ARP160

Arp 160 was in the news after an image of it combining white light data from Hubble and X-ray data from Chandra has been recently released and picked up by many astronomy news websites. I imaged it the night before the image was released so have rushed it to the top of the processing list.

Arp 160 is known as the Medusa Galaxies though Arp never even knew it was two galaxies. He considered it one and classed it as a galaxy not classifiable as "either elliptical or spiral that is disturbed with interior absorption". In fact, it is two galaxies that are in the process of merging. The fan-shaped blue object above and the spiral-like, mostly reddish object below. Using Chandra's X-ray vision (better than Superman's) the black hole that was at the core of the upper galaxy has been spotted proving it is two galaxies.

The Chandra press release is at:
http://chandra.harvard.edu/photo/2009/medusa/

I had a heck of a time processing this image as there was a 5th magnitude star just out of frame at the top right that must have hit something reflective in the camera. It sent ghost images all over the field. Many overlapped. It took me a couple days work to remove them. In doing so I lost faint parts of the image but none involving Arp 160. Which is also known as NGC 4194 and is in Ursa Major. It was discovered by William Herschel on April 2, 1791. It isn't in either Herschel 400 observing program.

Arp's image with the 200" Palomar scope is at:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp160.jpeg
Film has far less dynamic range than today's digital sensors so the core is burned out in Arp's image loosing the spiral nature of that region in an attempt to show the fainter parts.

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

Related Designations for ARP160

ARP161

Arp 161/UGC 6665 is thought to be a merger of two spiral galaxies located in western Virgo almost on the Leo border. It is about 270 million light-years distant. Arp put it in his class of galaxies with diffuse elements. An obvious reference to its cone-shaped jet/plume. Arp's comment "Faint, diffuse material extends away from neck." Several sources seem to see the bright region at the "neck" as Arp calls it, as a jet with the plume extending from it. While the night I took this was awful with resolution of only about 3.5" of arc or worse, the "jet" is really two point sources, better seen in the Sloan image. Also better seen in the Sloan image is the spiral structure of the galaxy. It was blurred out of existence by the horrid seeing I experienced the night I took my image. The plume appears the result of the merger and there is no "jet". The lower of the two star-like objects is shown at NED to be a 20th magnitude star on the Sloan survey. The upper, brighter object isn't listed at NED. Likely, it too is just a star in our galaxy confounding the issue. Arp had even worse seeing than I did so his image is of even less help here. Odd to out resolve the 200" scope when I'm having a bad night. Arp must have been desperate that night. I know the feeling.

NED classes the galaxy as Sb pec;HII;WR Sbrst. The starburst is likely due to the merger. I don't know what NED means by "WR". Usually, that refers to a Wolf-Rayet star. Anyone know what it means in the case of galaxy classification? NED's own reference page fails to define the term. All I can think of is the spectra has features of Wolf-Rayet stars. A starburst galaxy, like Arp 161, would likely have a strong population of such stars.

Near the bottom edge, left of center, is CGCG 012-064. It has the same redshift as Arp 161 so likely part of its local group.

The annotated image shows a galaxy cluster, SDSS CE J175.616547+00.441206 northeast of Arp 161 at 3.5 billion light-years. NED shows it with 24 members in a circle 3.8 minutes across. The center of the label marks the center of the cluster. No galaxy marked that point that I could see or NED mentions. One at that distance is seen however it isn't marked in NED as a bright core or cD galaxy. Still, it is likely a member of the cluster. Another cluster, MaxBCG J175.68388+00.38916, at 3.2 billion light-years is also northeast of Arp 161. It has 17 galaxies but no size was listed. A bright core galaxy is shown at the same position but without a distance estimate. I show it as GC/G with the galaxy distance a question mark. I'm not done yet! A third galaxy cluster at 3.2 billion light years, SDSS CE J175.678543+00.482395 is further northeast. It has no galaxy at its core though a red one is just right of the core with the label for it to its immediate left. The cluster is listed as 1.6 minutes in diameter containing 23 galaxies. Don't think we are done with galaxy clusters in this image. Mostly east from Arp 161 is the galaxy cluster SDSS CE J175.833755+00.375661 at 3.9 billion light-years. It is 3.6 minutes in diameter with 23 members, one of which has a redshift value of 4.0 billion light-years. I used one label for both though they aren't at the same position. The center of the cluster is behind the glare of a bright star while the galaxy, and a second one without a redshift measurement are just southeast of the star's glare circle.

