The Deepest Chandra View of RBS 797: Evidence for Two Pairs of Equidistant X-ray Cavities
Speakers: Giorgia Peluso (Università degli Studi di Padova)
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 theradio emission detected at 1.4 GHz 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 which is excavating coeval pairs of cavities in perpendicular directions, or a fast (<10 Myr) jet reorientation event which produced subsequent,misaligned outbursts.