Arp’s Peculiar Galaxies
Page 8 of 18
Arp observations 71-80 of 171 total to date.
| Thumbnail | Title/link | Arp Category | Date Observed | Observer Description |
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Arp 137 / NGC 2914 | Material emanating from elliptical galaxies | 2025-01-26 22:19:00 | This is a bonus object, imaged within the same field of view as Arp 232. I was not aware of their proximity when I captured the observation. I did process this differently with two levels of sharpening to emphasize the separation of the upper arm from the galaxy center. When I created the comparison image, I noticed that the smaller of the double stars to the left (west) of the target has orbited to new position since Arp's image. This is a first for me. As for Arp's classifying this as "material emanating from an elliptical galaxy," I'm not sure he's right. My first clue was the size of the stars. Normally the Arp images are pinpoint compared to my 8" EdgeHD, but here (as you can see in the comparison image) the stars are similarly sized. This suggests to me that Arp's image is overexposed and blew out any detail in the galaxy disk, making it appear elliptical. I then went searching for sources after the fact and discovered Gary Imm's images of Arp 137 that he classifies as a barred spiral. It seems to me that interpreting this image as a spiral galaxy with one extended arm, is more likely, even given Arp's image. Arp may have been excited to find an elliptical emanating material, but may be victim to his own confirmation bias. |
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Arp 141 / UGC 3730 | 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. In reviewing this prior to submission to the AL, I found Arp's category unconvincing. There are no remarks to assist. While it's possible we're seeing "material emanating" it strikes me that material could equally-likely be merging. There is a highly distorted structure to the emanations, and it looks suspiciously like a low surface brightness barred-spiral galaxy getting compressed by (presumably) a much denser elliptical galaxy. Either way it's a "peculiar" galaxy in Arp's terms, but common sense suggests structured material is more likely to be coming in that out. |
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Arp 143 | NGC 2445 & 2444 | Material emanating from elliptical galaxies | 2026-01-22 21:19:00 | This is a classic peculiar galaxy where the interaction between NGC 2445 and 2444, after modern observations, is thought to have stimulated intense star formation along the bridge between them. Most of the bright spots on 2445 (dark in the inverted images) are thought to be new star formation structures as well. From the category, Arp seemed to thing that NGC 2445 "emanated" from the Elliptical galaxy NGC 2444. His remarks, "Diffuse counter filament" is a bit challenging to interpret, though I take it to mean the gray "haze" that shows up in his image, and the "dust" that seems to surround both galaxies in my wider field image. |
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Arp 145 / UGC 1840 | Material emanating from elliptical galaxies | 2024-02-29 20:00:01 | Reviewing this before submission to the AL in Feb 2025, a year after the original capture,, I feel the same about this target as I do Arp 141: this is as likely to be a merger as a showing "emanating material". As part of this "rethinking", I created the inverted monochrome image from my original OSC capture, which depicts things much more clearly in combination with the positive. The galactic center of the elliptical galaxy is obviously the large, medium-bright object just left of image center (the three stars in a line are lower in the image and point to it). All of the other bright objects are imo field stars, EXCEPT the medium bright object which forms the upper vertex of a triangle in combination with the two brightest field stars. If you look at my inverted image, it's the smallest of the three. If believe this could be the center of a spiral galaxy being absorbed into the Elliptical rather than emanating from it. This capture took place despite an 88% moon. I was determined to capture a number of Arp galaxies in Andromeda, recognizing the window of opportunity in Feb 2024 was short. This was the second observation of the evening, and the target was fairly low in the west. I captured as much data as I could until I judged the thicker atmosphere and glow at the horizon would render further integration useless. |
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Arp 150 / NGC 7609 | Galaxies with jets | 2024-11-03 21:36:00 | Arp's designated this cluster as one of a group of "Galaxies with jets." The image suggests that NGC 7609 is in fact two galaxies, a larger one (left) connected to a smaller one by two major arms. The "jet" is likely the emanations from the smaller 7609 galactic center, but that's just a guess. It's more readily seen as an inverted (negative) image, so I prepped the "comparison" accordingly. |