Southwest of Arp 161 is a trio of objects. The most obvious a rather large galaxy, MGC 0023433/MGC 0096273 at 1.2 billion light-years. Why it has two designations I don't know. Above it is the Ultraviolet Excess Source, SDSS J114150.08+001314.3. At least that's how the Sloan survey categorizes it. The MGC calls it just a star as does the 2QZ. But with a measured redshift that puts it 9.5 billion light-years away, it sounds more like a quasar to me. There appears to be a possible tidal tail coming from the galaxy. Apparently, it is the separate galaxy SDSS J114150.87+001307.4 with an unknown redshift. Several other UvES objects with large redshifts are also identified in the image. I assume they are all quasar-like objects. I suppose it is possible they are extreme starburst galaxies but that these distances I find that unlikely.

Also to the northeast is a quasar, SDSS J114239.34+002640.4. While NED puts its redshift at z=1.872 for a distance of about 10.2 billion light-years one source, the 2QZ catalog gives a z of only 0.103 for a distance of about 1.3 billion light-years. This doesn't seem reasonable to me, especially for a 20.5 magnitude quasar so I went with the value NED prefers.

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp161.jpeg

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

Related Designations for ARP161

ARP162

Arp 162/NGC 3414, located in Leo Minor about 80 light-years away is one strange galaxy. Arp put it in his galaxies with diffuse elements (filaments). It shows a huge halo and a diffuse disk. NED classes it as S0 pec. Modern rotational measurements show an interesting twist. The inner parts of the galaxy rotate one direction with maximum measured velocities along the disk as you'd expect but once you get out further suddenly the velocities slow and then reverse! But now are aligned on a different axis rotated 10 or 15 degrees counterclockwise from the disk. See http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?2004MNRAS.352..721E&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf for the velocity map and other information. They draw no conclusions. I would suspect this is an indication of a merger. That would explain most of the features. The galaxy was discovered by William Herschel on April 11, 1785. It is in the original Herschel 400 observing program. I don't understand my notes from that, however. They were made on April 16, 1985 at 100x with my 10" f/5 under humid conditions. That apparently limited my ability to see faint objects as my entry reads "Small, round galaxy. Faint but easy due to its small size. A star-like nucleus seen with averted vision." Obviously, I was seeing only its center portion due to the conditions being worse than I realized.

From my image, it appears Arp could have also put it into his category for galaxies with shells. Though they aren't visible in his mono image taken in blue light with a yellow filter. I'm assuming that was done, it was his normal imaging mode. The shells show mostly in red light which he likely wasn't seeing. Shells are usually caused by mergers. It shows a LINER spectrum which is often caused by an interaction with another galaxy of some sort. It has two companions at about the same distance. I screwed up my position entry when programming the imaging of this galaxy and used the position of one of the companions, UGC 5958. This put Arp 162 at the top of my image and caused me to miss the more interesting companion NGC 3418 further north. The former has a redshift distance of 68 million light-years but a Tully-Fisher measurement of about 90 million light-years. NGC 3418 out of my image has a redshift distance of 70 million light-years and no other distance estimate. It's quite likely all three are actually about the same distance from us.

There's yet another member of the group though never mentioned as a companion that I saw. It is SDSS J105137.14+274919.6 at a redshift distance of 75 million light-years. It is east and a bit south of UGC 5958. It is classed as a dwarf though seems as large in angular size as UGC 5958 just with a much lower surface brightness. There are other galaxies closer to Arp 162 that are far smaller with similar redshift distance. These are noted in the annotated image. There's an obviously close galaxy similar to and further east and south of SDSS J105137.14+274919.6 that has no distance data. Many other dwarfs without distance data may also be members of the group.

The image contains at least 10 quasars, all in the upper 2/3rds of the image. One of them has a redshift of z=3.9 which translates to a light travel time of 12.2 billion light-years. A z of 3.9 means the light I imaged was well into the far ultraviolet region when it left the quasar. Most of its ultraviolet light is now seen here as infrared light it has been so red shifted. The quasar is now so far from us, nearly 24 billion light-years, that light it emits "today" will never reach us. The expansion of the universe will keep its "current" light forever beyond our reach. I use quotes because these words have no real meaning in Einstein's universe at these distances and speeds.

