"According to cosmological simulations it is not surprising that galaxies as DDO 68 can host satellite galaxies of smaller mass. The researchers therefore concluded that the irregularities observed throughout DDO 68 are not due to an interaction with a smaller companion as DDO 68 C, and are more probably the result of multiple accretion of smaller systems. The N-body model reproduced several known features of DDO 68, mainly the very asymmetric and disturbed shape of the stellar component, the overall neutral atomic hydrogen (HI) distribution and its velocity field, the arc-like stellar structure to the west, as well the low-surface brightness stellar stream observed to the north.īased on the simulations, the astronomers found that the galaxy is most likely a result of the interaction between three systems, namely a dominant galaxy, DDO 68, with a dynamical mass at a level of 10 billion solar masses and two smaller satellite galaxies-with masses of about 0.05 and 0.0067 times the mass of DDO 68. "We have presented state-of-the-art hydrodynamical N-body simulations able to explain most of the peculiarities observed in DDO 68," the researchers state. They performed hydrodynamical N-body simulations of DDO 68 aimed at reproducing most of the available structural and kinematical observations of this galaxy derived in the past years. Moreover, it has a roundish structure to the north, the so-called "cometary head." Astronomers found that DDO 68 is, in fact, composed of two distinct systems: the main body DDO 68 A (including the cometary head) and a disrupted satellite DDO 68 B being currently accreted by DDO 68 A and producing the cometary tail.Ī team of astronomers led by Raffaele Pascale of the Astronomical Observatory of Bologna, Italy, took a closer look at DDO 68 and its peculiarities. The galaxy showcases a large, bright and distorted stellar component, dubbed the "cometary tail," emerging from the south-eastern edge of its main body. Previous observations of DDO 68 have shown that it has an unusual shape. Its extremely low metallicity is peculiar in light of its relatively large total stellar mass (117 million solar masses) and luminosity. It has a low average oxygen abundance and is one of the most metal-poor dwarf galaxies known to date. Galaxies with low metallicity are of special importance for astronomers as they could provide crucial insights about chemical evolution of stars and astrophysical processes occurring in the early universe.Īt a distance of about 41.2 million light years away from the Earth, DDO 68 (also known as UGC 5340) is a dwarf irregular galaxy.
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