Our observing nights have had the temperatures plummet, the observing clothing has gone from t-shirts and light sweatshirts to several layers of arctic gear. Numb fingers, toes and faces have become the norm. We wonder if it is really worth it to risk frostbite, fogged or frosted optics or worse just to get out under the stars. We know that if we do brave the cold, we will be repaid with some of the steadiest and clearest nights of the year in the northern hemisphere. We can only envy our brethren in the southern hemisphere who are currently enjoying warm observing conditions, although we have said goodbye to the attendant insect pests for a few months.
As promised, this chapter picks up in Cetus and will end up somewhere around Lynx. If you have been following this journey thus far, when we get to the end of this season's observations I will have covered 100 of the 338 objects in the "Atlas of Peculiar Galaxies". If you have been duplicating these observations then with these four installments there are enough to get you the AL Arp certificate. Even if you have no interest in getting the certificate, you will find these objects challenging, fun and very interesting.
Cetus is home to 28 Arp galaxies and galaxy groups running the gamut from the bright Seyfert galaxy M 77 (Arp 37) to MCG-2-3-37 (Arp 251), the most distant object that I have found in the Arp catalog to date.
Arp 4 - MCG-2-5-50 m13.7 sb 15.1 2.8'x2.4' Irr 1h48.5m -12°22'. Arp Classification - Low surface brightness spiral galaxy. In the 20" at 317x this galaxy has a very faint core surrounded by a 2' diameter barely detectable brightening of the sky background. At the E edge of this is MCG-2-5-50A, a brighter small galaxy with a stellar core. 50A is actually a distant background object with a redshift over 10 times as much as 50.
Arp 10 - UGC 1775 m14 1.5'x1.5' Sb(r) 2h18.4m +5°39'. Arp Classification - Spiral galaxy with split arm. In the 20" at 317x 1775 is a small oval object about .8'x.5' aligned NS. The core is bright and off-centered towards the S end surrounded by a faint haze. About 5-10% of the time the skies steadied enough to show a small portion of the ring at the northern end. Even less frequently there would be a small very faint hazy area extending further S from the southern end.
|Arp 19 - NGC 145 - m12.7 sb 14 1.8'x1.5' SBd 0h32m -5°8'. Arp Classification - Spiral galaxy with detached segments. In the 16" at 233x NGC 145 is an elongated object stretching for about 1.5' from NW-SE. There is a brighter N-S bar about .7' in length. On the N end of the bar the arm extending to the W is brighter than the other arm to the SE. The N arm extends about .5' to the W and then curves down. The S arm is about .5' in length and abruptly ends. There is a very faint hazy area about .1' diameter immediately to the E of the bar.|
Arp 67 - UGC 892 - m14.2 1.6'x1.4' SBab 1h21m -0°33'. Arp Classification - Spiral galaxy with small high surface brightness companion on arm. In the 20" at 282x UGC 92 is a small faint oval 1'x1.2' in size aligned E-W. It has a brighter almost stellar core with a faint bar aligned NE-SW about .7' in length. Occasionally I would detect an extremely faint outer haze surrounding the oval, this is brighter on the E and W ends. There are two brighter spots in this outer envelope about 1' to the S and SE of the nucleus at the location of the companion galaxies in the Arp photo. There are two other dim galaxies in the field, MCG+0-4-92 about 3' to the WNW, and MCG+0-4-94 about 3' to the S. Both of these are small and faint.
Arp 118 - NGCs 1143&4 - 1143 m14 sb 14.5 .9'x.7' E - 1144 m12.9 sb 13 .9'x.5' S/Pec 2h55m -0°10'. Arp Classification - E Galaxy close to and perturbing spiral. In the 16" at 233x these two are an elongated NW-SE object about 1.2'x.6' in size with a double nucleus. NGC 1144 is the object to the SW and showed some signs of mottling around its core region. 1143 has a gradual fade out at its end like a typical eliptical galaxy.
Arp 121 - MCG-1-3-51&52 - MCG-1-3-51 m14.6 2'x.6' Sa/p - MCG-1-3-52 m14.5 .9'x.8' SO 0h59m -4°48'. Arp Classification - E-like galaxy close to and perturbing spiral. In the 20" at 363x MCG-1-3-51 is a small elongated NS object about 1.2' in length with a slightly brighter core. About 1' to the NE is MCG-1-3-52, a faint .7' diameter round galaxy that has a slightly brighter core. There is a faint 14th magnitude field star at the NE edge of 52.