Many distant galaxies are in the image. Some with redshift data are over 4 billion light-years light travel time from us. They must be very large and bright galaxies for me to pick them up. My limiting galaxy magnitude is about 23 for this image. Must have been a good night.

Sloan image:
http://astronomerica.awardspace.com/SDSS-24/NGC3414.php

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp162.jpeg

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

Related Designations for ARP162

ARP163

Arp 163/Haro 09/NGC 4670 is an SB(s)0/a pec: BCDG galaxy in Coma Berenices. BCDG means Blue Compact Dwarf Galaxy. If the distance is 60 million light-years as its redshift and a couple other sources indicate then it is about 27 thousand light-years in size. Some sources put it only 36 million light-years away which cuts it down to 16 thousand light-years which certainly is a dwarf galaxy. Arp put it in his class of "galaxies with diffuse filaments, diffuse counter-tails." He left no comment about it. I can't see either filaments or a counter tail. Today it is thought to be rapidly forming stars but not at the starburst level. Still sufficient to color the galaxy blue due to the massive and thus bright blue stars it is making which cover up the far more common but much fainter main population of red stars.

With normal stretching or any of the canned stretches found in many programs as well as DDP and other techniques, the core showed just a bright white oval. I had to do some rather strong processing to hold back the core while the rest of the image was stretched to show what detail I was able to capture in the core region. The HST image of the core shows it better. That image is oriented with north to the lower right corner of the image while north is straight up in my image. The HST image (link below) is taken using near-infrared light for red with very blue light for green and near ultraviolet light for the blue channel. So the image is false color and won't match my visual light colored image. The Haro catalog entry describes it as "Muy violeta" which translates from Spanish to very violet indicating the UV light from these new stars really does color the galaxy. The Haro catalog is a catalog of blue galaxies and UV excess sources that have emission lines.

After I looked at Arp's image with the 200" Palomar telescope taken mid 60's I was expecting a rather featureless S0 or E galaxy so when this blue galaxy with star clouds and dust lanes showed up I first thought I'd missed my target. It's not often I can get this much more detail than Arp did using the world's largest telescope of its day. His log does show seeing as below normal for this image. Still, it is nice to beat the socks off that monster scope even with the help of modern technology.

The other NGC galaxy in the image is NGC 4673. While it appears slightly smaller it is some 5 times further away so actually much larger, about 120 million light-years across. That makes it more massive than our galaxy. It is classed E1-2 by NED and some other sources but S0: by the NGC project and a few other sources I looked at. So flip a coin. In any case, it appears to be a shell galaxy to me. At least I see what appear to be faint shells about it. If so it is the result of a merger in the past. Maybe several mergers. Oddly much literature refers to NGC 4670 and 4673 as a non-interacting pair. Since one is 6 times the distance to the other they aren't a real pair except as seen from our galaxy and others in the line of sight and couldn't possibly be interacting.

On the upper right below a bright star is the odd pair ASK 577888.0 and ASK 578732.0. The latter appears to be a knot in the former but NED doesn't call it part of a galaxy. It could be this is an interacting pair. This would explain the odd arm on the right side. I found absolutely nothing on this pair, however.

NGC 4673 seems to be the center of a rather large group of galaxies. At least there's a surprising number at its redshift in my image. This includes the ASK galaxies mentioned above. I found no cluster or galaxy group listed for the field, however. Though I didn't look far beyond the bounds of the image. There's another group at about 1.3 billion light-years also without a designated group or cluster.

Both NGC galaxies were discovered by William Herschel on April 6, 1785. Neither are in a Herschel 400 observing program.