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Arp 151 / Markarian 40 | Galaxies with jets | 2025-05-11 22:42:00 | The first observation following a clear day, but with a full moon. As it turned out clear enough. |
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Arp 152 / Virgo A / M87 | Galaxies with jets | 2024-03-13 00:42:00 | The fourth of 9 entries added to the Messier catalog on March 8, 1781, also (#37) credited to Messier. "Nebula without star, in Virgo, below & very near a star of eighth magnitude.... This nebula appears at the same luminosity as the two nebulae Nos. 84 and 86." Halton Arp included M87 as Arp 152 in his Atlas of Peculiar Galaxies. He classified it with "Galaxies with Jets" and remarked "Short exposure to show jet. Virgo A radio source." <--> The toughest aspect for me was to set the black level appropriately to show the diffuse outer ring of this nebulous, elliptical galaxy while not obscuring the jet(s)... It's so large, I thought for a while my dark-subtraction in SharpCap was failing, and I was seeing amp glow! However, I was able to identify that the diffusion wasn't quite round, and not "quite" as large as uncontrolled amp-glow with my 294 sensor. This became obvious after about 15m of integration. The S/N ratio was so high, and since there is no structure to speak of in the outer disc, there seemed no advantage to continuing integration longer than the 25m once the two tiny galaxies, LEDA 139919 and UGC 7652, and the connecting jet were clear. Note that the "short exposure" Arp alludes to allows his image to show the jet right to the galactic center. My exposure wasn't so expert, and the inverted image is still blown out, but does appear to show the jet continuing a little deeper into the disk. Then a friend pointed out that it's actually second "jet" in this image that Arp did not detect: which appears as a tiny bump on the edge of the galactic core. You can see it the enlarged closeup is in the gallery. It is barely visible in the Arp photograph; note the Arp comparison is rotated 180° relative to the original capture, featured image, and jet enlargement. |
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Arp 155 / NGC 3656 | Galaxies disturbed by interior absorption | 2024-03-12 13:38:32 | The first challenge here is understanding what "disturbed by interior absorption" means. I searched carefully on the Internet for a definitive source and found found nothing very convincing. As is typical in the Arp world, many sources quote the category but explain nothing, as if Arp's perceptions were self-evident (they often aren't, I find). So I'm falling back onto the common meanings of these words, which would be a galaxy where the interior of the disk is seriously disturbed or disrupted. Examining the galaxies so categorized (153-160), I can confirm that this describes all of them to some degree. Certainly, in the case of Arp 153. the galaxy appears to be lenticular, but the core is bifurcated and divided by large dust lanes. This seems consistent with a galaxy consolidating its core after a merger. |
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Arp 157 / NGC 520 | Galaxies disturbed by interior absorption | 2026-02-24 20:30:00 | Discovered originally by William Herschel in 1784, this is a truly enigmatic galaxy of magnitude 11.8. Most modern commentator suggest its a merger in progress. Arp, himself, despised what he called "merger mania" and gave it a cryptic classification of "Galaxies, disturbed with interior absorption", whatever that means. Arp's remarks were "Note segment in NE direction" which presumably refers to the faint tidal trail continuing to the upper right from the galactic center. |
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Arp 158 / NGC 537 | Galaxies disturbed by interior absorption | 2024-02-29 19:39:57 | This is a highly disturbed galaxy, no doubt, but I'm a bit puzzled why "disturbance of interior absorption" is the most salient feature here. As a first approximation, young galaxies start with a coherent shape, often sprial and circular. As the galaxy matures and evolves through gravitational interactions with other galaxies, some sort of elliptical shape is often preserved, as well as a high degree of symmetry. This galaxy has been severely elongated in one direction and cut off in the other. The core appears to be separated into two planes: the top level, smaller, perhaps showing the remnants of a formerly "S" curved bar. The lower level, perhaps twice as long, and rotated counter-clockwise 10 or 15 degrees. |