|Arp 127 - NGC 191 and IC 1563 - NGC 191 m14.1 sb 13.7 1.4'x1.2' SBb/p IC 1563 m14.1 sb 13.5 .6'x.3' SO 0h39m -8°59'. Arp Classification - E-like galaxy close to and perturbing spiral. These last three are all examples of the same classification, but have very different appearances in the eyepiece. Arps 118 and 121 have a common space "velocity" with a redshift difference between the galaxies in each object being around 200 kps. The galaxies in Arp 127 have a difference in redshift of 8587 kps. Either they are exhibiting a tidal tail over 430 MLY long, or again we are going to have to find another mechanism to explain redshift. In the 16" at 233x NGC 191 was the smaller of the two initially. The core and bar region is an oval object about .5'x.3' elongated EW. The core itself is occasionally stellar. South about .8' is IC 1563, a brighter elongated NW-SE edge-on galaxy about .6'x.3' in size. It has a fairly even brightness throughout, with a slightly brighter nuclear region. There is a faint 16th magnitude field star almost between these two. At moments there is a very faint haze around both galaxies.|
Arp 133 - NGC 541 m12.1 sb 14 2.4'x2.4' SO 1h26m -1°23'. Arp Classification - E-like galaxies with nearby fragments. The fragments referred to are LEDA 73957, a mag 17 collection of wisps about 1' to the ENE of 541, and LEDA 86298, a mag 13.3 small high surface brightness elliptical about the same distance to the E of 541. NGC 541 is also one of the central dominant galaxies of Abell 194, the other being the galaxy pair NGCs 545 and 547 (Arp 308) located 4.3' to the NE of 541. This whole field is liberally sprinkled with faint galaxies. There were 9 visible in the field of a 9mm Nagler with my 12.5" at 159x. In the 20" at 212x (12mm Nagler) there were 24 galaxies visible at one time with hints of others. NGC 541 at 282x is a round object about 2' in diameter with a bright non-stellar core. LEDA 86298 is a small .2' diameter brightening at the E edge of 541's envelope. LEDA 73957 is a very faint brightening of the envelope 1' E of 541's core. NGCs 545 and 547 at 363x are a pair of bright nucleii in a common envelope 4.3' NE from 541.
|Arp 147 - IC 298 & 298A - IC 298 m15.2 sb 13.1 24"x18" Ring - IC 298A m16 24"x10" SBbc 3h11m +1°19'. Arp Classification - Galaxies with associated rings. In the 20" at 318x 298A was easily held, seeming much brighter than it's published magnitude. A small object aligned NS about 18"x10" in size with a brighter core. IC 298 is a small faint round patch about 18" in diameter. Occasionally the NE portion of the ring would come clear as the skies steadied. Definitely worth another look.|
Arp 251 - MCG-2-3-37 m15.3 .8'x.4' multi-galaxy system 0h54m -13°51'. Arp Classification - Galaxies with adjacent loops and the appearance of fission. This is one of the more challenging Arp groups that I have observed to date. First, there is a magnitude 7.5 star, TYC 5272-1192-1, located 4' SSW of the group. You need to keep this star outside of the field of view to have a chance of detecting these galaxies. In the 20" at 363x there is a very small faint bit of fuzz nestled between a pair of very faint field stars. At moments this faint glow would break up into two objects extending NS about 20" apart. At even rarer moments there would be a third object about 15" to the E of the southern galaxy. With a redshift of 22575 kps for this group they are between 1.1 and 1.4 billion light years away. With all of this I feel good having detected this group at all.
Arp 256 - MCG-2-1-51 & -2-1-52 - MCG 2-1-51 m14.8 1'x.6' Sb - MCG-2-1-52 m14.1 sb 13.6 1.1'x.7' Sc/p 0h19m -10°22'. Arp Classification - Galaxies with the appearance of fission. In the 20" at 363x MCG-2-1-51 is a small faint oval elongated NS about .4'x.2' in size. It has a brighter non-stellar core. About 1' N is MCG-2-1-52. It is elongated NS and about .8'x.3' in size. The southern end is patchy with a small segment that appears to be detached. About 1.5' W of 51 is MAC 0018-1022, a very small faint almost stellar glow.
Arp 318 - Hickson 16 - NGCs 833, 835, 838 and 839 - 833 m12.7 sb 13.4 1.9'x1' Sa/p - 835 m12.1 sb 12.5 1.4'x1.2' SBb/p - 838 m12.9 sb 10.8 1.7'x1.7' I/p - 839 m13.1 sb 11.9 1.8'x.9' SO/p 2h9m -10°8'. Arp Classification - Group of galaxies. This group is a beautiful sight in any scope of 8" or more of aperture. In the 20" at 363x your eye is immediately drawn to NGC 835. It has a very bright almost stellar core, but the ring surrounding is easily apparent in anything larger than a 12" instrument. It has the same structure as the Cartwheel galaxy, but at an age probably 100 million years earlier. The galaxy that center punched it is not NGC 833 immediately to the W of it, but NGC 838, about 3' to the east. On the Arp photograph there is a very faint tidal trail connecting these two. All four galaxies fit into a 7' field of view.