Also in the image are two very distant quasars. Using NED's 5 year WMAP calculations the one in the upper right is 11.55 billion light years distant while the one on the left is 11.88. At these distances, things are very confusing. Redshift while linear at say 300 million light-years (double the redshift and the distance doubles) it is far from linear at these distances as the redshift z value of the former quasar is 2.989888 while the later only slightly further away is 3.439000. This also means the light was so severely redshifted most of it went out of the passband of my CCD so it is very faint. A z of 3.4 means the wavelength of each spectral line is 4.4 times longer than it was when emitted. Shifting Ultra violet into the infrared part of the spectrum. Also while it was only 5 billion light-years from us when its light was emitted those 11.88 billion years ago, the light had to travel those extra 6.8 billion years thanks to the ever-expanding universe. In those 11.88 billion years it has been moving away from us at an ever-increasing speed and is now some 22.5 billion light-years away. So the expansion of the universe has carried it 17.5 billion light-years in 11.9 billion years. Yes, the universe can and does expand faster than the speed of light. That means the light it emits today (if it even exists today) will never reach us. The fact the universe was much smaller 11.88 billion years ago than it was when the other quasar's light left it plus this faster than light expansion plus relativity issues create the very counter-intuitive situation that the quasar we now see 11.55 billion years later was 5.3 billion light-years distant when its light left. Yes, it was further away but its light got here quicker as it didn't have as far to go through the ever-expanding universe. These figures are using NED's 5 year WMAP calculator. I didn't do the math, NED did it. You can enter your own parameters and rerun the calculations if you don't like this result. Now, where's the Jack Daniels when I need it?

Arp's image with the 200" Palomar telescope (north to the left)
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp163.jpeg

The HST image of the core region can be seen at:
http://upload.wikimedia.org/wikipedia/commons/thumb/f/fe/NGC_4670.jpg/622px-NGC_4670.jpg
I don't know who assembled it from images at the Hubble Legacy Archive site. North is to the lower right corner.

14" LX200R @ f/10, L=4x10x2' RGB=2x10'x3, STL-11000XM, Paramount ME

Related Designations for ARP163

ARP164

Arp 164/NGC 455 is a merger remnant in Pisces some 250 million light-years distant. Arp put it in his category for galaxies with diffuse elements. It appears these diffuse elements are looping tidal trails of stars ripped from the merging galaxy showing the path of the merging galaxy as it was torn apart orbiting the larger galaxy. The NGC Project classifies it simply as peculiar. NED says S?. It likely will settle down to become an elliptical galaxy. It was discovered by Albert Marth on October 27, 1864.

The field seems to contain a few galaxies with the somewhat closer redshift of about 210 million light-years, two of which are in the image. A couple others are just outside it. Is Arp 164 related to these? It seems likely they are. NED has little data on this field. Only a few galaxies in my image are in NED's database and most have no redshift data. All galaxies NED catalogs are shown in the annotated image. A question mark is used for the distance of most since they don't have any redshift data. Those without any catalog entry and therefore left blank on the annotated image are apparently anonymous.

I wasn't going to prepare an annotated image but then 9 asteroids showed up in the image (actually more but many didn't survive the processing). Within 20 minutes of Arp 164, the minor planet center showed 18 asteroids down to magnitude 21 which was my limit at the rate these were moving. The 9 that survived the color combine are:

(180762) 2004 PC14 magnitude 19.3
(105898) 2000 SC188 magnitude 18.5
2007 VJ230 magnitude 19.5
(256661) 2007 XD22 magnitude 20.1
2010 TH124 magnitude 20.2
(102564) 1999 UH30 magnitude 19.9
(279746) 1998 MK6 magnitude 20.6
2010 TC159 magnitude 20.9
(251674) 1995 SP22 magnitude 20.5

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp164.jpeg

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

Related Designations for ARP164

ARP165

Arp 165/NGC2418. A very large galaxy some 240 million light-years away. It is located on the eastern edge of Gemini. Arp 165 is classed as an elliptical peculiar galaxy. It has one low contrast blue arm against what otherwise is a galaxy that looks much like a typical elliptical, until you notice the odd tidal extension on the side opposite the blue arm. Arp classed it under "Galaxies (not classifiable as S(piral) or E(lliptical); with diffuse elements. This seems rather appropriate. It appears there has been very little study of this galaxy as I could find little on it. There are a couple small galaxies right near it (north) but I found no redshift data on them so can't tell if they are really companions or just apparent ones due to line of sight. One paper did call them companions but did so in a way that didn't indicate if the author considered them actual companions. In fact only one other galaxy in the entire field had any distance data I could find. That is CGCG 087-015, toward the upper right corner of my image at about the same distance as Arp 165. It is very blue but otherwise, shows no sign of interacting with Arp 165. To the lower left of Arp 165 is a pair of galaxies that could be interacting, PGC 3090318/17 left to right. Since this was written a few more galaxies now have redshift data. Including this pair that have the same redshift but it was determined photographically apparently using the combined colors of both galaxies under the assumption they were at the same distance. Thus it is still debatable if these two are interacting. I think they are but this doesn't prove it as far as I'm concerned. Arp 165/NGC 2418 was discovered by Édouard Stephan on January 23, 1874.

