Arp’s Peculiar Galaxies
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Arp observations 31-40 of 88 total to date.
| Thumbnail | Title/link | Arp Category | Date Observed | Observer Description |
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Arp 104 / Keenans System | Elliptical galaxies connected to spiral galaxies | 2024-02-21 01:00:44 | This was the last observation of a very clear night, marred only by a 94% moon. I chose Arp 104 in part because I could point in the opposite direction. The key feature here is the dust lane connecting the two galaxies. Luckily it became evident after about half an hour and I was able to continue observing for a total of 60m. The featured image here was enhanced in Affinity Photo to accentuate the dust. A "natural" colored image is in the gallery. |
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Arp 112 / NGC 7805, 7806 and KUG 2359+311 | Elliptical galaxies repelling spiral arms | 2024-10-28 23:19:00 | A compact cluster of 3 galaxies, clearly interacting. The third galaxy is indicated by the bright side-segment slightly below and right of NGC 7806.... it appears to be a very low surface brightness spiral which I can see nearly complete if I overstretch it and blow out the rest of the image. It is apparently a very strong UV emitter as it shows up on the KUG catalog, which is reserved for strong UV sources. It's unclear to me why the lower arm of NGC 7806 is so elongated. Arp categorizes it as a galaxy "repelling spiral arms". Really? Seems to me that gravity attracts not repels. An alternative explanation might be that one of the other galaxies passed below from right to left before being captured and pulled back into the current orientation. The extended arm, therefore, might be a legacy of the "fly by". |
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Arp 114 / NGC 2300 | Elliptical galaxies close to and perturbing spiral galaxies | 2024-04-15 21:30:00 | Arp 25 (upper left) was visible from the first light frame. Arp 114's center looked like a bright star at first and capturing the rest of its disc required most of the integration time of 40m. I presume Arp concluded the two galaxies were perturbing each other because "the one heavy arm" in Arp 25 stretches outward towards Arp 114. |
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Arp 116 / M60 / NGC 4649-4647 | Elliptical galaxies close to and perturbing spiral galaxies | 2024-04-16 00:15:00 | NGC 4647 makes a lovely contrast with M60... a spiral galaxy with lots of structure vs. eliptical with virtually none other than a bright center. Certainly does appear that M60 is perturbing NGC 4647. Assuming NGC 4647 was close to circular when formed, the attraction has elongated its current shape and given the center of mass a slight kink to the south (towards M60). |
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Arp 117 / IC 982-983 | Elliptical galaxies close to and perturbing spiral galaxies | 2024-06-01 00:12:00 | Another reasonably bright Arp Peculiar Galaxy (or galaxy pair), with a large spiral galaxy (IC 983) interacting with (absorbing?) a dwarf. Essentially the spiral arms of 983 are directly connected to 982. Also, note the large, right-hand circle is a Milky Way star, not another galaxy. Surprising a galaxy as large as 983 didn't get discovered in time to be published in the NGC catalog. But this is likely because the surface brightness is a bit low, and it wasn't until photographic plates came into use that it was discovered. All NGC objects were discovered visually. The IC catalog, which was an extension of NGC was published in 1888 and 1905. IC objects were discovered both visually and with photo-plates. Anything discovered later was almost certainly discovered using photography. |
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Arp 120 / Eyes Galaxies | Elliptical galaxies close to and perturbing spiral galaxies | 2024-03-13 12:11:14 | What a fun target! The two galaxy centers are bright and were evident from the first 30 second frame. So the two galaxies "close to each other" is obvious, but it takes a while for the "perterbation" to become obvious. The extensive dust clouds connecting these galaxies are much lower brightness and took a while to become evident. Luckily it was a clear, dark night and I was able to continue integration until I judged minimal additional detail was forthcoming, after about half an hour. Very peculiar! |
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Arp 124 / NGC 6361 | Elliptical galaxies close to and perturbing spiral galaxies | 2024-06-13 23:45:00 | NGC 6361 is a straightforward target, but the tiny galaxy on its tail, MCG +10-25-3 is magnitude 15.8 and another story altogether. And, of course, the connecting dust lanes are even more obscure. BTW, the MCG catalog was based on the Palomar Sky Survey, and contains only a few galaxies above magnitude 15. Presumably this galaxy is cataloged in MCG because of its importance to Arp. Unfortunately, the evening's transparency, never very good, took a big hit after 20 minutes of integration, with a now thickened layer of high clouds shutting me down. It was tough to distinguish any connecting lane from general noise in the SharpCap capture... I processed it heavily in Affinity Photo and just managed to bring it out (note it's not terribly evident in the Palomar capture either). |
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Arp 130 / IC 5378 | Elliptical galaxies close to and perturbing spiral galaxies | 2024-11-03 20:23:00 | Based on Arp's category description, it's clear that Arp felt IC 5738 is actually two galaxies: an elliptical galaxy (left/lower) perturbing a spiral galaxy (right/upper). It seems likely that when initially observed as an entry in the IC, the spiral component of the pair was not resolved. Even with the benefit of CMOS cameras and stacking, distinguishing an elliptical and spiral component is tough. Arp's image, benefiting from the resolution supported by a 200" aperture plus a photographic plate does support that distinction. Of course, it seems highly likely that we're observing a merger in mid-process. |
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Arp 135 / NGC 1023 | Galaxies with nearby fragments | 2024-03-13 11:09:27 | First observation of the evening starting with Astronomical Dusk. Altitude just under 40° at start. This is a relatively large and bright object that appeared almost immediately in SharpCap. I stayed on it as long as needed to clearly see the bulge at the bottom which is NGC 1023A merging into it; the enhanced version of the image makes this obvious, though increases noise. Note Arp comparison is rotate 180° to match Arp's original image. |
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Arp 141 | Material emanating from elliptical galaxies | 2024-03-24 23:22:32 | A clear night, but a full moon. I searched for Arp targets that would be as far from the moon as possible, and this was the first I came up with... The two nucleii came up almost immediately. The bulbous end next. Eventually the loop structure began to fill in. |