Mapping the ionised gas around the luminous QSO HE 1029-1401: Evidence for minor merger events?

Abstract: We present VIMOS integral field spectroscopy of the brightest radio-quiet QSO on the southern sky HE 1029-1401 at a redshift of z=0.086. Standard decomposition techniques for broad-band imaging are extended to integral field data in order to deblend the QSO and host emission. We perform a tentative analysis of the stellar continuum finding a young stellar population (<100Myr) or a featureless continuum embedded in an old stellar population (10Gyr) typical for a massive elliptical galaxy. The stellar velocity dispersion of sigma_=320\pm90 km/s and the estimated black hole mass log(M_BH/M_sun)=8.7\pm0.3 are consistent with the local M_BH-sigma_ relation within the errors. For the first time we map the two-dimensional ionised gas distribution and the gas velocity field around HE 1029-1401. While the stellar host morphology is purely elliptical we find a highly structured distribution of ionised gas out to 16 kpc from the QSO. The gas is highly ionised solely by the QSO radiation and has a significantly lower metallicity than would be expected for the stellar mass of the host, indicating an external origin of the gas most likely due to minor mergers. We find a rotating gas disc around the QSO and a dispersion-dominated non-rotating gas component within the central 3 kpc. At larger distances the velocity field is heavily disturbed, which could be interpreted as another signature of past minor merger events. Alternatively, the arc-like structure seen in the ionised gas might also be indicative of a large-scale expanding bubble, centred on and possibly driven by the active nucleus.