5 asteroids are in the image. See the annotated image for details.

Arp's image with the 200" Palomar telescope is at:
http://ned.ipac.caltech.edu/level5/Arp/Figures/arp165.gif
Seeing was poor on Palomar mountain when he took this image. The above link is to the small version. Here's the large one but it shows no more detail, at least on my monitor.
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp165.jpeg

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

Related Designations for ARP165

ARP166

Arp 166 is composed of two interacting elliptical galaxies NGC 750 and NGC 751 (lower). Both are classed E pec though one source says they are two normal E0 galaxies. While the NGC project classes them as E1 and E respectively. Redshift data puts them about 225 million light-years away in the constellation of Triangulum. Arp put the pair in his category; Galaxies (not classifiable as S or E), with diffuse elements. Note the bright short bridge between the two galaxies. Arp didn't mention this feature, however. His only comment refers to a third galaxy saying "Small spiral at end of plume." The galaxy wasn't cataloged at the time of Arp's comment. Now it is known as 2MASX J01572652+3314452. I find little on it, however. It is likely unrelated to Arp 166 however. Did it have anything to do with the plume? I doubt it as the interaction of the two elliptical galaxies could easily account for it though its alignment is suggestive of more than a coincidence. NGC 750 was discovered by William Herschel on September 12, 1784. It's not in either Herschel 400 observing program. He found others in this field that night as well. NGC 751 was discovered by Bindon Stoney on October 11, 1850. He found several others in this field that same night as you will see below.

There are many other galaxies in the field but many of them, other than the brightest or IR galaxies aren't cataloged at NED. Several though are NGC objects. At the top of the image, partly out of frame is NGC 761, an SBa galaxy about 218 million light-years away so likely related to those in Arp 166. It was discovered by Bindon Stoney on October 11, 1850. The double star below it is NGC 760. In the rush to find and catalog galaxies many such double stars were seen as galaxies, some single stars as well. The misidentification was made by Ralph Copeland on December 19, 1873. He was using Lord Rosse's 72" scope at the time yet still made the mistake. Photography has greatly reduced but not totally eliminated such errors.

NGC 739 is the S0? galaxy 40% of the way to the upper right corner. It is about 200 million light-years away per redshift data. It was discovered by Ralph Copeland on January 9, 1874. Copeland got its position in relation to NGC 750 correct but then described it is south preceding rather than north preceding. This has led to some catalogs considering it lost but since its coordinates in relation to NGC 750 are correct there's no doubt this is the galaxy he saw.

NGC 736 is the large elliptical galaxy toward the lower right. Notes refer to an outer halo or pseudo outer ring. Does this include to the odd plume to the north that spreads out east and west at the top making a ring arc? That reminds me of the Umbrella Galaxy, Arp 189/NGC 4651. Its redshift indicates a distance of about 190 million light years. Could the plume be due to a galaxy it ate? That is what caused the Umbrella Galaxy's similar plume. It was discovered by William Herschel on September 12, 1784. It isn't in either Herschel 400 program. NE of it is NGC 738 at 189 million light-years, a much smaller, elliptical red compact galaxy. To the southeast of NGC 736 is NGC 740 described as a very red spindle and classed SBb?. Redshift says 199 million light-years. Other measurements vary between 178 and 215 million light-years with a weighted average of 201 million light years in good agreement with RS data.

Another NGC galaxies around NGC 736 is NGC 738. NED doesn't classify it. The NGC project says C which likely stands for compact. Seligman says S0? which seems more correct to my eye. It was discovered by Bindon Stoney on October 11, 1850. NGC 740 is listed as Sb? or SBb??. It was discovered by William Herschel the same night he found NGC 736, September 12, 1784 according to some sources. Others say he didn't see it and it wasn't found until the night that Stoney found NGC 738. Seligman votes for Stoney. It isn't in either Herschel 400 programs. The same night Stoney found stars within NGC 736 that are recorded as NGC 737. Some sources call all three NGC 737 while others say it is just the center star.

