Chandra and XMM-Newton Observations of the Group of Galaxies HCG 62

Abstract

We present results from Chandra and XMM-Newton observations of the bright group of galaxies HCG 62. There are two cavities at about 30 ′′ northeast and 20 ′′ southwest of the central galaxy in the Chandra image. The energy spectrum shows no significant change in the cavity compared with that in the surrounding region. The radial X-ray profile is described by a sum of 3-β components with core radii about 2, 10, and 160 kpc, respectively. We studied radial distributions of temperature and metal abundance with joint spectral fit for the Chandra and XMM-Newton data, and two temperatures were required in the inner r < 2 ′ (35 kpc) region. The sharp drop of temperature at r ∼ 5 ′ implies the gravitational mass density even lower than the gas density, suggesting the gas may not be in hydrostatic equilibrium. Fe and Si abundances are 1-2 solar at the center and drop to about 0.1 solar at r ∼ 10 ′ . O abundance is less than 0.5 solar and shows a flatter profile. Observed metal distribution supports the view that iron and silicon are produced by type Ia supernova in the central galaxy, while galactic winds by type II supernova have caused wide distribution of oxygen. The supporting mechanism of the cavity is discussed. Pressure for the sum of electrons and magnetic field is too low to displace the hot group gas, and the required pressure due to high energy protons are nearly 700 times higher than the electron pressure. This leaves the origin of the cavities a puzzle, and we discuss other possible origins of the cavities.