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Astronomy Picture of the Day

Similar in size to the Milky Way, elliptical galaxy NGC 7600 is about 160 million light-years distant. In this deep image, spanning about 1/2 degree on the sky toward the constellation Aquarius, NGC 7600 sports a remarkable outer halo of nested shells and broad circumgalactic structures. The tantalizing features can be explained by the accretion of dark matter and stars on a cosmic timescale.

 

 

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Shell Galaxy NGC 7600 
Image Credit & Copyright [2]Ken Crawford (Rancho Del Sol Observatory [3])
Collaboration: Andrew Cooper (MPA [4]), Carlos Frenk, John Helly, Shaun Cole (Institute for Computational Cosmology [5]),
David Martinez-Delgado (MPIA [4]), Star Stream Pilot Survey [6] Group

Explanation: Similar in size to the Milky Way, elliptical galaxy NGC 7600 is about 160 million light-years distant. In this deep image [7], spanning about 1/2 degree on the sky toward [8] the constellation Aquarius, NGC 7600 sports a remarkable outer halo of nested shells and broad circumgalactic structures. The tantalizing features can be explained by the accretion of dark matter and stars on a cosmic timescale [9]. In fact, a movie generated by simulating galaxy formation using a cosmological model [10] with cold dark matter [11] for the halos of merging galaxies reproduces the appearance of NGC 7600 in amazing detail. The remarkable simulation movie is available here on Vimeo [12] and here in other formats [13]. It presents compelling evidence that detailed features of galaxy mergers observed with small, wide field telescopes on planet Earth, are natural consequences of galaxy formation and fundamental properties of dark matter [14].