Then there's NGC 733 also found by Stoney the same night as the others he found. Most likely it is the star the annotated image points to but some sources equate it with PGC 7255 so I drew lines to both. To add to the confusion NED indicates the star is PGC 7255 and NGC 733 while my The Sky program shows the galaxy as both as does SIMBAD.

Some of the fainter galaxies of interest include 2MFGC 01479 (2MASS Flat Galaxy Catalog) which is 70% of the way from Arp 166 to the 15th magnitude NGC 739. In K band IR light this little guy shines at magnitude 14, a full magnitude brighter than NGC 739 in visual light! A short hop east and a bit north brings you to VI Zw 116 just 6" south of a star. It is a Red spherical compact galaxy that is also an IR bright galaxy.

The asteroid north of Arp 166 is (126304) 2002 AX119 at magnitude 18.6.

Besides the full image, I've included a 125% enlarged crop of the pair which shows the bridge between them a bit better than the normal size image. It also includes the asteroid and an inset of NGC 736.

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp166.jpeg

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

Related Designations for ARP166

ARP167

Arp 167 is a pair of interacting galaxies located in Cancer, just east of M44, at a distance of about -- Houston we have a problem. There seems to be some uncertainty about these two galaxy's distance.

The two galaxies are NGC 2672 and NGC 2673 right to left. NED classes them as E1-2 and E0 pec respectively. Arp put them in his class of Galaxies with Diffuse Counter-tails saying; "Companion galaxy very condensed, has curved plume." NGC 2672 was discovered by William Herschel on March 14, 1784. It isn't in either Herschel 400 observing program. NGC 2673 was discovered by George Stoney on December 19, 1849.

Now back to the problems. While I called them interacting galaxies some papers say they are non-interacting. I see two reasons for this. First only NGC 2673 seems distorted. You'd think if they really did interact NGC 2672 would show some sign of it but I don't see any. The other reason is the redshift distances are different. By redshift, NGC 2672 is about 211 million light-years distant while NGC 2673 about 185 million light years. Relative speed in a galaxy group, however, can vary by this much and more. So it could be they had a fast interaction due to their high relative speeds. Still, you have the problem of NGC 2672's lack of apparent distortion. Yet most sources do consider them interacting and one puts them both at a distance of about 167 million light-years using the D-Sigma method. See http://adsabs.harvard.edu/abs/1994AAS...185.5217G for more on how this works for elliptical galaxies. Does it work for peculiar ones? Or was this just a measurement of NGC 2672 and NGC 2673 was assumed to be the same distance? I can't tell from the abstract. For now, I'll say they are interacting as I don't see any other candidate for the distortion. A large galaxy can survive such an interaction without much distortion.

The two spindle galaxies on the right (west) side of the image are NGC 2667/IC 2410 (lower) and NGC 2667B/IC 2411 (upper) at 195 and 211 million light years. About the same as the two galaxies in Arp 167. Obviously, these two aren't interacting. NGC 2667 was discovered by Heinrich d'Arrest on February 18, 1862. It was later photographed along with IC 2411 by Max Wolf on January 13, 1901 and given its IC number. Due to an error in position by d'Arrest, it wasn't realized these were the same galaxy until after the NGC was released. NGC 2677, to the southeast (lower left) of Arp 167 is the other major galaxy in the image. It splits the difference at 206 million light years. It was discovered by John Herschel on March 17, 1831. Certainly, these are all part of the same group.

Zwicky shows a galaxy cluster centered about 7 minutes south-southwest of Arp 167 with over 250 members and a distance of about 200 million light years. It covers an area almost 2 degrees across so goes far outside of my frame. It is listed as UGCl 131/ZwCl 0846.3+1910.

I've provided an annotated image showing distances to (G) Galaxies and (Q) Quasars. As usual, the label is to the immediate right of the object when possible. A line points to the object when it might not be obvious. The quasar east of Arp 167 appears elongated north/south and not a point source. NED gives two SDSS designations for it, one labeled quasar (main one) and a second one labeled galaxy though the quasar designation is the default one. It's about the same distance as a much brighter galaxy so seems dim for a quasar. I've given it a Q label as that is NED's preferred designation. It looks more like a galaxy to me. Compare it to the far more distant but brighter quasar to the northwest of Arp 167 at nearly 11 billion light years.

