| Designation(s) | Arp 181, NGC 3215, NGC 3212 |
| Object Type(s) | Galaxy |
| Relevant Catalog(s) | All (Chron), Arp, NGC |
| Arp Category | Galaxies with narrow filaments |
| Obs. Lat/Long | 42° 17', 073° 57' |
| Constellation | Draco |
| Date and Time Observed | 2024-12-25 21:08:00 |
| Instrument | EdgeHD 8" w/f7 reducer-1,422mm FL |
| Camera | Player One Apollo-M Mini |
| Image Details | Up is 280.5 degrees E of N. Total integration time was 56m. Exposures 15s@300g, UV/IR Cut Filter. Darks subtracted, no flats. Dithered and recentered in SharpCap. No guiding. |
| Description | We focused on illustrating the key feature that Arp called out: the "narrow filaments" or tidal tails emanating from NGC 3212. He remarked on the "long faint filament extend[ing] westward from south arm". This tests the limits of EAA techniques. While the galaxies themselves are reasonably bright at mag. 10.3 for NGC 3215, and 11.2 for 3212, the surface brightness of the long filament is MUCH dimmer. Note it's barely visible in Arp's plate, and this is one of the few faint details I was not able make readily visible in an inverted version. This despite 56m integration using a mono camera, which is normally more than adequate. While barely visible in the "as captured" EAA positive-image, visibility was enhanced using stretching and sharpening. The "annotated" image came from a 2013 paper in the Monthly Notices of the RAA. This notice, based principally on radio observations, concludes that the interaction has shifted an estimated 90% of the H1 mass outside the optical discs of the two galaxies. The interaction has triggered a burst of star formation activity in two "Tidal Dwarf Galaxies" which peak close to the end of the long filament which Arp called out, labelled TDG and SDSS, respectively. TDG is close to the end of the optical filament but not visible in optical wavelengths; SDSS corresponds to the middle smudge cut off by the western (bottom) border of the comparison images. It is fully visible in the "featured image" reproduced next to the table on wide screen devices. |
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