X-Ray Emission from the Jets and Lobes of the Spiderweb

Abstract

Deep Chandra and Very Large Array imaging reveals a clear correlation between X-ray and radio emission on scales ~100 kpc in the Spiderweb radio galaxy at z = 2.16. The X-ray emission associated with the extended radio source is likely dominated by inverse Compton upscattering of cosmic microwave background photons by the radio-emitting relativistic electrons. For regions dominated by high surface brightness emission, such as hot spots and jet knots, the implied magnetic fields are ~50-70 μG. The nonthermal pressure in these brighter regions is then ~9 × 10<SUP>-10</SUP> dynes cm<SUP>-2</SUP>, or three times larger than the nonthermal pressure derived assuming minimum energy conditions, and an order of magnitude larger than the thermal pressure in the ambient cluster medium. Assuming ram pressure confinement implies an average advance speed for the radio source of ~2400 km s<SUP>-1</SUP> and a source age of ~3 × 10<SUP>7</SUP> yr. Considering the lower surface brightness, diffuse radio-emitting regions, we identify an evacuated cavity in the Lyα emission coincident with the tail of the eastern radio lobe. Making reasonable assumptions for the radio spectrum, we find that the relativistic electrons and fields in the lobe are plausibly in pressure equilibrium with the thermal gas and close to a minimum energy configuration. The radio morphology suggests that the Spiderweb is a high-z example of the rare class of hybrid morphology radio sources (or HyMoRS), which we attribute to interaction with the asymmetric gaseous environment indicated by the Lyα emission.