There are two asteroids in the image. The bright one is just southeast of Arp 167 and is named (23153) Andrewnowell and is at an estimated magnitude 19.1. The dedication for its name reads: "Andrew John Nowell (b. 1988) was awarded first place in the 2007 Intel International Science and Engineering Fair for his electrical and mechanical engineering project. He attends the Nottingham High School, Nottingham, England." The other one is hiding in the north end of NGC 2677. It is (118611) 2000 GG143 shining at an estimated magnitude 20.0.

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp167.jpeg

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

Related Designations for ARP167

ARP168

M32 is Number 168 in Arp's peculiar galaxy atlas. That puts it in his Galaxies (not classifiable as S or E): Diffuse counter-tails. How many times have you seen this companion to M31 yet not seen the counter-tail? Yeah, me neither. Arp's comment to this one: "Faint diffuse plume curved away from M31's disk." Odd Arp would consider it neither Elliptical or Spiral. Every source I checked classed it as a compact elliptical galaxy, most saying cE2. The "c" for compact. Most sources say much of its outer halo has been stripped away by the tidal forces of M32 yet the counter tail remains, albeit very faintly. If you blow up the image some of the stars of M32 are resolved around the left and bottom edges. At least I think they are members of M32 rather than M31. Blue M31 stars are seen along the right and top edges of M32 however.

To try and find this nearly invisible plume I exposed for several hours but skies were awful. Only 4 frames had decent seeing and halfway usable transparency. I didn't realize this at the time as I looked only at the first and last of the series and they looked good. But CCDSoft's auto histogram stretch can hide a lot. I didn't realize the first frame had 8 times the light throughput as the last. I ended up using only 4 of the series as that gave the best image. Including more just made the plume even harder to see. Note this was taken the day before my high-resolution C179 image and seeing was very good. Good enough to have binned 1x1 but I wanted the added speed of the 2x2 binning. That was a good choice as only 40 minutes of 1x1 binned data wouldn't have been as good due to added read noise. The color data was useless due to clouds so used the same low-resolution data I used for the previous C179 shot. It wasn't as bad of a match for this image so worked somewhat better.

In the raw data, M32 goes to the far lower left corner of the image. When stretched to bring this out the plume vanished into the background of M31. Probably why few are aware of its existence. Since this outer part of M31 is very blue but the plume from M31 rather red I dimmed down the blue parts of M31 in this area letting the redder features remain. This makes the plume visible though I'm not sure it is curving like Arp says. I don't see the curve on his image either. M32 was first seen by Guillaume Le Gentil on October 29, 1749.

Some of the same features on my close-up of M32 that I ran earlier are seen in this lower resolution image. Many other features beyond the edges of that image are seen as well so I've prepared an annotated image showing these as well. A few on the edges are shown on both but most objects already shown on my C179's annotated image are not included for the most part. Also, see that for details on the labeling scheme used.

G117 is a bit of a puzzle. It is on both Chart 5 and 6 of the atlas but the lines connect to different star-like objects! NED shows the lower and brighter one to be a globular so that is the one I chose to use. NED refers to it as SKHV 117. I put a ? by the other object as it has the PSF of an extended object, rather than a star. Just that it isn't in NED and only "half in" the Hodge atlas.

The image is full of open clusters. I've only identified a few of them. In one place I just put OC and ran lines to three in the area. Many fuzzy patches were not in the Hodge atlas nor NED. I gave up trying to track them down. I could spend months on this image alone. Just not worth it.

What I noticed most was the color of the globulars. Many appeared identical to orange stars but for their PSF not being starlike. Seems most globulars I image in our galaxy seem to have a slightly blue overall color thanks to the highly luminously blue stragglers. Are M31 globulars lacking in such stars, are we seeing them through lots of reddening dust? In any case, the tendency of neutral to orange color seems surprising to me.

There are many differences between NED and the Hodge atlas. For instance, the cluster C205 in the upper right corner is at the location of a very blue starlike object. NED shows no cluster at that point but does show the round emission object just below and left of it as a cluster. This whole region seems to be rather poorly mapped to RA/DEC coordinates. It made it impossible to really pin down which of the many HII regions in this area are which on my image. While NED says the position error is 5" on both axes I was finding nothing within that range. Even when I put those coordinates into the DSS it came up with nothing in that range either but maybe 10" away there was something that might be the object but go 10" another direction and there was another possible object. Move a couple minutes from the area and everything was fine again, I was agreeing within a tenth of a second of arc, not tens of seconds as I and the DSS were in this area. The round bubble below the bright star Hodge sees as a cluster is likely one of the Wolf Rayet bubbles listed by NED in the area. I just can't tell which one. In NED its position is nearly that of a cluster with the WR bubbles further away. I've given up, just enjoy the region. Blow up the image 2x for a better view.

