NGC 985

Background

NGC 985 is characterized by its ring shape, believed to have formed as a result of a galaxy merger. Evidence for this includes the observation of a second nucleus, found 3.8 arcseconds northwest of the active nucleus when observed in infrared light.

This secondary nucleus is much redder than the rest of the galaxy, indicating the presence of old stars. It has been suggested that the collision between a disk galaxy and another galaxy caused the formation of the ring and displaced the nucleus, creating an empty ring. Based on kinematics, the secondary nucleus belonged to the intruder galaxy, while the active nucleus is associated with the main stellar component.

As is common with merger remnants, NGC 985 has an increased star formation rate and shines bright in the infrared. Very large molecular clouds exist near the nuclei; they may be clouds gathering around the nucleus in the process of forming a disk around the two nuclei, or molecular clouds disrupted by an outflow from the nucleus. The total molecular gas mass of the galaxy is estimated, though the specific value is not given.

NGC 985 is a powerful X-ray source, detected by ROSAT. Its X-ray spectrum is complex, not accounted for by a simple power law at 0.6 keV, suggesting the presence of a warm absorber. The hard X-ray emission is characterized by a simple power law.

The X-ray flux, especially soft X-rays, diminished in 2013. Variability of X-ray and ultraviolet emission from the nucleus was observed using XMM-Newton and the Hubble Space Telescope, revealing outflowing wind from an accretion disk around a supermassive black hole that obstructed the nucleus in soft X-rays and UV. The nucleus is otherwise seen unobstructed.