Direct detection of gas motions in the Perseus core with XMM-Newton

Unbeknownst to most but not all the EPIC MOS detectors can be used to detectsubsonic gas motions in cluster cores. From our work on calibration data we findthat the relative energy across the EPIC MOS detectors can be reconstructed witha precision better than sim 1.5 eV. This can be used to detect velocities inexcess of sim 70 km/s in cluster cores from the Fe K alpha line. From theanalysis of a public Perseus observation we find various indications of gasmotions with typical velocities of the order of a few 100 km/s. Our analysis ofthe Perseus motions is however limited by the statistics of the observation, wetherefore request a new, longer, Perseus observation to secure sufficient countsto measure velocity shifts down to sim 200 km/s. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]