as having a candidate BH nucleus. BH at NED stands for black hole. Since most galaxies have a black hole in their nucleus I don't know quite what they are trying to say. Probably something like a candidate AGN?

PGC 034895 to the lower right appears to have two blue blobs at its north end. Are these star clouds? Are they the result of something it ate? Is there more than one galaxy here? I found nothing to answer my questions.

There are a heck of a lot of really distant galaxies at a billion or so light years in this image. One group is seen above PGC 34975, another group at the lower right corner and dozens of others scattered about the frame. If it is star-like but fuzzier than it should be or elongated it is a galaxy, not a star. Their great distance puts a lot of dust between us and them so they do get reddened by the dust. Look close in any part of this image and you'll see many of these. A couple hundred overall. Keep in mind, that due to the flat problem I am not going as deep into this image as I could with proper flats. Unfortunately, there's no way to take flats that cover this temperature range so this is the best I can do until I retake it under more steady temperature. But I have a ton of objects that haven't been looked at at all so that will have to wait for some time in the future.

I've since prepared an annotated image. NED shows a galaxy east of Arp 155 as a possible dwarf galaxy but then lists its distance as 1.29 billion light-years. That makes it some 130,000 light-years across, possibly bigger than the Milky Way we live in. It isn't the only one so listed but is the biggest. Why this discrepancy I don't know.

I measure ARP 155 as being about 90,000 light-years wide. It was discovered by William Herschel on April 14, 1789 but isn't in either of the Herschel 400 observing programs.

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp155.jpeg

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

Related Designations for ARP155