Discovery of a superluminal Fe K echo at the Galactic Center: The glorious past of Sgr A* preserved by molecular clouds

Understand

We present the result of a study of the X-ray emission from the Galactic Centre (GC) Molecular Clouds (MC) within 15 arcmin from Sgr A*.

• We use XMM-Newton data (about 1.2 Ms of observation time) spanning about 8 years.
• The MC spectra show all the features characteristic of reflection: i) intense Fe Kalpha, with EW of about 0.7-1 keV, and the associated Kbeta line; ii) flat power law continuum and iii) a significant Fe K edge (tau~0.1-0.3).
• The diffuse low ionisation Fe K emission follows the MC distribution, nevertheless not all MC are Fe K emitters.