NGC 2110

Background

NGC 2110 was discovered by William Herschel on October 5, 1785. It is classified as a lenticular galaxy, though it was once considered elliptical.

Characteristics

Hubble Space Telescope images revealed curved dust lanes about one arcsecond west of the nucleus, and infrared observations detected a bar of material measuring 90 by 35 parsecs at the nucleus. Four star clusters in the circumnuclear region, observed by the Keck Observatory in the near infrared, form a semicircular structure 90 parsecs in diameter. Gemini Observatory observations indicate a ring of intermediate-age stars (100–700 million years) with a diameter of 140 parsecs, while the star population closer to the nucleus is predominantly old.

Active nucleus

The galaxy's nucleus is active, classified as a type II Seyfert galaxy. It is a bright X-ray source, and a broad double-peaked H-alpha emission line suggests a hidden broad line region obscured by a dust torus. The energy source is believed to be an accretion disk around a supermassive black hole, with an estimated mass of 1.95 billion solar masses based on velocity dispersion. The X-ray spectrum resembles that of Seyfert 1 galaxies but is obstructed by a complex absorber with column densities between 4 and 30 × 10^22/cm².

Observations by Chandra, XMM-Newton, and Suzaku confirmed a patchy absorber around the nucleus. The FeKα line has two components: one from distant Compton-thick material and one variable from material near the black hole. The hot corona temperature is estimated in keV.

Radio observations show emission extending 4 arcseconds, with two S-shaped jets emanating north and south from the nucleus. H-alpha and OIII imaging reveal a narrow, curved outflow north of the nucleus, and ionized gas in an s-shaped pattern extends 4 arcseconds north and south. Soft X-ray emission is detected north of the nucleus beyond the radio jet and south of the nucleus extending 30 arcseconds.

Gas kinematics indicate an inflow of cold gas of 2.2 × 10⁻² solar masses per year and an outflow of 0.9 or 0.5 solar masses per year. The outflow produces blueshifted gas (100 km/s) southwest and redshifted gas (40 km/s) northeast. Other kinematic components include a cold gas disk (velocity dispersion 60–90 km/s), a hot gas disk (220–600 km/s), and an ionized gas cloud 1–4 arcseconds north of the nucleus, which is devoid of CO 2–1 emission.