Astrophysics & Particle Physics-APPC 2026

Elliptical galaxies are one of the two most prominent types of galaxies, which are distinguished by their smooth, featureless, ellipsoidal appearance and with overwhelmingly old stellar populations. Unlike spiral galaxies, elliptical galaxies have no substantial disks, spiral arms, or active star formation, which makes them dominated by old, metal-rich stars and with a low interstellar medium content.Elliptical galaxy formation and evolution are strongly associated with galaxy mergers and interactions. Large mergings of spiral galaxies can create giant ellipticals, redistributing gas and stars and suppressing star formation. Most ellipticals live in high-density environments such as galaxy clusters, where merger rates are high.Elliptical galaxies are usually halos of dark matter, inferred through stellar kinematics and gravitational lensing, and sometimes include hot X-ray-luminous gas in their halos, particularly the large ones. Observations on optical, infrared, and X-ray wavelengths give us clues about their stellar content, mass distribution, and evolution.In brief, elliptical galaxies are ellipsoidal galaxies with smooth shapes and characterized by old stars and low star formation. They give us important information about the formation of galaxies, galaxy mergers, stellar populations, and the structure of galaxies due to dark matter and hence are important objects in extragalactic astronomy and cosmology