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NGC 1097 (also known as Caldwell 67) is a barred spiral galaxy about 45 million light-years away in the constellation Fornax. This Hubble image shows the central ring of star formation in NGC 1097. NGC 1097 is also a Seyfert galaxy. Deep photographs revealed four narrow optical jets that appear to emanate from the nucleus. Arp interpreted these as manifestations of the (currently weak) active nucleus. Subsequent analysis of the brightest jet's radio-to-X-ray spectral energy distribution by Carter, Allen & Malin (1984), Wehrle, Keel, & Jones (1997) and Higdon & Wallin (2003) were able to rule out synchrotron and thermal free-free emission. The jets are in fact composed of stars. The failure to detect atomic hydrogen gas in the jets (under the assumption that they were an example of tidal tails) using deep 21 cm HI imaging with the Very Large Array radio telescope and numerical simulations led to the current interpretation that the jets are actually the shattered remains of a cannibalized dwarf galaxy (Higdon & Wallin 2003). Like most massive galaxies, NGC 1097 has a supermassive black hole at its center. Around the central black hole is a ring of star-forming regions with a network of gas and dust that spirals from the ring to the black hole. NGC 1097 has two satellite galaxies. Dwarf elliptical galaxy NGC 1097A is the larger of the two. It is a peculiar elliptical galaxy that orbits 42,000 light-years from the center of NGC 1097. Dwarf galaxy NGC 1097B, the outermost one, was discovered by its HI emission (5 x 10^6 solar masses; Higdon & Wallin 2003), and appears to be a typical dwarf irregular. Little else is known about it. The field of view is about 0.9 arcminutes across.
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Credit: ESA and NASA