Moving south to Fornax, we have a couple of very nice bright objects.
|Arp 77 - NGC 1097 and 1097A - 1097 m9.5 sb 12.7 9.3'x6.3' SBb - 1097A m13.6 sb 11.5 .8'x.5' E5 2h46m -30°16'. Arp Classification - Spiral galaxy with small high surface brightness companion on arm. In the 12.5" at 178x 1097 is a very bright oval about 5'x2.5' with faint arms extending from either end of the bar. There is a very bright stellar nucleus with low contrast dust lanes extending to either end of the bar. The arm at the NW end of the bar extends about 45° to the NE before fading into the sky background. The southern arm is fainter but has a brighter patch about 2' W of the SE end of the bar. 1097A is just off the end of the bar to the NW and is a small bright condensed object.|
Arp 154 - NGC 1316 m8.5 sb 12.5 7'x5.5' SBO/p 3h23m -37°13'. Arp Classification - Disturbed galaxy with interior absorption. In the 16" at 233x 1316 is a bright oval aligned NE-SW about 7'x5' in size. It gradually brightens until reaching a very bright non-stellar core. There are dark bands about 1.5' both N and S of the core, with the band to the S being larger, about 2' extending E-W. The band to the north is smaller and does not have as much contrast. It is immediately to the E of a stellar point that must be a superimposed foreground star. NGC 1317 is 6' N in the same field, a 2.5' diameter 11th magnitude SBa galaxy. There are quite a few galaxies from the Fornax cluster in the immediate neighborhood.
From here we move north into Eridanus, home to another 14 Arp galaxies.
Arp 39 - NGC 1347 & MAC 0329-2217 - NCG 1347 m13 sb 13.7 1.5'x1.3' SBc - MAC 0329-2217 m16.5 .6'x.4' S? 3h30m -22°16'. Arp Classification - Spiral galaxy with small low surface brightness companion. In the 20" at 318x NGC 1347 is a faint 1.2' diameter round object with a brighter core. Occasionally there is a very dim extension to the south about .3' in diameter at the position of the MAC galaxy.
|Arp 41 - NGC 1232 & 1232A - 1232 m9.9 sb 13.7 8'x7' Sc - 1232A m14.7 sb 14.2 1'x1' 3h10m -20°35'. Arp Classification - Spiral galaxy with small low surface brightness companion. NGC 1232 is one of the nicest face-on spirals in the sky, especially for southern hemisphere observers where it is more nearly overhead than it is for us northern observers. In the 20" at 282x 1232 is a large 7' diameter object. It has a brighter core region about .8' in diameter brightening to a bright non-stellar nucleus. There are many faint arms spiraling out from the nuclear region with several knotty condensations of star clouds and HII regions. 1232A is 4' to the E of the core of 1232, and is a small bar shaped object surrounded by a very faint haze. In the Arp photograph it appears to be at the end of one of the principle arms of the main galaxy. The resolution of 1232A appears to be about the same as the main galaxy. It is when you get into the redshifts that this neat picture starts to fall apart. Dr. Arp spent a couple of pages in his 1987 book "Quasars, Redshifts and Controversy" discussing the puzzle of this galaxy. 1232 itself has a corrected redshift of 1518 Kps, however 1232A has a redshift of 6496 Kps. But the degree of resolution argues that this is a physical pair, and that 1232A is a Magellanic type satellite of 1232. And as if that is not enough of a puzzle, in the same arm that ends at 1232A there is a prominant "HII" region. This HII region has a redshift of over 23000 Kps. (Arp, "Quasars, Redshift and Controversy", c 1987 Interstellar Media, pp 88-9).|
Arp 108 - ESO 547-2 and 547-3 - 547-2 m16.1 sb 12.8 .6'x.4' SO - 547-3 m15.4 sb 13.7 .8'x.6' Sc 3h3m -22°12'. Arp Classification - E-like galaxy connected to spiral. In the 20" at 363x these are a pair of small very faint objects separated by about .7' aligned NE-SW. 547-2 is the SW object about 15-20" in diameter surrounded by a small very faint haze. 547-3 is the NW object with a small occasionally stellar nucleus. At moments of better seeing there would be an extremely faint arm on the northern side about 15" N of the core.
