IC 1459

Characteristics

IC 1459 is a giant elliptical galaxy. In its core has been observed a fast counter-rotating stellar component, with an estimated total mass of 3×10⁹ M_☉. The stars of this component have circular orbits on a flat disk with a radius of less than two arcseconds. It has been suggested that the stars of the counterrotating disk are of external origin, either by the accretion of a stellar satellite or of a dense molecular cloud from which the stars were created. The galaxy also features multiple shells and disturbed isophotes, which indicate that it has accreted material, probably by the merger of smaller galaxies with the elliptical galaxy. Enhanced photography revealed the presence of a diffuse spiral pattern at the outer regions of IC 1459.

It has been suggested that a merger started a starburst event in IC 1459. The total duration of this event has not been well constrained, but it is estimated it lasted less than 80 million years. Young stars make up approximately 3% of the total stellar population of the galaxy. They have an average age of 400 million years. Metallicity has been found to decrease as the radial distance from the center increases.

The nucleus of IC 1459 is active and has been characterised as a LINER based on its optical spectrum. The most accepted theory for the power source of active galactic nuclei is the presence of an accretion disk around a supermassive black hole. In the centre of IC 1459 lies a supermassive black hole with an estimated mass (2.6±1.0)×10⁹ M_☉ based on stellar velocities. Estimates of the mass of the black hole based on gas kinematics are lower, from (1-4) × 10⁸ to 10⁹ M_☉, although the presence of non-gravitational forces acting on the circumnuclear gas renders them less accurate. The disturbed kinematics of the circumnuclear gas may be caused by an outflow. In the circumnuclear region there is also dust with irregular distribution, indicating nonequilibrium motions.

The galaxy is characterised as low-power radio loud, with gigahertz-peaked spectrum, and has two symmetrical radio jets. In a 3.5 year observation period, the galaxy showed little variability. The galaxy also has weak X-ray emission. The nucleus appears unabsorbed in lower energy X-ray, with X-ray luminosity 7.9×10⁴⁰ ergs s-1, while the Fe-Kα fluorescence line, is not strong. The infrared emission of the nucleus is also less than the one expected by an AGN hidden by a dust torus. This indicates that the AGN is seen unobstructed. The galaxy possess an X-ray halo, whose modelling indicated the presence of dark matter at a distance larger than 3 effective radii.

In images by the Hubble Space Telescope, 199 globular clusters were recognised, with an indication of a decrease of their number near the core and statistically non-significant evidence of dimodial color distribution.