ABSTRACT. We present Chandra observations of the young elliptical galaxy NGC 1700. The X-ray isophotes are highly flattened between semimajor axes of 30'' and 80'', reaching a maximum ellipticity _X 0.65 at 60'' (15 kpc). The surface brightness profile in the spectrally soft flattened region is shallower than that of the starlight, indicating that the emission comes from hot gas rather than stellar sources. The flattening is so extreme that the gas cannot be in hydrostatic equilibrium in any plausible potential. A likely alternative is that the gas has significant rotational support. A simple model, representing isothermal gas distributed about a particular angular momentum, can reproduce the X-ray morphology while staying consistent with stellar kinematics. The specific angular momentum of the gas matches that of the stars in the most isophotally distorted outer part of the galaxy, and its cooling time matches the time since the last major merger. We infer that the gas was acquired in that merger, which involved a preexisting elliptical galaxy with a hot interstellar medium. The hot gas carried the angular momentum of the encounter and has since gradually settled into a rotationally flattened cooling disk.

Subject headings: cooling flows; galaxies: elliptical and lenticular, cD; galaxies: ISM; X-rays: galaxies; X-rays: ISM

Print publication: Issue 2 (2002 December 20)
Received 2002 January 29, accepted for publication 2002 August 23