The Deepest Chandra View of RBS 797: Evidence for Two Pairs of Equidistant X-ray Cavities

Abstract

Abstract We present the first results of a deep Chandra observation of the galaxy cluster RBS 797 whose previous X-ray studies revealed two pronounced X-ray cavities in the east–west (E–W) direction. Follow-up VLA radio observations of the central active galactic nucleus (AGN) uncovered different jet and lobe orientations, with radio lobes filling the E–W cavities and perpendicular jets showing emission in the north–south (N–S) direction over the same scale (≈30 kpc). With the new ∼427 ks total exposure, we report the detection of two additional, symmetric X-ray cavities in the N–S direction at nearly the same radial distance as the E–W ones. The newly discovered N–S cavities are associated with the radio emission detected at 1.4 and 4.8 GHz in archival VLA data, making RBS 797 the first galaxy cluster found to have four equidistant, centrally symmetric, radio-filled cavities. We derive the dynamical and radiative ages of the four cavities from X-ray and radio data, respectively, finding that the two outbursts are approximately coeval, with an age difference of ⪅10 Myr between the E–W and N–S cavities. We discuss two scenarios for the origin of the two perpendicular, equidistant cavity systems: either the presence of a binary AGN that is excavating coeval pairs of cavities in perpendicular directions or a fast (<10 Myr) jet reorientation event that produced subsequent, misaligned outbursts.