Arp 131 - PGC 10561 & 10564 - 10561 m14.4 .7'x.5' Sa 10564 m15.4 .6'x.4' Sb/p 2h47m -14°48'. Arp Classification - E-like galaxy close to and perturbing spiral. In the 20" at 318x 10561 is small, faint, about .5'x.4' elongated EW with a slightly brighter core. 10564 is located about .8' to the NE of 10561 and is smaller and fainter, about .3'x.2' aligned NS and irregular in shape, being narrow on the S and wider on the N end. It has a brighter core that is offset to the W side.
Arp 304 - NGCs 1241 & 1242 - 1241 m12 sb 12.4 3'x2' Sb - 1242 m13.7 sb 13.2 1'x.6' SBc 3h11m -8°55'. Arp Classification - Spiral galaxy with large high surface brightness companion? This last is a guess on my part, as Dr. Arp did not fit objects 298-310 into any of his classifications. This pair is located 3' S of 9th magnitude T 5294:802:1, so it is necessary to use higher power to move the star out of the field in order to see any detail. At 363x 1241 is a large oval 2'x1' in size aligned NW-SE. There is a brighter oval core region .6'x1' in size brightening to a bright non-stellar core. 1242 is 1.5' to the NE about 1'x.6' in size aligned NW-SE. It is brighter in the core area, but I could not see a definite nucleus.
Orion has a pair of Arps framed by its star studded fields, one of which is:
Arp 327 - NGC 1875, PGC 17173, PGC 17175 and PGC 17176 - NGC 1875 m13.6 sb 12.6 .8'x.8' SO - 17173 m18.4 .3'x.2' E - 17175 m17.4 .6'x.2' - 17176 m17.6 .7'x.2' 5h21.8m +6°41'. Arp Classification - Chains of galaxies. In the 20" at 363x the only galaxy in this group that I was able to detect for sure was NGC 1875, a small elliptical system about .7' in diameter with a bright non-stellar core. This is a very rich stellar field with several fairly bright stars in the near neighborhood. I thought that I had possibly detected the cores of PGCs 17175 and 17176, but it was not a definite detection.
There is a single Arp galaxy in Gemini:
Arp 165 - NGC 2418 m12.2 sb 14.7 1.8'x1.8' E 7h36.7m +17°53'. Arp Classification - Galaxy with diffuse counter tail. In the 20" at 363x 2418 is a small bright core surrounded by a faint haze about 1.2' in diameter. The nucleus seems to be off center in the surrounding haze, but that may be an effect of the dense star field that this galaxy is located in.
Another in Cepheus:
Arp 25 and 114 - NGCs 2276 and 2300 - 2276 m11.4 sb 13.2 2.6'x2.3' Sab/p - 2300 m11 sb 13.2 3.2'x2.8' SO-a 7h32m +85°43'. NGC 2276 is all of Arp 25 and included in Arp 114 with NGC 2300. Arp Classification - Arp 25 - Spiral galaxy with one heavy arm - Arp 114 - E-like galaxy close to and perturbing spiral. With these two you get two Arps for the price of one. The challenging part of this is that there is a mag 7.8 star only 1.7' W of NGC 2276. This makes 2276 hard to see at moderate powers. In the 16" at 233x it was only visible using averted vision as a dim 2' diameter object with an off-centered nucleus. It did not really start to shine until the magnification was cranked up to 423x in the 20" and the star was moved out of the field. Then the filamentary structure of its arms became obvious, with a single arm on the S side of the galaxy standing out due to its isolation. The north side of the core is a tangled thicket of several arms and arm segments. NGC 2300 is located 6.5' ESE of 2276. It appeared pretty much the same in both scopes, a round 2' diameter galaxy with a bright non-stellar core.
And a couple in Cancer:
|Arp 82 - NGCs 2535 and 2536 - 2535 m12.8 sb 14.8 3.3'x2.2' Sc/p - 2536 m14.2 sb 12.9 .7'x.5' SBc/p 8h11.2m +25°12'. Arp Classification - Spiral galaxy with large high surface brightness companion on arm. In the 16" at 233x NGC 2535 is a large faint object with a brighter central body that is about 1'x.7' elongated in an E-W orientation. There are very faint arms extending about 1' to the N and S fron this core area. There is no central brightening of the nucleus. 2536 is at the end of the S arm, a small bright oval about .5'x.3' aligned NE-SW with a very bright non-stellar core.|
Arp 243 - NGC 2623 m13.1 sb 15.1 2.4'x.7' Sb/p 8h38.4m +25°45'. Arp Classification - Galaxy with the appearance of fission with adjacent loops. In photographs this system looks like other galaxy pairs involved in a merger dance with long tidal tails extending for large cosmological distances from either end. In the 20" at 363x this is a small oval object about .5'x.4' extended NS. The tails are very faint with the tail extending to the W from the S end of the oval being slightly brighter and extending about .5' to the W. The tail on the N end extending to the E is more diffuse and harder to perceive, but is visible for about the same distance to the E.