To take out the bad taste left by the above fiasco scan down about halfway to the bottom on the right edge of my image and you'll find a small round red blob. That is listed by NED (coordinates match!) as a Super Nova Remnant they call MLA 0266. Looks like it would be grand as seen from a few thousand light years rather than a few million.

Arp's image, apparently with the Schmidt camera not 200" (at least his resolution is well below mine) and rotated so east is up rather than north is at:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp168.jpeg

14" LX200R @ f/10, L=4x10', RGB=4x10'x3 (same as used for C179 image), STL-11000XM, Paramount ME

Related Designations for ARP168

ARP169

Arp 169 is a trio of galaxies sharing a common envelope of stars, or at least they appear to. Redshift would put these at about 340 million light years. But studies using the D-sigma method which is often quite accurate when applied to elliptical galaxies put the distance much closer, say about 280 million light years. The group appears to be part of the ZWCl 2212.0+1326 galaxy cluster, a group of some 138 galaxies about 340 million light years distant. If so then the redshift distance to Arp 169 is probably correct. I suspect that the fact these are S0 galaxies and share a common halo has skewed the D-sigma calculation. Still, this galaxy cluster has galaxies with redshifts that match the D-sigma value as well. In any case its a ways from us. I've marked the approximate center of the cluster and its details on the annotated image. The center is just left of the annotation. Thus much of it is off the southwest portion of my image. It's size being 44' in radius fully covers my frame even this far off center.

Arp 169 is Arp's class: Galaxies (not classifiable as S or E) with diffuse counter tails. I see mostly a common envelope of stars, not a counter tail. I think Arp is referring to the somewhat north-northeast extension of the halo off the upper right galaxy NGC 7236. The middle galaxy is NGC 7237 with the small galaxy to the southeast being NGC 7237C/PGC 200377. Arp's comment; "Faint diffuse plumes coming away from two galaxies. 3C442." This would indicate he sees a plume from NGC 7237 or 7237C as well. I see a hint of one, maybe. The reference to 3C442 is because it seems to be coming from the core of NGC 7237 a radio galaxy also known as 3C442. This could be a sign they are actually interacting causing its black hole to be very well fed at the moment. While one source describes these as elliptical galaxies with no sign of recent star formation most describe all three as blue compact S0 galaxies. From the color of the halos in my image, I'd agree with the latter. The halo doesn't have the orange color most always seen with elliptical galaxies. Though there are some exceptions 3 in one spot would seem a bit too much of a coincidence to me anyway. The two NGC galaxies were discovered by Albert Marth on August 25, 1864. I measure the full extent of the halo that surrounds all 3 galaxies as about 250,000 light-years assuming a distance of 320,000,000 light-years.

While most galaxy clusters are populated with elliptical galaxies as their most common members this cluster seems to be mostly S0 galaxies. I don't recall seeing so many on one image before. One of the few exceptions is the face on, low surface brightness spiral south and a bit west of Arp 169. It is PGC 068368 a 15th magnitude galaxy. NED describes it as a Malin-like galaxy. These are usually huge low surface brightness galaxies but this one is only slightly larger than our galaxy at 125,000 light-years.

The annotated image shows all galaxies and quasars NED had redshift for. There's a very blue quasar at 8.4 light years right beside a galaxy that is quite likely far closer than the quasar. The most distant galaxy I know of in the image is about halfway toward the lower right corner. It is SDSS J221402.08+134424.9 at a magnitude of 21.1. It must be a big one for me to see it at a distance of 4,300,000,000 light-years. It anchors a group of 17 galaxies toward the lower right corner. The cluster's distance is by photographic spectroscopic methods (p) which gives only 4.04 billion light-years for the distance. The measurement of the galaxy itself is likely more accurate.

The rather bright asteroid is (88528) 2001 QU177 which is shining at about magnitude 17.4.

Arp's 200" image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp169.jpeg

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

Related Designations for ARP169