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

¹ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany e-mail: bhusemann@aip.de
² Centro de Estudios de Física del Cosmos de Aragon (CEFCA), C/General Pizarro 1, 41001 Teruel, Spain
³ Fundación Agencia Aragonesa para la Investigación y el Desarrollo (ARAID), Spain
⁴ Centro Astronómico Hispano-Alemán, Calar Alto, (CSIC-MPG), C/Jesús Durbán Remón 2-2, 04004 Almeria, Spain
⁵ Max-Planck-Institut für Astronomie, Königsstuhl 17, 69117 Heidelberg, Germany
⁶ Department of Astronomy, Kyoto University, Kyoto 606-8502, Japan

Received: 30 March 2010
Accepted: 12 May 2010

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 (<100 Myr) or a featureless continuum embedded in an old stellar population (10 Gyr) typical for a massive elliptical galaxy. The stellar velocity dispersion of σ_* = 320±90 km s^-1 and the estimated black hole mass log(M_BH/) = 8.7±0.3 are consistent with the local M_BH–σ_* 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.