A study of the galaxy distribution in the field of the elliptical galaxy NGC1600 has been undertaken . Although this galaxy is often classified as a member of a loose group , all the neighbouring galaxies are much fainter and could be taken as satellites of NGC1600 . The number density profile of galaxies in the field of this galaxy shows a decline with radius , with evidence of a background at approximately 1.3 Mpc . The density and number density profile are consistent with that found for other isolated early-type galaxies . NGC1600 appears as an extended source in X-rays , and the center of the X-ray emission seems not to coincide with the center of the galaxy . The velocity distribution of neighbouring galaxies has been measured from optical spectroscopic observations and shows that the mean radial velocity is approximately 85 km s ^ { -1 } less than that of NGC1600 , indicating that the centre of mass could lie outside the galaxy . The velocity dispersion of the ‘ group ’ is estimated at 429 \pm 57 km s ^ { -1 } . The inferred mass of the system is therefore of the order of 10 ^ { 14 } M _ { \odot } , a value that corresponds to a large group . NGC1600 therefore shares some similarities , but is not identical to , the ‘ fossil clusters ’ detected in X-ray surveys . Implications of this result for studies of isolated early-type galaxies are briefly discussed .