In Lynx there are another seven Arp galaxies.
Arp 6 - NGC 2537 m11.7 sb 12.3 1.7'x1.5' S(?) 8h13.1m +45°59'. Arp Classification - Spiral galaxy with low surface brightness. This is the "Bear Claw" galaxy. In the 16" at 262x 2537 is a medium sized 1.5' diameter fairly bright galaxy. There is heavy mottling on the E and W sides that meet at the N edge. There is some central to S edge brightening. NGC 2537A is a tiny mag 15.4 bit of faint fluff about 4.5' to the E. 17' to the SSE is IC 2233. At 4.5'x.5' it is one of the narrowest edge-on galaxies in the northern sky. Just a skinny streak of light.
Arp 202 - NGCs 2719 & 2719A - 2719 m13.5 sb 12.8 1.4'x.4' Ir/p - 2719A m13.5 sb 12.9 .6'x.4' Ir/p 9h0.3m +35°43'. Arp Classification - Galaxy with material ejected from nucleus. In the 20" at 317x these two looked just like the Arp photograph. 2719 is elongated NW-SE and about 1.4'x.3' in size. It has a very faint haze of material surrounding either end, beeing a little easier to see at the SE end. 2719A is located about .3' to the W of the SE end of 2719. It is irregular in shape but is elongated along the same axis as 2719. There is a bright stellar knot at the NW end.
|Arp 283 - NGCs 2798 & 2799 - 2798 m12.3 sb 11.3 2.8'x.9' SBa/p - 2799 m13.8 sb 14 2.1'x.5' SBm 9h17.5m +41°59'. Arp Classification - Double galaxies with infall and attraction. In the 20" at 317x 2798 is a large oval aligned NW-SE and about 2.5'x.9' in size. It has a bright core region about .6'x.4' aligned in the same direction with a brighter foreshortened bar .4'x.2' aligned NE-SW. The arm extending to the NW is easy to hold, but the very faint SE arm was only occasionally visible as a slight brightening of the sky background. 2799 is a fainter streak starting about 1' E from 2798's core and stretching from there 2' to the SE.|
Arp 315 - NGCs 2830, 2831 & 2832 - 2830 m14.2 sb15.3 1.2'x.3' SBa - 2831 m14.5 sb 13.9 1.4'x1.4' EO - 2832 m11.9 sb 13.1 3'x2' E4 9h19.8m +33°45'. Arp Classification - Groups of galaxies. This is another group that has some puzzling aspects. NGC 2832 is the cD galaxy at the heart of Abell 779, a cluster of 32 galaxies per the RCG. NGC 2831 and 2830, the other two objects in Dr. Arps photograph, have redshift figures that put them very much in the foreground.
In other Abell clusters it has been accepted that galaxies with redshifts measuring as much as 4500 kps ± from the dominant galaxy in that cluster are cluster members, but in this cluster, those members that have published redshifts seem to be within two to three hundred kps of 2832. There are two redshifts (NGCs 2825 and 2839) that go the other way with redshifts that are 1000 kps higher than the mean. In the 20" at 317x 2831 & 2 share a common envelope with 2830 located about 1' to the SW of these two. As I panned around the immediate area there were always several galaxies in the eyepiece field within the 50' diameter boundries of the cluster. Megastar plots over 50 galaxies within the cluster boundary, and at times there were as many as 12 faint to bright galaxies in the field. Another wonderful area to while away a few hours at the eyepiece while pondering the wonders of this universe that we live in.
In the four parts of this observing series I have tried to cover a fair sampling of the easiest to the more challenging objects from the "Atlas of Peculiar Galaxies". With an 8" instrument you will be able to see quite a few of these fascinating galaxies, with 12" as many as half of the catalog can be seen, but as I've found, with larger instruments they can not only be detected, but a fair amount of detail can be seen with patient inspection. With my current 20" f/5 Dobsonian I expect to be able to detect and log all 338 objects in this list. If you meet me at star parties in the future, come talk about them. I will probably still be getting the last few Arps tracked down. And when this list is completed, there is still the "Southern Catalog and Atlas of Peculiar Galaxies". There are over ten times as many objects in that list. A galaxy observer's cornucopia.